bluuebunny/crossref_metadata_2025 huggingface dataset:
Social Identity and Youth Aggressive and Delinquent Behaviors in a Context of Political Violence
Authors: Merrilees Christine E. , Cairns Ed , Taylor Laura K. , Goeke‐Morey Marcie C. , Shirlow Peter , Cummings E. Mark
Published: April 2013

The goal of the current study was to examine the moderating role of in‐group social identity on relations between youth exposure to sectarian antisocial behavior in the community and aggressive behaviors. Participants included 770 mother‐child dyads living in interfaced neighborhoods of Belfast. Youth answered questions about aggressive and delinquent behaviors as well as the extent to which they targeted their behaviors toward members of the other group. Structural equation modeling results show that youth exposure to sectarian antisocial behavior is linked with increases in both general and sectarian aggression and delinquency over one year. Reflecting the positive and negative effects of social identity, in‐group social identity moderated this link, strengthening the relationship between exposure to sectarian antisocial behavior in the community and aggression and delinquency towards the out‐group. However, social identity weakened the effect for exposure to sectarian antisocial behavior in the community on general aggressive behaviors. Gender differences also emerged; the relation between exposure to sectarian antisocial behavior and sectarian aggression was stronger for boys. The results have implications for understanding the complex role of social identity in intergroup relations for youth in post‐accord societies.
Evidence of low levels of genetic diversity for the Phytophthora austrocedrae population in Patagonia, Argentina
Authors: Vélez M. L. , Coetzee M. P. A. , Wingfield M. J. , Rajchenberg M. , Greslebin A. G.
Published: April 2013

Phytophthora austrocedrae is a recently discovered pathogen that causes severe mortality of Austrocedrus chilensis in Patagonia. The high level of susceptibility of the host tree, together with the distribution pattern of the pathogen, have led to the hypothesis that P. austrocedrae was introduced into Argentina. The aim of this study was to assess the population structure of P. austrocedrae isolates from Argentina in order to gain an understanding of the origin and spread of the pathogen. Genetic diversity was determined based on amplified fragment length polymorphisms (AFLPs). In total, 48 isolates of P. austrocedrae were obtained from infected A. chilensis trees, representing the geographical range of the host. Four primer combinations were used for the AFLP analysis. Of the 332 scored bands, 12% were polymorphic. Gene diversity (h) ranged from 0·01 to 0·03; the Shannon index (I) ranged from 0·01 to 0·04. A high degree of genetic similarity was observed among the isolates (pairwise S values = 0·958–1; 0·993 ± 0·009, mean ± SD). A frequency histogram showed that most of the isolate pairs were identical. Principal coordinate analysis using three‐dimensional plots did not group any of the isolates based on their geographical origin. The low genetic diversity (within and between sites) and absence of population structure linked to geographic origin, together with the aggressiveness of the pathogen and the disease progression pattern, suggest that P. austrocedrae might have been introduced into Argentina.
Metallosis and Cutaneous Metal Pigmentation in a Reverse Shoulder Replacement
Authors: Berber Onur , Pearse Eyiyemi O. , Tennent Thomas D.
Published: April 2013

Metallosis with an associated cutaneous pigmentation as a result of metal dispersion has not been reported in the literature. A case is described in a patient who developed an extensive metallosis that presented with cutaneous pigmentation 8 years after a reverse shoulder replacement.
A numerical study of particle motion and two‐phase interaction in aeolian sand transport using a coupled large eddy simulation – discrete element method
Authors: Li Zhiqiang , Wang Yuan , Zhang Yang
Published: April 2013

Wind‐blown sand movement, considered as a particle‐laden two‐phase flow, was simulated by a new numerical code developed in the present study. The discrete element method was employed to model the contact force between sand particles. Large eddy simulation was used to solve the turbulent atmospheric boundary layer. Motions of sand particles were traced in the Lagrangian frame. Within the near‐surface region of the atmospheric boundary layer, interparticle collisions will significantly alter the velocity of sand. The sand phase is quite dense in this region, and its feedback force on fluid motion cannot be ignored. By considering the interparticle collision and two‐phase interaction, four‐way coupling was achieved in the numerical code. Profiles of sand velocity from the simulations were in good agreement with experimental measurements. The mass flux shows an exponential decay and is comparable to reported experimental and field measurements. The turbulence intensities and shear stress of sand particles were estimated from particle root‐mean‐square velocities. Distributions of slip velocity and feedback force were analysed to reveal the interactions between sand particles and the continuous fluid phase.
Changes in soil organic carbon and its chemical fractions under different tillage practices on loess soils of the Guanzhong Plain in north‐west China
Authors: Sun H. Y. , Wang C. X. , Wang X. D. , Rees R. M.
Published: April 2013

Over the past 20 years, conservation tillage has been used on the loess plateau of north‐west China to improve the sustainability of local agriculture. There had been particular concern about loss of soil organic matter associated with traditional tillage. We examined the influence of four tillage treatments: conventional tillage (CT), subsoiling tillage (SST), rotary tillage (RT) and no‐tillage (NT), with two straw residue management treatments (return and removal) on the distribution with soil depth (0–20 cm, 20–40 cm) of total organic carbon, labile organic carbon (KMnO4‐C) and bound organic carbon. The study was carried out on a Loutu soil (Earth‐cumuli‐Orthic Anthrosol) over seven consecutive years of a winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) crop rotation. By the end of this period, conservation tillage (SST, RT and NT) led to greater storage of soil organic carbon (SOC) (22.7, 14.9 and 16.3% with straw return in contrast to 21.4, 15.8 and 12.3% with no straw return, respectively) compared with CT in the surface soil (0–20 cm). The reduced tillage treatments (SST and RT) both increased significantly the highly labile organic carbon (HLOC) content of the surface soil (50% in both SST and RT) and mildly labile organic matter (MLOC) (49.4 in SST and 53.5% in RT) when straw was removed. The largest pool of bound carbon was observed in the Humin‐C pool, and the smallest in the free humic acids C (FHA‐C) in each tillage treatment. Conservation tillage led to an increased content of FHA‐C and CHA‐C. Results from correlation analyses indicate that SOC enrichment might have resulted from the increase in HLOC, MLOC, FHA‐C and CHA‐C over a short period. Labile organic carbon was associated with the organic carbon that was more loosely combined with clay (FHA‐C and CHA‐C). We conclude that both SST and RT are effective in maintaining or restoring organic matter in Loutu soils in this region, and the effect is greater when they are used in combination with straw return.
Anopheles culicifacies sibling species in Odisha, eastern India: First appearance of Anopheles culicifacies E and its vectorial role in malaria transmission
Authors: Das Mumani , Das Biswadeep , Patra Aparna P. , Tripathy Hare K. , Mohapatra Namita , Kar Santanu K. , Hazra Rupenangshu K.
Published: April 2013

Objective

To identify the Anopheles culicifacies sibling species complex and study their vectorial role in malaria endemic regions of Odisha.

Methods

Mosquitoes were collected from 6 malaria endemic districts using standard entomological collection methods. An. culicifacies sibling species were identified by multiplex polymerase chain reaction (PCR) using cytochrome oxidase subunit II (COII) region of mitochondrial DNA. Plasmodium falciparum (Pf) sporozoite rate and human blood fed percentage (HBF) were estimated by PCR using Pf‐ and human‐specific primers. Sequencing and phylogenetic analysis were performed to confirm the type of sibling species of An. culicifacies found in Odisha.

Results

Multiplex PCR detected An. culicifacies sibling species A, B, C, D and E in the malaria endemic regions of Odisha. An. culicifacies E was detected for the first time in Odisha, which was further confirmed by molecular phylogenetics. Highest sporozoite rate and HBF percentage were observed in An. culicifacies E in comparison with other sibling species. An. culicifacies E collected from Nawarangapur, Nuapara and Keonjhar district showed high HBF percentage and sporozoite rates.

Conclusion

An. culicifacies B was the most abundant species, followed by An. culicifacies C and E. High sporozoite rate and HBF of An. culicifacies E indicated that it plays an important role in malaria transmission in Odisha. Appropriate control measures against An. culicifacies E at an early stage are needed to prevent further malaria transmission in Odisha.
SPL8 and miR156‐targeted SPL genes redundantly regulate Arabidopsis gynoecium differential patterning
Authors: Xing Shuping , Salinas María , Garcia‐Molina Antoni , Höhmann Susanne , Berndtgen Rita , Huijser Peter
Published: April 2013

SPL8 and miR156‐targeted SPL genes are known to play an essential role in Arabidopsis anther development. Here we show that these SPL genes are also expressed within the developing gynoecium, where they redundantly control development of the female reproductive tract. Whereas the gynoecium morphology in the spl8 single mutant is largely normal, additional down‐regulation of miR156‐targeted SPL genes results in a shortened style and an apically swollen ovary narrowing onto an elongated gynophore. In particular, the septum does not form properly and lacks a transmitting tract. Loss of SPL8 function enhances the mutant phenotypes of ett, crc and spt, indicating a functional overlap between SPL8 and these genes in regulating gynoecium development. Furthermore, gynoecium development of 35S:MIR156b spl8–1 double mutants shows enhanced sensitivity to a polar auxin transport inhibitor, and the expression pattern of the auxin biosynthesis gene YUCCA4 is altered compared to wild‐type. Our observations imply that SPL8 and miR156‐targeted SPL genes control gynoecium patterning through interference with auxin homeostasis and signalling.
Requirement for the plastidial oxidative pentose phosphate pathway for nitrate assimilation in Arabidopsis
Authors: Bussell John D. , Keech Olivier , Fenske Ricarda , Smith Steven M.
Published: April 2013

Sugar metabolism and the oxidative pentose phosphate pathway (OPPP) are strongly implicated in N assimilation, although the relationship between them and the roles of the plastidial and cytosolic OPPP have not been established genetically. We studied a knock‐down mutant of the plastid‐localized OPPP enzyme 6‐phosphogluconolactonase 3 (PGL3). pgl3‐1 plants exhibited relatively greater resource allocation to roots but were smaller than the wild type. They had a lower content of amino acids and free in leaves than the wild type, despite exhibiting comparable photosynthetic rates and efficiency, and normal levels of many other primary metabolites. When N‐deprived plants were fed via the roots with , pgl3‐1 exhibited normal induction of OPPP and nitrate assimilation genes in roots, and amino acids in roots and shoots were labeled with 15N at least as rapidly as in the wild type. However, when N‐replete plants were fed via the roots with sucrose, expression of specific OPPP and N assimilation genes in roots increased in the wild type but not in pgl3‐1. Thus, sugar‐dependent expression of N assimilation genes requires OPPP activity and the specificity of the effect of the pgl3‐1 mutation on N assimilation genes establishes that it is not the result of general energy deficiency or accumulation of toxic intermediates. We conclude that expression of specific nitrate assimilation genes in the nucleus of root cells is positively regulated by a signal emanating from OPPP activity in the plastid.
Pulmonary hypertension and the right ventricle in hypoxia
Authors: Naeije Robert , Dedobbeleer Chantal
Published: April 2013

New Findings

What is the topic of this review?

Studies a,contabs,longabsre reviewed showing that hypoxic pulmonary vasoconstriction and subsequent remodelling expose the right ventricle to increased afterload, and that this is occasionally a cause of high‐altitude right heart failure.

What advances does it highlight?

Non‐invasive field studies have shown that hypoxic pulmonary hypertension limits exercise capacity in relationship to increased pulmonary artery pressures in high‐altitude newcomers. This is compensated for by increased lung diffusing capacity, decreased ventilator response and polycythaemia in high‐altitude inhabitants. There is recently reported echocardiographic evidence of altered right ventricular function at high altitudes at rest. These data need to be confirmed with measurements during exercise.

Hypoxia causes pulmonary vasoconstriction. Regional hypoxic vasoconstriction improves the matching of perfusion to alveolar ventilation. Global hypoxic vasoconstriction increases right ventricular afterload. The hypoxic pulmonary pressor response is universal in mammals and in birds, but with considerable interspecies and interindividual variability. Chronic hypoxia induces pulmonary hypertension in proportion to initial vasoconstriction. Prolonged hypoxic exposure is also associated with an increase in red blood cell mass, which aggravates pulmonary hypertension by an increase in blood viscosity. Hypoxic pulmonary hypertension in humans is usually mild to moderate, but pulmonary vascular pressure–flow relationships are steep, which corresponds to a substantial afterload on the right ventricle during exercise. A partial recovery of 10–25% of the hypoxia‐induced decrease in maximal oxygen uptake has been reported with intake‐specific pulmonary vasodilating interventions. Hypoxia has been reported to decrease myocardial fibre contractility in vitro. However, the acutely hypoxic right ventricle remains able to preserve the coupling of its contractility to increased afterload in intact animals. Echocardiographic studies of the right ventricle in healthy hypoxic human subjects show altered diastolic function, but systolic function that is preserved or even increased acutely and slightly depressed chronically. These findings are more pronounced in patients with chronic mountain sickness. Their clinical significance remains incompletely understood. Almost no imaging studies of right ventricular function have been reported in a minority of subjects who develop severe pulmonary hypertension and clinical right ventricular failure in hypoxia. No imaging studies of right ventricular function during hypoxic exercise in normal subjects are yet available. Thus, while it is plausible that the right ventricle limits exercise capacity in hypoxia, this still needs to be firmly established.
The influence of gender on the development of pulmonary arterial hypertension
Authors: Dempsie Yvonne , MacLean Margaret R.
Published: April 2013

New Findings

What is the topic of this review?

Pulmonary arterial hypertension (PAH) in its idiopathic and familial forms occurs more frequently in females than in males (>2:1 incidence ratio). Experimentally, however, female gender and oestrogens can both protect against and exacerbate PAH. This review will discuss our current understanding of the influence of sex hormones on the development of PAH.

What advances does it highlight?

Findings from recently described female gender‐specific murine models of PAH will be highlighted. Specifically, the role of oestrogen metabolism and the oestrogen‐metabolizing enzyme CYP1B1 in the development of PAH are discussed. Recent evidence suggesting that sex hormones have direct effects on the right ventricle is also discussed.

Pulmonary arterial hypertension (PAH) is a progressive disease in which increased pulmonary arterial pressure and remodelling eventually lead to right heart failure and death. Idiopathic and familial PAH occur far more frequently in women than in men. Historically, investigations into this gender bias have been impeded because female gender and oestrogens paradoxically protect against PAH in commonly used rodent models. However, recent descriptions of female gender‐specific murine models of PAH have led to an increased understanding of the role of oestrogens in disease development. Specifically, oestrogen metabolism has been highlighted as playing an important role in disease development, and the oestrogen‐metabolizing enzyme CYP1B1 may represent a novel therapeutic target. In addition, emerging evidence suggests that sex hormones may have direct effects on the right ventricle independent of haemodynamic effects. This review discusses our current understanding of the role of sex hormones in the development of PAH.
Cardiorespiratory coupling of sympathetic outflow in humans: a comparison of respiratory and cardiac modulation of sympathetic nerve activity to skin and muscle
Authors: Fatouleh Rania , Macefield Vaughan G.
Published: April 2013

New Findings

What is the central question of this study?

Muscle sympathetic nerve activity (MSNA) is well known to be modulated by the arterial baroreceptors and respiration, but what are the magnitudes of cardiac and respiratory modulation of skin sympathetic nerve activity (SSNA), which primarily subserves thermoregulation?

What is the main finding and what is its importance?

Using direct microelectrode recordings of MSNA and SSNA in awake humans, we show that the magnitude of respiratory modulation of SSNA is identical to that of MSNA, the primary difference between the two sources of sympathetic outflow being the greater cardiac modulation of MSNA. This emphasises the role of the baroreceptors in entraining sympathetic outflow to muscle.

It is well known that microelectrode recordings of skin sympathetic nerve activity (SSNA) in awake human subjects reveal spontaneous bursts of activity with no overt modulation by changes in blood pressure or respiration, in contrast to the clear cardiac and respiratory modulation of muscle sympathetic nerve activity (MSNA). However, cross‐correlation analysis has revealed that, like individual muscle vasoconstrictor neurones, the firing of individual cutaneous vasoconstrictor neurones is temporally coupled to both the cardiac and respiratory rhythms during cold‐induced cutaneous vasoconstriction, and the same is true of single sudomotor neurones during heat‐induced sweating. Here, we used cross‐correlation analysis to determine whether SSNA exhibits cardiac and respiratory modulation in thermoneutral conditions and to compare respiratory and cardiac modulation of SSNA with that of MSNA. Oligounitary recordings of spontaneous SSNA (n= 20) and MSNA (n= 18) were obtained during quiet, unrestrained breathing. Respiration was recorded by a strain‐gauge transducer around the chest and ECG recorded by surface electrodes. Respiratory and cardiac modulation of SSNA and MSNA were quantified by fitting polynomial equations to the cross‐correlation histograms constructed between the sympathetic spikes and respiration or ECG. The amplitude of the respiratory modulation (52.5 ± 3.4%) of SSNA was not significantly different from the amplitude of the cardiac modulation (46.6 ± 3.2%). Both were comparable to the respiratory modulation of MSNA (47.7 ± 4.2%), while cardiac modulation of MSNA was significantly higher (89.8 ± 1.5%). We conclude that SSNA and MSNA share similar levels of respiratory modulation, the primary difference between the two sources of sympathetic outflow being the marked cardiac modulation of MSNA provided by the baroreceptors.
Mitochondrial dysfunction and therapeutic approaches in respiratory and limb muscles of cancer cachectic mice
Authors: Fermoselle Clara , García‐Arumí Elena , Puig‐Vilanova Ester , Andreu Antoni L. , Urtreger Alejandro J. , de Kier Joffé Elisa D. Bal , Tejedor Alberto , Puente‐Maestu Luís , Barreiro Esther
Published: April 2013

New Findings

What is the central question of this study?

We explored whether experimental cancer‐induced cachexia may alter mitochondrial respiratory chain (MRC) complexes and oxygen uptake in respiratory and peripheral muscles, and whether signalling pathways, proteasome and oxidative stress influence that process.

What is the main finding and what is its importance?

In cancer cachectic mice, MRC complexes and oxygen consumption were decreased in the diaphragm and gastrocnemius. Blockade of nuclear factor‐κB and mitogen‐activated protein kinase actions partly restored the muscle mass and force and corrected the MRC dysfunction, while concomitantly reducing tumour burden. Antioxidants improved mitochondrial oxygen consumption without eliciting effects on the loss of muscle mass and force or the tumour size, whereas bortezomib reduced tumour burden without influencing muscle mass and strength or MRC function.

Abnormalities in mitochondrial content, morphology and function have been reported in several muscle‐wasting conditions. We specifically explored whether experimental cancer‐induced cachexia may alter mitochondrial respiratory chain (MRC) complexes and oxygen uptake in respiratory and peripheral muscles, and whether signalling pathways, proteasomes and oxidative stress may influence that process. We evaluated complex I, II and IV enzyme activities (specific activity assays) and MRC oxygen consumption (polarographic measurements) in diaphragm and gastrocnemius of cachectic mice bearing the LP07 lung tumour, with and without treatment with N‐acetylcysteine, bortezomib and nuclear factor‐κB (sulfasalazine) and mitogen‐activated protein kinases (MAPK, U0126) inhibitors (n= 10 per group for all groups). Whole‐body and muscle weights and limb muscle force were also assessed in all rodents at baseline and after 1 month. Compared with control animals, cancer cachectic mice showed a significant reduction in body weight gain, smaller sizes of the diaphragm and gastrocnemius, lower muscle strength, decreased activity of complexes I, II and IV and decreased oxygen consumption in both muscles. Blockade of nuclear factor‐κB and MAPK actions restored muscle mass and force and corrected the MRC dysfunction in both muscles, while partly reducing tumour burden. Antioxidants improved mitochondrial oxygen uptake without eliciting significant effects on the loss of muscle mass and force or tumour size, whereas the proteasome inhibitor reduced tumour burden without significantly influencing muscle mass and strength or mitochondrial function. In conclusion, nuclear factor‐κB and MAPK signalling pathways modulate muscle mass and performance and MRC function of respiratory and limb muscles in this model of experimental cancer cachexia, thus offering targets for therapeutic intervention.
Evidence of Microbial Regulation of Biogeochemical Cycles from a Study on Methane Flux and Land Use Change
Authors: Nazaries Loïc , Pan Yao , Bodrossy Levente , Baggs Elizabeth M. , Millard Peter , Murrell J. Colin , Singh Brajesh K.
Published: April 2013

Microbes play an essential role in ecosystem functions, including carrying out biogeochemical cycles, but are currently considered a black box in predictive models and all global biodiversity debates. This is due to (i) perceived temporal and spatial variations in microbial communities and (ii) lack of ecological theory explaining how microbes regulate ecosystem functions. Providing evidence of the microbial regulation of biogeochemical cycles is key for predicting ecosystem functions, including greenhouse gas fluxes, under current and future climate scenarios. Using functional measures, stable-isotope probing, and molecular methods, we show that microbial (community diversity and function) response to land use change is stable over time. We investigated the change in net methane flux and associated microbial communities due to afforestation of bog, grassland, and moorland. Afforestation resulted in the stable and consistent enhancement in sink of atmospheric methane at all sites. This change in function was linked to a niche-specific separation of microbial communities (methanotrophs). The results suggest that ecological theories developed for macroecology may explain the microbial regulation of the methane cycle. Our findings provide support for the explicit consideration of microbial data in ecosystem/climate models to improve predictions of biogeochemical cycles.
U(VI) Reduction in Sulfate-Reducing Subsurface Sediments Amended with Ethanol or Acetate
Authors: Converse Brandon J. , Wu Tao , Findlay Robert H. , Roden Eric E.
Published: April 2013

An experiment was conducted with subsurface sediments from Oak Ridge National Laboratory to determine the potential for reduction of U(VI) under sulfate-reducing conditions with either ethanol or acetate as the electron donor. The results showed extensive U(VI) reduction in sediments supplied with either electron donor, where geochemical and microbiological analyses demonstrated active sulfate reduction.
Improving the Thermostability and Catalytic Efficiency of Bacillus deramificans Pullulanase by Site-Directed Mutagenesis
Authors: Duan Xuguo , Chen Jian , Wu Jing
Published: April 2013

Pullulanase (EC 3.2.1.41) is a well-known starch-debranching enzyme. Its instability and low catalytic efficiency are the major factors preventing its widespread application. To address these issues, Asp437 and Asp503 of the pullulanase from
Bacillus deramificans
were selected in this study as targets for site-directed mutagenesis based on a structure-guided consensus approach. Four mutants (carrying the mutations D503F, D437H, D503Y, and D437H/D503Y) were generated and characterized in detail. The results showed that the D503F, D437H, and D503Y mutants had an optimum temperature of 55°C and a pH optimum of 4.5, similar to that of the wild-type enzyme. However, the half-lives of the mutants at 60°C were twice as long as that of the wild-type enzyme. In addition, the D437H/D503Y double mutant displayed a larger shift in thermostability, with an optimal temperature of 60°C and a half-life at 60°C of more than 4.3-fold that of the wild-type enzyme. Kinetic studies showed that the

K
m

values for the D503F, D437H, D503Y, and D437H/D503Y mutants decreased by 7.1%, 11.4%, 41.4%, and 45.7% and the
K
cat
/

K
m

values increased by 10%, 20%, 140%, and 100%, respectively, compared to those of the wild-type enzyme. Mechanisms that could account for these enhancements were explored. Moreover, in conjunction with the enzyme glucoamylase, the D503Y and D437H/D503Y mutants exhibited an improved reaction rate and glucose yield during starch hydrolysis compared to those of the wild-type enzyme, confirming the enhanced properties of the mutants. The mutants generated in this study have potential applications in the starch industry.
Effect of Pressure-Induced Changes in the Ionization Equilibria of Buffers on Inactivation of Escherichia coli and Staphylococcus aureus by High Hydrostatic Pressure
Authors: Gayán Elisa , Condón Santiago , Álvarez Ignacio , Nabakabaya Maria , Mackey Bernard
Published: April 2013

Survival rates of
Escherichia coli
and
Staphylococcus aureus
after high-pressure treatment in buffers that had large or small reaction volumes (Δ
V
°), and which therefore underwent large or small changes in pH under pressure, were compared. At a low buffer concentration of 0.005 M, survival was, as expected, better in MOPS (morpholinepropanesulfonic acid), HEPES, and Tris, whose Δ
V
° values are approximately 5.0 to 7.0 cm
3
mol
−1
, than in phosphate or dimethyl glutarate (DMG), whose Δ
V
° values are about −25 cm
3
mol
−1
. However, at a concentration of 0.1 M, survival was unexpectedly better in phosphate and DMG than in MOPS, HEPES, or Tris. This was because the baroprotective effect of phosphate and DMG increased much more rapidly with increasing concentration than it did with MOPS, HEPES, or Tris. Further comparisons of survival in solutions of salts expected to cause large electrostriction effects (Na
2
SO
4
and CaCl
2
) and those causing lower electrostriction (NaCl and KCl) were made. The salts with divalent ions were protective at much lower concentrations than salts with monovalent ions. Buffers and salts both protected against transient membrane disruption in
E. coli
, but the molar concentrations necessary for membrane protection were much lower for phosphate and Na
2
SO
4
than for HEPES and NaCl. Possible protective mechanisms discussed include effects of electrolytes on water compressibility and kosmotropic and specific ion effects. The results of this systematic study will be of considerable practical significance in studies of pressure inactivation of microbes under defined conditions but also raise important fundamental questions regarding the mechanisms of baroprotection by ionic solutes.
Inactivation of Ca
2+
/H
+
Exchanger in Synechocystis sp. Strain PCC 6803 Promotes Cyanobacterial Calcification by Upregulating CO
2
-Concentrating Mechanisms
Authors: Jiang Hai-Bo , Cheng Hui-Min , Gao Kun-Shan , Qiu Bao-Sheng
Published: April 2013

Cyanobacteria are important players in the global carbon cycle, accounting for approximately 25% of global CO
2
fixation. Their CO
2
-concentrating mechanisms (CCMs) are thought to play a key role in cyanobacterial calcification, but the mechanisms are not completely understood. In
Synechocystis
sp. strain PCC 6803, a single Ca
2+
/H
+
exchanger (Slr1336) controls the Ca
2+
/H
+
exchange reaction. We knocked out the exchanger and investigated the effects on cyanobacterial calcification and CCMs. Inactivation of
slr1336
significantly increased the calcification rate and decreased the zeta potential, indicating a relatively stronger Ca
2+
-binding ability. Some genes encoding CCM-related components showed increased expression levels, including the
cmpA
gene, which encodes the Ca
2+
-dependent HCO
3
−
transporter BCT1. The transcript level of
cmpA
in the mutant was 30 times that in wild type. A Western blot analysis further confirmed that protein levels of CmpA were higher in the mutant than the wild type. Measurements of inorganic carbon fluxes and O
2
evolution proved that both the net HCO
3
−
uptake rate and the BCT1 transporter supported photosynthetic rate in the
slr1336
mutant were significantly higher than in the wild type. This would cause the mutant cells to liberate more OH
−
ions out of the cell and stimulate CaCO
3
precipitation in the microenvironment. We conclude that the mutation of the Ca
2+
/H
+
exchanger in
Synechocystis
promoted the cyanobacterial calcification process by upregulating CCMs, especially the BCT1 HCO
3
−
transporter. These results shed new light on the mechanism by which CCM-facilitated photosynthesis promotes cyanobacterial calcification.
Field Evaluation of Arbuscular Mycorrhizal Fungal Colonization in Bacillus thuringiensis Toxin-Expressing (Bt) and Non-Bt Maize
Authors: Cheeke Tanya E. , Cruzan Mitchell B. , Rosenstiel Todd N.
Published: April 2013

The cultivation of genetically engineered
Bacillus thuringiensis
toxin-expressing (Bt) maize continues to increase worldwide, yet the effects of Bt crops on arbuscular mycorrhizal fungi (AMF) in soil are poorly understood. In this field experiment, we investigated the impact of seven different genotypes of Bt maize and five corresponding non-Bt parental cultivars on AMF and evaluated plant growth responses at three different physiological time points. Plants were harvested 60 days (active growth), 90 days (tasseling and starting to produce ears), and 130 days (maturity) after sowing, and data on plant growth responses and percent AMF colonization of roots at each harvest were collected. Spore abundance and diversity were also evaluated at the beginning and end of the field season to determine whether the cultivation of Bt maize had a negative effect on AMF propagules in the soil. Plant growth and AMF colonization did not differ between Bt and non-Bt maize at any harvest period, but AMF colonization was positively correlated with leaf chlorophyll content at the 130-day harvest. Cultivation of Bt maize had no effect on spore abundance and diversity in Bt versus non-Bt plots over one field season. Plot had the most significant effect on total spore counts, indicating spatial heterogeneity in the field. Although previous greenhouse studies demonstrated that AMF colonization was lower in some Bt maize lines, our field study did not yield the same results, suggesting that the cultivation of Bt maize may not have an impact on AMF in the soil ecosystem under field conditions.
Linked Expressions of
nap
and
nos
Genes in a Bradyrhizobium japonicum Mutant with Increased N
2
O Reductase Activity
Authors: Sánchez Cristina , Itakura Manabu , Mitsui Hisayuki , Minamisawa Kiwamu
Published: April 2013

To understand the mechanisms underlying the increased N
2
O reductase activity in the
Bradyrhizobium japonicum
5M09 mutant from enrichment culture under N
2
O respiration, we analyzed the expression of genes encoding denitrification reductases and regulators. Our results suggest a common regulation of
nap
(encoding periplasmic nitrate reductase) and
nos
(encoding N
2
O reductase).
Nitrate-Dependent Ferrous Iron Oxidation by Anaerobic Ammonium Oxidation (Anammox) Bacteria
Authors: Oshiki M. , Ishii S. , Yoshida K. , Fujii N. , Ishiguro M. , Satoh H. , Okabe S.
Published: April 2013

We examined nitrate-dependent Fe
2+
oxidation mediated by anaerobic ammonium oxidation (anammox) bacteria. Enrichment cultures of “
Candidatus
Brocadia sinica” anaerobically oxidized Fe
2+
and reduced NO
3
−
to nitrogen gas at rates of 3.7 ± 0.2 and 1.3 ± 0.1 (mean ± standard deviation [SD]) nmol mg protein
−1
min
−1
, respectively (37°C and pH 7.3). This nitrate reduction rate is an order of magnitude lower than the anammox activity of “
Ca
. Brocadia sinica” (10 to 75 nmol NH
4
+
mg protein
−1
min
−1
). A
15
N tracer experiment demonstrated that coupling of nitrate-dependent Fe
2+
oxidation and the anammox reaction was responsible for producing nitrogen gas from NO
3
−
by “
Ca
. Brocadia sinica.” The activities of nitrate-dependent Fe
2+
oxidation were dependent on temperature and pH, and the highest activities were seen at temperatures of 30 to 45°C and pHs ranging from 5.9 to 9.8. The mean half-saturation constant for NO
3
−
± SD of “
Ca
. Brocadia sinica” was determined to be 51 ± 21 μM. Nitrate-dependent Fe
2+
oxidation was further demonstrated by another anammox bacterium, “
Candidatus
Scalindua sp.,” whose rates of Fe
2+
oxidation and NO
3
−
reduction were 4.7 ± 0.59 and 1.45 ± 0.05 nmol mg protein
−1
min
−1
, respectively (20°C and pH 7.3). Co-occurrence of nitrate-dependent Fe
2+
oxidation and the anammox reaction decreased the molar ratios of consumed NO
2
−
to consumed NH
4
+
(ΔNO
2
−
/ΔNH
4
+
) and produced NO
3
−
to consumed NH
4
+
(ΔNO
3
−
/ΔNH
4
+
). These reactions are preferable to the application of anammox processes for wastewater treatment.
Predicting Salmonella Populations from Biological, Chemical, and Physical Indicators in Florida Surface Waters
Authors: McEgan Rachel , Mootian Gabriel , Goodridge Lawrence D. , Schaffner Donald W. , Danyluk Michelle D.
Published: April 2013

Coliforms,
Escherichia coli
, and various physicochemical water characteristics have been suggested as indicators of microbial water quality or index organisms for pathogen populations. The relationship between the presence and/or concentration of
Salmonella
and biological, physical, or chemical indicators in Central Florida surface water samples over 12 consecutive months was explored. Samples were taken monthly for 12 months from 18 locations throughout Central Florida (
n
= 202). Air and water temperature, pH, oxidation-reduction potential (ORP), turbidity, and conductivity were measured. Weather data were obtained from nearby weather stations. Aerobic plate counts and most probable numbers (MPN) for
Salmonella
,
E. coli
, and coliforms were performed. Weak linear relationships existed between biological indicators (
E. coli
/coliforms) and
Salmonella
levels (
R
2
< 0.1) and between physicochemical indicators and
Salmonella
levels (
R
2
< 0.1). The average rainfall (previous day, week, and month) before sampling did not correlate well with bacterial levels. Logistic regression analysis showed that
E. coli
concentration can predict the probability of enumerating selected
Salmonella
levels. The lack of good correlations between biological indicators and
Salmonella
levels and between physicochemical indicators and
Salmonella
levels shows that the relationship between pathogens and indicators is complex. However,
Escherichia coli
provides a reasonable way to predict
Salmonella
levels in Central Florida surface water through logistic regression.
Distribution of cp32 Prophages among Lyme Disease-Causing Spirochetes and Natural Diversity of Their Lipoprotein-Encoding
erp
Loci
Authors: Brisson Dustin , Zhou Wei , Jutras Brandon L. , Casjens Sherwood , Stevenson Brian
Published: April 2013

Lyme disease spirochetes possess complex genomes, consisting of a main chromosome and 20 or more smaller replicons. Among those small DNAs are the cp32 elements, a family of prophages that replicate as circular episomes. All complete cp32s contain an
erp
locus, which encodes surface-exposed proteins. Sequences were compared for all 193
erp
alleles carried by 22 different strains of Lyme disease-causing spirochete to investigate their natural diversity and evolutionary histories. These included multiple isolates from a focus where Lyme disease is endemic in the northeastern United States and isolates from across North America and Europe. Bacteria were derived from diseased humans and from vector ticks and included members of 5 different
Borrelia
genospecies. All
erp
operon 5′-noncoding regions were found to be highly conserved, as were the initial 70 to 80 bp of all
erp
open reading frames, traits indicative of a common evolutionary origin. However, the majority of the protein-coding regions are highly diverse, due to numerous intra- and intergenic recombination events. Most
erp
alleles are chimeras derived from sequences of closely related and distantly related
erp
sequences and from unknown origins. Since known functions of Erp surface proteins involve interactions with various host tissue components, this diversity may reflect both their multiple functions and the abilities of Lyme disease-causing spirochetes to successfully infect a wide variety of vertebrate host species.
Enumeration of Salmonella and Campylobacter spp. in Environmental Farm Samples and Processing Plant Carcass Rinses from Commercial Broiler Chicken Flocks
Authors: Berghaus Roy D. , Thayer Stephan G. , Law Bibiana F. , Mild Rita M. , Hofacre Charles L. , Singer Randall S.
Published: April 2013

A prospective cohort study was performed to evaluate the prevalences and loads of
Salmonella
and
Campylobacter
spp. in farm and processing plant samples collected from 55 commercial broiler chicken flocks. Environmental samples were collected from broiler houses within 48 h before slaughter, and carcass rinses were performed on birds from the same flocks at 4 different stages of processing.
Salmonella
was detected in farm samples of 50 (90.9%) flocks and in processing samples of 52 (94.5%) flocks.
Campylobacter
was detected in farm samples of 35 (63.6%) flocks and in processing samples of 48 (87.3%) flocks. There was a significant positive relationship between environmental farm samples and processing plant carcass rinses with respect to both
Salmonella
and
Campylobacter
prevalences and loads.
Campylobacter
loads were significantly higher than
Salmonella
loads, and the correlations between samples collected from the same flocks were higher for
Campylobacter
than they were for
Salmonella
. Boot socks were the most sensitive sample type for detection of
Salmonella
on the farm, whereas litter samples had the strongest association with
Salmonella
loads in pre- and postchill carcass rinses. Boot socks, drag swabs, and fecal samples all had similar sensitivities for detecting
Campylobacter
on the farm, and all were more strongly associated with
Campylobacter
loads in carcass rinses than were litter samples. Farm samples explained a greater proportion of the variability in carcass rinse prevalences and loads for
Campylobacter
than they did for
Salmonella. Salmonella
and
Campylobacter
prevalences and loads both decreased significantly as birds progressed through the processing plant.
Salmonella enterica Diversity in Central Californian Coastal Waterways
Authors: Walters Sarah P. , Gonzï¿½lez-Escalona Narjol , Son Insook , Melka David C. , Sassoubre Lauren M. , Boehm Alexandria B.
Published: April 2013

Salmonella enterica
is one of the most important bacterial enteric pathogens worldwide. However, little is known about its distribution and diversity in the environment. The present study explored the diversity of 104 strains of
Salmonella enterica
isolated over 2 years from 12 coastal waterways in central California. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing were used to probe species diversity. Seventy-four PFGE patterns and 38 sequence types (STs) were found, including 18 newly described STs. Nineteen of 25 PFGE patterns were indistinguishable from those of clinical isolates in PulseNet. The most common ST was consistent with
S. enterica
serovar Typhimurium, and other frequently detected STs were associated with the serovars Heidelberg and Enteritidis; all of these serovars are important etiologies of salmonellosis. An investigation into
S. enterica
biogeography was conducted at the level of ST and subspecies. At the ST and subspecies level, we found a taxon-time relationship but no taxon-area or taxon-environmental distance relationships. STs collected during wet versus dry conditions tended to be more similar; however, STs collected from waterways adjacent to watersheds with similar land covers did not tend to be similar. The results suggest that the lack of dispersal limitation may be an important factor affecting the diversity of
S. enterica
in the region.
Novel PCR-Based Methods Enhance Characterization of Vaginal Microbiota in a Bacterial Vaginosis Patient before and after Treatment
Authors: Lambert Janet A. , Kalra Apoorv , Dodge Cristina T. , John Susan , Sobel Jack D. , Akins Robert A.
Published: April 2013

Deep characterization, even by next-generation sequencing, of the vaginal microbiota in healthy women or posttreatment bacterial vaginosis patients is limited by the dominance of lactobacilli. To improve detection, we offer two approaches: quantitative PCR (qPCR) using phylogenetic branch-inclusive primers and sequencing of broad-spectrum amplicons generated with oligomers that block amplification of lactobacilli.
Inactivation of the Pta-AckA Pathway Causes Cell Death in Staphylococcus aureus
Authors: Sadykov Marat R. , Thomas Vinai C. , Marshall Darrell D. , Wenstrom Christopher J. , Moormeier Derek E. , Widhelm Todd J. , Nuxoll Austin S. , Powers Robert , Bayles Kenneth W.
Published: April 2013

During growth under conditions of glucose and oxygen excess,
Staphylococcus aureus
predominantly accumulates acetate in the culture medium, suggesting that the phosphotransacetylase-acetate kinase (Pta-AckA) pathway plays a crucial role in bacterial fitness. Previous studies demonstrated that these conditions also induce the
S. aureus
CidR regulon involved in the control of cell death. Interestingly, the CidR regulon is comprised of only two operons, both encoding pyruvate catabolic enzymes, suggesting an intimate relationship between pyruvate metabolism and cell death. To examine this relationship, we introduced
ackA
and
pta
mutations in
S. aureus
and tested their effects on bacterial growth, carbon and energy metabolism,
cid
expression, and cell death. Inactivation of the Pta-AckA pathway showed a drastic inhibitory effect on growth and caused accumulation of dead cells in both
pta
and
ackA
mutants. Surprisingly, inactivation of the Pta-AckA pathway did not lead to a decrease in the energy status of bacteria, as the intracellular concentrations of ATP, NAD
+
, and NADH were higher in the mutants. However, inactivation of this pathway increased the rate of glucose consumption, led to a metabolic block at the pyruvate node, and enhanced carbon flux through both glycolysis and the tricarboxylic acid (TCA) cycle. Intriguingly, disruption of the Pta-AckA pathway also induced the CidR regulon, suggesting that activation of alternative pyruvate catabolic pathways could be an important survival strategy for the mutants. Collectively, the results of this study demonstrate the indispensable role of the Pta-AckA pathway in
S. aureus
for maintaining energy and metabolic homeostasis during overflow metabolism.
Mutations in the Escherichia coli Ribosomal Protein L22 Selectively Suppress the Expression of a Secreted Bacterial Virulence Factor
Authors: Mee-Ngan Yap F. , Bernstein Harris D.
Published: April 2013

Mutations in the ribosomal protein L22 that impair peptide-mediated translation arrest inEscherichia colihave been shown to reduce the expression of several genes, includingsecA, which encodes an ATPase that drives protein export via the Sec pathway. Here, we used a comparative proteomic approach to obtain insight into the global effects of the L22(Δ82-84) mutation on gene expression and protein synthesis. While the mutation did not affect or modestly affected the level of most soluble proteins, it dramatically reduced the level of antigen 43 (Ag43), a secreted virulence factor that promotes autoaggregation. The reduced protein concentration correlated with a sharp decrease in the abundance and stability of Ag43 mRNA. We found that the overexpression ofsecAor the inactivation of genes that encode presecretory and membrane proteins restored Ag43 production in the L22 mutant strain. Furthermore, impairment of the Sec pathway in a wild-type strain reduced Ag43 production but did not significantly affect the synthesis of other presecretory proteins. Taken together, these results indicate that Ag43 gene expression is exquisitely sensitive to the status of the Sec machinery and strongly suggest that the L22 mutation decreases the Ag43 concentration indirectly by reducingsecAexpression. Our results imply the existence of a novel regulatory mechanism in which the efficiency of protein export is coupled to gene expression and help to explain the modulation of SecA synthesis that has been observed in response to secretion stress.
Identification of New Proteins That Modulate the Germination of Spores of Bacillus Species
Authors: Ramirez-Peralta Arturo , Gupta Srishti , Butzin Xuan Yi , Setlow Barbara , Korza George , Leyva-Vazquez Marco-Antonio , Christie Graham , Setlow Peter
Published: April 2013

A number of operons encoding the nutrient germinant receptors (GRs) in dormant spores of
Bacillus megaterium
and
Bacillus subtilis
species have small open reading frames (ORFs) of unknown function within or immediately adjacent to the operons. Inactivation of the genes in these ORFs, encoding proteins now termed D proteins, either significantly increased or decreased spore germination via the associated GR but had no effects on germination via non-GR-dependent germinants. These effects on GR-dependent germination were complemented by ectopic expression of the appropriate
D
gene (gene encoding D protein). However, substitution of noncognate
D
genes in two GR operons resulted in inhibition of germination via the GR manipulated, although ectopic overexpression of a
D
gene had no effect on overall GR-dependent germination. The various
D
genes studied were expressed in the forespore during sporulation in parallel with the associated GR operon, and transcription of a
B. subtilis
D
gene was controlled by RNA polymerase sigma factor σ
G
. These results indicate that proteins encoded by small ORFs within or adjacent to operons encoding GRs play major roles in modulating GR function in spores of
Bacillus
species. In
B. subtilis
, deletion of a
D
gene (
B. subtilis
gerKD
[
gerKDbs
]) adjacent to the
gerK
operon encoding the GerK GR or ectopic expression or overexpression of
gerKDbs
had no major effect on the levels of GR subunits or of two other germination proteins.