bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microbial Iron Redox Cycling in a Circumneutral-pH Groundwater Seep
Authors: Blöthe Marco , Roden Eric E. 
Published: December 2008

ABSTRACT

The potential for microbially mediated redox cycling of iron (Fe) in a circumneutral-pH groundwater seep in north central Alabama was studied. Incubation of freshly collected seep material under anoxic conditions with acetate-lactate or H
2
as an electron donor revealed the potential for rapid Fe(III) oxide reduction (ca. 700 to 2,000 μmol liter
−1
day
−1
). Fe(III) reduction at lower but significant rates took place in unamended controls (ca. 300 μmol liter
−1
day
−1
). Culture-based enumerations (most probable numbers [MPNs]) revealed significant numbers (10
2
to 10
6
cells ml
−1
) of organic carbon- and H
2
-oxidizing dissimilatory Fe(III)-reducing microorganisms. Three isolates with the ability to reduce Fe(III) oxides by dissimilatory or fermentative metabolism were obtained (
Geobacter
sp. strain IST-3,
Shewanella
sp. strain IST-21, and
Bacillus
sp. strain IST-38). MPN analysis also revealed the presence of microaerophilic Fe(II)-oxidizing microorganisms (10
3
to 10
5
cells ml
−1
). A 16S rRNA gene library from the iron seep was dominated by representatives of the
Betaproteobacteria
including
Gallionella, Leptothrix
, and
Comamonas
species. Aerobic Fe(II)-oxidizing
Comamonas
sp. strain IST-3 was isolated. The 16S rRNA gene sequence of this organism is 100% similar to the type strain of the betaproteobacterium
Comamonas testosteroni
(M11224). Testing of the type strain showed no Fe(II) oxidation. Collectively our results suggest that active microbial Fe redox cycling occurred within this habitat and support previous conceptual models for how microbial Fe oxidation and reduction can be coupled in surface and subsurface sedimentary environments.
Large-Scale Production of Poly(3-Hydroxyoctanoic Acid) by
Pseudomonas putida
GPo1 and a Simplified Downstream Process
Authors: Elbahloul Yasser , Steinbüchel Alexander 
Published: December 2008

ABSTRACT

The suitability of
Pseudomonas putida
GPo1 for large-scale cultivation and production of poly(3-hydroxyoctanoate) (PHO) was investigated in this study. Three fed-batch cultivations of
P. putida
GPo1 at the 350- or 400-liter scale in a bioreactor with a capacity of 650 liters were done in mineral salts medium containing initially 20 mM sodium octanoate as the carbon source. The feeding solution included ammonium octanoate, which was fed at a relatively low concentration to promote PHO accumulation under nitrogen-limited conditions. During cultivation, the pH was regulated by addition of NaOH, NH
4
OH, or octanoic acid, which was used as an additional carbon source. Partial O
2
pressure (pO
2
) was adjusted to 20 to 40% by controlling the airflow and stirrer speed. Under the optimized conditions,
P. putida
GPo1 was able to grow to cell densities as high as 18, 37, and 53 g cells (dry mass) (CDM) per liter containing 49, 55, and 60% (wt/wt) of PHO, respectively. The resulting 40 kg CDM from these three cultivations was used directly for extraction of PHO. Three different methods of extraction of PHO were applied. From these, only acetone extraction showed better performance and resulted in 94% recovery of the PHO contents of cells. A novel mixture of precipitation solvents composed of 70% (vol/vol) methanol and 70% (vol/vol) ethanol was identified in this study. The ratio of PHO concentrate to the mixture was 0.2:1 (vol/vol) and allowed complete precipitation of PHO as white flakes. However, at a ratio of 1:1 (vol/vol) of the solvent mixture to PHO concentrate, a highly purified PHO was obtained. Precipitation yielded a dough-like polymeric material which was cast into thin layers and then shredded into small strips to allow evaporation of the remaining solvents. Gas chromatographic analysis revealed a purity of about 99% ± 0.2% (wt/wt) of the polymer, which consisted mainly of 3-hydroxyoctanoic acid (96 mol%).
Ecological Specialization in a Spatially Structured Population of the Thermophilic Cyanobacterium
Mastigocladus laminosus
Authors: Miller Scott R. , Williams Carin , Strong Aaron L. , Carvey Darla 
Published: December 2008

ABSTRACT

Laboratory evolution experiments suggest the potential for microbial populations to contribute significant ecological variation to ecosystems, yet the functional importance of genetic diversity within natural populations of microorganisms is largely unknown. Here, we investigated the distribution of genetic and phenotypic variation for a population of the cyanobacterium
Mastigocladus laminosus
distributed along the temperature gradient of White Creek, Yellowstone NP. A total of 153 laboratory strains were directly isolated from five sites with mean annual temperatures ranging between 39 and 54°C. Genetic characterization at four nitrogen metabolism genes identified 15 closely related lineages in the population sample. These lineages were distributed nonrandomly along White Creek, but the observed geographic structure could not be explained by limited dispersal capabilities. Temperature performance experiments with six
M. laminosus
lineages that maximized their respective relative abundances at different positions along the gradient provided evidence for niche differentiation within the population. Niche differentiation included a tradeoff in performance at high and low temperatures, respectively. The physiological variation of these lineages in laboratory culture was generally well matched to the prevailing temperature conditions experienced by these organisms in situ. These results suggest that sympatric diversification along an ecological selection gradient can be a potent source of evolutionary innovation in microbial populations.
Quantifying Transmission of
Campylobacter jejuni
in Commercial Broiler Flocks
Authors: van Gerwe Twan , Miflin Jeanette K. , Templeton Jillian M. , Bouma Annemarie , Wagenaar Jaap A. , Jacobs-Reitsma Wilma F. , Stegeman Arjan , Klinkenberg Don 
Published: December 2008

ABSTRACT

Since meat from poultry colonized with
Campylobacter
spp. is a major cause of bacterial gastroenteritis, human exposure should be reduced by, among other things, prevention of colonization of broiler flocks. To obtain more insight into possible sources of introduction of
Campylobacter
into broiler flocks, it is essential to estimate the moment that the first bird in a flock is colonized. If the rate of transmission within a flock were known, such an estimate could be determined from the change in the prevalence of colonized birds in a flock over time. The aim of this study was to determine the rate of transmission of
Campylobacter
using field data gathered for 5 years for Australian broiler flocks. We used unique sampling data for 42
Campylobacter jejuni
-colonized flocks and estimated the transmission rate, which is defined as the number of secondary infections caused by one colonized bird per day. The estimate was 2.37 ± 0.295 infections per infectious bird per day, which implies that in our study population colonized flocks consisting of 20,000 broilers would have an increase in within-flock prevalence to 95% within 4.4 to 7.2 days after colonization of the first broiler. Using Bayesian analysis, the moment of colonization of the first bird in a flock was estimated to be from 21 days of age onward in all flocks in the study. This study provides an important quantitative estimate of the rate of transmission of
Campylobacter
in broiler flocks, which could be helpful in future studies on the epidemiology of
Campylobacter
in the field.
Molecular Epidemiology of
Campylobacter jejuni
Isolates from Wild-Bird Fecal Material in Children's Playgrounds
Authors: French Nigel P. , Midwinter Anne , Holland Barbara , Collins-Emerson Julie , Pattison Rebecca , Colles Frances , Carter Philip 
Published: December 2008

ABSTRACT

In many countries relatively high notification rates of campylobacteriosis are observed in children under 5 years of age. Few studies have considered the role that environmental exposure plays in the epidemiology of these cases. Wild birds inhabit parks and playgrounds and are recognized carriers of
Campylobacter
, and young children are at greater risk of ingesting infective material due to their frequent hand-mouth contact. We investigated wild-bird fecal contamination in playgrounds in parks in a New Zealand city. A total of 192 samples of fresh and dried fecal material were cultured to determine the presence of
Campylobacter
spp.
Campylobacter jejuni
isolates were also characterized by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST), and the profiles obtained were compared with those of human isolates.
C. jejuni
was isolated from 12.5% of the samples. MLST identified members of clonal complexes ST-45, ST-682, and ST-177; all of these complexes have been recovered from wild birds in Europe. PFGE of ST-45 isolates resulted in profiles indistinguishable from those of isolated obtained from human cases in New Zealand. Members of the ST-177 and ST-682 complexes have been found in starlings (
Sturnus vulgaris
) in the United Kingdom, and these birds were common in playgrounds investigated in New Zealand in this study. We suggest that feces from wild birds in playgrounds could contribute to the occurrence of campylobacteriosis in preschool children. Further, the
C. jejuni
isolates obtained in this study belonged to clonal complexes associated with wild-bird populations in the northern hemisphere and could have been introduced into New Zealand in imported wild garden birds in the 19th century.
Host Cell Cytokines Induced by
Chlamydia pneumoniae
Decrease the Expression of Interstitial Collagens and Fibronectin in Fibroblasts
Authors: Baumert Jürgen , Schmidt Karl-Hermann , Eitner Annett , Straube Eberhard , Rödel Jürgen 
Published: December 2008

ABSTRACT

Chlamydia pneumoniae
infection has been associated with chronic obstructive airway disease (COPD), asthma, and atherosclerosis. Inflammation and airway remodeling in asthma and COPD result in subepithelial fibrosis that is characterized by the deposition of interstitial collagens and fibronectin. The progression of atherosclerosis is also accompanied by an increased production of interstitial collagens in the intima. As shown by reverse transcription-PCR and immunoblotting, infection of human fibroblasts and smooth muscle cells by
C. pneumoniae
TW-183 downregulated the expression of type I and III collagen and fibronectin, whereas the level of type IV collagen remained unchanged. Conditioned medium from infected fibroblasts as well as epithelial WISH cells also reduced the expression of interstitial collagens and fibronectin in uninfected cells. In experiments using blocking antibodies, beta interferon was found to contribute to the inhibitory effects of conditioned medium collected from infected fibroblasts. In contrast, downregulation of matrix protein expression by conditioned medium from epithelial cells was caused by interleukin-1α, which was not secreted from fibroblasts following chlamydial infection.
C. pneumoniae
-mediated inhibition of collagen and fibronectin expression was diminished following transfection of fibroblasts with specific small interfering RNA targeting the transcription factor CCAAT/enhancer-binding protein β. The downregulation of interstitial collagens and fibronectin by the
Chlamydia
-induced host cell cytokine response may modulate tissue remodeling processes in airway diseases. In atherosclerosis the inhibition of collagen synthesis by
C. pneumoniae
infection may promote plaque vulnerability, thereby increasing the risk of plaque rupture.
Phosphoinositide 3-Kinase-Dependent Inhibition of Dendritic Cell Interleukin-12 Production byGiardia lamblia
Authors: Kamda Joel Désiré , Singer Steven M. 
Published: December 2008

ABSTRACTDendritic cell interactions with pathogenic microbes initiate and direct the development of subsequent adaptive responses. The protozoan pathogenGiardia lambliainfects the mammalian small intestine, leading to nutrient malabsorption and diarrhea but rarely causing inflammation. In order to begin to understand how the innate immune system responds to this parasite and shapes the eventual adaptive response, we examined the interaction between parasites and murine bone marrow-derived dendritic cells (DCs). DCs incubated with live parasites or parasite extracts displayed enhanced levels of CD40. The expression of CD80 and CD86 also increased, but less than was seen with lipopolysaccharide-activated DCs. Small amounts of interleukin-6 (IL-6) and tumor necrosis factor alpha were secreted by these DCs, whereas no IL-10 or IL-12 could be detected. Coincubation of DCs with parasite extracts along with known Toll-like receptor (TLR) ligands resulted in enhanced secretion of IL-10 and reduced secretion of IL-12. The levels of major histocompatibility complex class II, CD80, and CD86 were also reduced compared to DCs stimulated with TLR ligands alone. Finally, studies with an extracellular signal-regulated kinase 1/2 pathway inhibitor, a phosphoinositide 3-kinase (PI3K) inhibitor, and anti-IL-10 receptor antibody revealed that the PI3K pathway is the dominant mechanism of inhibition in DCs incubated with both lipopolysaccharide andGiardia. These data suggest that this parasite actively interferes with host innate immunity, resulting in an immune response able to control the infection but devoid of strong inflammatory signals.
Inhibition of Complement and CD14 Attenuates theEscherichia coli-Induced Inflammatory Response in Porcine Whole Blood
Authors: Thorgersen Ebbe Billmann , Pharo Anne , Haverson Karin , Axelsen Anne K. , Gaustad Peter , Kotwal Girish J. , Sfyroera Georgia , Mollnes Tom Eirik 
Published: December 2008

ABSTRACTThe innate immune response is a double-edged sword in systemic inflammation and sepsis. Uncontrolled or inappropriate activation can damage and be lethal to the host. Several studies have investigated inhibition of downstream mediators, including tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β). Emerging evidence indicates that upstream inhibition is a better therapeutic approach for attenuating damaging immune activation. Therefore, we investigated inhibition of two central innate immune pathways, those of complement and CD14/Toll-like receptor 4 (TLR4)/myeloid differentiation protein 2 (MD-2), in a porcine in vitro model ofEscherichia coli-induced inflammation. Porcine whole blood anticoagulated with lepuridin, which did not interfere with the complement system, was incubated withE. colilipopolysaccharide (LPS) or whole bacteria. Inhibitors of complement and CD14 and thus the LPS CD14/TLR4/MD-2 receptor complex were tested to investigate the effect on the inflammatory response. A broad range of inflammatory readouts were used to monitor the effect. Anti-CD14 was found to saturate the CD14 molecule on granulocytes and completely inhibited LPS-induced proinflammatory cytokines in a dose-dependent manner. Anti-CD14 significantly reduced the levels of theE. coli-induced proinflammatory cytokines TNF-α and IL-1β, but not IL-8, in a dose-dependent manner. No effect on bacterial clearance was seen. Vaccinia complement control protein and smallpox inhibitor of complement enzymes, twoOrthopoxvirus-encoded complement inhibitors, completely inhibited complement activation. Furthermore, these agents almost completely inhibited the expression of wCD11R3, which is associated with CD18 as a β2 integrin, on porcine granulocytes and decreased IL-8 levels significantly in a dose-dependent manner. As expected, complement inhibition reduced bacterial clearance. We conclude that inhibition of complement and CD14 attenuatesE. coli-induced inflammation and might be used as a therapeutic regimen in gram-negative sepsis along with appropriate treatment with antibiotics.
Protein A-Mediated Multicellular Behavior inStaphylococcus aureus
Authors: Merino Nekane , Toledo-Arana Alejandro , Vergara-Irigaray Marta , Valle Jaione , Solano Cristina , Calvo Enrique , Lopez Juan Antonio , Foster Timothy J. , Penadés José R. , Lasa Iñigo 
Published: December 2008

ABSTRACTThe capacity ofStaphylococcus aureusto form biofilms on host tissues and implanted medical devices is one of the major virulence traits underlying persistent and chronic infections. The matrix in whichS. aureuscells are encased in a biofilm often consists of the polysaccharide intercellular adhesin (PIA) or poly-N-acetyl glucosamine (PNAG). However, surface proteins capable of promoting biofilm development in the absence of PIA/PNAG exopolysaccharide have been described. Here, we used two-dimensional nano-liquid chromatography and mass spectrometry to investigate the composition of a proteinaceous biofilm matrix and identified protein A (spa) as an essential component of the biofilm; protein A induced bacterial aggregation in liquid medium and biofilm formation under standing and flow conditions. Exogenous addition of synthetic protein A or supernatants containing secreted protein A to growth media induced biofilm development, indicating that protein A can promote biofilm development without being covalently anchored to the cell wall. Protein A-mediated biofilm formation was completely inhibited in a dose-dependent manner by addition of serum, purified immunoglobulin G, or anti-protein A-specific antibodies. A murine model of subcutaneous catheter infection unveiled a significant role for protein A in the development of biofilm-associated infections, as the amount of protein A-deficient bacteria recovered from the catheter was significantly lower than that of wild-type bacteria when both strains were used to coinfect the implanted medical device. Our results suggest a novel role for protein A complementary to its known capacity to interact with multiple immunologically important eukaryotic receptors.
Evolution of Penicillin-Binding Protein 2 Concentration and Cell Shape during a Long-Term Experiment withEscherichia coli
Authors: Philippe Nadège , Pelosi Ludovic , Lenski Richard E. , Schneider Dominique 
Published: December 2008

ABSTRACTPeptidoglycan is the major component of the bacterial cell wall and is involved in osmotic protection and in determining cell shape. Cell shape potentially influences many processes, including nutrient uptake as well as cell survival and growth. Peptidoglycan is a dynamic structure that changes during the growth cycle. Penicillin-binding proteins (PBPs) catalyze the final stages of peptidoglycan synthesis. Although PBPs are biochemically and physiologically well characterized, their broader effects, especially their effects on organismal fitness, are not well understood. In a long-term experiment, 12 populations ofEscherichia colihaving a common ancestor were allowed to evolve for more than 40,000 generations in a defined environment. We previously identified mutations in thepbpAoperon in one-half of these populations; this operon encodes PBP2 and RodA proteins that are involved in cell wall elongation. In this study, we characterized the effects of two of these mutations on competitive fitness and other phenotypes. By constructing and performing competition experiments with strains that are isogenic except for thepbpAalleles, we showed that both mutations that evolved were beneficial in the environment used for the long-term experiment and that these mutations caused parallel phenotypic changes. In particular, they reduced the cellular concentration of PBP2, thereby generating spherical cells with an increased volume. In contrast to their fitness-enhancing effect in the environment where they evolved, both mutations decreased cellular resistance to osmotic stress. Moreover, one mutation reduced fitness during prolonged stationary phase. Therefore, alteration of the PBP2 concentration contributed to physiological trade-offs and ecological specialization during experimental evolution.
Involvement of the LuxR-Type Transcriptional Regulator RamA in Regulation of Expression of thegapAGene, Encoding Glyceraldehyde-3-Phosphate Dehydrogenase ofCorynebacterium glutamicum
Authors: Toyoda Koichi , Teramoto Haruhiko , Inui Masayuki , Yukawa Hideaki 
Published: December 2008

ABSTRACTSugR, RamA, GlxR, GntR1, and a MarR-type transcriptional regulator bind to the promoter region of thegapAgene encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH), essential for glycolysis inCorynebacterium glutamicum. We previously showed that SugR, a transcriptional repressor of phosphotransferase system genes for the sugar transport system, is involved in the downregulation ofgapAexpression in the absence of sugar. In this study, the role of RamA in the expression of thegapAgene was examined. Comparing thegapAexpression and GAPDH activity of aramAmutant with those of the wild type revealed that RamA is involved in upregulation ofgapAexpression in glucose-grown cells. DNase I footprint analyses and electrophoretic mobility shift assays revealed that RamA binds with different affinities to three sites in thegapApromoter.lacZreporter assays with mutated RamA binding sites in thegapApromoter showed that the middle binding site is the most important for RamA to activategapAexpression and that binding of RamA to thegapApromoter activates the gene expression not only in glucose-grown cells but also in acetate-grown cells. Furthermore, RamA also directly activatessugRexpression, indicating that two global regulators, RamA and SugR, are coordinately involved in the complex regulation ofgapAexpression inC. glutamicum.
The MalF P2 Loop of the ATP-Binding Cassette Transporter MalFGK
2
from
Escherichia coli
and
Salmonella enterica
Serovar Typhimurium Interacts with Maltose Binding Protein (MalE) throughout the Catalytic Cycle
Authors: Daus Martin L. , Grote Mathias , Schneider Erwin 
Published: December 2008

ABSTRACT

We have investigated the interaction of the uncommonly large periplasmic P2 loop of the MalF subunit of the maltose ATP-binding cassette transporter (MalFGK
2
) from
Escherichia coli
and
Salmonella enterica
serovar Typhimurium with maltose binding protein (MalE) by site-specific chemical cross-linking in the assembled transport complex. We focused on possible distance changes between two pairs of residues of the P2 loop and MalE during the transport cycle. The distance between MalF(S205C) and MalE(T80C) (∼5 Å) remained unchanged under all conditions tested. Cross-linking did not affect the ATPase activity of the complex. The distance between MalF(T177C) and MalE(T31C) changed from ∼10 Å to ∼5 Å upon binding of ATP (or maltose, with a less pronounced result) and was reset to ∼10 Å after hydrolysis of one ATP. A cross-link (∼25 Å) between MalF(S205C) and MalE(T31C) was observed only when the transporter resided in a transition state-like conformation, as was the case after vanadate trapping or in a binding protein-independent mutant, both of which are characterized by tight binding of unliganded MalE to the transporter. Thus, we propose that the observed cross-link is indicative of catalytic intermediates of the transporter. Together, our results strengthen the notion that the MalF P2 loop plays an important role in intersubunit communication. In particular, this loop is involved in keeping MalE in close contact with the transporter. The data are discussed with respect to a crystal structure and current transport models.