bluuebunny/crossref_metadata_2025_split huggingface dataset:
Luminescent Whole-Cell Cyanobacterial Bioreporter for Measuring Fe Availability in Diverse Marine Environments
Authors: Boyanapalli Ramakrishna , Bullerjahn George S. , Pohl Christa , Croot Peter L. , Boyd Philip W. , McKay R. Michael L. 
Published: December 2006

ABSTRACT

A
Synechococcus
sp. strain PCC 7002 Fe bioreporter was constructed containing the
isiAB
promoter fused to the
Vibrio harveyi luxAB
genes. Bioreporter luminescence was characterized with respect to the free ferric ion concentration in trace metal-buffered synthetic medium. The applicability of the Fe bioreporter to assess Fe availability in the natural environment was tested by using samples collected from the Baltic Sea and from the high-nutrient, low-chlorophyll subarctic Pacific Ocean. Parallel assessment of dissolved Fe and bioreporter response confirmed that direct chemical measurements of dissolved Fe should not be considered alone when assessing Fe availability to phytoplankton.
Use of Artificial Neural Networks and a Gamma-Concept-Based Approach To Model Growth of and Bacteriocin Production by
Streptococcus macedonicus
ACA-DC 198 under Simulated Conditions of Kasseri Cheese Production
Authors: Poirazi Panayiota , Leroy Frédéric , Georgalaki Marina D. , Aktypis Anastassios , De Vuyst Luc , Tsakalidou Effie 
Published: December 2006

ABSTRACT

Growth of and bacteriocin production by
Streptococcus macedonicus
ACA-DC 198 were assessed and modeled under conditions simulating Kasseri cheese production. Controlled fermentations were performed in milk supplemented with yeast extract at different combinations of temperature (25, 40, and 55°C), constant pH (pHs 5 and 6), and added NaCl (at concentrations of 0, 2, and 4%, wt/vol). The data obtained were used to construct two types of predictive models, namely, a modeling approach based on the gamma concept, as well as a model based on artificial neural networks (ANNs). The latter computational methods were used on 36 control fermentations to quantify the complex relationships between the conditions applied (temperature, pH, and NaCl) and population behavior and to calculate the associated biokinetic parameters, i.e., maximum specific growth and cell count decrease rates and specific bacteriocin production. The functions obtained were able to estimate these biokinetic parameters for four validation fermentation experiments and obtained good agreement between modeled and experimental values. Overall, these experiments show that both methods can be successfully used to unravel complex kinetic patterns within biological data of this kind and to predict population kinetics. Whereas ANNs yield a better correlation between experimental and predicted results, the gamma-concept-based model is more suitable for biological interpretation. Also, while the gamma-concept-based model has not been designed for modeling of other biokinetic parameters than the specific growth rate, ANNs are able to deal with any parameter of relevance, including specific bacteriocin production.
Response ofNitrosospirasp. Strain AF-Like Ammonia Oxidizers to Changes in Temperature, Soil Moisture Content, and Fertilizer Concentration
Authors: Avrahami Sharon , Bohannan Brendan J. M. 
Published: December 2006

ABSTRACTVery little is known regarding the ecology ofNitrosospirasp. strain AF-like bacteria, a unique group of ammonia oxidizers within theBetaproteobacteria. We studied the response ofNitrosospirasp. strain AF-like ammonia oxidizers to changing environmental conditions by applying molecular methods and physiological measurements to Californian grassland soil manipulated in the laboratory. This soil is naturally high inNitrosospirasp. strain AF-like bacteria relative to the much-better-studiedNitrosospira multiformis-like ammonia-oxidizing bacteria. Increases in temperature, soil moisture, and fertilizer interacted to reduce the relative abundance ofNitrosospirasp. strain AF-like bacteria, although they remained numerically dominant. The overall abundance of ammonia-oxidizing bacteria increased with increasing soil moisture and decreased with increasing temperature. Potential nitrification activity was altered by interactions among temperature, soil moisture, and fertilizer, with activity tending to be higher when soil moisture and temperature were increased. The increase in potential nitrification activity with increased temperature was surprising, given that the overall abundance of ammonia-oxidizing bacteria decreased significantly under these conditions. This observation suggests that (i)Nitrosospirasp. strain AF-like bacteria may respond to increased temperature with an increase in activity, despite a decrease in abundance, or (ii) that potential nitrification activity in these soils may be due to organisms other than bacteria (e.g., archaeal ammonia oxidizers), at least under conditions of increased temperature.
Altered Metabolic Flux due to Deletion of
odhA
causes
l
-Glutamate Overproduction in
Corynebacterium glutamicum
Authors: Asakura Yoko , Kimura Eiichiro , Usuda Yoshihiro , Kawahara Yoshio , Matsui Kazuhiko , Osumi Tsuyoshi , Nakamatsu Tsuyoshi 
Published: December 2006

ABSTRACT

l
-Glutamate overproduction in
Corynebacterium glutamicum
, a biotin auxotroph, is induced by biotin limitation or by treatment with certain fatty acid ester surfactants or with penicillin. We have analyzed the relationship between the inductions, 2-oxoglutarate dehydrogenase complex (ODHC) activity, and
l
-glutamate production. Here we show that a strain deleted for
odhA
and completely lacking ODHC activity produces
l
-glutamate as efficiently as the induced wild type (27.8 mmol/g [dry weight] of cells for the
ohdA
deletion strain compared with only 1.0 mmol/g [dry weight] of cells for the uninduced wild type). This level of production is achieved without any induction or alteration in the fatty acid composition of the cells, showing that
l
-glutamate overproduction can be caused by the change in metabolic flux alone. Interestingly, the
l
-glutamate productivity of the
odhA
-deleted strain is increased about 10% by each of the
l
-glutamate-producing inductions, showing that the change in metabolic flux resulting from the
odhA
deletion and the inductions have additive effects on
l
-glutamate overproduction. Tween 40 was indicated to induce drastic metabolic change leading to
l
-glutamate overproduction in the
odhA
-deleted strain. Furthermore, optimizing the metabolic flux from 2-oxoglutarate to
l
-glutamate by tuning glutamate dehydrogenase activity increased the
l
-glutamate production of the
odhA
-deleted strain.
Colonization, Persistence, and Tissue Tropism ofEscherichia coliO26 in Conventionally Reared Weaned Lambs
Authors: Aktan İlknur , La Ragione Roberto M. , Woodward Martin J. 
Published: December 2006

ABSTRACTEscherichia coliO26 is recognized as an emerging pathogen associated with disease in both ruminants and humans. Compared to those ofE. coliO157:H7, the shedding pattern and location ofE. coliO26 in the gastrointestinal tract (GIT) of ruminants are poorly understood. In the studies reported here, anstx-negativeE. coliO26 strain of ovine origin was inoculated orally into 6-week-old lambs and the shedding pattern of the O26 strain was monitored by serial bacteriological examination of feces. The location of colonization in the GIT was examined at necropsy at two time points. The numbers of O26 organisms excreted in feces declined from approximately 107to 104CFU per gram of feces by day 7 and continued at this level for a further 3 weeks. Beyond day 30, excretion was from few animals, intermittent, and just above the detection limit. By day 38, all fecal samples were negative, but at necropsy, O26 organisms were recovered from the upper GIT, specifically the ileum. However, no attaching-effacing (AE) lesions were observed. To identify the location ofE. coliO26 within the GIT early after inoculation, two lambs were examined postmortem, 4 days postinoculation. High numbers of O26 organisms were recovered from all GIT sites examined, and ∼109CFU were recovered from 1 gram of ileal tissue from one animal. Despite high numbers of O26 organisms, AE lesions were identified on the mucosa of the ascending colon of only one animal. These data indicate thatE. coliO26 readily colonizes 6-week-old lambs, but the sparseness of AE lesions suggests that O26 is well adapted to this host, and mechanisms other than those dependent upon intimin may play a role in persistence.
Prevalence of
Escherichia coli
O157:H7 in Gallbladders of Beef Cattle
Authors: Reinstein S. , Fox J. T. , Shi X. , Nagaraja T. G. 
Published: December 2006

ABSTRACT

Gallbladders and rectal contents were collected from cattle (
n
= 933) at slaughter to determine whether the gallbladder harbors
Escherichia coli
O157:H7. Both gallbladder mucosal swabs and homogenized mucosal tissues were used for isolation. Only five gallbladders (0.54%) were positive for
E. coli
O157:H7. Fecal prevalence averaged 7.1%; however, none of the cattle that had
E. coli
O157:H7 in the gallbladder was positive for
E. coli
O157:H7 in feces. Therefore, the gallbladder does not appear to be a common site of colonization for
E. coli
O157:H7 in beef cattle.
Transcriptional Activation Domains of the
Candida albicans
Gcn4p and Gal4p Homologs
Authors: Martchenko Mikhail , Levitin Anastasia , Whiteway Malcolm 
Published: December 2006

ABSTRACT

Many putative transcription factors in the pathogenic fungus
Candida albicans
contain sequence similarity to well-defined transcriptional regulators in the budding yeast
Saccharomyces cerevisiae
, but this sequence similarity is often limited to the DNA binding domains of the molecules. The Gcn4p and Gal4p proteins of
Saccharomyces cerevisiae
are highly studied and well-understood eukaryotic transcription factors of the basic leucine zipper (Gcn4p) and C
6
zinc cluster (Gal4p) families;
C. albicans
has
C. albicans
Gcn4p (CaGcn4p) and CaGal4p with DNA binding domains highly similar to their
S. cerevisiae
counterparts. Deletion analysis of the CaGcn4p protein shows that the N′ terminus is needed for transcriptional activation; an 81-amino-acid region is critical for this function, and this domain can be coupled to a
lexA
DNA binding module to provide transcription-activating function in a heterologous reporter system. Deletion analysis of the
C. albicans
Gal4p identifies a C-terminal 73-amino-acid-long transcription-activating domain that also can be transferred to a heterologous reporter construct to direct transcriptional activation. These two transcriptional activation regions show no sequence similarity to the respective domains in their
S. cerevisiae
homologs, and the two
C. albicans
transcription-activating domains themselves show little similarity.
Cryptococcus neoformans
Produces Authentic Prostaglandin E
2
without a Cyclooxygenase
Authors: Erb-Downward John R. , Huffnagle Gary B. 
Published: December 2006

ABSTRACT

Many single-celled eukaryotes produce prostaglandin-like molecules, but these have not been absolutely verified by mass spectrometry. We have isolated, and identified by liquid chromatography-tandem mass spectrometry, authentic prostaglandin E
2
from
Cryptococcus neoformans
. Cyclooxygenase inhibitors did not inhibit prostaglandin synthesis, and the cryptococcal genome lacks a cyclooxygenase homolog. Thus, novel enzymes must exist.
The Anaphase-Promoting Complex/Cyclosome Is Required for Anaphase Progression in Multinucleated
Ashbya gossypii
Cells
Authors: Gladfelter Amy S. , Sustreanu Nicoleta , Hungerbuehler A. Katrin , Voegeli Sylvia , Galati Virginie , Philippsen Peter 
Published: December 2006

ABSTRACT

Regulated protein degradation is essential for eukaryotic cell cycle progression. The anaphase-promoting complex/cyclosome (APC/C) is responsible for the protein destruction required for the initiation of anaphase and the exit from mitosis, including the degradation of securin and B-type cyclins. We initiated a study of the APC/C in the multinucleated, filamentous ascomycete
Ashbya gossypii
to understand the mechanisms underlying the asynchronous mitosis observed in these cells. These experiments were motivated by previous work which demonstrated that the mitotic cyclin AgClb1/2p persists through anaphase, suggesting that the APC/C may not be required for the division cycle in
A. gossypii
. We have now found that the predicted APC/C components AgCdc23p and AgDoc1p and the targeting factors AgCdc20p and AgCdh1p are essential for growth and nuclear division. Mutants lacking any of these factors arrest as germlings with nuclei blocked in mitosis. A likely substrate of the APC/C is the securin homologue AgPds1p, which is present in all nuclei in hyphae except those in anaphase. The destruction box sequence of AgPds1p is required for this timed disappearance. To investigate how the APC/C may function to degrade AgPds1p in only the subset of anaphase nuclei, we localized components and targeting subunits of the APC/C. Remarkably, AgCdc23p, AgDoc1p, and AgCdc16p were found in all nuclei in all cell cycle stages, as were the APC/C targeting factors AgCdc20p and AgCdh1p. These data suggest that the AgAPC/C may be constitutively active across the cell cycle and that proteolysis in these multinucleated cells may be regulated at the level of substrates rather than by the APC/C itself.
Mutations in Alternative Carbon Utilization Pathways in
Candida albicans
Attenuate Virulence and Confer Pleiotropic Phenotypes
Authors: Ramírez Melissa A. , Lorenz Michael C. 
Published: December 2006

ABSTRACT

The interaction between
Candida albicans
and cells of the innate immune system is a key determinant of disease progression. Transcriptional profiling has revealed that
C. albicans
has a complex response to phagocytosis, much of which is similar to carbon starvation. This suggests that nutrient limitation is a significant stress in vivo, and we have shown that glyoxylate cycle mutants are less virulent in mice. To examine whether other aspects of carbon metabolism are important in vivo during an infection, we have constructed strains lacking
FOX2
and
FBP1
, which encode key components of fatty acid β-oxidation and gluconeogenesis, respectively. As expected,
fox2
Δ mutants failed to utilize several fatty acids as carbon sources. Surprisingly, however, these mutants also failed to grow in the presence of several other carbon sources, whose assimilation is independent of β-oxidation, including ethanol and citric acid. Mutants lacking the glyoxylate enzyme ICL1 also had more severe carbon utilization phenotypes than were expected. These results suggest that the regulation of alternative carbon metabolism in
C. albicans
is significantly different from that in other fungi. In vivo,
fox2
Δ mutants show a moderate but significant reduction in virulence in a mouse model of disseminated candidiasis, while disruption of the glyoxylate cycle or gluconeogenesis confers a severe attenuation in this model. These data indicate that
C. albicans
often encounters carbon-poor conditions during growth in the host and that the ability to efficiently utilize multiple nonfermentable carbon sources is a virulence determinant. Consistent with this in vivo requirement,
C. albicans
uniquely regulates carbon metabolism in a more integrated manner than in
Saccharomyces cerevisiae
, such that defects in one part of the machinery have wider impacts than expected. These aspects of alternative carbon metabolism may then be useful as targets for therapeutic intervention.
Effect of Corticosteroids and Neuropeptides on the Expression of Defensins in Bovine Tracheal Epithelial Cells
Authors: Mitchell Gordon B. , Al-Haddawi Muthafar H. , Clark Mary Ellen , Beveridge Jennifer D. , Caswell Jeff L. 
Published: December 2006

ABSTRACTSusceptibility to bacterial pneumonia in cattle is enhanced by stressors such as transportation, weaning, and commingling, which trigger a physiologic stress response resulting in elevated levels of endogenous corticosteroids and catecholamines. To determine the effect of neuroendocrine mediators on the expression of innate defense peptides in the lung, bovine tracheal epithelial cells were exposed to dexamethasone, catecholamines, acetylcholine, or substance P, and then β-defensin expression was quantified using real-time reverse transcription-PCR. Basal expression of tracheal antimicrobial peptide (TAP) mRNA was not affected by any of the mediators tested. However, induction of TAP expression by lipopolysaccharide was significantly inhibited by pretreatment with dexamethasone. Bronchial biopsy specimens from dexamethasone-treated calves had significantly lower expression of TAP and lingual antimicrobial peptide (LAP) mRNA than saline-treated controls following 48 h of treatment. Lipopolysaccharide-elicited neutrophil recruitment was enhanced in the lungs of dexamethasone-treated calves compared to saline-treated controls. These findings indicate that modulation of epithelial antimicrobial peptide expression is one mechanism through which corticosteroids and stress may impair innate pulmonary defenses.
SseL Is a
Salmonella
-Specific Translocated Effector Integrated into the SsrB-Controlled
Salmonella
Pathogenicity Island 2 Type III Secretion System
Authors: Coombes Brian K. , Lowden Michael J. , Bishop Jennifer L. , Wickham Mark E. , Brown Nat F. , Duong Nancy , Osborne Suzanne , Gal-Mor Ohad , Finlay B. Brett 
Published: December 2006

ABSTRACT

Bacterial pathogens use horizontal gene transfer to acquire virulence factors that influence host colonization, alter virulence traits, and ultimately shape the outcome of disease following infection. One hallmark of the host-pathogen interaction is the prokaryotic type III secretion system that translocates virulence factors into host cells during infection.
Salmonella enterica
possesses two type III secretion systems that are utilized during host colonization and intracellular replication.
Salmonella
pathogenicity island 2 (SPI2) is a genomic island containing approximately 30 contiguous genes required to assemble a functional secretion system including the two-component regulatory system called SsrA-SsrB that positively regulates transcription of the secretion apparatus. We used transcriptional profiling with DNA microarrays to search for genes that coregulate with the SPI2 type III secretion machinery in an SsrB-dependent manner. Here we report the identification of a
Salmonella
-specific translocated effector called SseL that is required for full virulence during murine typhoid-like disease. Analysis of infected macrophages using fluorescence-activated cell sorting revealed that
sseL
is induced inside cells and requires SsrB for expression. SseL is retained predominantly in the cytoplasm of infected cells following translocation by the type III system encoded in SPI2. Animal infection experiments with
sseL
mutant bacteria indicate that integration of SseL into the SsrB response regulatory system contributes to systemic virulence of this pathogen.
Evaluation of the Ability of
Streptococcus agalactiae
Strains Isolated from Genital and Neonatal Specimens To Bind to Human Fibrinogen and Correlation with Characteristics of the
fbsA
and
fbsB
Genes
Authors: Rosenau Agnès , Martins Karine , Amor Souheila , Gannier François , Lanotte Philippe , van der Mee-Marquet Nathalie , Mereghetti Laurent , Quentin Roland 
Published: December 2006

ABSTRACT

The ability of 111
Streptococcus agalactiae
strains to bind to human fibrinogen was quantified. We correlated the percentages of bacteria that bound to immobilized fibrinogen with fibrinogen-binding (
fbs
) gene characteristics of strains and with clinical origin, serotypes, and phylogenetic positions of strains. Percentages varied from 0.4 to 29.9%. Fifty-five strains (49.5%) had the
fbsB
gene sensu stricto described by Gutekunst et al. (Infect. Immun., 72:3495-3504, 2004), allowing adhesion to human fibrinogen, and all of the other strains had an
fgag
variant gene. Ninety strains (81.1%) had a
fbsA
gene and 55 of them also had the
fbsB
gene. The other 21 strains (18.9%) had a truncated form of
fbsA
without the
fbsB
gene sensu stricto. The numbers of 48-nucleotide repeat sequences (rs) in the
fbsA
gene varied from 2 to 26. The population of strains with the highest ability to bind to human fibrinogen significantly more frequently had the
fbsB
gene sensu stricto and 4 to 7 rs in the
fbsA
gene (
P
< 0.05). However, the single strain that carried the highest number of rs (26 rs) in the
fbsA
gene showed high fibrinogen-binding activity (24.3%). Strains exhibiting significantly higher levels of binding to human fibrinogen belonged to a phylogenetic group of strains associated with neonatal meningitis, currently known as the ST-17 clone, that is mostly composed of serotype III strains. These findings indicate that
S. agalactiae
strains possess a wide variety of
fbs
gene content that markedly influences the ability of strains to bind to human fibrinogen. Variations in the configuration and the expression of the Fbs proteins may therefore partly explain the variability of virulence in
S. agalactiae
species.
Characterization of Early Gamma Interferon (IFN-γ) Expression during Murine Listeriosis: Identification of NK1.1+CD11c+Cells as the Primary IFN-γ-Expressing Cells
Authors: Chang Shu-Rung , Wang Kung-Jiun , Lu Yan-Feng , Yang Lii-Jia , Chen Wei-Jie , Lin Yu-Hsiang , Chang Hsin-Hou , Wang Shih-Lien 
Published: December 2006

ABSTRACTThough it is well established that gamma interferon (IFN-γ) is crucial to the early innate defense of murine listeriosis, its sources remain controversial. In this study, intracellular cytokine staining of IFN-γ-expressing splenocytes early afterListeria monocytogenesinfection revealed that NK1.1+, CD11c+, CD8+T, and CD4+T cells expressed IFN-γ 24 h after infection. Contrary to the previous report, most IFN-γ+dendritic cells (DC) were CD8α−DC. Unexpectedly, almost all CD11c+IFN-γ-expressing cells also expressed NK1.1. These NK1.1+CD11c+cells represented primary IFN-γ-expressing cells after infection. In situ studies showed these NK1.1+CD11c+cells were recruited to the borders of infectious foci and expressed IFN-γ. A significant NK1.1+CD11c+population was found in uninfected spleen, lymph node, blood, and bone marrow cells. And its number increased significantly in spleen, lymph node, and bone marrow afterL. monocytogenesinfection. Using interleukin-12 (IL-12) p40−/−mice, IFN-γ expression was found to be largely IL-12 p40 dependent, and the number of IFN-γ-expressing cells was only about one-third of that of wild-type mice. Moreover, the IFN-γ expression was absolutely dependent on liveL. monocytogenesinfection, as no IFN-γ was detected after inoculation of heat-killedL. monocytogenes. Our findings not only provide an insight into IFN-γ expression after in vivo infection but may also change the current perceptions of DC and natural killer cells.