bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphotransferase System-Dependent Extracellular Growth of Listeria monocytogenes Is Regulated by Alternative Sigma Factors σLand σH
Authors: Wang Siyun , Orsi Renato H. , Tang Silin , Zhang Wei , Wiedmann Martin , Boor Kathryn J. 
Published: October 2014

ABSTRACTAlternative sigma (σ) factors and phosphotransferase systems (PTSs) play pivotal roles in the environmental adaptation and virulence ofListeria monocytogenes. The growth of theL. monocytogenesparent strain 10403S and 15 isogenic alternative σ factor mutants was assessed in defined minimal medium (DM) with PTS-dependent or non-PTS-dependent carbon sources at 25°C or 37°C. Overall, our results suggested that the regulatory effect of alternative σ factors on the growth ofL. monocytogenesis dependent on the temperature and the carbon source. One-way analysis of variance (one-way ANOVA) showed that the factor “strain” had a significant effect on the maximum growth rate (μmax), lag phase duration (λ), and maximum optical density (ODmax) in PTS-dependent carbon sources (P< 0.05) but not in a non-PTS-dependent carbon source. Also, the ODmaxwas not affected by strain for any of the three PTS-dependent carbon sources at 25°C but was affected by strain at 37°C. Monitoring by quantitative real-time PCR (qRT-PCR) showed that transcript levels forlmo0027, a glucose-glucoside PTS permease (PTSGlc-1)-encoding gene, were higher in the absence of σL, and lower in the absence of σH, than in the parent strain. Our data thus indicate that σLnegatively regulateslmo0027and that the increased μmaxobserved for the ΔsigLstrain in DM with glucose may be associated with increased expression of PTSGlc-1 encoded bylmo0027. Our findings suggest that σHand σLmediate the PTS-dependent growth ofL. monocytogenesthrough complex transcriptional regulations and fine-tuning of the expression of specificptsgenes, includinglmo0027. Our findings also reveal a more important and complex role of alternative σ factors in the regulation of growth in different sugar sources than previously assumed.
Genetic Diversity of Picocyanobacteria in Tibetan Lakes: Assessing the Endemic and Universal Distributions
Authors: Huang Sijun , Liu Yongqin , Hu Anyi , Liu Xiaobo , Chen Feng , Yao Tandong , Jiao Nianzhi 
Published: October 2014

ABSTRACT

The phylogenetic diversity of picocyanobacteria in seven alkaline lakes on the Tibetan Plateau was analyzed using the molecular marker 16S-23S rRNA internal transcribed spacer sequence. A total of 1,077 environmental sequences retrieved from the seven lakes were grouped into seven picocyanobacterial clusters, with two clusters newly described here. Each of the lakes was dominated by only one or two clusters, while different lakes could have disparate communities, suggesting low alpha diversity but high beta diversity of picocyanobacteria in these high-altitude freshwater and saline lakes. Several globally distributed clusters were found in these Tibetan lakes, such as subalpine cluster I and the
Cyanobium gracile
cluster. Although other clusters likely exhibit geographic restriction to the plateau temporally, reflecting endemicity, they can indeed be distributed widely on the plateau. Lakes with similar salinities may have similar genetic populations despite a large geographic distance. Canonical correspondence analysis identified salinity as the only environmental factor that may in part explain the diversity variations among lakes. Mantel tests suggested that the community similarities among lakes are independent of geographic distance. A portion of the picocyanobacterial clusters appear to be restricted to a narrow salinity range, while others are likely adapted to a broad range. A seasonal survey of Lake Namucuo across 3 years did not show season-related variations in diversity, and depth-related population partitioning was observed along a vertical profile of the lake. Our study emphasizes the high dispersive potential of picocyanobacteria and suggests that the regional distribution may result from adaptation to specified environments.
Impact of Ralstonia eutropha's Poly(3-Hydroxybutyrate) (PHB) Depolymerases and Phasins on PHB Storage in Recombinant Escherichia coli
Authors: Eggers Jessica , Steinbüchel Alexander 
Published: October 2014

ABSTRACT

The model organism for polyhydroxybutyrate (PHB) biosynthesis,
Ralstonia eutropha
H16, possesses multiple isoenzymes of granules coating phasins as well as of PHB depolymerases, which degrade accumulated PHB under conditions of carbon limitation. In this study, recombinant
Escherichia coli
BL21(DE3) strains were used to study the impact of selected PHB depolymerases of
R. eutropha
H16 on the growth behavior and on the amount of accumulated PHB in the absence or presence of phasins. For this purpose, 20 recombinant
E. coli
BL21(DE3) strains were constructed, which harbored a plasmid carrying the
phaCAB
operon from
R. eutropha
H16 to ensure PHB synthesis and a second plasmid carrying different combinations of the genes encoding a phasin and a PHB depolymerase from
R. eutropha
H16. It is shown in this study that the growth behavior of the respective recombinant
E. coli
strains was barely affected by the overexpression of the phasin and PHB depolymerase genes. However, the impact on the PHB contents was significantly greater. The strains expressing the genes of the PHB depolymerases PhaZ1, PhaZ2, PhaZ3, and PhaZ7 showed 35% to 94% lower PHB contents after 30 h of cultivation than the control strain. The strain harboring
phaZ7
reached by far the lowest content of accumulated PHB (only 2.0% [wt/wt] PHB of cell dry weight). Furthermore, coexpression of phasins in addition to the PHB depolymerases influenced the amount of PHB stored in cells of the respective strains. It was shown that the phasins PhaP1, PhaP2, and PhaP4 are not substitutable without an impact on the amount of stored PHB. In particular, the phasins PhaP2 and PhaP4 seemed to limit the degradation of PHB by the PHB depolymerases PhaZ2, PhaZ3, and PhaZ7, whereas almost no influence of the different phasins was observed if
phaZ1
was coexpressed. This study represents an extensive analysis of the impact of PHB depolymerases and phasins on PHB accumulation and provides a deeper insight into the complex interplay of these enzymes.
A Hidden Pitfall in the Preparation of Agar Media Undermines Microorganism Cultivability
Authors: Tanaka Tomohiro , Kawasaki Kosei , Daimon Serina , Kitagawa Wataru , Yamamoto Kyosuke , Tamaki Hideyuki , Tanaka Michiko , Nakatsu Cindy H. , Kamagata Yoichi 
Published: October 2014

ABSTRACT

Microbiologists have been using agar growth medium for over 120 years. It revolutionized microbiology in the 1890s when microbiologists were seeking effective methods to isolate microorganisms, which led to the successful cultivation of microorganisms as single clones. But there has been a disparity between total cell counts and cultivable cell counts on plates, often referred to as the “great plate count anomaly,” that has long been a phenomenon that still remains unsolved. Here, we report that a common practice microbiologists have employed to prepare agar medium has a hidden pitfall: when phosphate was autoclaved together with agar to prepare solid growth media (PT medium), total colony counts were remarkably lower than those grown on agar plates in which phosphate and agar were separately autoclaved and mixed right before solidification (PS medium). We used a pure culture of
Gemmatimonas aurantiaca
T-27
T
and three representative sources of environmental samples, soil, sediment, and water, as inocula and compared colony counts between PT and PS agar plates. There were higher numbers of CFU on PS medium than on PT medium using
G. aurantiaca
or any of the environmental samples. Chemical analysis of PT agar plates suggested that hydrogen peroxide was contributing to growth inhibition. Comparison of 454 pyrosequences of the environmental samples to the isolates revealed that taxa grown on PS medium were more reflective of the original community structure than those grown on PT medium. Moreover, more hitherto-uncultivated microbes grew on PS than on PT medium.
Abundance of Vibrio cholerae, V. vulnificus, and V. parahaemolyticus in Oysters (Crassostrea virginica) and Clams (Mercenaria mercenaria) from Long Island Sound
Authors: Jones Jessica L. , Lüdeke Catharina H. M. , Bowers John C. , DeRosia-Banick Kristin , Carey David H. , Hastback William 
Published: October 2014

ABSTRACT

Vibriosis is a leading cause of seafood-associated morbidity and mortality in the United States. Typically associated with consumption of raw or undercooked oysters, vibriosis associated with clam consumption is increasingly being reported. However, little is known about the prevalence of
Vibrio
spp. in clams. The objective of this study was to compare the levels of
Vibrio cholerae
,
Vibrio vulnificus
, and
Vibrio parahaemolyticus
in oysters and clams harvested concurrently from Long Island Sound (LIS). Most probable number (MPN)–real-time PCR methods were used for enumeration of total
V. cholerae
,
V. vulnificus
,
V. parahaemolyticus
, and pathogenic (
tdh
+
and/or
trh
+
)
V. parahaemolyticus
.
V. cholerae
was detected in 8.8% and 3.3% of oyster (
n
= 68) and clam (
n
= 30) samples, with levels up to 1.48 and 0.48 log MPN/g in oysters and clams, respectively.
V. vulnificus
was detected in 97% and 90% of oyster and clam samples, with median levels of 0.97 and −0.08 log MPN/g, respectively.
V. parahaemolyticus
was detected in all samples, with median levels of 1.88 and 1.07 log MPN/g for oysters and clams, respectively. The differences between
V. vulnificus
and total and pathogenic
V. parahaemolyticus
levels in the two shellfish species were statistically significant (
P
< 0.001). These data indicate that
V. vulnificus
and total and pathogenic
V. parahaemolyticus
are more prevalent and are present at higher levels in oysters than in hard clams. Additionally, the data suggest differences in vibrio populations between shellfish harvested from different growing area waters within LIS. These results can be used to evaluate and refine illness mitigation strategies employed by risk managers and shellfish control authorities.
Positive Regulation of Botulinum Neurotoxin Gene Expression by CodY in Clostridium botulinum ATCC 3502
Authors: Zhang Zhen , Dahlsten Elias , Korkeala Hannu , Lindström Miia 
Published: October 2014

ABSTRACT

Botulinum neurotoxin, produced mainly by the spore-forming bacterium
Clostridium botulinum
, is the most poisonous biological substance known. Here, we show that CodY, a global regulator conserved in low-G+C Gram-positive bacteria, positively regulates the botulinum neurotoxin gene expression. Inactivation of
codY
resulted in decreased expression of
botA
, encoding the neurotoxin, as well as in reduced neurotoxin synthesis. Complementation of the
codY
mutation in
trans
rescued neurotoxin synthesis, and overexpression of
codY
in
trans
caused elevated neurotoxin production. Recombinant CodY was found to bind to a 30-bp region containing the
botA
transcription start site, suggesting regulation of the neurotoxin gene transcription through direct interaction. GTP enhanced the binding affinity of CodY to the
botA
promoter, suggesting that CodY-dependent neurotoxin regulation is associated with nutritional status.
Microarray-Based Detection of Salmonella enterica Serovar Enteritidis Genes Involved in Chicken Reproductive Tract Colonization
Authors: Raspoet R. , Appia-Ayme C. , Shearer N. , Martel A. , Pasmans F. , Haesebrouck F. , Ducatelle R. , Thompson A. , Van Immerseel F. 
Published: October 2014

ABSTRACT

Salmonella enterica
serovar Enteritidis has developed the potential to contaminate table eggs internally, by colonization of the chicken reproductive tract and internalization in the forming egg. The serotype Enteritidis has developed mechanisms to colonize the chicken oviduct more successfully than other serotypes. Until now, the strategies exploited by
Salmonella
Enteritidis to do so have remained largely unknown. For that reason, a microarray-based transposon library screen was used to identify genes that are essential for the persistence of
Salmonella
Enteritidis inside primary chicken oviduct gland cells
in vitro
and inside the reproductive tract
in vivo
. A total of 81 genes with a potential role in persistence in both the oviduct cells and the oviduct tissue were identified. Major groups of importance include the
Salmonella
pathogenicity islands 1 and 2, genes involved in stress responses, cell wall, and lipopolysaccharide structure, and the region-of-difference genomic islands 9, 21, and 40.
Molecular Epidemiology of Cryptosporidium spp. and Giardia spp. in Mussels (Mytilus californianus) and California Sea Lions (Zalophus californianus) from Central California
Authors: Adell A. D. , Smith W. A. , Shapiro K. , Melli A. , Conrad P. A. 
Published: October 2014

ABSTRACT

Cryptosporidium
and
Giardia
are of public health importance, with recognized transmission through recreational waters. Therefore, both can contaminate marine waters and shellfish, with potential to infect marine mammals in nearshore ecosystems. A 2-year study was conducted to evaluate the presence of
Cryptosporidium
and
Giardia
in mussels located at two distinct coastal areas in California, namely, (i) land runoff plume sites and (ii) locations near sea lion haul-out sites, as well as in feces of California sea lions (CSL) (
Zalophus californianus
) by the use of direct fluorescent antibody (DFA) detection methods and PCR with sequence analysis. In this study, 961 individual mussel hemolymph samples, 54 aliquots of pooled mussel tissue, and 303 CSL fecal samples were screened.
Giardia duodenalis
assemblages B and D were detected in hemolymph from mussels collected near two land runoff plume sites (Santa Rosa Creek and Carmel River), and assemblages C and D were detected in hemolymph from mussels collected near a sea lion haul-out site (White Rock). These results suggest that mussels are being contaminated by protozoa carried in terrestrial runoff and/or shed in the feces of CSL. Furthermore, low numbers of oocysts and cysts morphologically similar to
Cryptosporidium
and
Giardia
, respectively, were detected in CSL fecal samples, suggesting that CSL could be a source and a host of protozoan parasites in coastal environments. The results of this study showed that
Cryptosporidium
and
Giardia
spp. from the feces of terrestrial animals and CSL can contaminate mussels and coastal environments.
Hammondia hammondi Harbors Functional Orthologs of the Host-Modulating Effectors GRA15 and ROP16 but Is Distinguished from Toxoplasma gondii by a Unique Transcriptional Profile
Authors: Walzer Katelyn A. , Wier Gregory M. , Dam Rachel A. , Srinivasan Ananth R. , Borges Adair L. , English Elizabeth D. , Herrmann Daland C. , Schares Gereon , Dubey Jitender P. , Boyle Jon P. 
Published: October 2014

ABSTRACT

Toxoplasma gondii
and its nearest extant relative,
Hammondia hammondi
, are phenotypically distinct despite their remarkable similarity in gene content, synteny, and functionality. To begin to identify genetic differences that might drive distinct infection phenotypes of
T. gondii
and
H. hammondi
, in the present study we (i) determined whether two known host-interacting proteins, dense granule protein 15 (GRA15) and rhoptry protein 16 (ROP16), were functionally conserved in
H. hammondi
and (ii) performed the first comparative transcriptional analysis of
H. hammondi
and
T. gondii
sporulated oocysts. We found that GRA15 and ROP16 from
H. hammondi
(HhGRA15 and HhROP16) modulate the host NF-κB and STAT6 pathways, respectively, when expressed heterologously in
T. gondii
. We also found the transcriptomes of
H. hammondi
and
T. gondii
to be highly distinct. Consistent with the spontaneous conversion of
H. hammondi
tachyzoites into bradyzoites both
in vitro
and
in vivo
,
H. hammondi
high-abundance transcripts are enriched for genes that are of greater abundance in
T. gondii
bradyzoites. We also identified genes that are of high transcript abundance in
H. hammondi
but are poorly expressed in multiple
T. gondii
life stages, suggesting that these genes are uniquely expressed in
H. hammondi
. Taken together, these data confirm the functional conservation of known
T. gondii
virulence effectors in
H. hammondi
and point to transcriptional differences as a potential source of the phenotypic differences between these species.
Randomized Open-Label Pilot Study of the Influence of Probiotics and the Gut Microbiome on Toxic Metal Levels in Tanzanian Pregnant Women and School Children
Authors: Bisanz Jordan E. , Enos Megan K. , Mwanga Joseph R. , Changalucha John , Burton Jeremy P. , Gloor Gregory B. , Reid Gregor 
Published: October 2014

ABSTRACTExposure to environmental toxins is a 21st century global health problem that is often the result of dietary intake. Although efforts are made to reduce dietary toxin levels, they are often unsuccessful, warranting research into novel methods to reduce host exposure. Food-grade microbes that can be delivered to the gastrointestinal tract and that are capable of sequestering toxins present a safe and cost-effective intervention. We sought to investigate the potential for probiotic-supplemented yogurt to lower heavy metal levels in at-risk populations of pregnant women and in children in Mwanza, Tanzania, and to examine the microbiome in relation to toxin levels. Two populations suspected to have high toxic metal exposures were studied. A group of 44 school-aged children was followed over 25 days, and 60 pregnant women were followed over their last two trimesters until birth. A yogurt containing 1010 CFULactobacillus rhamnosusGR-1 per 250 g was administered, while control groups received either whole milk or no intervention. Changes in blood metal levels were assessed, and the gut microbiomes of the children were profiled by analyzing 16S rRNA sequencing via the Ion Torrent platform. The children and pregnant women in the study were found to have elevated blood levels of lead and mercury compared to age- and sex-matched Canadians. Consumption of probiotic yogurt had a protective effect against further increases in mercury (3.2 nmol/liter;P= 0.035) and arsenic (2.3 nmol/liter;P= 0.011) blood levels in the pregnant women, but this trend was not statistically significant in the children. Elevated blood lead was associated with increases inSuccinivibrionaceaeandGammaproteobacteriarelative abundance levels in stool.IMPORTANCEProbiotic food produced locally represents a nutritious and affordable means for people in some developing countries to counter exposures to toxic metals. Further research and field trials are warranted to explore this approach in countries where communities are located near mining sites and agricultural areas, two types of areas where toxins are likely to be elevated.
Septins Arrange F-Actin-Containing Fibers on the Chlamydia trachomatis Inclusion and Are Required for Normal Release of the Inclusion by Extrusion
Authors: Volceanov Larisa , Herbst Katharina , Biniossek Martin , Schilling Oliver , Haller Dirk , Nölke Thilo , Subbarayal Prema , Rudel Thomas , Zieger Barbara , Häcker Georg 
Published: October 2014

ABSTRACT

Chlamydia trachomatis
is an obligate intracellular human pathogen that grows inside a membranous, cytosolic vacuole termed an inclusion. Septins are a group of 13 GTP-binding proteins that assemble into oligomeric complexes and that can form higher-order filaments. We report here that the septins SEPT2, -9, -11, and probably -7 form fibrillar structures around the chlamydial inclusion. Colocalization studies suggest that these septins combine with F actin into fibers that encase the inclusion. Targeting the expression of individual septins by RNA interference (RNAi) prevented the formation of septin fibers as well as the recruitment of actin to the inclusion. At the end of the developmental cycle of
C. trachomatis
, newly formed, infectious elementary bodies are released, and this release occurs at least in part through the organized extrusion of intact inclusions. RNAi against SEPT9 or against the combination of SEPT2/7/9 substantially reduced the number of extrusions from a culture of infected HeLa cells. The data suggest that a higher-order structure of four septins is involved in the recruitment or stabilization of the actin coat around the chlamydial inclusion and that this actin recruitment by septins is instrumental for the coordinated egress of
C. trachomatis
from human cells. The organization of F actin around parasite-containing vacuoles may be a broader response mechanism of mammalian cells to the infection by intracellular, vacuole-dwelling pathogens.

IMPORTANCE
Chlamydia trachomatis
is a frequent bacterial pathogen throughout the world, causing mostly eye and genital infections.
C. trachomatis
can develop only inside host cells; it multiplies inside a membranous vacuole in the cytosol, termed an inclusion. The inclusion is covered by cytoskeletal “coats” or “cages,” whose organization and function are poorly understood. We here report that a relatively little-characterized group of proteins, septins, is required to organize actin fibers on the inclusion and probably through actin the release of the inclusion. Septins are a group of GTP-binding proteins that can organize into heteromeric complexes and then into large filaments. Septins have previously been found to be involved in the interaction of the cell with bacteria in the cytosol. Our observation that they also organize a reaction to bacteria living in vacuoles suggests that they have a function in the recognition of foreign compartments by a parasitized human cell.