bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Aerated Steam Treatment of Alfalfa and Mung Bean Seeds To Eliminate High Levels of Escherichia coli O157:H7 and O178:H12, Salmonella enterica, and Listeria monocytogenes
Authors: Studer Patrick , Heller Werner E. , Hummerjohann Jörg , Drissner David 
Published: May 2013

ABSTRACT

Sprouts contaminated with human pathogens are able to cause food-borne diseases due to the favorable growth conditions for bacteria during germination and because of minimal processing steps prior to consumption. We have investigated the potential of hot humid air, i.e., aerated steam, to treat alfalfa and mung bean seeds which have been artificially contaminated with
Escherichia coli
O157:H7,
Salmonella enterica
subsp.
enterica
serovar Weltevreden, and
Listeria monocytogenes
Scott A. In addition, a recently collected
E. coli
O178:H12 isolate, characterized by a reduced heat sensitivity, was exposed to the treatment described. Populations of
E. coli
O157:H7 and
S. enterica
on alfalfa and mung bean seeds could be completely eliminated by a 300-s treatment with steam at 70 ± 1°C as revealed by enrichment studies.
L. monocytogenes
and
E. coli
O178:H12 could not be completely eliminated from artificially inoculated seeds. However, bacterial populations were reduced by more than 5 log CFU/g on alfalfa and by more than 4 log CFU/g on mung bean seeds. The germination rate of mung beans was not affected by the 300-s treatment compared to the germination rate of untreated seeds whereas that of alfalfa seeds was significantly lower by 11.9%. This chemical-free method is an effective alternative to the 20,000-ppm hypochlorite treatment presently recommended by the U.S. Food and Drug Administration (FDA).
The Microbiome of the Red Sea Coral Stylophora pistillata Is Dominated by Tissue-Associated Endozoicomonas Bacteria
Authors: Bayer Till , Neave Matthew J. , Alsheikh-Hussain Areej , Aranda Manuel , Yum Lauren K. , Mincer Tracy , Hughen Konrad , Apprill Amy , Voolstra Christian R. 
Published: May 2013

ABSTRACT

Endozoicomonas
bacteria were found highly associated with the coral
Stylophora pistillata
, and these bacteria are also ubiquitously associated with diverse corals worldwide. Novel
Endozoicomonas
-specific probes revealed that
Endozoicomonas
bacteria were abundant in the endodermal tissues of
S. pistillata
and appear to have an intimate relationship with the coral.
Development of a Propionibacterium-Escherichia coli Shuttle Vector for Metabolic Engineering of Propionibacterium jensenii, an Efficient Producer of Propionic Acid
Authors: Zhuge Xin , Liu Long , Shin Hyun-dong , Chen Rachel R. , Li Jianghua , Du Guocheng , Chen Jian 
Published: May 2013

ABSTRACTPropionic acid (PA) is an important chemical building block and is widely applied for organic synthesis, food, feedstuff, and pharmaceuticals. To date, the strains that can efficiently produce PA have includedPropionibacterium thoenii,P. freudenreichii, andP. acidipropionici. In this report, we show thatP. jenseniiATCC 4868 is also able to produce PA in much higher yields than the previously reported strains. To further improve the production capacity, aP. jensenii-Escherichia colishuttle vector was developed for the metabolic engineering ofP. jensenii. Specifically, a 6.9-kb endogenous plasmid, pZGX01, was isolated fromP. acidipropioniciATCC 4875 and sequenced. Since the sequencing analysis indicated that pZGX01 could encode 11 proteins, the transcriptional levels of the corresponding genes were also investigated. Then, aP. jensenii-Escherichia colishuttle vector was constructed using the pZGX01 plasmid, theE. colipUC18 plasmid, and a chloramphenicol resistance gene. Interestingly, not only could the developed shuttle vector be transformed intoP. jenseniiATCC 4868 and 4870, but it also could be transformed intofreudenreichiiATCC 6207 subspecies ofP. freudenreichii. Finally, the glycerol dehydrogenase gene (gldA) fromKlebsiella pneumoniaewas expressed inP. jenseniiATCC 4868 with the constructed shuttle vector. In a 3-liter batch culture, the PA production by the engineeredP. jenseniiATCC 4868 strain reached 28.23 ± 1.0 g/liter, which was 26.07% higher than that produced by the wild-type strain (22.06 ± 1.2 g/liter). This result indicated that the constructed vector can be used a useful tool for metabolic engineering ofP. jensenii.
Involvement of the Novel Two-Component NsrRS and LcrRS Systems in Distinct Resistance Pathways against Nisin A and Nukacin ISK-1 in Streptococcus mutans
Authors: Kawada-Matsuo Miki , Oogai Yuichi , Zendo Takeshi , Nagao Junichi , Shibata Yukie , Yamashita Yoshihisa , Ogura Yoshitoshi , Hayashi Tetsuya , Sonomoto Kenji , Komatsuzawa Hitoshi 
Published: May 2013

ABSTRACT

The novel two-component systems NsrRS and LcrRS are individually associated with resistance against the distinct lantibiotics nisin A and nukacin ISK-1 in
Streptococcus mutans
. NsrRS regulates the expression of NsrX, which is associated with nisin A binding, and LcrRS regulates the expression of the ABC transporter LctFEG.
Development of Biotin-Prototrophic and -Hyperauxotrophic Corynebacterium glutamicum Strains
Authors: Ikeda Masato , Miyamoto Aya , Mutoh Sumire , Kitano Yuko , Tajima Mei , Shirakura Daisuke , Takasaki Manami , Mitsuhashi Satoshi , Takeno Seiki 
Published: May 2013

ABSTRACTTo develop the infrastructure for biotin production through naturally biotin-auxotrophicCorynebacterium glutamicum, we attempted to engineer the organism into a biotin prototroph and a biotin hyperauxotroph. To confer biotin prototrophy on the organism, the cotranscribedbioBFgenes ofEscherichia coliwere introduced into theC. glutamicumgenome, which originally lacked thebioFgene. The resulting strain still required biotin for growth, but it could be replaced by exogenous pimelic acid, a source of the biotin precursor pimelate thioester linked to either coenzyme A (CoA) or acyl carrier protein (ACP). To bridge the gap between the pimelate thioester and its dedicated precursor acyl-CoA (or -ACP), thebioIgene ofBacillus subtilis, which encoded a P450 protein that cleaves a carbon-carbon bond of an acyl-ACP to generate pimeloyl-ACP, was further expressed in the engineered strain by using a plasmid system. This resulted in a biotin prototroph that is capable of thede novosynthesis of biotin. On the other hand, thebioYgene responsible for biotin uptake was disrupted in wild-typeC. glutamicum. Whereas the wild-type strain required approximately 1 μg of biotin per liter for normal growth, thebioYdisruptant (ΔbioY) required approximately 1 mg of biotin per liter, almost 3 orders of magnitude higher than the wild-type level. The ΔbioYstrain showed a similar high requirement for the precursor dethiobiotin, a substrate forbioB-encoded biotin synthase. To eliminate the dependency on dethiobiotin, thebioBgene was further disrupted in both the wild-type strain and the ΔbioYstrain. By selectively using the resulting two strains (ΔbioBand ΔbioBY) as indicator strains, we developed a practical biotin bioassay system that can quantify biotin in the seven-digit range, from approximately 0.1 μg to 1 g per liter. This bioassay proved that the engineered biotin prototroph ofC. glutamicumproduced biotin directly from glucose, albeit at a marginally detectable level (approximately 0.3 μg per liter).
The Highly Autoaggregative and Adhesive Phenotype of the Vaginal Lactobacillus plantarum Strain CMPG5300 Is Sortase Dependent
Authors: Malik Shweta , Petrova Mariya I. , Claes Ingmar J. J. , Verhoeven Tine L. A. , Busschaert Pieter , Vaneechoutte Mario , Lievens Bart , Lambrichts Ivo , Siezen Roland J. , Balzarini Jan , Vanderleyden Jos , Lebeer Sarah 
Published: May 2013

ABSTRACT

Lactobacilli are important for the maintenance of a healthy ecosystem in the human vagina. Various mechanisms are postulated but so far are poorly substantiated by molecular studies, such as mutant analysis. Bacterial autoaggregation is an interesting phenomenon that can promote adhesion to host cells and displacement of pathogens. In this study, we report on the identification of a human vaginal isolate,
Lactobacillus plantarum
strain CMPG5300, which shows high autoaggregative and adhesive capacity. To investigate the importance of sortase-dependent proteins (SDPs) in these phenotypes, a gene deletion mutant was constructed for
srtA
, the gene encoding the housekeeping sortase that covalently anchors these SDPs to the cell surface. This mutant lost the capacity to autoaggregate, showed a decrease in adhesion to vaginal epithelial cells, and lost biofilm-forming capacity under the conditions tested. These results indicate that the housekeeping sortase SrtA of CMPG5300 is a key determinant of the peculiar surface properties of this vaginal
Lactobacillus
strain.
Precipitation of Iron on the Surface of Leptospira interrogans Is Associated with Mutation of the Stress Response Metalloprotease HtpX
Authors: Henry Rebekah , Lo Miranda , Khoo Chenai , Zhang Hailong , Boysen Reinhard I. , Picardeau Mathieu , Murray Gerald L. , Bulach Dieter M. , Adler Ben 
Published: May 2013

ABSTRACT

High concentrations of free metal ions in the environment can be detrimental to bacterial survival. However, bacteria utilize strategies, including the activation of stress response pathways and immobilizing chemical elements on their surface, to limit this toxicity. In this study, we characterized LA4131, the HtpX-like M48 metalloprotease from
Leptospira interrogans
, with a putative role in bacterial stress response and membrane homeostasis. Growth of the
la4131
transposon mutant strain (L522) in 360 μM FeSO
4
(10-fold the normal
in vitro
concentration) resulted in the production of an amorphous iron precipitate. Atomic force microscopy and transmission electron microscopy analysis of the strain demonstrated that precipitate production was associated with the generation and release of outer membrane vesicles (OMVs) from the leptospiral surface. Transcriptional studies indicated that inactivation of
la4131
resulted in altered expression of a subset of metal toxicity and stress response genes. Combining these findings, this report describes OMV production in response to environmental stressors and associates OMV production with the
in vitro
activity of an HtpX-like metalloprotease.
A Stable Hybrid Containing Haploid Genomes of Two Obligate Diploid Candida Species
Authors: Chakraborty Uttara , Mohamed Aiyaz , Kakade Pallavi , Mugasimangalam Raja C. , Sadhale Parag P. , Sanyal Kaustuv 
Published: May 2013

ABSTRACT

Candida albicans
and
Candida dubliniensis
are diploid, predominantly asexual human-pathogenic yeasts. In this study, we constructed tetraploid (4
n
) strains of
C. albicans
of the same or different lineages by spheroplast fusion. Induction of chromosome loss in the tetraploid
C. albicans
generated diploid or near-diploid progeny strains but did not produce any haploid progeny. We also constructed stable heterotetraploid somatic hybrid strains (2
n
+ 2
n
) of
C. albicans
and
C. dubliniensis
by spheroplast fusion. Heterodiploid (
n
+
n
) progeny hybrids were obtained after inducing chromosome loss in a stable heterotetraploid hybrid. To identify a subset of hybrid heterodiploid progeny strains carrying at least one copy of all chromosomes of both species, unique centromere sequences of various chromosomes of each species were used as markers in PCR analysis. The reduction of chromosome content was confirmed by a comparative genome hybridization (CGH) assay. The hybrid strains were found to be stably propagated. Chromatin immunoprecipitation (ChIP) assays with antibodies against centromere-specific histones (
C. albicans
Cse4/
C. dubliniensis
Cse4) revealed that the centromere identity of chromosomes of each species is maintained in the hybrid genomes of the heterotetraploid and heterodiploid strains. Thus, our results suggest that the diploid genome content is not obligatory for the survival of either
C. albicans
or
C. dubliniensis
. In keeping with the recent discovery of the existence of haploid
C. albicans
strains, the heterodiploid strains of our study can be excellent tools for further species-specific genome elimination, yielding true haploid progeny of
C. albicans
or
C. dubliniensis
in future.
Frequency and Genetic Diversity of the
MAT1
Locus of Histoplasma capsulatum Isolates in Mexico and Brazil
Authors: Rodríguez-Arellanes Gabriela , Nascimento de Sousa Carolina , de Medeiros-Muniz Mauro , Ramírez José A. , Pizzini Cláudia V. , de Abreu-Almeida Marcos , Evangelista de Oliveira Manoel M. , Fusco-Almeida Ana-Marisa , Vite-Garín Tania , Pitangui Nayla S. , Estrada-Bárcenas Daniel A. , González-González Antonio E. , Mendes-Giannini María José Soares , Zancopé-Oliveira Rosely M. , Taylor Maria-Lucia 
Published: May 2013

ABSTRACT

The
MAT1-1
and
MAT1-2
idiomorphs associated with the
MAT1
locus of
Histoplasma capsulatum
were identified by PCR. A total of 28 fungal isolates, 6 isolates from human clinical samples and 22 isolates from environmental (infected bat and contaminated soil) samples, were studied. Among the 14 isolates from Mexico, 71.4% (95% confidence interval [95% CI], 48.3% to 94.5%) were of the
MAT1-2
genotype, whereas 100% of the isolates from Brazil were of the
MAT1-1
genotype. Each
MAT1
idiomorphic region was sequenced and aligned, using the sequences of the G-217B (+ mating type) and G-186AR (− mating type) strains as references. BLASTn analyses of the
MAT1-1
and
MAT1-2
sequences studied correlated with their respective + and − mating type genotypes. Trees were generated by the maximum likelihood (ML) method to search for similarity among isolates of each
MAT1
idiomorph. All
MAT1-1
isolates originated from Brazilian bats formed a well-defined group; three isolates from Mexico, the G-217B strain, and a subgroup encompassing all soil-derived isolates and two clinical isolates from Brazil formed a second group; last, one isolate (EH-696P) from a migratory bat captured in Mexico formed a third group of the
MAT1-1
genotype. The
MAT1-2
idiomorph formed two groups, one of which included two
H. capsulatum
isolates from infected bats that were closely related to the G-186AR strain. The other group was formed by two human isolates and six isolates from infected bats. Concatenated ML trees, with internal transcribed spacer 1 (ITS1) -5.8S-ITS2 and
MAT1-1
or
MAT1-2
sequences, support the relatedness of
MAT1-1
or
MAT1-2
isolates.
H. capsulatum
mating types were associated with the geographical origin of the isolates, and all isolates from Brazil correlated with their environmental sources.
The Fission Yeast Synaptobrevin Ortholog Syb1 Plays an Important Role in Forespore Membrane Formation and Spore Maturation
Authors: Yamaoka Tomomi , Imada Kazuki , Fukunishi Kana , Yamasaki Yuriko , Shimoda Chikashi , Nakamura Taro 
Published: May 2013

ABSTRACT

Synaptobrevin, also called vesicle-associated membrane protein (VAMP), is a component of the plasma membrane N-methylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, which plays a key role in intracellular membrane fusion. Previous studies have revealed that, similar to synaptobrevin in other organisms, the fission yeast synaptobrevin ortholog Syb1 associates with post-Golgi secretory vesicles and is essential for cytokinesis and cell elongation. Here, we report that Syb1 has a role in sporulation. After nitrogen starvation, green fluorescent protein (GFP)-Syb1 is found in intracellular dots. As meiosis proceeds, GFP-Syb1 accumulates around the nucleus and then localizes at the forespore membrane (FSM). We isolated a
syb-S1
mutant, which exhibits a defect in sporulation. In
syb1-S1
mutants, the FSM begins to form but fails to develop a normal morphology. Electron microscopy shows that an abnormal spore wall is often formed in
syb1-S1
mutant spores. Although most
syb1-S1
mutant spores are germinated, they are less tolerant to ethanol than wild-type spores. The
syb1-S1
allele carries a missense mutation, resulting in replacement of a conserved cysteine residue adjacent to the transmembrane domain, which reduces the stability and abundance of the Syb1 protein. Taken together, these results indicate that Syb1 plays an important role in both FSM assembly and spore wall formation.
Environmentally Regulated Glycosome Protein Composition in the African Trypanosome
Authors: Bauer Sarah , Morris James C. , Morris Meredith T. 
Published: May 2013

ABSTRACT

Trypanosomes compartmentalize many metabolic enzymes in glycosomes, peroxisome-related microbodies that are essential to parasite survival. While it is understood that these dynamic organelles undergo profound changes in protein composition throughout life cycle differentiation, the adaptations that occur in response to changes in environmental conditions are less appreciated. We have adopted a fluorescent-organelle reporter system in procyclic
Trypanosoma brucei
by expressing a fluorescent protein (FP) fused to a glycosomal targeting sequence (peroxisome-targeting sequence 2 [PTS2]). In these cell lines, PTS2-FP is localized within import-competent glycosomes, and organelle composition can be analyzed by microscopy and flow cytometry. Using this reporter system, we have characterized parasite populations that differ in their glycosome composition. In glucose-rich medium, two parasite populations are observed; one population harbors glycosomes bearing the full repertoire of glycosome proteins, while the other parasite population contains glycosomes that lack the usual glycosome-resident proteins but do contain the glycosome membrane protein TbPEX11. Interestingly, these cells lack TbPEX13, a protein essential for the import of proteins into the glycosome. This bimodal distribution is lost in low-glucose medium. Furthermore, we have demonstrated that changes in environmental conditions trigger changes in glycosome protein composition. These findings demonstrate a level of procyclic glycosome diversity heretofore unappreciated and offer a system by which glycosome dynamics can be studied in live cells. This work adds to our growing understanding of how the regulation of glycosome composition relates to environmental sensing.
Three Prevacuolar Compartment Rab GTPases Impact Candida albicans Hyphal Growth
Authors: Johnston Douglas A. , Tapia Arturo Luna , Eberle Karen E. , Palmer Glen E. 
Published: May 2013

ABSTRACT

Disruption of vacuolar biogenesis in the pathogenic yeast
Candida albicans
causes profound defects in polarized hyphal growth. However, the precise vacuolar pathways involved in yeast-hypha differentiation have not been determined. Previously we focused on Vps21p, a Rab GTPase involved in directing vacuolar trafficking through the late endosomal
p
re
v
acuolar
c
ompartment (PVC). Herein, we identify two additional Vps21p-related GTPases, Ypt52p and Ypt53p, that colocalize with Vps21p and can suppress the hyphal defects of the
vps21
Δ/Δ mutant. Phenotypic analysis of gene deletion strains revealed that loss of both
VPS21
and
YPT52
causes synthetic defects in endocytic trafficking to the vacuole, as well as delivery of the virulence-associated vacuolar membrane protein Mlt1p from the Golgi compartment. Transcription of all three GTPase-encoding genes is increased under hyphal growth conditions, and overexpression of the transcription factor Ume6p is sufficient to increase the transcription of these genes. While only the
vps21
Δ/Δ single mutant has hyphal growth defects, these were greatly exacerbated in a
vps21
Δ/Δ
ypt52
Δ/Δ double mutant. On the basis of relative expression levels and phenotypic analysis of gene deletion strains, Vps21p is the most important of the three GTPases, followed by Ypt52p, while Ypt53p has an only marginal impact on
C. albicans
physiology. Finally, disruption of a nonendosomal AP-3-dependent vacuolar trafficking pathway in the
vps21
Δ/Δ
ypt52
Δ/Δ mutant, further exacerbated the stress and hyphal growth defects. These findings underscore the importance of membrane trafficking through the PVC in sustaining the invasive hyphal growth form of
C. albicans
.
Global Control of GacA in Secondary Metabolism, Primary Metabolism, Secretion Systems, and Motility in the Rhizobacterium Pseudomonas aeruginosa M18
Authors: Wei Xue , Huang Xianqing , Tang Lulu , Wu Daqiang , Xu Yuquan 
Published: May 2013

ABSTRACT

The rhizobacterium
Pseudomonas aeruginosa
M18 can produce a broad spectrum of secondary metabolites, including the antibiotics pyoluteorin (Plt) and phenazine-1-carboxylic acid (PCA), hydrogen cyanide, and the siderophores pyoverdine and pyochelin. The antibiotic biosynthesis of M18 is coordinately controlled by multiple distinct regulatory pathways, of which the GacS/GacA system activates Plt biosynthesis but strongly downregulates PCA biosynthesis. Here, we investigated the global influence of a
gacA
mutation on the M18 transcriptome and related metabolic and physiological processes. Transcriptome profiling revealed that the transcript levels of 839 genes, which account for approximately 15% of the annotated genes in the M18 genome, were significantly influenced by the
gacA
mutation during the early stationary growth phase of M18. Most secondary metabolic gene clusters, such as
pvd
,
pch
,
plt
,
amb
, and
hcn
, were activated by GacA. The GacA regulon also included genes encoding extracellular enzymes and cytochrome oxidases. Interestingly, the primary metabolism involved in the assimilation and metabolism of phosphorus, sulfur, and nitrogen sources was also notably regulated by GacA. Another important category of the GacA regulon was secretion systems, including H1, H2, and H3 (type VI secretion systems [T6SSs]), Hxc (T2SS), and Has and Apr (T1SSs), and CupE and Tad pili. More remarkably, GacA inhibited swimming, swarming, and twitching motilities. Taken together, the Gac-initiated global regulation, which was mostly mediated through multiple regulatory systems or factors, was mainly involved in secondary and primary metabolism, secretion systems, motility, etc., contributing to ecological or nutritional competence, ion homeostasis, and biocontrol in M18.
Carbohydrate Kinase (RhaK)-Dependent ABC Transport of Rhamnose in Rhizobium leguminosarum Demonstrates Genetic Separation of Kinase and Transport Activities
Authors: Rivers Damien , Oresnik Ivan J. 
Published: May 2013

ABSTRACT

In
Rhizobium leguminosarum
the ABC transporter responsible for rhamnose transport is dependent on RhaK, a sugar kinase that is necessary for the catabolism of rhamnose. This has led to a working hypothesis that RhaK has two biochemical functions: phosphorylation of its substrate and affecting the activity of the rhamnose ABC transporter. To address this hypothesis, a linker-scanning random mutagenesis of
rhaK
was carried out. Thirty-nine linker-scanning mutations were generated and mapped. Alleles were then systematically tested for their ability to physiologically complement kinase and transport activity in a strain carrying an
rhaK
mutation. The
rhaK
alleles generated could be divided into three classes: mutations that did not affect either kinase or transport activity, mutations that eliminated both transport and kinase activity, and mutations that affected transport activity but not kinase activity. Two genes of the last class (
rhaK72
and
rhaK73
) were found to have similar biochemical phenotypes but manifested different physiological phenotypes. Whereas
rhaK72
conferred a slow-growth phenotype when used to complement
rhaK
mutants, the
rhaK73
allele did not complement the inability to use rhamnose as a sole carbon source. To provide insight to how these insertional variants might be affecting rhamnose transport and catabolism, structural models of RhaK were generated based on the crystal structure of related sugar kinases. Structural modeling suggests that both
rhaK72
and
rhaK73
affect surface-exposed residues in two distinct regions that are found on one face of the protein, suggesting that this protein's face may play a role in protein-protein interaction that affects rhamnose transport.