bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microbial Interactions within a Cheese Microbial Community
Authors: Mounier Jérôme , Monnet Christophe , Vallaeys Tatiana , Arditi Roger , Sarthou Anne-Sophie , Hélias Arnaud , Irlinger Françoise 
Published: November 2007

ABSTRACT

The interactions that occur during the ripening of smear cheeses are not well understood. Yeast-yeast interactions and yeast-bacterium interactions were investigated within a microbial community composed of three yeasts and six bacteria found in cheese. The growth dynamics of this community was precisely described during the ripening of a model cheese, and the Lotka-Volterra model was used to evaluate species interactions. Subsequently, the effects on ecosystem functioning of yeast omissions in the microbial community were evaluated. It was found both in the Lotka-Volterra model and in the omission study that negative interactions occurred between yeasts.
Yarrowia lipolytica
inhibited mycelial expansion of
Geotrichum candidum
, whereas
Y. lipolytica
and
G. candidum
inhibited
Debaryomyces hansenii
cell viability during the stationary phase. However, the mechanisms involved in these interactions remain unclear. It was also shown that yeast-bacterium interactions played a significant role in the establishment of this multispecies ecosystem on the cheese surface. Yeasts were key species in bacterial development, but their influences on the bacteria differed. It appeared that the growth of
Arthrobacter arilaitensis
or
Hafnia alvei
relied less on a specific yeast function because these species dominated the bacterial flora, regardless of which yeasts were present in the ecosystem. For other bacteria, such as
Leucobacter
sp. or
Brevibacterium aurantiacum
, growth relied on a specific yeast, i.e.,
G. candidum
. Furthermore,
B. aurantiacum
,
Corynebacterium casei
, and
Staphylococcus xylosus
showed reduced colonization capacities in comparison with the other bacteria in this model cheese. Bacterium-bacterium interactions could not be clearly identified.
Novel Candidate Virulence Factors in Rice Pathogen
Xanthomonas oryzae
pv. oryzicola as Revealed by Mutational Analysis
Authors: Wang Li , Makino Seiko , Subedee Ashim , Bogdanove Adam J. 
Published: November 2007

ABSTRACT

Bacterial leaf streak, caused by
Xanthomonas oryzae
pv. oryzicola, is an important disease of rice. Transposon-mediated mutational analysis of the pathogen with a quantitative assay revealed candidate virulence factors including genes involved in the pathogenesis of other phytopathogenic bacteria, virulence factors of animal pathogens, and genes not previously associated with virulence.
Novel Mechanism for Conditional Aerobic Growth of the Anaerobic Bacterium
Treponema denticola
Authors: Lai Yanlai , Chu Lianrui 
Published: November 2007

ABSTRACT

Treponema denticola
, a periodontal pathogen, has recently been shown to exhibit properties of a facultative anaerobic spirochete, in contrast to its previous recognition as an obligate anaerobic bacterium. In this study, the capacity and possible mechanism of
T. denticola
survival and growth under aerobic conditions were investigated. Factors detrimental to the growth of
T. denticola
ATCC 33405, such as oxygen concentration and hydrogen sulfide (H
2
S) levels as well as the enzyme activities of gamma-glutamyltransferase, cysteinylglycinase, and cystalysin associated with the cells were monitored. The results demonstrated that
T. denticola
grew only at deeper levels of broth (≥3 ml in a 10-ml tube), high inoculation ratios (≥20% of culture in medium), and short cultivation times (≤4 days for one passage) and in media containing
l
-cysteine or glutathione as the substrate for H
2
S production during aerobic growth. The determination of the factors showed that oxygen levels were always lower (0 to 0.6%) with significantly higher concentrations of H
2
S and higher activities of the three enzymes in all cultures grown aerobically. Further data revealed that H
2
S production from the
T. denticola
enzymes plus their substrates resulted in removal of dissolved O
2
in the growth cultures in a dose-dependent manner. These results demonstrated that
T. denticola
was able to generate microanaerobic environments in growth media for its survival and growth under aerobic conditions. Furthermore, the organism can be defined as a true obligate anaerobic spirochete. These findings suggest that spirochetes may play a significant role in maintaining the anaerobic environment at diseased sites in periodontitis.
Defining Targets for Complement Components C4b and C3b on the Pathogenic Neisseriae
Authors: Lewis Lisa A. , Ram Sanjay , Prasad Alpana , Gulati Sunita , Getzlaff Silke , Blom Anna M. , Vogel Ulrich , Rice Peter A. 
Published: November 2007

ABSTRACTComplement is a key arm of the innate immune defenses against the pathogenic neisseriae. We previously identified lipooligosaccharide onNeisseria meningitidisas an acceptor for complement C4b. Little is known about other neisserial targets for complement proteins C3 and C4, which covalently attach to bacterial surfaces and initiate opsonization and killing. In this study we demonstrate thatNeisseria gonorrhoeaeporin (Por) 1B selectively binds C4b via amide linkages and C3b via ester linkages. Using strains expressing hybrid Por1A/1B molecules, a region spanned by loops 4 and 5 of Por1B was identified as the preferred binding site for C4b. We also identified the opacity protein (Opa), a major adhesin of pathogenic neisseriae, as a target for C4b and C3b on bothN. meningitidisandN. gonorrhoeae. UsingN. gonorrhoeaevariants that predominantly expressed individual Opa proteins, we found that all Opa proteins tested (A, B, C, D, E, F, and I) bound C4b and C3b via amide and ester linkages, respectively. Amide linkages with Por1B and Opa were confirmed using serum containing only the C4A isoform, which exclusively forms amide linkages with targets. While monomers and heterodimers of C4Ab were detected on bacterial targets, C4Bb appeared to preferentially participate in heterodimer (C5 convertase) formation. Our data provide another explanation for the enhanced serum sensitivity of Por1B-bearing gonococci. The binding of C3b and C4b to Opa provides a rationale for the recovery of predominantly “transparent” (Opa-negative) neisserial isolates from persons with invasive disease, where the bacteria encounter high levels of complement.
Duplicate Copies oflic1Direct the Addition of Multiple Phosphocholine Residues in the Lipopolysaccharide ofHaemophilus influenzae
Authors: Fox Kate L. , Li Jianjun , Schweda Elke K. H. , Vitiazeva Varvara , Makepeace Katherine , Jennings Michael P. , Moxon E. Richard , Hood Derek W. 
Published: November 2007

ABSTRACTThe genes of thelic1operon (lic1Atolic1D) are responsible for incorporation of phosphocholine (PCho) into the lipopolysaccharide (LPS) ofHaemophilus influenzae. PCho plays a multifaceted role in the commensal and pathogenic lifestyles of a range of mucosal pathogens, includingH. influenzae. Structural studies of the LPS of nontypeableH. influenzae(NTHI) have revealed that PCho can be linked to a hexose on any one of the oligosaccharide chain extensions from the conserved inner core triheptosyl backbone. In a collection of NTHI strains we found several strains in which there were two distinct but variantlic1DDNA sequences, genes predicted to encode the transferase responsible for directing the addition of PCho to LPS. The same isolates were also found to express concomitantly two PCho residues at distinct positions in their LPS. In one such NTHI isolate, isolate 1158, structural analysis of LPS fromlic1mutants confirmed that each of the two copies oflic1Ddirects the addition of PCho to a distinct location on the LPS. One position for PCho addition is a novel heptose, which is part of the oligosaccharide extension from the proximal heptose of the LPS inner core. Modification of the LPS by addition of two PCho residues resulted in increased binding of C-reactive protein and had consequential effects on the resistance of the organism to the killing effects of normal human serum compared to the effects of glycoforms containing one or no PCho. When bound, C-reactive protein leads to complement-mediated killing, indicating the potential biological significance of multiple PCho residues.
Global Transcriptome Analysis ofBorrelia burgdorferiduring Association with Human Neuroglial Cells
Authors: Livengood Jill A. , Schmit Virginia L. , Gilmore Robert D. 
Published: November 2007

ABSTRACTAs adherence and entry of a pathogen into a host cell are key components to an infection, identifying the molecular mechanisms responsible for cellular association will provide a better understanding of a microbe's pathogenesis. We previously established an in vitro model forBorrelia burgdorferiinfection of human neuroglial cells. To expand on our earlier study, we performedB. burgdorferiwhole-genome expression analysis following a 20-hour infection of human neuroglial cells to identify borrelial genes that were differentially regulated during host-cell association compared with culturedBorreliain cell-free medium. This study identifies several regulated genes, the products of which may be important mediators of cellular pathogenesis.
Role of the BBA64 Locus of
Borrelia burgdorferi
in Early Stages of Infectivity in a Murine Model of Lyme Disease
Authors: Maruskova Mahulena , Esteve-Gassent M. Dolores , Sexton Valerie L. , Seshu J. 
Published: November 2007

ABSTRACT

Borrelia burgdorferi
, the causative agent of Lyme disease, undergoes rapid adaptive gene expression in response to environmental signals encountered during different stages of its life cycle in the arthropod vector or the mammalian host. Among all the plasmid-encoded genes of
B. burgdorferi
, several linear plasmid 54 (lp54)-encoded open reading frames (ORFs) exhibit the greatest differential expression in response to mammalian host-specific temperature, pH, and other uncharacterized signals. These ORFs include members of the paralogous gene family 54 (pgf 54), such as BBA64, BBA65, and BBA66, present on lp54. In an attempt to correlate transcriptional up-regulation of these pgf 54 members to their role in infectivity, we inactivated BBA64 and characterized the phenotype of this mutant both in vitro and in vivo. There were no major differences in the protein profiles between the BBA64 mutant and the control strains, while immunoblot analysis indicated that inactivation of BBA64 resulted in increased levels of BBA65. Moreover, there was no significant difference in the ability of the BBA64 mutant to infect C3H/HeN mice compared to that of its parental or complemented control strains as determined by culturing of viable spirochetes from infected tissues. However, enumeration of spirochetes using quantitative real-time PCR revealed tissue-specific differences, suggesting a minimal role for BBA64 in the survival of
B. burgdorferi
in select tissues. Infectivity analysis of the BBA64 mutant suggests that
B. burgdorferi
may utilize multiple determinants to establish infection in mammalian hosts.
Enteropathogenic
Escherichia coli
O125:H6 Triggers Attaching and Effacing Lesions on Human Intestinal Biopsy Specimens Independently of Nck and TccP/TccP2
Authors: Bai Li , Schüller Stephanie , Whale Andrew , Mousnier Aurelie , Marches Olivier , Wang Lei , Ooka Tadasuke , Heuschkel Robert , Torrente Franco , Kaper James B. , Gomes Tânia A. T. , Xu Jianguo , Phillips Alan D. , Frankel Gad 
Published: November 2007

ABSTRACT

Typical enteropathogenic
Escherichia coli
(EPEC) and enterohemorrhagic
E. coli
(EHEC) employ either Nck, TccP/TccP2, or Nck and TccP/TccP2 pathways to activate the neuronal Wiskott-Aldrich syndrome protein (N-WASP) and to trigger actin polymerization in cultured cells. This phenotype is used as a marker for the pathogenic potential of EPEC and EHEC strains. In this paper we report that EPEC O125:H6, which represents a large category of strains, lacks the ability to utilize either Nck or TccP/TccP2 and hence triggers actin polymerization in vitro only inefficiently. However, we show that infection of human intestinal biopsies with EPEC O125:H6 results in formation of typical attaching and effacing lesions. Expression of TccP in EPEC O125:H6, which harbors an EHEC O157-like Tir, resulted in efficient actin polymerization in vitro and enhanced colonization of human intestinal in vitro organ cultures with detectable N-WASP and electron-dense material at the site of bacterial adhesion. These results show the existence of a natural category of EPEC that colonizes the gut mucosa using Nck- and TccP-independent mechanisms. Importantly, the results highlight yet again the fact that conclusions made on the basis of in vitro cell culture models cannot be extrapolated wholesale to infection of mucosal surfaces and that the ability to induce actin polymerization on cultured cells should not be used as a definitive marker for EPEC and EHEC virulence.
Lipidation of an FlrC-Dependent Protein Is Required for Enhanced Intestinal Colonization by
Vibrio cholerae
Authors: Morris David C. , Peng Fen , Barker Jeffrey R. , Klose Karl E. 
Published: November 2007

ABSTRACT

Vibrio cholerae
, the causative agent of cholera, has a sheathed, polar flagellum, and motility has been linked to virulence. An operon with two genes,
flgO
and
flgP
(VC2207 and VC2206), is positively regulated by FlrC, the activator of class III flagellar genes. Deletion of
flgP
results in a nonmotile phenotype, demonstrating the requirement of this gene for
V. cholerae
motility.
V. cholerae
Δ
flgP
cells synthesize fragile and defective flagella but transcribe flagellar genes similar to the wild-type strain. PhoA fusion analysis indicated that the putative lipoprotein FlgP is localized external to the cytoplasm, and fractionation demonstrated that it was localized to the outer membrane. Mutagenesis of the site of lipidation of FlgP (C18G) prevented [
3
H]palmitate incorporation and outer membrane localization. Interestingly, FlgP with the mutation C18G [FlgP(C18G)] could complement the Δ
flgP
mutant for motility, and the cells synthesized wild-type flagella. The Δ
flgP
mutant strain was defective for intestinal colonization (∼20-fold), but FlgP(C18G) was unable to complement this defect, demonstrating that lipidation of FlgP is essential for its role in intestinal colonization but not flagellar synthesis. FlgP thus represents a novel
V. cholerae
intestinal colonization factor that is regulated by the flagellar transcription hierarchy.
Extensive Proliferation of Transposable Elements in Heritable Bacterial Symbionts
Authors: Plague Gordon R. , Dunbar Helen E. , Tran Phat L. , Moran Nancy A. 
Published: November 2007

ABSTRACT
We found that insertion sequence (IS) elements are unusually abundant in the relatively recently evolved bacterial endosymbionts of maize weevils. Because multicopy elements can facilitate genomic recombination and deletion, this IS expansion may represent an early stage in the genomic reduction that is common in most ancient endosymbionts.
Interactions of an EssentialBacillus subtilisGTPase, YsxC, with Ribosomes
Authors: Wicker-Planquart Catherine , Foucher Anne-Emmanuelle , Louwagie Mathilde , Britton Robert A. , Jault Jean-Michel 
Published: November 2007

ABSTRACTYsxC is a small GTPase ofBacillus subtiliswith essential but still unknown function, although recent works have suggested that it might be involved in ribosome biogenesis. Here, purified YsxC overexpressed inEscherichia coliwas found to be partly associated with high-molecular-weight material, most likely rRNA, and thus eluted from gel filtration as a large complex. In addition, purification of ribosomes from anE. colistrain overexpressing YsxC allowed the copurification of the YsxC protein. Purified YsxC was shown to bind preferentially to the 50S subunit ofB. subtilisribosomes; this interaction was modulated by nucleotides and was stronger in the presence of a nonhydrolyzable GTP analogue than with GTP. Far-Western blotting analysis performed with His6-YsxC and ribosomal proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that YsxC interacted with at least four ribosomal proteins from the 50S subunit. Two of these putative protein partners were identified by mass spectrometry as L1 and L3, while the third reactive band in the one-dimensional gel contained L6 and L10. The fourth band that reacted with YsxC contained a mixture of three proteins, L7/L12, L23, and L27, suggesting that at least one of them binds to YsxC. Coimmobilization assays confirmed that L1, L6, and L7/L12 interact with YsxC. Together, these results suggest that YsxC plays a role in ribosome assembly.
Characterization of Integrative and Conjugative Element ICEKp1-Associated Genomic Heterogeneity in aKlebsiella pneumoniaeStrain Isolated from a Primary Liver Abscess
Authors: Lin Tzu-Lung , Lee Cha-Ze , Hsieh Pei-Fang , Tsai Shih-Feng , Wang Jin-Town 
Published: November 2007

ABSTRACTGenomic heterogeneity has been shown to be associated withKlebsiella pneumoniaestrains causing pyogenic liver abscesses (PLA) and metastatic infections. In order to explore the mechanism responsible for genomic heterogeneity inK. pneumoniae, we compared the complete genomic sequences of strains NTUH-K2044 and MGH78578. An ∼76-kbp DNA fragment located adjacent to an asparagine (asn) tRNA gene was present in NTUH-K2044 but not in MGH78578. This fragment could be divided into three regions with different functions, and structurally it resembled a functional integrative and conjugative element (ICE), ICEEc1, inEscherichia coli. The 5′ region of this fragment contained genes similar to a high-pathogenicity island (HPI) ofYersinia pestisandYersinia pseudotuberculosis. The middle region was similar to part of a large plasmid inK. pneumoniae, and the 3′ region contained genes responsible for DNA conjugative transfer. Therefore, this DNA fragment was designated ICEKp1. Precise excision and extrachromosomal circularization of ICEKp1were detected inK. pneumoniaewild-type strain NTUH-K2044. ICEKp1could integrate into theasntRNA loci of the chromosome of anotherK. pneumoniaeisolate. The prevalence of ICEKp1was higher in PLA strains (38 of 42 strains) than in non-tissue-invasive strains (5 of 32 strains). Therefore, ICEKp1may contribute to the transmission of the HPI and result inK. pneumoniaePLA infection-associated genomic heterogeneity.
One Pathway Can Incorporate either Adenine or Dimethylbenzimidazole as an α-Axial Ligand of B
12
Cofactors in
Salmonella enterica
Authors: Anderson Peter J. , Lango Jozsef , Carkeet Colleen , Britten Audrey , Kräutler Bernhard , Hammock Bruce D. , Roth John R. 
Published: November 2007

ABSTRACT

Corrinoid (vitamin B
12
-like) cofactors contain various α-axial ligands, including 5,6-dimethylbenzimidazole (DMB) or adenine. The bacterium
Salmonella enterica
produces the corrin ring only under anaerobic conditions, but it can form “complete” corrinoids aerobically by importing an “incomplete” corrinoid, such as cobinamide (Cbi), and adding appropriate α- and β-axial ligands. Under aerobic conditions,
S. enterica
performs the corrinoid-dependent degradation of ethanolamine if given vitamin B
12
, but it can make B
12
from exogenous Cbi only if DMB is also provided. Mutants isolated for their ability to degrade ethanolamine without added DMB converted Cbi to pseudo-B
12
cofactors (having adenine as an α-axial ligand). The mutations cause an increase in the level of free adenine and install adenine (instead of DMB) as an α-ligand. When DMB is provided to these mutants, synthesis of pseudo-B
12
cofactors ceases and B
12
cofactors are produced, suggesting that DMB regulates production or incorporation of free adenine as an α-ligand. Wild-type cells make pseudo-B
12
cofactors during aerobic growth on propanediol plus Cbi and can use pseudo-vitamin B
12
for all of their corrinoid-dependent enzymes. Synthesis of coenzyme pseudo-B
12
cofactors requires the same enzymes (CobT, CobU, CobS, and CobC) that install DMB in the formation of coenzyme B
12
. Models are described for the mechanism and control of α-axial ligand installation.
The Leucine-Responsive Regulatory Protein, Lrp, Activates Transcription of thefimOperon inSalmonella entericaSerovar Typhimurium via thefimZRegulatory Gene
Authors: McFarland Kirsty A. , Lucchini Sacha , Hinton Jay C. D. , Dorman Charles J. 
Published: November 2007

ABSTRACTThefimoperon ofSalmonella entericaserovar Typhimurium encodes type 1 fimbriae. The expression offimis controlled in response to environmental signals through a complex regulatory cascade involving the proteins FimW, FimY, and FimZ and a genetic locus,fimU, that encodes a rare arginine tRNA. We discovered that a knockout mutation inlrp, the gene that codes for the leucine-responsive regulatory protein (Lrp), inhibitedfimtranscription. The loss offimgene expression was accompanied by a corresponding loss of the mannose-sensitive hemagglutination that is a characteristic of type 1 fimbriae. Normal type 1 fimbrial expression was restored following the introduction into the knockout mutant of a plasmid carrying a functional copy of thelrpgene. Electrophoretic mobility shift analysis revealed no interactions between purified Lrp protein and the regulatory region of thefimA,fimU, orfimWgene. Instead, Lrp produced protein-DNA complexes with the regulatory region of thefimZgene, and the nature of these complexes was leucine sensitive. DNase I footprinting showed that Lrp binds within a region between −65 and −170 with respect to thefimZtranscription start site, consistent with the binding and wrapping of the DNA in this upstream region. Ectopic expression of thefimZgene from an inducible promoter caused Lrp-independent type 1 fimbriation in serovar Typhimurium. These data show that Lrp makes a positive contribution tofimgene expression through direct interaction with thefimZpromoter region, possibly by antagonizing the binding of the H-NS global repressor protein.
Effect of L-carnitine administration on the modulated rat brain protein concentration, acetylcholinesterase, Na+K+-ATPase and Mg2+-ATPase activities induced by forced swimming
Authors: Tsakiris T , Angelogianni P , Tesseromatis C , Tsakiris S , Schulpis K H 
Published: November 2007

Background:Forced exercise produces free radicals and L-carnitine (L-C) administration reduces oxidative stress.Aim:To investigate whether short (2 hours) or prolonged (3 hours) forced swimming could modulate total antioxidant status (TAS), protein concentration and activities of acetylcholinesterase (AChE), Na+K+-ATPase and Mg2+-ATPase in rat brain following intraperitonal administration of L-C (300 mg/kg).Methods:TAS, protein and enzyme activities were measured spectrophotometrically.Results:TAS, protein concentration and AChE activity were reduced, whereas Na+K+-ATPase and Mg2+-ATPase were significantly increased after either 2 or 3 hours of training. L-C administration resulted in a profound restoration of TAS and protein concentration whereas AChE and Na+K+-ATPase were increased before exercise, followed by AChE restoration and Na+K+-ATPase reduction after exercise. Mg2+-ATPase remained unchanged. An in vitro study using L-C incubation of brain homogenates previously treated with L-C resulted in complete restoration of the modulated enzymes, whereas the enzyme activities from untreated animals remained unaltered.Conclusions:Short or prolonged swimming in rats may result in a reduction of brain TAS, protein concentration and AChE activity, and an activation of Na+K+-ATPase and Mg2+-ATPase. L-C administration may prevent reduction in TAS and protein concentration, and a decrease in AChE and Na+K+-ATPase activity; the latter reached pre-exercise values after L-C incubation.