bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inc A/C Plasmids Are Prevalent in Multidrug-Resistant
Salmonella enterica
Isolates
Authors: Lindsey Rebecca L. , Fedorka-Cray Paula J. , Frye Jonathan G. , Meinersmann Richard J. 
Published: January 2009

ABSTRACT

Bacterial plasmids are fragments of extrachromosomal double-stranded DNA that can contain a variety of genes that are beneficial to the host organism, like those responsible for antimicrobial resistance. The objective of this study was to characterize a collection of 437
Salmonella enterica
isolates from different animal sources for their antimicrobial resistance phenotypes and plasmid replicon types and, in some cases, by pulsed-field gel electrophoresis (PFGE) in an effort to learn more about the distribution of multidrug resistance in relation to replicon types. A PCR-based replicon typing assay consisting of three multiplex PCRs was used to detect 18 of the 26 known plasmid types in the
Enterobacteriaceae
based on their incompatibility (Inc) replicon types. Linkage analysis was completed with antibiograms, replicon types, serovars, and Inc A/C. Inc A/C plasmids were prevalent in multidrug-resistant isolates with the notable exception of
Salmonella enterica
serovar Typhimurium. Cluster analysis based on PFGE of a subset of 216 isolates showed 155 unique types, suggesting a variable population, but distinct clusters of isolates with Inc A/C plasmids were apparent. Significant linkage of serovar was also seen with Inc replicon types B/O, I1, Frep, and HI1. The present study showed that the combination of
Salmonella
, the Inc A/C plasmids, and multiple-drug-resistant genes is very old. Our results suggest that some strains, notably serovar Typhimurium and closely related types, may have once carried the plasmid but that the resistance genes were transferred to the chromosome with the subsequent loss of the plasmid.
Insights into Structure-Activity Relationships in the C-Terminal Region of Divercin V41, a Class IIa Bacteriocin with High-Level Antilisterial Activity
Authors: Rihakova Jitka , Petit Vanessa W. , Demnerova Katerina , Prévost Hervé , Rebuffat Sylvie , Drider Djamel 
Published: January 2009

ABSTRACT

Divercin V41 (DvnV41) is a class IIa bacteriocin with potent antilisterial activity isolated from
Carnobacterium divergens
V41. Previously, we expressed from a synthetic gene, in
Escherichia coli
Origami, a recombinant DvnV41 designated DvnRV41, which possesses four additional amino acids (AMDP) in the N-terminal region that result from enzymatic cleavage and retains the initial DvnV41 activity. To unravel the relationship between the structure of DvnRV41 and its particularly elevated activity, we produced by site-directed mutagenesis eight variants in which a single amino acid replacement was specifically introduced into the sequence. The point mutations were designed to change either conserved residues in class IIa bacteriocins or residues specific to DvnV41 located mainly in the C-terminal region. The fusion proteins were purified from the cytosoluble fractions by immobilized affinity chromatography. DvnRV41 and its variants were released from the fusion proteins by enzymatic cleavage, using enterokinase. The purity of DvnRV41 and of the variants was checked by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, high-performance liquid chromatography, and mass spectrometry. The antibacterial activity of DvnRV41 and its variants was assessed using different indicator strains, including
Listeria monocytogenes
EGDe and
Enterococcus faecalis
JH2-2. The activity of all of the variants appeared to be less than the activity of DvnRV41. The decrease in activity did not appear to be related to a global conformational change, as determined by circular dichroism. Overall, the variants of DvnRV41 produced in the present study provide interesting insights into structure-activity relationships of class IIa bacteriocins.
Complete Genome of the Broad-Host-Range
Erwinia amylovora
Phage ΦEa21-4 and Its Relationship to
Salmonella
Phage Felix O1
Authors: Lehman Susan M. , Kropinski Andrew M. , Castle Alan J. , Svircev Antonet M. 
Published: January 2009

ABSTRACT

The first complete genome sequence for a myoviridal bacteriophage, ΦEa21-4, infecting
Erwinia amylovora, Erwinia pyrifoliae
, and
Pantoea agglomerans
strains has been determined. The unique sequence of this terminally redundant, circularly permuted genome is 84,576 bp. The ΦEa21-4 genome has a GC content of 43.8% and contains 117 putative protein-coding genes and 26 tRNA genes. ΦEa21-4 is the first phage in which a precisely conserved rho-independent terminator has been found dispersed throughout the genome, with 24 copies in all. Also notable in the ΦEa21-4 genome are the presence of tRNAs with six- and nine-base anticodon loops, the absence of a small packaging terminase subunit, and the presence of
nadV
, a principle component of the NAD
+
salvage pathway, which has been found in only a few phage genomes to date. ΦEa21-4 is the first reported Felix O1-like phage genome; 56% of the predicted ΦEa21-4 proteins share homology with those of the
Salmonella
phage. Apart from this similarity to Felix O1, the ΦEa21-4 genome appears to be substantially different, both globally and locally, from previously reported sequences. A total of 43 of the 117 genes are unique to ΦEa21-4, and 32 of the Felix O1-like genes do not appear in any phage genome sequences other than ΦEa21-4 and Felix O1. N-terminal sequencing and matrix-assisted laser desorption ionization-time of flight analysis resulted in the identification of five ΦEa21-4 genes coding for virion structural proteins, including the major capsid protein.
Disruption of
Plasmodium
Sporozoite Transmission by Depletion of Sporozoite Invasion-Associated Protein 1
Authors: Engelmann Sabine , Silvie Olivier , Matuschewski Kai 
Published: January 2009

ABSTRACT

Accumulation of infectious
Plasmodium
sporozoites in
Anopheles
spp. salivary glands marks the final step of the complex development of the malaria parasite in the insect vector. Sporozoites are formed inside midgut-associated oocysts and actively egress into the mosquito hemocoel. Traversal of the salivary gland acinar cells correlates with the sporozoite's capacity to perform continuous gliding motility. Here, we characterized the cellular role of the
Plasmodium berghei
sporozoite invasion-associated protein 1 (SIAP-1). Intriguingly,
SIAP-1
orthologs are found exclusively in apicomplexan hemoprotozoa, parasites that are transmitted by arthropod vectors, e.g.,
Plasmodium
,
Babesia
, and
Theileria
species. By fluorescent tagging with mCherry, we show that SIAP-1 is expressed in oocyst-derived and salivary gland-associated sporozoites, where it accumulates at the apical tip. Targeted disruption of
SIAP-1
does not affect sporozoite formation but causes a partial defect in sporozoite egress from oocysts and abolishes sporozoite colonization of mosquito salivary glands. Parasites with the
siap-1
(−) mutation are blocked in their capacity to perform continuous gliding motility. We propose that arthropod-transmitted apicomplexan parasites specifically express secretory factors, such as SIAP-1, that mediate efficient oocyst exit and migration to the salivary glands.
Generation of Branched-Chain Fatty Acids through Lipoate-Dependent Metabolism Facilitates Intracellular Growth of
Listeria monocytogenes
Authors: Keeney Kristie , Colosi Lisa , Weber Walter , O'Riordan Mary 
Published: January 2009

ABSTRACT

The gram-positive bacterial pathogen
Listeria monocytogenes
has evolved mechanisms to rapidly replicate in the host cytosol, implying efficient utilization of host-derived nutrients. However, the contribution of host nutrient scavenging versus that of bacterial biosynthesis toward rapid intracellular growth remains unclear. Nutrients that contribute to growth of
L. monocytogenes
include branched-chain fatty acids (BCFAs), amino acids, and other metabolic intermediates generated from acyl-coenzyme A, which is synthesized using lipoylated metabolic enzyme complexes. To characterize which biosynthetic pathways support replication of
L. monocytogenes
inside the host cytosol, we impaired lipoate-dependent metabolism by disrupting two lipoate ligase genes that are responsible for bacterial protein lipoylation. Interrupting lipoate-dependent metabolism modestly impaired replication in rich broth medium but strongly inhibited growth in defined medium and host cells and impaired the generation of BCFAs. Addition of short BCFAs and amino acids restored growth of the A1A2-deficient (A1A2
−
) mutant in minimal medium, implying that lipoate-dependent metabolism generates amino acids and BCFAs. BCFAs alone rescued intracellular growth and spread in L2 fibroblasts of the A1A2
−
mutant. Lipoate-dependent metabolism was also required in vivo, as a wild-type strain robustly outcompeted the lipoylation-deficient mutant in a murine model of listeriosis. The results of this study suggest that lipoate-dependent metabolism contributes to both amino acid and BCFA biosynthesis and that BCFA biosynthesis is preferentially required for intracellular growth of
L. monocytogenes
.
The Orphan Response Regulator CovR: a Globally Negative Modulator of Virulence inStreptococcus suisSerotype 2
Authors: Pan Xiuzhen , Ge Junchao , Li Ming , Wu Bo , Wang Changjun , Wang Jing , Feng Youjun , Yin Zhimin , Zheng Feng , Cheng Gong , Sun Wen , Ji Hongfeng , Hu Dan , Shi Peiju , Feng Xiaodan , Hao Xina , Dong Ruiping , Hu Fuquan , Tang Jiaqi 
Published: January 2009

ABSTRACTStreptococcus suisserotype 2 is an emerging zoonotic pathogen responsible for a wide range of life-threatening diseases in pigs and humans. However, the pathogenesis ofS. suisserotype 2 infection is not well understood. In this study, we report that an orphan response regulator, CovR, globally regulates gene expression and negatively controls the virulence ofS. suis05ZYH33, a streptococcal toxic shock syndrome (STSS)-causing strain. AcovR-defective (ΔcovR) mutant of 05ZYH33 displayed dramatic phenotypic changes, such as formation of longer chains, production of thicker capsules, and increased hemolytic activity. Adherence of the ΔcovRmutant to epithelial cells was greatly increased, and its resistance to phagocytosis and killing by neutrophils and monocytes was also significantly enhanced. More importantly, inactivation ofcovRincreased the lethality ofS. suisserotype 2 in experimental infection of piglets, and this phenotype was restored bycovRcomplementation. Colonization experiments also showed that the ΔcovRmutant exhibited an increased ability to colonize susceptible tissues of piglets. The pleiotropic phenotype of the ΔcovRmutant is in full agreement with the large number of genes controlled by CovR as revealed by transcription profile analysis: 2 genes are positively regulated, and 193 are repressed, including many that encode known or putative virulence factors. These findings suggested that CovR is a global repressor in virulence regulation of STSS-causingS. suisserotype 2.
The Putrescine Importer PuuP of
Escherichia coli
K-12
Authors: Kurihara Shin , Tsuboi Yuichi , Oda Shinpei , Kim Hyeon Guk , Kumagai Hidehiko , Suzuki Hideyuki 
Published: January 2009

ABSTRACT

The Puu pathway is a putrescine utilization pathway involving gamma-glutamyl intermediates. The genes encoding the enzymes of the Puu pathway form a gene cluster, the
puu
gene cluster, and
puuP
is one of the genes in this cluster. In
Escherichia coli
, three putrescine importers, PotFGHI, PotABCD, and PotE, were discovered in the 1990s and have been studied; however, PuuP had not been discovered previously. This paper shows that PuuP is a novel putrescine importer whose kinetic parameters are equivalent to those of the polyamine importers discovered previously. A
puuP
+
strain absorbed up to 5 mM putrescine from the medium, but a Δ
puuP
strain did not.
E. coli
strain MA261 has been used in previous studies of polyamine transporters, but PuuP had not been identified previously. It was revealed that the
puuP
gene of MA261 was inactivated by a point mutation. When
E. coli
was grown on minimal medium supplemented with putrescine as the sole carbon or nitrogen source, only PuuP among the polyamine importers was required.
puuP
was expressed strongly when putrescine was added to the medium or when the
puuR
gene, which encodes a putative repressor, was deleted. When
E. coli
was grown in M9-tryptone medium, PuuP was expressed mainly in the exponential growth phase, and PotFGHI was expressed independently of the growth phase.
Creation of a Large Deletion Mutant ofCampylobacter jejuniReveals that the Lipooligosaccharide Gene Cluster Is Not Required for Viability
Authors: Marsden Gemma L. , Li Jianjun , Everest Paul H. , Lawson Andrew J. , Ketley Julian M. 
Published: January 2009

ABSTRACTDeletion of the lipooligosaccharide biosynthesis region (Cj1132c to Cj1152c) from the genome ofCampylobacter jejuniNCTC11168 shows that the core is not required for viability. The mutant was attenuated for growth and has increased sensitivity to antibiotics and detergents. Natural transformation and invasion of cultured host cells was abolished.
Two Redundant Sodium-Driven Stator Motor Proteins Are Involved in
Aeromonas hydrophila
Polar Flagellum Rotation
Authors: Wilhelms Markus , Vilches Silvia , Molero Raquel , Shaw Jonathan G. , Tomás Juan M. , Merino Susana 
Published: January 2009

ABSTRACT

Motility is an essential characteristic for mesophilic
Aeromonas
strains. We identified a new polar flagellum region (region 6) in the
A. hydrophila
AH-3 (serotype O34) chromosome that contained two additional polar stator genes, named
pomA
2
and
pomB
2.
A. hydrophila
PomA
2
and PomB
2
are highly homologous to other sodium-conducting polar flagellum stator motors as well as to the previously described
A. hydrophila
AH-3 PomA and PomB.
pomAB
and
pomA
2
B
2
were present in all the mesophilic
Aeromonas
strains tested and were independent of the strains' ability to produce lateral flagella. Unlike MotX, which is a stator protein that is essential for polar flagellum rotation, here we demonstrate that PomAB and PomA
2
B
2
are redundant sets of proteins, as neither set on its own is essential for polar flagellum motility in either aqueous or high-viscosity environments. Both PomAB and PomA
2
B
2
are sodium-coupled stator complexes, although PomA
2
B
2
is more sensitive to low concentrations of sodium than PomAB. Furthermore, the level of transcription in aqueous and high-viscosity environments of
pomA
2
B
2
is reduced compared to that of
pomAB
. The
A. hydrophila
AH-3 polar flagellum is the first case described in which two redundant sodium-driven stator motor proteins (PomAB and PomA
2
B
2
) are found.
Peptide wrwycr Inhibits the Excision of Several Prophages and Traps Holliday Junctions inside Bacteria
Authors: Gunderson Carl W. , Boldt Jeffrey L. , Authement R. Nathan , Segall Anca M. 
Published: January 2009

ABSTRACT

Peptide inhibitors of phage lambda site-specific recombination were previously isolated by screening synthetic combinatorial peptide libraries. These inhibitors cause the accumulation of complexes between the recombinase and the Holliday junction intermediate of several highly divergent tyrosine recombinases. Peptide WRWYCR and its
d
-amino acid derivative bind to the center of protein-free junctions and prevent their resolution either by site-specific recombinases or by junction resolvases or helicases. With lesser affinity, the peptides also bind to branched DNA molecules that mimic replication forks. The peptides are bactericidal to both gram-positive and gram-negative bacteria, presumably because they can interfere with DNA repair and with chromosome dimer resolution by the XerC and XerD tyrosine recombinases. In order to test the correspondence between their mechanism in vivo and in vitro, we have tested and shown peptide wrwycr's ability to inhibit the excision of several prophages (lambda, P22, Gifsy-1, Gifsy-2, Fels-1, Fels-2) and to trap Holliday junction intermediates of phage lambda site-specific recombination in vivo. In addition, we found that the peptide inhibits replication of the
Salmonella
prophage Fels-1 while integrated in the chromosome. These findings further support the proposed mechanistic basis for the antimicrobial activity of the peptide and its use as a tool to dissect strand exchange-dependent DNA repair within cells.
Role of Clp Proteins in Expression of Virulence Properties ofStreptococcus mutans
Authors: Kajfasz Jessica K. , Martinez Alaina R. , Rivera-Ramos Isamar , Abranches Jacqueline , Koo Hyun , Quivey Robert G. , Lemos José A. 
Published: January 2009

ABSTRACTMutational analysis revealed that members of the Clp system, specifically the ClpL chaperone and the ClpXP proteolytic complex, modulate the expression of important virulence attributes ofStreptococcus mutans. Compared to its parent, the ΔclpLstrain displayed an enhanced capacity to form biofilms in the presence of sucrose, had reduced viability, and was more sensitive to acid killing. The ΔclpPand ΔclpXstrains displayed several phenotypes in common: slow growth, tendency to aggregate in culture, reduced autolysis, and reduced ability to grow under stress, including acidic pH. Unexpectedly, the ΔclpPand ΔclpXmutants were more resistant to acid killing and demonstrated enhanced viability in long-term survival assays. Biofilm formation by the ΔclpPand ΔclpXstrains was impaired when grown in glucose but enhanced in sucrose. In an animal study, the average number ofS. mutanscolonies recovered from the teeth of rats infected with the ΔclpPor ΔclpXstrain was slightly lower than that of the parent strain. InBacillus subtilis, the accumulation of the Spx global regulator, a substrate of ClpXP, has accounted for the ΔclpXPphenotypes. Searching theS. mutansgenome, we identified two putativespxgenes, designatedspxAandspxB. The inactivation of either of these genes bypassed phenotypes of theclpPandclpXmutants. Western blotting demonstrated that Spx accumulates in the ΔclpPand ΔclpXstrains. Our results reveal that the proteolysis of ClpL and ClpXP plays a role in the expression of key virulence traits ofS. mutansand indicates that the underlying mechanisms by which ClpXP affect virulence traits are associated with the accumulation of two Spx orthologues.
YbeY, a Heat Shock Protein Involved in Translation in
Escherichia coli
Authors: Rasouly Aviram , Schonbrun Miriam , Shenhar Yotam , Ron Eliora Z. 
Published: January 2009

ABSTRACT

Here we provide evidence that YbeY, a conserved heat shock protein with unknown function, is involved in the translation process.
ybeY
deletion mutants are temperature sensitive and have a significantly reduced thermotolerance. Nonetheless, there appears to be no damage of the protein quality control of mature polypeptides, as the levels of chaperones and proteases are normal and there is no accumulation of aggregates. Rather, the mutation results in a significant reduction in the level of polysomes, and upon a shift to a restrictive temperature (42°C), there is an immediate and severe slowdown of translation. Taken together, the data indicate that YbeY is an important factor for bacterial translation even at 37°C but becomes essential at high temperatures.
Regulation of the
mazEF
Toxin-Antitoxin Module in
Staphylococcus aureus
and Its Impact on
sigB
Expression
Authors: Donegan Niles P. , Cheung Ambrose L. 
Published: January 2009

ABSTRACT

In
Staphylococcus aureus
, the
sigB
operon codes for the alternative sigma factor σ
B
and its regulators that enable the bacteria to rapidly respond to environmental stresses via redirection of transcriptional priorities. However, a full model of σ
B
regulation in
S. aureus
has not yet emerged. Earlier data has suggested that
mazEF
, a toxin-antitoxin (TA) module immediately upstream of the
sigB
operon, was transcribed with the
sigB
operon. Here we demonstrate that the promoter P

mazE

upstream of
mazEF
is essential for full σ
B
activity and that instead of utilizing autorepression typical of TA systems,
sigB
downregulates this promoter, providing a negative-feedback loop for
sigB
to repress its own transcription. We have also found that the transcriptional regulator SarA binds and activates P

mazE

. In addition, P

mazE

was shown to respond to environmental and antibiotic stresses in a way that provides an additional layer of control over
sigB
expression. The antibiotic response also appears to occur in two other TA systems in
S. aureus
, indicating a shared mechanism of regulation.
In vitro and In vivo Anticancer Effects of the Novel Vitamin E Ether Analogue RRR-α-Tocopheryloxybutyl Sulfonic Acid in Prostate Cancer
Authors: Ni Jing , Mai Tiejun , Pang See-Tong , Haque Imranul , Huang Kaohsing , DiMaggio Matthew A. , Xie Shaozhen , James Nadine S. , Kasi Dhanalakshmi , Chemler Sherry R. , Yeh Shuyuan 
Published: February 2009

Abstract
Purpose: Among derivatives of α-vitamin E, α-vitamin E succinate (VES), has attracted much attention due to its potent anti–prostate cancer activity in vitro and in vivo. However, the in vivo antitumor activity of VES might be compromised if administrated orally due to the VES hydrolysis by esterases in the gastrointestinal tract.
Experimental Design: New nonhydrolyzable VES ether analogues were synthesized and their growth inhibition was screened by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide growth assay. Among them, RRR-α-tocopheryloxybutyl sulfonic acid (VEBSA) was further characterized by terminal deoxyribonucleotidyl transferase–mediated dUTP nick end labeling apoptosis assay, soft agar assay, and in vivo tumor formation.
Results: VEBSA has potent antitumor ability, albeit to a lesser extent than VES, in in vitro cultured prostate cancer LNCaP and PC3 cells. Like VES, VEBSA induced apoptosis, repressed androgen receptor protein expression, and enhanced vitamin D receptor expression, suggesting that VEBSA can go through mechanisms similar to those used by VES to inhibit the growth of prostate cancer cells in vitro. However, 6 weeks of oral consumption of VEBSA, but not of VES, reduced the tumor burden in the xenografted prostate tumors in nude mice. Furthermore, oral intake of VEBSA for 20 weeks inhibited prostate tumor growth and progression more efficiently compared with VES in the prostate cancer tumor model of TRAMP mice.
Conclusion: Oral consumption of VEBSA allows a greater anticancer activity compared with VES. Chemoprevention prefers the oral consumption of agents; the advantage of VEBSA over VES to be administrated orally will allow VEBSA to serve as an agent for both preventive and therapeutic purposes for prostate cancer.