bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification and Sequence Analysis of a 27-Kilobase Chromosomal Fragment Containing a
Salmonella
Pathogenicity Island Located at 92 Minutes on the Chromosome Map of
Salmonella enterica
Serovar Typhimurium LT2
Authors: Wong Kwong-Kwok , McClelland Michael , Stillwell Lisa C. , Sisk Ellen C. , Thurston Sarah J. , Saffer Jeffrey D. 
Published: December 2019

ABSTRACT

Using a genomic approach, we have identified a new
Salmonella
pathogenicity island, SPI-4, which is the fourth
Salmonella
pathogenicity island to be identified. SPI-4 was located at 92 min on the chromosome map and was flanked by the
ssb
and
soxSR
loci. The DNA sequence covering the entire SPI-4 and both boundaries was determined. The size of SPI-4 was about 25 kb and it contains 18 putative open reading frames (ORFs). Three of these ORFs encode proteins that have significant homology with proteins involved in toxin secretion. Another five ORFs encode proteins that have significant homology with hypothetical proteins from
Synechocystis
sp. strain PCC6803 or
Acinetobacter calcoaceticus
. The rest of the ORFs encode novel proteins, one of which has five membrane-spanning domains. SPI-4 is likely to carry a type I secretion system involved in toxin secretion. Furthermore, a previously identified locus (
ims98
), which is required for intramacrophage survival, was also mapped within the SPI-4 region. These findings suggested that SPI-4 is needed for intramacrophage survival.
Characterization of MGC2, a
Mycoplasma gallisepticum
Cytadhesin with Homology to the
Mycoplasma pneumoniae
30-Kilodalton Protein P30 and
Mycoplasma genitalium
P32
Authors: Hnatow Linda L. , Keeler Calvin L. , Tessmer Laura L. , Czymmek Kirk , Dohms John E. 
Published: December 2019

ABSTRACT

A second cytadhesin-like protein, MGC2, was identified in the avian respiratory pathogen
Mycoplasma gallisepticum
. The 912-nucleotide
mgc2
gene encodes a 32.6-kDa protein with 40.9 and 31.4% identity with the
M. pneumoniae
P30 and
M. genitalium
P32 cytadhesins, respectively. Functional studies with reverse transcription-PCR, immunoblotting, double-sided immunogold labeling, and attachment inhibition assays demonstrated homology to the human mycoplasmal P30 and P32 cytadhesins. These findings suggest that there is a family of cytadhesin genes conserved among pathogenic mycoplasmas infecting widely divergent hosts.
Identification of an Insertion Sequence Located in a Region Encoding Virulence Factors of
Streptococcus pyogenes
Authors: Berge Andreas , Rasmussen Magnus , Björck Lars 
Published: December 2019

ABSTRACT

An insertion sequence, IS
1562
, was identified in a
Streptococcus pyogenes
strain of the clinically important M1 serotype. IS
1562
is located in the
mga
regulon between the genes coding for the M protein and the C5a peptidase, both important virulence factors. The same or similar insertion sequences were found in most
S. pyogenes
strains, but the chromosomal location differed among isolates.
Inhibition of Class II Major Histocompatibility Complex Antigen Processing byEscherichia coliHeat-Labile Enterotoxin Requires an Enzymatically Active A Subunit
Authors: Matousek Milita P. , Nedrud John G. , Cieplak Witold , Harding Clifford V. 
Published: December 2019

ABSTRACTEscherichia coliheat-labile enterotoxin (LT) and cholera toxin (CT) were found to inhibit intracellular antigen processing. Processing was not inhibited by mutant LT with attenuated ADP-ribosyltransferase activity, CT B or LT B subunit, which enhanced presentation of preexisting cell surface peptide-class II major histocompatibility complex complexes. Inhibition of antigen processing correlated with A subunit ADP-ribosyltransferase activity.
Altered Cytokine Production and Impaired Antimycobacterial Immunity in Protein-Malnourished Guinea Pigs
Authors: Dai Guixiang , McMurray David N. 
Published: December 2019

ABSTRACTProtein malnutrition leads to multiple detrimental alterations of host immune responses to mycobacterial infection. In this study, we demonstrated that splenocytes from low-protein (LP) guinea pigs vaccinated 6 weeks previously with attenuatedMycobacterium tuberculosisH37Ra failed to control the accumulation of virulentM. tuberculosisH37Rv in cocultured autologous peritoneal macrophages, despite the fact that they were able to control the accumulation of virulent tubercle bacilli in cocultured syngeneic peritoneal macrophages from normally nourished guinea pigs as successfully as did those from high-protein (HP) counterparts. Vaccine-induced growth control of virulentM. tuberculosisH37Rv in these cocultures appeared to be mediated by CD4 lymphocytes but not CD8 cells. Tuberculin (purified protein derivative [PPD])-induced lymphoproliferation was markedly impaired in vaccinated LP guinea pigs, and the depletion of CD4 lymphocytes significantly decreased lymphocyte proliferation whereas CD8 cell depletion did not. Protein malnutrition also impaired the abilities of cells from vaccinated LP guinea pigs to produce cytokines, including interferon, tumor necrosis factor alpha (TNF-α) and transforming growth factor beta (TGF-β), in response to PPD, despite the demonstration of higher serum levels of TNF-α and TGF-β after an intravenous injection of PPD into LP guinea pigs. In contrast, peritoneal macrophages from protein-malnourished guinea pigs produced a higher level of TGF-β 4 days after infection in vitro withM. tuberculosisH37Rv than did those from protein adequate controls. These results suggest that dietary protein malnutrition impairs vaccine-induced resistance toM. tuberculosis, in part, by altering the cytokine profile to favor macrophage deactivation.
Molecular Basis for Antigenic Variation of a Protective Strain-Specific Antigen of
Ehrlichia risticii
Authors: Biswas Biswajit , Vemulapalli Ramesh , Dutta Sukanta K. 
Published: December 2019

ABSTRACT

Ehrlichia risticii
, the causative agent of Potomac horse fever, has recently been isolated from many vaccinated horses with typical clinical signs of the disease. The heterogeneity of the
E. risticii
isolates obtained from the vaccinated horses necessitates the identification of the molecular basis of strain variations to elucidate the vaccine failure and to aid in the development of an efficient vaccine against this disease. As an attempt, two major cross-reacting surface antigen genes of 50- and 85-kDa antigens, present separately in strains 25-D (isolated in 1984) and 90-12 (isolated in 1990 from a vaccinated horse), respectively, were cloned and sequenced. A comparative sequence analysis revealed differences and similarities between these two antigens with strain-specific sizes (SSA). The 2.5- and 1.6-kb genes coding for the 85- and 50-kDa proteins, respectively, contained many different tandem repeats. The identical repeat motifs were more frequent in the middle of both genes, but the numbers and positions of the repeats were altogether different in the genes. Many of these direct repeats of both genes had exact sequence homology and coded for the same amino acids. The homology of the 5′- and 3′-flanking regions of the two genes was greater than that of the regions in the central part of the genes. A comparative analysis of the deduced amino acid sequences of these two antigen genes indicated eight common domains, which were designated identical domains. Although the sequence homologies of these identical domains were the same, the positions of the domains in their respective strains were completely different. This finding might be one of the bases of antigenic variation between the strains. In addition, there were a few unique regions in both antigen genes where no sequence homology existed. These specific regions were designated unique domains. The 50-kDa protein had two such unique domains, and the 85-kDa protein had six such unique domains. The presence of such unique domains contributed to the large size variation of these SSA. The cross-reactivity of recombinant proteins confirmed the presence of conserved epitopes between these two antigens. The SSA have been determined to be apparent protective antigens of
E. risticii
.
Phospholipid Composition of PurifiedChlamydia trachomatisMimics That of the Eucaryotic Host Cell
Authors: Hatch Grant M. , McClarty Grant 
Published: December 2019

ABSTRACTChlamydia trachomatisis an obligate intracellular eubacterial parasite capable of infecting a wide range of eucaryotic host cells. Purified chlamydiae contain several lipids typically found in eucaryotes, and it has been established that eucaryotic lipids are transported from the host cell to the parasite. In this report, we examine the phospholipid composition ofC. trachomatispurified from host cells grown under a variety of conditions in which the cellular phospholipid composition was altered. A mutant CHO cell line, with a thermolabile CDP-choline synthetase, was used to show that decreased host cell phosphatidylcholine levels had no significant effect onC. trachomatisgrowth. However, less phosphatidylcholine was transported to the parasite and purified elementary bodies contained decreased levels of phosphatidylcholine. Brefeldin A, fumonisin B1, and exogenous sphingomyelinase were used to alter levels of host cell sphingomyelin. None of the agents had a significant effect onC. trachomatisreplication. Treatment with fumonisin B1and exogenous sphingomyelinase resulted in decreased levels of host cell sphingomyelin. This had no effect on glycerophospholipid trafficking to chlamydiae; however, sphingomyelin trafficking was reduced and elementary bodies purified from treated cells had reduced sphingomyelin content. Exposure to brefeldin A, which had no adverse effect on chlamydia growth, resulted in an increase in cellular levels of sphingomyelin and a concomitant increase in the amount of sphingomyelin in purified chlamydiae. Under the experimental conditions used, brefeldin A treatment had only a small effect on sphingomyelin trafficking to the host cell surface or toC. trachomatis. Thus, the final phospholipid composition of purifiedC. trachomatismimics that of the host cell in which it is grown.
Induction of the Lysogenic Phage Encoding Cholera Toxin in Naturally Occurring Strains of Toxigenic
Vibrio cholerae
O1 and O139
Authors: Faruque Shah M. , Asadulghani  , Abdul Alim A. R. M. , Albert M. John , Nasirul Islam K. M. , Mekalanos John J. 
Published: December 2019

ABSTRACT

In toxigenic
Vibrio cholerae
, the CTX genetic element which carries the genes for cholera toxin (CT) is the genome of a lysogenic bacteriophage (CTXΦ). Clinical and environmental strains of
V. cholerae
O1 or O139 and stools that were culture positive for cholera were analyzed to study the induction and transmission of CTXΦ. To our knowledge, this is the first report of the examination of CTXΦ in clinical materials and in naturally occurring strains. DNA probe analysis revealed that 4.25% (6 of 141) of the isolated
V. cholerae
strains spontaneously produced a detectable level of extracellular CTXΦ particles in the culture supernatants whereas another 34.04% (48 of 141) produced CTXΦ particles when induced with mitomycin C. CTXΦ isolated from 10 clinical or environmental strains infected a CT-negative recipient strain, CVD103, both inside the intestines of infant mice and under laboratory conditions. All culture-positive stools analyzed were negative for the presence of CTXΦ both in the DNA probe assay and by in vivo assay for the infection of the recipient strain in infant mice. These results suggested that naturally occurring strains of toxigenic
V. cholerae
are inducible lysogens of CTXΦ but that cholera pathogenesis in humans is not associated with the excretion of CTXΦ particles in stools, indicating that induction of the phage may not occur efficiently inside the human intestine. However, in view of the efficient transmission of the phage under conditions conducive to the expression of toxin-coregulated pili, it appears that propagation of CTXΦ in the natural habitat may involve both environmental and host factors.
Interactions of the Invasive PathogensSalmonella typhimurium,Listeria monocytogenes, andShigella flexneriwith M Cells and Murine Peyer’s Patches
Authors: Jensen V. Behrana , Harty John T. , Jones Bradley D. 
Published: December 2019

ABSTRACTInvasive enteric bacteria must pass through the intestinal epithelium in order to establish infection. It is becoming clear that a common target for intestinal mucosa penetration is the specialized epithelial cell of Peyer’s patches, the M cell. In order to gain a better understanding of how bacteria interact with M cells, we have compared the interactions ofSalmonella typhimurium,Listeria monocytogenes, andShigella flexneriwith M cells by using a murine ligated-loop model. Our results indicate thatS. typhimuriumpossesses a highly efficient mechanism for M cell entry that targets and destroys these cells, whileL. monocytogenesandS. flexneriappear to be internalized into M cells in a less disruptive fashion. Early uptake ofListeriaorShigellainto M cells appeared to lead to the death of some cells, as evidenced by the appearance of holes in the intestinal epithelium. At later time points, the follicle-associated epithelium of animals infected with these bacteria displayed extensive destruction. These data indicate that enteric pathogens use different strategies to interact with M cells and initiate infection of a host.
Magnesium and the Role of
mgtC
in Growth of
Salmonella typhimurium
Authors: Moncrief Mary Beth C. , Maguire Michael E. 
Published: December 2019

ABSTRACT

Salmonella typhimurium
has three distinct transport systems for Mg
2+
: CorA, MgtA, and MgtB. The
mgtCB
operon encodes two proteins, MgtC, a hydrophobic protein with a predicted molecular mass of 22.5 kDa, and MgtB, a 102-kDa P-type ATPase Mg
2+
transport protein. The
mgtCB
locus has been identified as part of a new
Salmonella
pathogenicity island, SPI-3. Transcription of
mgtCB
is regulated by extracellular Mg
2+
via the two-component PhoPQ regulatory system important for virulence. To elucidate MgtC’s role in a low-Mg
2+
environment, we looked at growth and transport in strains lacking the CorA and MgtA Mg
2+
transporters but expressing MgtB, MgtC, or both.

mgtC mgtB
+

and

mgtC
+
mgtB
+

strains exhibited growth in N minimal medium without added Mg
2+
with a 1- to 2-h lag phase. An

mgtC
+
mgtB

strain was also able to grow in N minimal medium without added Mg
2+
but only after a 24-h lag phase. In N minimal medium containing 10 mM Mg
2+
, all strains grew after a short lag phase; the

mgtC
+
mgtB

strain grew to a higher optical density at 600 nm than an

mgtC
+
mgtB
+

strain and was comparable to wild type. The lengthy lag phase before growth in an

mgtC
+
mgtB

strain was not due to lack of expression of MgtC. Western blot analysis indicated that substantial MgtC protein is present by 2 h after suspension in N minimal medium. Surprisingly, in an

mgtC
+
mgtB
+

strain, MgtC was undetectable during Mg
2+
starvation, although large amounts of MgtB were observed. The lack of expression of MgtC is not dependent on functional MgtB, since a strain carrying a nonfunctional MgtB with a mutation (D379A) also did not make MgtC. Since, during invasion of eukaryotic cells,
S. typhimurium
appears to be exposed to a low-pH as well as a low-Mg
2+
environment, the growth of an

mgtC
+
mgtB

strain was tested at low pH with and without added Mg
2+
. While significant quantities of MgtC could be detected after suspension at pH 5.2, the

mgtC
+
mgtB

strain was unable to grow at pH 5.2 whether or not Mg
2+
was present. Finally, using
63
Ni
2+
and
57
Co
2+
as alternative substrates for the unavailable
28
Mg
2+
, cation uptake could not be detected in an

mgtC
+
mgtB

strain after Mg
2+
starvation. We conclude that MgtC is not a Mg
2+
transporter and that it does not have a primary role in the survival of
S. typhimurium
at low pH.
Identification and Characterization of a Phase-Specific, Nuclear DNA Binding Protein from the Dimorphic Pathogenic Fungus
Histoplasma capsulatum
Authors: Abidi Fatima E. , Roh Haeri , Keath Elizabeth J. 
Published: December 2019

ABSTRACT

Genes expressed in the parasitic yeast (Y) phase of the dimorphic fungal pathogen
Histoplasma capsulatum
which are transcriptionally silent in the mycelial (M) phase have recently been cloned and analyzed. To understand the molecular regulation of genes involved in the transition to and maintenance of the Y phase, the presumptive 5′ regulatory regions of two Y phase-specific genes (
yps-3
and
yps 21:E-9
) were PCR amplified as labelled probes to identify nuclear DNA binding proteins which may influence phase-specific gene transcription. Protein-DNA interactions were assessed by Southwestern blot analysis in which sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated protein extracts from Y and M phases of the virulent G217B strain of
H. capsulatum
were visualized by their capability for in situ binding to the labelled 517-bp (G217B
yps-3
) or the 395-bp (G217B
yps 21:E-9
) putative 5′ regulatory regions. A 30-kDa nuclear protein unique to the M-phase extracts of the highly virulent G217B strain, but absent in the Y phase of the same organism, was identified. In contrast, the low-virulence, thermal-sensitive Downs strain of
H. capsulatum
lacked detectable p30 binding activity in either yeast- or mycelial phase extracts, regardless of the source of labelled probe (395-bp G217B
yps 21:E-9
probe or 512-bp
Hin
dIII-
Eco
RI-labelled Downs
yps21:E-9
). A decanucleotide motif, TCCTTTTTTT, was identified in the upstream regulatory regions of these
yps
genes, as well as in the putative α-tubulin promoter, and was conserved with 70 to 100% homology. This recognition sequence was sufficient for p30M binding with
32
P-labelled ligated oligonucleotides when used in the Southwestern assay. These findings describe the first nuclear DNA binding factor identified in
H. capsulatum
which binds to target sequences in a phase-specific manner, suggesting that p30M may govern aspects of gene transcription in this pathogenic fungus, in which a temperature-sensitive switch influences morphology and virulence.
Regulation of Macrophage Gene Expression byMycobacterium tuberculosis: Down-Regulation of Mitochondrial CytochromecOxidase
Authors: Ragno Silvia , Estrada-Garcia Iris , Butler Robert , Colston M. Joseph 
Published: December 2019

ABSTRACTWe have investigated changes in gene expression in mouse peritoneal macrophages following infection with virulentMycobacterium tuberculosis. Using differential-display reverse transcription-PCR (RT-PCR), we have identified a gene that was markedly down-regulated within 6 h of infection and remained so for the duration of the experiment (5 days). On sequencing, this gene was found to encode the murine cytochromecoxidase subunit VIIc (COX VIIc). Down-regulation of COX VIIc duringM. tuberculosisinfection was confirmed by three independent techniques: limiting-dilution RT-PCR, RNase protection assay, and Northern analysis. Limiting-dilution RT-PCR and Northern analysis were also used to analyze the specificity of this regulation; heat-killedM. tuberculosis,Mycobacterium bovisBCG, and latex beads had no effect on expression of COX VIIc. Down-regulation of this enzyme was also confirmed by using adherent cells isolated from spleens ofM. tuberculosis-infected mice. These ex vivo macrophages showed apoptotic features, suggesting a possible involvement of cytochromecoxidase in the programmed cell death of the host cells.
Characterization of BrkA Expression in
Bordetella bronchiseptica
Authors: Rambow Amy A. , Fernandez Rachel C. , Weiss Alison A. 
Published: December 2019

ABSTRACT

BrkA confers resistance to killing by complement in
Bordetella pertussis
. Complement resistance in
Bordetella bronchiseptica
was examined. Four
B. bronchiseptica
strains possessed the
brkA
gene; however, only three expressed the protein. Only the strain lacking BrkA was susceptible to complement. Introduction of the
B. pertussis brkA
gene restored BrkA expression to this strain but did not confer resistance.
brkA
was mutated in the strains that naturally expressed BrkA, and loss of BrkA did not confer sensitivity to complement. As a species,
B. bronchiseptica
is more resistant to complement than
B. pertussis
, and BrkA does not mediate resistance.
Vag8, a
Bordetella pertussis bvg
-Regulated Protein
Authors: Finn Theresa M. , Amsbaugh Diana F. 
Published: December 2019

ABSTRACT

Bordetella pertussis
expresses a
bvg
-regulated 95-kDa protein, Vag8, encoded by
vag-8
. Southern blot analysis indicates that strains of
Bordetella bronchiseptica
and
Bordetella parapertussis
have DNA homologous to
vag-8
. Antiserum raised to a fusion of maltose binding protein to an N-terminal 60-kDa fragment of Vag8 recognizes the native 95-kDa protein in immunoblots of
B. pertussis
and
B. bronchiseptica
but not
B. parapertussis
. A 95-kDa protein-negative derivative of
B. pertussis
18323 containing a deletion of
vag-8
colonized mice as efficiently as the parent
B. pertussis
strain in a mouse aerosol model of pertussis.
Identification and Characterization of a 14-KilodaltonBrucella abortusProtein Reactive with Antibodies from Naturally and Experimentally Infected Hosts and T Lymphocytes from Experimentally Infected BALB/c Mice
Authors: Chirhart-Gilleland Rebecca L. , Kovach Michael E. , Elzer Philip H. , Jennings Stephen R. , Roop R. Martin 
Published: December 2019

ABSTRACTA low-molecular-weight recombinantBrucella abortusprotein reactive with antibodies from a variety of naturally and experimentally infected hosts and T lymphocytes from experimentally infected mice was identified and given the designation BA14K. The gene encoding BA14K was cloned and characterized, and the predicted amino acid sequence of this immunoreactive protein showed no significant homology with previously described proteins. Sequences homologous to the cloned fragment encoding BA14K were identified by Southern blot analysis of genomic DNAs from representatives of all of the currently recognizedBrucellaspecies. Studies employing BA14K should contribute to our efforts to better understand the antigenic specificity of protective immunity to brucellosis.
Catecholamine Oxidative Products, but Not Melanin, Are Produced byCryptococcus neoformansduring Neuropathogenesis in Mice
Authors: Liu Lide , Wakamatsu Kazumasa , Ito Shosuke , Williamson Peter R. 
Published: December 2019

ABSTRACTMelanin has been proposed as a virulence factor inCryptococcus neoformans, but its presence has not been shown unambiguously in vivo. Validated methods used previously to show production of cryptococcal eumelanin pigment in vitro (P. R. Williamson, K. Wakamatsu, and S. Ito, J. Bacteriol. 180:1570–1572, 1998) were used to assess for production of laccase-derived products in mouse brain of the Lacc+strains, 2E-TUC, H99 (serotype A), and ATCC 34873 (serotype D), and the Lacc−strain, 2E-TU. Pyrrole-2,3,5-tricarboxylic and pyrrole-2,3-dicarboxylic acid, specific degradation products of catecholamine derivatives such as melanin, were found in all Lacc+strains, but not in the Lacc−strain, 2E-TU. However, the presence of melanin pigment itself could not be demonstrated in the same cells. Lack of the specific degradation products aminohydroxyphenylalanine and aminohydroxyphenylethylamine in Lacc+strains upon hydriodic acid hydrolysis showed that pheomelanin was also not produced by the fungus in vivo. These are the first data to support the generation of catecholamine oxidation products byC. neoformansin vivo, but they do not support postenzymatic polymerization of these products to form typical eumelanin, as previously proposed.