bluuebunny/crossref_metadata_2025_split huggingface dataset:
Putative Virulence Traits and Pathogenicity of
Vibrio cholerae
Non-O1, Non-O139 Isolates from Surface Waters in Kolkata, India
Authors: Bag Prasanta K. , Bhowmik Poulami , Hajra Tapas K. , Ramamurthy T. , Sarkar Pradipta , Majumder Mrinmoyee , Chowdhury Goutam , Das Suresh C. 
Published: July 2008

ABSTRACT

Vibrio cholerae
non-O1, non-O139 was isolated from natural surface waters from different sites sampled in diarrhea endemic zones in Kolkata, India. Twenty-one of these isolates were randomly selected and included in the characterization. The multiserogroup isolates were compared by their virulence traits with a group of clinical non-O1, non-O139 isolates from the same geographic area. Of the 21 environmental isolates, 6 and 14 strains belonged to Heiberg groups I and II, respectively. Three of the environmental isolates showed resistance to 2,2-diamine-6,7-diisopropylpteridine phosphate. All of the non-O1, non-O139 strains were positive for
toxR
, and except for one environmental isolate, none of them were positive for
tcpA
in the PCR assay. None of the isolates were positive for genes encoding cholera toxin (
ctxA
), heat-stable toxin (
est
), heat-labile toxin (
elt
), and Shiga toxin variants (
stx
) of
Escherichia coli
. Additionally, except for one environmental isolate (PC32), all were positive for the gene encoding El Tor hemolysin (
hly
). The culture supernatants of 86% (18 of 21) of the environmental isolates showed a distinct cytotoxic effect on HeLa cells, and some of these strains also produced cell-rounding factor. The lipase, protease, and cell-associated hemagglutination activities and serum resistance properties of the environmental and clinical isolates did not differ much. However, seven environmental isolates exhibited very high hemolytic activities (80 to 100%), while none of the clinical strains belonged to this group. The environmental isolates manifested three adherence patterns, namely, carpet-like, diffuse, and aggregative adherence, and the clinical isolates showed diffuse adherence on HeLa cells. Of the 11 environmental isolates tested for enteropathogenic potential, 8 (73%) induced positive fluid accumulation (≥100) in a mouse model, and the reactivities of these isolates were comparable to those of clinical strains of non-O1, non-O139 and toxigenic O139
V. cholerae
. Comparison of the counts of the colonized environmental and clinical strains in the mouse intestine showed that the organisms of both groups had similar colonizing efficiencies. These findings indicate the presence of potentially pathogenic
V. cholerae
non-O1, non-O139 strains in surface waters of the studied sites in Kolkata.
Cloning and Overexpression of Alkaline Phosphatase PhoK from
Sphingomonas
sp. Strain BSAR-1 for Bioprecipitation of Uranium from Alkaline Solutions
Authors: Nilgiriwala Kayzad S. , Alahari Anuradha , Rao Amara Sambasiva , Apte Shree Kumar 
Published: July 2008

ABSTRACT

Cells of
Sphingomonas
sp. strain BSAR-1 constitutively expressed an alkaline phosphatase, which was also secreted in the extracellular medium. A null mutant lacking this alkaline phosphatase activity was isolated by Tn
5
random mutagenesis. The corresponding gene, designated
phoK
, was cloned and overexpressed in
Escherichia coli
strain BL21(DE3). The resultant
E. coli
strain EK4 overexpressed cellular activity 55 times higher and secreted extracellular PhoK activity 13 times higher than did BSAR-1. The recombinant strain very rapidly precipitated >90% of input uranium in less than 2 h from alkaline solutions (pH, 9 ± 0.2) containing 0.5 to 5 mM of uranyl carbonate, compared to BSAR-1, which precipitated uranium in >7 h. In both strains BSAR-1 and EK4, precipitated uranium remained cell bound. The EK4 cells exhibited a much higher loading capacity of 3.8 g U/g dry weight in <2 h compared to only 1.5 g U/g dry weight in >7 h in BSAR-1. The data demonstrate the potential utility of genetically engineering PhoK for the bioprecipitation of uranium from alkaline solutions.
Genetic Diversity of
Porphyromonas gingivalis
Isolates Recovered from Single “Refractory” Periodontitis Sites
Authors: Enersen Morten , Olsen Ingar , Caugant Dominique A. 
Published: July 2008

ABSTRACT

Multilocus sequence typing and
fimA
genotyping were performed on
Porphyromonas gingivalis
isolates from 15 subjects with “refractory” periodontitis. Several sequence types were detected for most individual pockets. The variation indicated recombination at the
recA
and
pepO
genes. The prevalence of
fimA
genotypes II and IV confirmed their association with periodontitis.
Prevalence and Genetic Characterization of
Cryptosporidium
Isolates from Common Brushtail Possums (
Trichosurus vulpecula
) Adapted to Urban Settings
Authors: Hill Nichola J. , Deane Elizabeth M. , Power Michelle L. 
Published: July 2008

ABSTRACT

The common brushtail possum (
Trichosurus vulpecula
) is one of the most abundant native marsupials in urban Australia, having successfully adapted to utilize anthropogenic resources. The habituation of possums to food and shelter available in human settlements has facilitated interaction with people, pets, and zoo animals, increasing the potential for transmission of zoonotic
Cryptosporidium
pathogens. This study sought to examine the identity and prevalence of
Cryptosporidium
species occurring in possums adapted to urban settings compared to possums inhabiting remote woodlands far from urban areas and to characterize the health of the host in response to oocyst shedding. Findings indicated that both populations were shedding oocysts of the same genotype (brushtail possum 1 [BTP1]) that were genetically and morphologically distinct from zoonotic species and genotypes and most closely related to
Cryptosporidium
species from marsupials. The urban population was shedding an additional five
Cryptosporidium
isolates that were genetically distinct from BTP1 and formed a sister clade with
Cryptosporidium parvum
and
Cryptosporidium hominis
. Possums that were shedding oocysts showed no evidence of pathogenic changes, including elevated levels of white blood cells, diminished body condition (body mass divided by skeletal body length), or reduced nutritional state, suggesting a stable host-parasite relationship typical of
Cryptosporidium
species that are adapted to the host. Overall,
Cryptosporidium
occurred with a higher prevalence in possums from urban habitat (11.3%) than in possums from woodland habitat (5.6%); however, the host-specific nature of the genotypes may limit spillover infection in the urban setting. This study determined that the coexistence of possums with sympatric populations of humans, pets, and zoo animals in the urban Australian environment is unlikely to present a threat to public health safety.
Relative Importance of H
2
and H
2
S as Energy Sources for Primary Production in Geothermal Springs
Authors: D'Imperio Seth , Lehr Corinne R. , Oduro Harry , Druschel Greg , Kühl Michael , McDermott Timothy R. 
Published: July 2008

ABSTRACT

Geothermal waters contain numerous potential electron donors capable of supporting chemolithotrophy-based primary production. Thermodynamic predictions of energy yields for specific electron donor and acceptor pairs in such systems are available, although direct assessments of these predictions are rare. This study assessed the relative importance of dissolved H
2
and H
2
S as energy sources for the support of chemolithotrophic metabolism in an acidic geothermal spring in Yellowstone National Park. H
2
S and H
2
concentration gradients were observed in the outflow channel, and vertical H
2
S and O
2
gradients were evident within the microbial mat. H
2
S levels and microbial consumption rates were approximately three orders of magnitude greater than those of H
2
.
Hydrogenobaculum
-like organisms dominated the bacterial component of the microbial community, and isolates representing three distinct 16S rRNA gene phylotypes (phylotype = 100% identity) were isolated and characterized. Within a phylotype, O
2
requirements varied, as did energy source utilization: some isolates could grow only with H
2
S, some only with H
2
, while others could utilize either as an energy source. These metabolic phenotypes were consistent with in situ geochemical conditions measured using aqueous chemical analysis and in-field measurements made by using gas chromatography and microelectrodes. Pure-culture experiments with an isolate that could utilize H
2
S and H
2
and that represented the dominant phylotype (70% of the PCR clones) showed that H
2
S and H
2
were used simultaneously, without evidence of induction or catabolite repression, and at relative rate differences comparable to those measured in ex situ field assays. Under in situ-relevant concentrations, growth of this isolate with H
2
S was better than that with H
2
. The major conclusions drawn from this study are that phylogeny may not necessarily be reliable for predicting physiology and that H
2
S can dominate over H
2
as an energy source in terms of availability, apparent in situ consumption rates, and growth-supporting energy.
Prevalence and Genetic Characterization of Shiga Toxin-Producing
Escherichia coli
Isolates from Slaughtered Animals in Bangladesh
Authors: Islam Mohammad A. , Mondol Abdus S. , de Boer Enne , Beumer Rijkelt R. , Zwietering Marcel H. , Talukder Kaisar A. , Heuvelink Annet E. 
Published: July 2008

ABSTRACT

To determine the prevalence of Shiga toxin (Stx)-producing
Escherichia coli
(STEC) in slaughter animals in Dhaka, Bangladesh, we collected rectal contents immediately after animals were slaughtered. Of the samples collected from buffalo (
n
= 174), cows (
n
= 139), and goats (
n
= 110), 82.2%, 72.7%, and 11.8% tested positive for
stx
1
and/or
stx
2
, respectively. STEC could be isolated from 37.9%, 20.1%, and 10.0% of the buffalo, cows, and goats, respectively. STEC O157 samples were isolated from 14.4% of the buffalo, 7.2% of the cows, and 9.1% of the goats. More than 93% (
n
= 42) of the STEC O157 isolates were positive for the
stx
2
,
eae
,
katP
,
etpD
, and enterohemorrhagic
E. coli hly
(
hly
EHEC
) virulence genes. STEC O157 isolates were characterized by seven recognized phage types, of which types 14 (24.4%) and 31 (24.4%) were predominant. Subtyping of the 45 STEC O157 isolates by pulsed-field gel electrophoresis showed 37 distinct restriction patterns, suggesting a heterogeneous clonal diversity. In addition to STEC O157, 71 STEC non-O157 strains were isolated from 60
stx
-positive samples from 23.6% of the buffalo, 12.9% of the cows, and 0.9% of the goats. The STEC non-O157 isolates belonged to 36 different O groups and 52 O:H serotypes. Unlike STEC O157, most of the STEC non-O157 isolates (78.9%) were positive for
stx
1
. Only 7.0% (
n
= 5) of the isolates were positive for
hly
EHEC
, and none was positive for
eae
,
katP
, and
etpD
. None of the isolates was positive for the
iha
,
toxB
, and
efa1
putative adhesion genes. However, 35.2% (
n
= 25), 11.3% (
n
= 8), 12.7% (
n
= 9), and 12.7% (
n
= 9) of the isolates were positive for the
lpf
O113
,
saa
,
lpfA
O157/01-141
, and
lpfA
O157/OI-154
genes, respectively. The results of this study provide the first evidence that slaughtered animals like buffalo, cows, and goats in Bangladesh are reservoirs for STEC, including the potentially virulent STEC strain O157.
Global Gene Expression Profiles Suggest an Important Role for Nutrient Acquisition in Early Pathogenesis in a Plant Model ofPseudomonas aeruginosaInfection
Authors: Weir Tiffany L. , Stull Valerie J. , Badri Dayakar , Trunck Lily A. , Schweizer Herbert P. , Vivanco Jorge 
Published: July 2008

ABSTRACTAlthoughPseudomonas aeruginosais an opportunistic pathogen that does not often naturally infect alternate hosts, such as plants, the plant-P. aeruginosamodel has become a widely recognized system for identifying new virulence determinants and studying the pathogenesis of the organism. Here, we examine how both host factors andP. aeruginosaPAO1 gene expression are affected in planta after infiltration into incompatible and compatible cultivars of tobacco (Nicotiana tabacumL.).N. tabacumhas a resistance gene (N) against tobacco mosaic virus, and although resistance to PAO1 infection is correlated with the presence of a dominant N gene, our data suggest that it is not a factor in resistance against PAO1. We did observe that the resistant tobacco cultivar had higher basal levels of salicylic acid and a stronger salicylic acid response upon infiltration of PAO1. Salicylic acid acts as a signal to activate defense responses in plants, limiting the spread of the pathogen and preventing access to nutrients. It has also been shown to have direct virulence-modulating effects onP. aeruginosa. We also examined host effects on the pathogen by analyzing global gene expression profiles of bacteria removed from the intracellular fluid of the two plant hosts. We discovered that the availability of micronutrients, particularly sulfate and phosphates, is important for in planta pathogenesis and that the amounts of these nutrients made available to the bacteria may in turn have an effect on virulence gene expression. Indeed, there are several reports suggesting thatP. aeruginosavirulence is influenced in mammalian hosts by the availability of micronutrients, such as iron and nitrogen, and by levels of O2.
Microscopic and Molecular Studies of the Diversity of Free-Living Protozoa in Meat-Cutting Plants
Authors: Vaerewijck Mario J. M. , Sabbe Koen , Baré Julie , Houf Kurt 
Published: July 2008

ABSTRACT

The diversity of free-living protozoa in five meat-cutting plants was determined. Light microscopy after enrichment culturing was combined with sequencing of PCR-amplified, denaturing gradient gel electrophoresis (DGGE)-separated 18S rRNA gene fragments, which was used as a fast screening method. The general results of the survey showed that a protozoan community of amoebae, ciliates, and flagellates was present in all of the plants. Protozoa were detected mainly in floor drains, in standing water on the floor, on soiled bars of cutting tables, on plastic pallets, and in out-of-use hot water knife sanitizers, but they were also detected on surfaces which come into direct contact with meat, such as conveyer belts, working surfaces of cutting tables, and needles of a meat tenderizer. After 7 days of incubation at refrigerator temperature, protozoa were detected in about one-half of the enrichment cultures. Based on microscopic observations, 61 morphospecies were found, and
Bodo saltans, Bodo
spp.,
Epistylis
spp.,
Glaucoma scintillans, Petalomonas
spp.,
Prodiscophrya collini
, and
Vannella
sp. were the most frequently encountered identified organisms. Sequencing of DGGE bands resulted in identification of a total of 49 phylotypes, including representatives of the Amoebozoa, Chromalveolata, Excavata, Opisthokonta, and Rhizaria. Sequences of small heterotrophic flagellates were affiliated mainly with the Alveolata (Apicomplexa), Stramenopiles (Chrysophyceae), and Rhizaria (Cercozoa). This survey showed that there is high protozoan species richness in meat-cutting plants and that the species included species related to known hosts of food-borne pathogens.
Self-Cloning Baker's Yeasts That Accumulate Proline Enhance Freeze Tolerance in Doughs
Authors: Kaino Tomohiro , Tateiwa Tetsuya , Mizukami-Murata Satomi , Shima Jun , Takagi Hiroshi 
Published: July 2008

ABSTRACT

We constructed self-cloning diploid baker's yeast strains by disrupting
PUT1
, encoding proline oxidase, and replacing the wild-type
PRO1
, encoding γ-glutamyl kinase, with a
pro1
(
D154N
) or
pro1
(
I150T
) allele. The resultant strains accumulated intracellular proline and retained higher-level fermentation abilities in the frozen doughs than the wild-type strain. These results suggest that proline-accumulating baker's yeast is suitable for frozen-dough baking.
Plant Lesions Promote the Rapid Multiplication of
Escherichia coli
O157:H7 on Postharvest Lettuce
Authors: Brandl M. T. 
Published: July 2008

ABSTRACT

Several outbreaks of
Escherichia coli
O157:H7 infections have been associated with minimally processed leafy vegetables in the United States. Harvesting and processing cause plant tissue damage. In order to assess the role of plant tissue damage in the contamination of leafy greens with
E. coli
O157:H7, the effect of mechanical, physiological, and plant disease-induced lesions on the growth of this pathogen on postharvest romaine lettuce was investigated. Within only 4 h after inoculation, the population sizes of
E. coli
O157:H7 increased 4.0-, 4.5-, and 11.0-fold on lettuce leaves that were mechanically bruised, cut into large pieces, and shredded into multiple pieces, respectively. During the same time,
E. coli
O157:H7 population sizes increased only twofold on leaves that were left intact after harvest. Also, the population size of
E. coli
O157:H7 was 27 times greater on young leaves affected by soft rot due to infection by
Erwinia chrysanthemi
than on healthy middle-aged leaves. Confocal microscopy revealed that leaf tip burn lesions, which are caused by a common physiological disorder of lettuce, harbored dense populations of
E. coli
O157:H7 cells both internally and externally. Investigation of the colonization of cut lettuce stems by
E. coli
O157:H7 showed that the pathogen grew 11-fold over 4 h of incubation after its inoculation onto the stems, from which large amounts of latex were released. The results of this study indicate that plant tissue damage of various types can promote significant multiplication of
E. coli
O157:H7 over a short time and suggest that harvesting and processing are critical control points in the prevention or reduction of
E. coli
O157:H7 contamination of lettuce.
Diversity of Bacterial Endosymbionts of Environmental
Acanthamoeba
Isolates
Authors: Schmitz-Esser Stephan , Toenshoff Elena R. , Haider Susanne , Heinz Eva , Hoenninger Verena M. , Wagner Michael , Horn Matthias 
Published: July 2008

ABSTRACT

Free-living amoebae are frequent hosts for bacterial endosymbionts. In this study, the symbionts of eight novel environmental
Acanthamoeba
strains isolated from different locations worldwide were characterized. Phylogenetic analysis revealed that they were related to one of four evolutionary lineages of amoeba symbionts recognized previously. This study provides evidence for the existence of only a small number of phylogenetically well-separated groups of obligate intracellular endosymbionts of acanthamoebae with global distribution.
Transmission of
Yersinia pseudotuberculosis
in the Pork Production Chain from Farm to Slaughterhouse
Authors: Laukkanen Riikka , Martínez Pilar Ortiz , Siekkinen Kirsi-Maarit , Ranta Jukka , Maijala Riitta , Korkeala Hannu 
Published: July 2008

ABSTRACT

The transmission of
Yersinia pseudotuberculosis
in the pork production chain was followed from farm to slaughterhouse by studying the same 364 pigs from different production systems at farm and slaughterhouse levels. In all, 1,785 samples were collected, and the isolated
Y. pseudotuberculosis
strains were analyzed by pulsed-field gel electrophoresis. The results of microbial sampling were combined with data from an on-farm observation and questionnaire study to elucidate the associations between farm factors and the prevalence of
Y. pseudotuberculosis
. Following the same pigs in the production chain from farm to slaughterhouse, we were able to show similar
Y. pseudotuberculosis
genotypes in live animals, pluck sets (containing tongue, tonsils, esophagus, trachea, heart, lungs, diaphragm, liver, and kidneys), and carcasses and to conclude that
Y. pseudotuberculosis
contamination originates from the farms, is transported to slaughterhouses with pigs, and transfers to pluck sets and carcasses in the slaughter process. The study also showed that the high prevalence of
Y. pseudotuberculosis
in live pigs predisposes carcasses and pluck sets to contamination. When production types and capacities were compared, the prevalence of
Y. pseudotuberculosis
was higher in organic production than in conventional production and on conventional farms with high rather than low production capacity. We were also able to associate specific farm factors with the prevalence of
Y. pseudotuberculosis
by using a questionnaire and on-farm observations. On farms, contact with pest animals and the outside environment and a rise in the number of pigs on the farm appear to increase the prevalence of
Y. pseudotuberculosis
.
Dynamics of Introduced Populations of
Phragmidium violaceum
and Implications for Biological Control of European Blackberry in Australia
Authors: Gomez D. R. , Evans K. J. , Baker J. , Harvey P. R. , Scott E. S. 
Published: July 2008

ABSTRACT

Phragmidium violaceum
causes leaf rust on the European blackberry (
Rubus fruticosus
L. aggregate). Multiple strains of this pathogen have been introduced into southern Australia for the biological control of at least 15 taxa of European blackberry, a nonindigenous, invasive plant. In climates conducive to leaf rust, the intensity of disease varies within and among infestations of the genetically variable host. Genetic markers developed from the selective amplification of microsatellite polymorphic loci were used to assess the population genetic structure and reproductive biology of
P. violaceum
within and among four geographically isolated and diseased infestations of the European blackberry in Victoria, Australia. Despite the potential for long-distance aerial dispersal of urediniospores, there was significant genetic differentiation among all populations, which was not associated with geographic separation. An assessment of multilocus linkage disequilibrium revealed temporal and geographic variation in the occurrence of random mating among the four populations. The presence of sexual spore states and the results of genetic analyses indicated that recombination, and potentially random migration and genetic drift, played an important role in maintaining genotypic variation within populations. Recombination and genetic differentiation in
P. violaceum
, as well as the potential for metapopulation structure, suggest the need to release additional, genetically diverse strains of the biocontrol agent at numerous sites across the distribution of the Australian blackberry infestation for maximum establishment and persistence.
TolC-Dependent Exclusion of Porphyrins in
Escherichia coli
Authors: Tatsumi Ryoko , Wachi Masaaki 
Published: July 2008

ABSTRACT

We found that
Escherichia coli tolC
mutants showed increased sensitivity to 5-aminolevulinic acid (ALA), a precursor of porphyrins. The
tolC
mutant cells grown in the presence of ALA showed a reddish brown color under visible light and a strong red fluorescence under near-UV irradiation. Fluorescence spectrometry and high-performance liquid chromatography analysis showed that the
tolC
mutant cells grown in the presence of ALA accumulated a large amount of coproporphyrin(ogen) intracellularly. In contrast, the wild-type cells produced coproporphyrin extracellularly. The
tolC
mutant cells grown in the presence of ALA, which were capable of surviving in the dark, were killed by near-UV irradiation, suggesting that the intracellular coproporphyrin(ogen) renders these cells photosensitive. These results suggest that the TolC-dependent efflux system is involved in the exclusion of porphyrin(ogen)s in
E. coli
.