bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Extracellular Products of
Pseudoalteromonas atlantica
on the Edible Crab
Cancer pagurus
Authors: Costa-Ramos Carolina , Rowley Andrew F. 
Published: February 2004

ABSTRACT

Previous studies have shown that injection of extracellular products (ECP) of
Pseudoalteromononas atlantica
isolated from shell disease-infected edible crabs (
Cancer pagurus
) into healthy crabs causes rapid death. In this study we examined the nature of the active lethal factor(s) in ECP. Injection of ECP into crabs caused a rapid decline in the total number of circulating hemocytes (blood cells), and the crabs died within 60 to 90 min. The individuals that died showed eyestalk retraction, limb paralysis, and lack of antennal sensitivity, suggesting that the active factor(s) targeted the nervous system. Histopathological investigations showed that affected crabs had large aggregates of hemocytes in the gills, and there was destruction of the tubules in the hepatopancreas. The active factor in ECP was not sensitive to heat treatment (100°C for 30 min) and proteinase K digestion. As lipopolysaccharide (LPS) was a potential candidate for the lethal factor, it was purified from whole
P. atlantica
bacteria or ECP and subsequently injected into crabs. These crabs had all of the external symptoms observed previously with ECP, such as limb paralysis and eyestalk retraction, and they died within 90 min after challenge, although no significant decline in the number of circulating hemocytes was observed. Similarly, in vitro incubation of hemocytes with purified LPS (1 to 20 μg) from
P. atlantica
did not result in the clumping reaction observed with ECP but did result in a degranulation reaction and eventual cell lysis. Injection of crabs with
Escherichia coli
or
Pseudomonas aeruginosa
LPS (1 μg g of body weight
−1
) did not cause any of the characteristic symptoms observed following exposure to
P. atlantica
LPS. No mortality of crabs followed the injection of
E. coli
LPS, but
P. aeruginosa
LPS caused ca. 80% mortality at 2 h after injection. Overall, these results show that the main virulence factor of
P. atlantica
for edible crabs is LPS either alone or in combination with other heat-stable factors.
Stable Carbon Isotope Ratios of Lipid Biomarkers of Sulfate-Reducing Bacteria
Authors: Londry K. L. , Jahnke L. L. , Des Marais D. J. 
Published: February 2004

ABSTRACT

We examined the potential use of natural-abundance stable carbon isotope ratios of lipids for determining substrate usage by sulfate-reducing bacteria (SRB). Four SRB were grown under autotrophic, mixotrophic, or heterotrophic growth conditions, and the δ
13
C values of their individual fatty acids (FA) were determined. The FA were usually
13
C depleted in relation to biomass, with Δδ
13
C
(FA − biomass)
of −4 to −17‰; the greatest depletion occurred during heterotrophic growth. The exception was
Desulfotomaculum acetoxidans
, for which substrate limitation resulted in biomass and FA becoming isotopically heavier than the acetate substrate. The δ
13
C values of FA in
Desulfotomaculum acetoxidans
varied with the position of the double bond in the monounsaturated C
16
and C
18
FA, with FA becoming progressively more
13
C depleted as the double bond approached the methyl end. Mixotrophic growth of
Desulfovibrio desulfuricans
resulted in little depletion of the i17:1 biomarker relative to biomass or acetate, whereas growth with lactate resulted in a higher proportion of i17:1 with a greater depletion in
13
C. The relative abundances of 10Me16:0 in
Desulfobacter hydrogenophilus
and
Desulfobacterium autotrophicum
were not affected by growth conditions, yet the Δδ
13
C
(FA − substrate)
values of 10Me16:0 were considerably greater during autotrophic growth. These experiments indicate that FA δ
13
C values can be useful for interpreting carbon utilization by SRB in natural environments.
Role of Calf-Adapted
Escherichia coli
in Maintenance of Antimicrobial Drug Resistance in Dairy Calves
Authors: Khachatryan Artashes R. , Hancock Dale D. , Besser Thomas E. , Call Douglas R. 
Published: February 2004

ABSTRACT

The prevalence of antimicrobial drug-resistant bacteria is typically highest in younger animals, and prevalence is not necessarily related to recent use of antimicrobial drugs. In dairy cattle, we hypothesize that antimicrobial drug-resistant, neonate-adapted bacteria are responsible for the observed high frequencies of resistant
Escherichia coli
in calves. To explore this issue, we examined the age distribution of antimicrobial drug-resistant
E. coli
from Holstein cattle at a local dairy and conducted an experiment to determine if low doses of oxytetracycline affected the prevalence of antimicrobial drug-resistant
E. coli
. Isolates resistant to tetracycline (>4 μg/ml) were more prevalent in <3-month-old calves (79%) compared with lactating cows (14%). In an experimental trial where calves received diets supplemented with or without oxytetracycline, the prevalence of tetracycline-resistant
E. coli
was slightly higher for the latter group (
P
= 0.039), indicating that drug use was not required to maintain a high prevalence of resistant
E. coli
. The most common resistance pattern among calf
E. coli
isolates included resistance to streptomycin (>12 μg/ml), sulfadiazine (>512 μg/ml), and tetracycline (>4 μg/ml) (SSuT), and this resistance pattern was most prevalent during the period when calves were on milk diets. To determine if prevalence was a function of differential fitness, we orally inoculated animals with nalidixic acid-resistant strains of SSuT
E. coli
and susceptible
E. coli
. Shedding of SSuT
E. coli
was significantly greater than that of susceptible strains in neonatal calves (
P
< 0.001), whereas there was no difference in older animals (
P
= 0.5). These data support the hypothesis that active selection for traits linked to the SSuT phenotype are responsible for maintaining drug-resistant
E. coli
in this population of dairy calves.
Phylogenetic Composition of Arctic Ocean Archaeal Assemblages and Comparison with Antarctic Assemblages
Authors: Bano Nasreen , Ruffin Shomari , Ransom Briana , Hollibaugh James T. 
Published: February 2004

ABSTRACT

Archaea
assemblages from the Arctic Ocean and Antarctic waters were compared by PCR-denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes amplified using the
Archaea
-specific primers 344f and 517r. Inspection of the DGGE fingerprints of 33 samples from the Arctic Ocean (from SCICEX submarine cruises in 1995, 1996, and 1997) and 7 Antarctic samples from Gerlache Strait and Dallman Bay revealed that the richness of
Archaea
assemblages was greater in samples from deep water than in those from the upper water column in both polar oceans. DGGE banding patterns suggested that most of the
Archaea
ribotypes were common to both the Arctic Ocean and the Antarctic Ocean. However, some of the
Euryarchaeota
ribotypes were unique to each system. Cluster analysis of DGGE fingerprints revealed no seasonal variation but supported depth-related differences in the composition of the Arctic Ocean
Archaea
assemblage. The phylogenetic composition of the
Archaea
assemblage was determined by cloning and then sequencing amplicons obtained from the
Archaea
-specific primers 21f and 958r. Sequences of 198 clones from nine samples covering three seasons and all depths grouped with marine group I
Crenarchaeota
(111 clones), marine group II
Euryarchaeota
(86 clones), and group IV
Euryarchaeota
(1 clone). A sequence obtained only from a DGGE band was similar to those of the marine group III
Euryarchaeota
.
Impact of Virioplankton on Archaeal and Bacterial Community Richness as Assessed in Seawater Batch Cultures
Authors: Winter Christian , Smit Arjan , Herndl Gerhard J. , Weinbauer Markus G. 
Published: February 2004

ABSTRACT

During cruises in the tropical Atlantic Ocean (January to February 2000) and the southern North Sea (December 2000), experiments were conducted to monitor the impact of virioplankton on archaeal and bacterial community richness. Prokaryotic cells equivalent to 10 to 100% of the in situ abundance were inoculated into virus-free seawater, and viruses equivalent to 35 to 360% of the in situ abundance were added. Batch cultures with microwave-inactivated viruses and without viruses served as controls. The apparent richness of archaeal and bacterial communities was determined by terminal restriction fragment length polymorphism (T-RFLP) analysis of PCR-amplified 16S rRNA gene fragments. Although the estimated richness of the prokaryotic communities generally was greatly reduced within the first 24 h of incubation due to confinement, the effects of virus amendment were detected at the level of individual operational taxonomic units (OTUs) in the T-RFLP patterns of both groups,
Archaea
and
Bacteria
. One group of OTUs was detected in the control samples but was absent from the virus-treated samples. This negative response of OTUs to virus amendment probably was caused by viral lysis. Additionally, we found OTUs not responding to the amendments, and several OTUs exhibited variable responses to the addition of inactive or active viruses. Therefore, we conclude that individual members of pelagic archaeal and bacterial communities can be differently affected by the presence of virioplankton.
Effect of Environmental Factors on the Relationship between Concentrations of Coprostanol and Fecal Indicator Bacteria in Tropical (Mekong Delta) and Temperate (Tokyo) Freshwaters
Authors: Isobe Kei O. , Tarao Mitsunori , Chiem Nguyen H. , Minh Le Y. , Takada Hideshige 
Published: February 2004

ABSTRACT

A reliable assessment of microbial indicators of fecal pollution (total coliform,
Escherichia coli
, and fecal streptococcus) is critical in tropical environments. Therefore, we investigated the relationship between concentrations of indicator bacteria and a chemical indicator, coprostanol (5β-cholestan-3β-ol), in tropical and temperate regions. Water samples were collected from the Mekong Delta, Vietnam, during wet and dry seasons, and from Tokyo, Japan, during summer, the aftermath of a typhoon, and winter. During the wet season in the Mekong Delta, higher bacterial densities were observed in rivers, probably due to the higher bacterial inputs from soil particles with runoff. In Tokyo, higher bacterial densities were usually observed during summer, followed by those in the typhoon aftermath and winter. A strong logarithmic correlation between the concentrations of
E. coli
and coprostanol was demonstrated in all surveys. Distinctive seasonal fluctuations were observed, as concentrations of coprostanol corresponding to 1,000 CFU of
E. coli
/100 ml were at their lowest during the wet season in the Mekong Delta and the typhoon aftermath in Tokyo (30 ng/liter), followed by the dry season in the Mekong Delta and the summer in Tokyo (100 ng/liter), and they were much higher during the winter in Tokyo (400 ng/liter). These results suggested that
E. coli
is a specific indicator of fecal contamination in both tropical and temperate regions but that the densities are affected by elevated water temperature and input from runoff of soil particles. The concurrent determination of
E. coli
and coprostanol concentrations could provide a possible approach to assessing the reliability of fecal pollution monitoring data.
Genotypic and Antibiotic Susceptibility Characteristics of a
Campylobacter coli
Population Isolated from Dairy Farmland in the United Kingdom
Authors: Leatherbarrow A. J. H. , Hart C. A. , Kemp R. , Williams N. J. , Ridley A. , Sharma M. , Diggle P. J. , Wright E. J. , Sutherst J. , French N. P. 
Published: February 2004

ABSTRACT

Campylobacter
infections are the most common cause of bacterial enteritis in humans, and nearly 8% of such infections are caused by
Campylobacter coli
. Most studies have concentrated on
Campylobacter jejuni
, frequently isolated from intensively farmed poultry and livestock production units, and few studies have examined the spread and relatedness of
Campylobacter
across a range of geographical and host boundaries. Systematic sampling of a 100-km
2
area of mixed farmland in northwest England yielded 88 isolates of
C. coli
from a range of sample types and locations, and water was heavily represented. Screening for antibiotic resistance revealed a very low prevalence of resistance, while genotyping performed by using three methods (
flaA
PCR restriction fragment length polymorphism [RFLP], pulsed-field gel electrophoresis [PFGE], and fluorescent amplified fragment length polymorphism [fAFLP]) provided insights into the genomic relatedness of isolates from different locations and hosts. Isolates were classified into 23
flaA
groups, 34 PFGE groups, and five major fAFLP clusters. PFGE banding analysis revealed a high level of variability and no clustering by sample type. fAFLP and
flaA
analyses successfully grouped the isolates by sample type. We report preliminary findings suggesting that there is a strain of
C. coli
which may have become adapted to survival or persistence in water and that there is a group of mainly water-derived isolates from which unusual
flaA
PCR fragments were recovered.
Genetic Diversity of
Cryptosporidium
spp. in Captive Reptiles
Authors: Xiao Lihua , Ryan Una M. , Graczyk Thaddeus K. , Limor Josef , Li Lixia , Kombert Mark , Junge Randy , Sulaiman Irshad M. , Zhou Ling , Arrowood Michael J. , Koudela Břetislav , Modrý David , Lal Altaf A. 
Published: February 2004

ABSTRACT

The genetic diversity of
Cryptosporidium
in reptiles was analyzed by PCR-restriction fragment length polymorphism and sequence analysis of the small subunit rRNA gene. A total of 123 samples were analyzed, of which 48 snake samples, 24 lizard samples, and 3 tortoise samples were positive for
Cryptosporidium
. Nine different types of
Cryptosporidium
were found, including
Cryptosporidium serpentis
,
Cryptosporidium
desert monitor genotype,
Cryptosporidium muris
,
Cryptosporidium parvum
bovine and mouse genotypes, one
C. serpentis
-like parasite in a lizard, two new
Cryptosporidium
spp. in snakes, and one new
Cryptosporidium
sp. in tortoises.
C. serpentis
and the desert monitor genotype were the most common parasites and were found in both snakes and lizards, whereas the
C. muris
and
C. parvum
parasites detected were probably the result of ingestion of infected rodents. Sequence and biologic characterizations indicated that the desert monitor genotype was
Cryptosporidium saurophilum
. Two host-adapted
C. serpentis
genotypes were found in snakes and lizards.
Biodiversity of Exopolysaccharides Produced by
Streptococcus thermophilus
Strains Is Reflected in Their Production and Their Molecular and Functional Characteristics
Authors: Vaningelgem Frederik , Zamfir Medana , Mozzi Fernanda , Adriany Tom , Vancanneyt Marc , Swings Jean , De Vuyst Luc 
Published: February 2004

ABSTRACT

Twenty-six lactic acid bacterium strains isolated from European dairy products were identified as
Streptococcus thermophilus
and characterized by bacterial growth and exopolysaccharide (EPS)-producing capacity in milk and enriched milk medium. In addition, the acidification rates of the different strains were compared with their milk clotting behaviors. The majority of the strains grew better when yeast extract and peptone were added to the milk medium, although the presence of interfering glucomannans was shown, making this medium unsuitable for EPS screening. EPS production was found to be strain dependent, with the majority of the strains producing between 20 and 100 mg of polymer dry mass per liter of fermented milk medium. Furthermore, no straightforward relationship between the apparent viscosity and EPS production could be detected in fermented milk medium. An analysis of the molecular masses of the isolated EPS by gel permeation chromatography revealed a large variety, ranging from 10 to >2,000 kDa. A distinction could be made between high-molecular-mass EPS (>1,000 kDa) and low-molecular-mass EPS (<1,000 kDa). Based on the molecular size of the EPS, three groups of EPS-producing strains were distinguished. Monomer analysis of the EPS by high-performance anion-exchange chromatography with amperometric detection was demonstrated to be a fast and simple method. All of the EPS from the
S. thermophilus
strains tested were classified into six groups according to their monomer compositions. Apart from galactose and glucose, other monomers, such as (
N
-acetyl)galactosamine, (
N
-acetyl)glucosamine, and rhamnose, were also found as repeating unit constituents. Three strains were found to produce EPS containing (
N
-acetyl)glucosamine, which to our knowledge was never found before in an EPS from
S. thermophilus
. Furthermore, within each group, differences in monomer ratios were observed, indicating possible novel EPS structures. Finally, large differences between the consistencies of EPS solutions from five different strains were assigned to differences in their molecular masses and structures.
Insecticidal
Bacillus thuringiensis
Silences
Erwinia carotovora
Virulence by a New Form of Microbial Antagonism, Signal Interference
Authors: Dong Yi-Hu , Zhang Xi-Fen , Xu Jin-Ling , Zhang Lian-Hui 
Published: February 2004

ABSTRACT

It is commonly known that bacteria may produce antibiotics to interfere with the normal biological functions of their competitors in order to gain competitive advantages. Here we report that
Bacillus thuringiensis
suppressed the quorum-sensing-dependent virulence of plant pathogen
Erwinia carotovora
through a new form of microbial antagonism, signal interference.
E. carotovora
produces and responds to acyl-homoserine lactone (AHL) quorum-sensing signals to regulate antibiotic production and expression of virulence genes, whereas
B. thuringiensis
strains possess AHL-lactonase, which is a potent AHL-degrading enzyme.
B. thuringiensis
did not seem to interfere with the normal growth of
E. carotovora
; rather, it abolished the accumulation of AHL signal when they were cocultured. In planta,
B. thuringiensis
significantly decreased the incidence of
E. carotovora
infection and symptom development of potato soft rot caused by the pathogen. The biocontrol efficiency is correlated with the ability of bacterial strains to produce AHL-lactonase. While all the seven AHL-lactonase-producing
B. thuringiensis
strains provided significant protection against
E. carotovora
infection,
Bacillus fusiformis
and
Escherichia coli
strains that do not process AHL-degradation enzyme showed little effect in biocontrol. Mutation of
aiiA
, the gene encoding AHL-lactonase in
B. thuringiensis
, resulted in a substantial decrease in biocontrol efficacy. These results suggest that signal interference mechanisms existing in natural ecosystems could be explored as a new version of antagonism for prevention of bacterial infections.
Genetic Selection Scheme for Isolation of Signal Transduction Pathway Mutants
Authors: Anandan Shivanthi , Uram Jennifer 
Published: February 2004

ABSTRACT

Genetic characterization of a signal transduction pathway requires the isolation of mutations in the pathway. Characterization of these mutated genes and their loci enumerates the components of the pathway and leads to an understanding of the role of each gene locus in the pathway under study. We have designed and developed a strategy based on resistance to the chemical flucytosine for the identification of mutations in a given pathway. In this study, the
Escherichia coli codA
gene, which encodes the enzyme cytosine deaminase, was fused to the light-intensity-regulated gene promoter
psbDII
. Cytosine deaminase converts 5′-fluorocytosine to the toxic product 5-fluorouracil. Wild-type cells containing an intact signal transduction pathway that regulates the
psbDII
promoter will die in the presence of this chemical. Cells that carry mutations in the pathway that inactivate the
psbDII
promoter will not express the
codA
gene and, consequently, will live on 5′-fluorocytosine, allowing the isolation and subsequent characterization of mutations in this signaling pathway. Utilizing this selection method, we have successfully isolated and characterized mutations in the
psbDII
pathway. This selection scheme can be used with a tissue-specific or phase-specific promoter fused to the
codA
gene to direct the timing of expression of
codA
to obtain mutants defective in temporal or cell-specific expression of a particular pathway. This scheme also allows the isolation of mutants even when a clearly identifiable phenotype is not available. The selection scheme presented here extends the molecular tools available for the genetic dissection of signal transduction pathways.
Impact of a Disruption of a Pathway Delivering Copper to Mitochondria onPodospora anserinaMetabolism and Life Span
Authors: Stumpferl Stefan W. , Stephan Oliver , Osiewacz Heinz D. 
Published: February 2004

ABSTRACTA global depletion of cellular copper as the result of a deficiency in high-affinity copper uptake was previously shown to affect the phenotype and life span of the filamentous fungusPodospora anserina. We report here the construction of a strain in which the delivery of copper to complex IV of the mitochondrial respiratory chain is affected. This strain, PaCox17::ble, is aPaCox17-null mutant that does not synthesize the molecular chaperone targeting copper to cytochromecoxidase subunit II. PaCox17::ble is characterized by a decreased growth rate, a reduction in aerial hyphae formation, reduced female fertility, and a dramatic increase in life span. The mutant respires via a cyanide-resistant alternative pathway, displays superoxide dismutase (SOD) activity profiles significantly differing from those of the wild-type strain and is characterized by a stabilization of the mitochondrial DNA. Collectively, the presented data define individual components of a molecular network effective in life span modulation and copper as an element with a dual effect. As a cofactor of complex IV of the respiratory chain, it is indirectly involved in the generation of reactive oxygen species (ROS) and thereby plays a life span-limiting role. In contrast, Cu/Zn SOD as a ROS-scavenging enzyme lowers molecular damage and thus positively affects life span. Such considerations explain the reported differences in life span of independent mutants and spread more light on the delicate tuning of the molecular network influencing biological ageing.
SmD1 Is Required for Spliced Leader RNA Biogenesis
Authors: Zeiner Gusti M. , Foldynová Silvie , Sturm Nancy R. , Lukeš Julius , Campbell David A. 
Published: February 2004

ABSTRACT

The Sm-binding site of the kinetoplastid spliced leader RNA has been implicated in accurate spliced leader RNA maturation and
trans
-splicing competence. In
Trypanosoma brucei
, RNA interference-mediated knockdown of SmD1 caused defects in spliced leader RNA maturation, displaying aberrant 3′-end formation, partial formation of cap 4, and overaccumulation in the cytoplasm; U
28
pseudouridylation was unaffected.