bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inactivation of
Escherichia coli
O157:H7 in Simulated Human Gastric Fluid
Authors: Tamplin Mark L. 
Published: January 2005

ABSTRACT

Human disease caused by
Escherichia coli
O157:H7 is a function of the number of cells that are present at potential sites of infection and host susceptibility. Such infectious doses are a result, in part, of the quantity of cells that are ingested and that survive human host defenses, such as the low-pH environment of the stomach. To more fully understand the kinetics of
E. coli
O157:H7 survival in gastric fluid, individual
E. coli
O157:H7 strains were suspended in various media (i.e., saline, cooked ground beef [CGB], and CGB containing a commercial antacid product [CGB+A]), mixed at various proportions with simulated human gastric fluid (SGF), and then incubated at 37°C for up to 4 h. The highest inactivation rate among nine
E. coli
O157:H7 strains was observed in saline. Specifically, the average survival rates in 100:1 and 10:1 proportions of SGF-saline were −1.344 ± 0.564 and −0.997 ± 0.388 log
10
CFU/h, respectively. In contrast, the average inactivation rate for 10
E. coli
O157:H7 strains suspended in 10:1 SGF-CGB was −0.081 ± 0.068, a rate that was 12-fold lower than that observed for SGF-saline. In comparison, the average inactivation rate for
Shigella flexneri
strain 5348 in 100:1 and 10:1 SGF-saline was −8.784 and −17.310, respectively. These latter inactivation rates were 7- to 17-fold higher than those for
E. coli
O157:H7 strains in SGF-saline and were 4-fold higher than those for
E. coli
O157:H7 strains in SGF-CGB. The survival rate of
E. coli
O157:H7 strain GFP80EC increased as the dose of antacid increased from one-half to twice the prescribed dose. A similar trend was observed for the matrix pH over the range of pH 1.6 to 5.7, indicating that pH is a primary factor affecting
E. coli
O157:H7 survival in SGF-CGB+A. These results can be used in risk assessment to define dose-response relationships for
E. coli
O157:H7 and to evaluate potential surrogate organisms.
High-Pressure Inactivation of Hepatitis A Virus within Oysters
Authors: Calci Kevin R. , Meade Gloria K. , Tezloff Robert C. , Kingsley David H. 
Published: January 2005

ABSTRACT

Previous results demonstrated that hepatitis A virus (HAV) could be inactivated by high hydrostatic pressure (HHP) (D. H. Kingsley, D. Hoover, E. Papafragkou, and G. P. Richards, J. Food Prot. 65:1605-1609, 2002); however, direct evaluation of HAV inactivation within contaminated oysters was not performed. In this study, we report confirmation that HAV within contaminated shellfish is inactivated by HHP. Shellfish were initially contaminated with HAV by using a flowthrough system. PFU reductions of >1, >2, and >3 log
10
were observed for 1-min treatments at 350, 375, and 400 megapascals, respectively, within a temperature range of 8.7 to 10.3°C. Bioconcentration of nearly 6 log
10
PFU of HAV per oyster was achieved under simulated natural conditions. These results suggest that HHP treatment of raw shellfish will be a viable strategy for the reduction of infectious HAV.
Interactions between Oral Bacteria: Inhibition of
Streptococcus mutans
Bacteriocin Production by
Streptococcus gordonii
Authors: Wang Bing-Yan , Kuramitsu Howard K. 
Published: January 2005

ABSTRACT

Streptococcus mutans
has been recognized as an important etiological agent in human dental caries. Some strains of
S. mutans
also produce bacteriocins. In this study, we sought to demonstrate that bacteriocin production by
S. mutans
strains GS5 and BM71 was mediated by quorum sensing, which is dependent on a competence-stimulating peptide (CSP) signaling system encoded by the
com
genes. We also demonstrated that interactions with some other oral streptococci interfered with
S. mutans
bacteriocin production both in broth and in biofilms. The inhibition of
S. mutans
bacteriocin production by oral bacteria was stronger in biofilms than in broth. Using transposon Tn
916
mutagenesis, we identified a gene (
sgc
; named for
Streptococcus gordonii
challisin) responsible for the inhibition of
S. mutans
bacteriocin production by
S. gordonii
Challis. Interruption of the
sgc
gene in
S. gordonii
Challis resulted in attenuated inhibition of
S. mutans
bacteriocin production. The supernatant fluids from the
sgc
mutant did not inactivate the exogenous
S. mutans
CSP as did those from the parent strain Challis.
S. gordonii
Challis did not inactivate bacteriocin produced by
S. mutans
GS5. Because
S. mutans
uses quorum sensing to regulate virulence, strategies designed to interfere with these signaling systems may have broad applicability for biological control of this caries-causing organism.
Bacillus subtilis
α-Phosphoglucomutase Is Required for Normal Cell Morphology and Biofilm Formation
Authors: Lazarevic Vladimir , Soldo Blazenka , Médico Noël , Pooley Harold , Bron Sierd , Karamata Dimitri 
Published: January 2005

ABSTRACT

Mutations designated
gtaC
and
gtaE
that affect α-phosphoglucomutase activity required for interconversion of glucose 6-phosphate and α-glucose 1-phosphate were mapped to the
Bacillus subtilis pgcA
(
yhxB
) gene. Backcrossing of the two mutations into the 168 reference strain was accompanied by impaired α-phosphoglucomutase activity in the soluble cell extract fraction, altered colony and cell morphology, and resistance to phages φ29 and ρ11. Altered cell morphology, reversible by additional magnesium ions, may be correlated with a deficiency in the membrane glycolipid. The deficiency in biofilm formation in
gtaC
and
gtaE
mutants may be attributed to an inability to synthesize UDP-glucose, an important intermediate in a number of cell envelope biosynthetic processes.
Use of Gradient Plates To Study Combined Effects of Temperature, pH, and NaCl Concentration on Growth of
Monascus ruber
van Tieghem, an Ascomycetes Fungus Isolated from Green Table Olives
Authors: Panagou E. Z. , Skandamis P. N. , Nychas G.-J. E. 
Published: January 2005

ABSTRACT

The effect of temperature, pH, and sodium chloride concentration on the growth of the Ascomycetes fungus
Monascus ruber
van Tieghem, the main spoilage microorganism during storage of table olives, was studied by using the gradient plate technique. Gradients of NaCl (3 to 9%, wt/vol) at right angles to gradients of pH (2 to 6.8) were prepared for the plates, which were incubated at 25, 30, and 35°C. Visible fungal growth, expressed in optical density units, was recorded by image analysis and graphically presented in the form of three-dimensional grids. Results obtained from the plates indicated that the fungus was salt and acid tolerant, being able to grow at NaCl concentrations of up to 9% (wt/vol) and pH values of as low as 2.2, depending on the incubation temperature. The inhibitory effect of NaCl increased as the pH decreased progressively at 25 and 30°C but not at 35°C. Growth was better at 30 and 25°C as judged by the larger extent of the plates covered by mycelium compared with that at 35°C, where no growth was observed at pHs below 3.7. Differentiation between vegetative (imperfect-stage) and reproductive (perfect-stage) growth was evident on all plates, providing useful information about the effect of environmental conditions on the form of fungal growth. When the growth/no-growth surface model was obtained by applying linear logistic regression, it was found that all factors (pH, NaCl, and temperature) and their interactions were significant. Plots of growth/no-growth interfaces for
P
values of 0.1, 0.5, and 0.9 described the results satisfactorily at 25 and 35°C, whereas at 35°C the model predicted lower minimum pH values for growth in the range of 7 to 10% NaCl than those observed on the plates. Overall, it is suggested that the fungus cannot be inhibited by any combination of pH and NaCl within the limits of the brine environment, so further processing is required to ensure product stability in the market.
Effect of Direct Electric Current on the Cell Surface Properties of Phenol-Degrading Bacteria
Authors: Luo Qishi , Wang Hui , Zhang Xihui , Qian Yi 
Published: January 2005

ABSTRACT

The change in cell surface properties in the presence of electric currents is of critical concern when the potential to manipulate bacterial movement with electric fields is evaluated. In this study, the effects of different direct electric currents on the cell surface properties involved in bacterial adhesion were investigated by using a mixed phenol-degrading bacterial culture in the exponential growth phase. The traits investigated were surface hydrophobicity (measured by adherence to
n
-octane), net surface electrostatic charge (determined by measurement of the zeta potential), and the cell surface shape and polymers (determined by scanning electron microscope analysis). The results showed that a lower current (less than 20 mA) induced no significant changes in the surface properties of phenol-degrading bacteria, that an electric current of 20 mA could increase the surface hydrophobicity and flatten the cell shape, and that a higher current (40 mA) could increase the surface extracellular substances and the net negative surface electrostatic charge. The results also revealed that the electric current effects on cell hydrophobicity varied with the suspending medium. We suggest that an electric current greater than 20 mA is not suitable for use in manipulation of the movement of the phenol-degrading bacteria, although such a current might favor the electrophoretic movement of the bacterial species.
Use of Fluorophore-Conjugated Lectins To Study Cell-Cell Interactions in Model Marine Biofilms
Authors: Wigglesworth-Cooksey Barbara , Cooksey Keith E. 
Published: January 2005

ABSTRACT

Biofilms dominated by pennate diatoms are important in fields as diverse as ship biofouling and marine littoral sediment stabilization. The architecture of a biofilm depends on the fact that much of its mass consists of extracellular polymers. Although most illuminated biofilms in nature are dominated by phototrophs, they also contain heterotrophic bacteria. Given the close spatial association of the two types of organisms, cell-cell interaction is likely. Fluorophore-conjugated lectins were used to demonstrate the sites of the various extracellular polymers in three species of diatoms. Based on their lectin staining properties, the polymers in different species appeared to be similar, but their involvement in the process of attachment to a surface differed. In a coculture
Pseudoalteromonas
sp. strain 4 or its sterilized spent medium reduced the ability of
Amphora coffeaeformis
and
Navicula
sp. strains 1 and D to adhere, inhibited motility, and caused agglutination and eventually diatom cell lysis. Diatoms could be protected from the negative effects of the bacterial spent medium if
d
-galactose or mannan was included in the incubation medium. The active principle of the spent medium is probably a lectin/agglutinin that is able to bind to the extracellular polymers of the diatoms that are involved in adhesion and motility. Awareness of interactions of this type is important in the study of natural biofilms.
Isolation of Llama Antibody Fragments for Prevention of Dandruff by Phage Display in Shampoo
Authors: Dolk Edward , van der Vaart Marcel , Lutje Hulsik David , Vriend Gert , de Haard Hans , Spinelli Silvia , Cambillau Christian , Frenken Leon , Verrips Theo 
Published: January 2005

ABSTRACT

As part of research exploring the feasibility of using antibody fragments to inhibit the growth of organisms implicated in dandruff, we isolated antibody fragments that bind to a cell surface protein of
Malassezia furfur
in the presence of shampoo. We found that phage display of llama single-domain antibody fragments (VHHs) can be extended to very harsh conditions, such as the presence of shampoo containing nonionic and anionic surfactants. We selected several VHHs that bind to the cell wall protein Malf1 of
M. furfur
, a fungus implicated in causing dandruff. In addition to high stability in the presence of shampoo, these VHHs are also stable under other denaturing conditions, such as high urea concentrations. Many of the stable VHHs were found to contain arginine at position 44. Replacement of the native amino acid at position 44 with arginine in the most stable VHH that lacked this arginine resulted in a dramatic further increase in the stability. The combination of the unique properties of VHHs together with applied phage display and protein engineering is a powerful method for obtaining highly stable VHHs that can be used in a wide range of applications.
Simultaneous Recovery of Extracellular and Intracellular DNA Suitable for Molecular Studies from Marine Sediments
Authors: Corinaldesi Cinzia , Danovaro Roberto , Dell'Anno Antonio 
Published: January 2005

ABSTRACT
The occurrence of high extracellular DNA concentrations in aquatic sediments (concentrations that are 3 to 4 orders of magnitude greater than those in the water column) might play an important role in biogeochemical cycling, as well as in horizontal gene transfer through natural transformation. Since isolation of extracellular DNA from sediments is a difficult and unsolved task, in this study we developed an efficient procedure to recover simultaneously DNA associated with microbial cells and extracellular DNA from the same sediment sample. This procedure is specifically suitable for studying extracellular DNA because it avoids any contamination with DNA released by cell lysis during handling and extraction. Applying this procedure to different sediment types, we obtained extracellular DNA concentrations that were about 10 to 70 times higher than the intracellular DNA concentrations. Using specific targeted prokaryotic primers, we obtained evidence that extracellular DNA recovered from different sediments did not contain amplifiable 16S rRNA genes. By contrast, using DNA extracted from microbial cells as the template, we always amplified 16S rRNA genes. Although 16S rRNA genes were not detected in extracellular DNA, analyses of the sizes of extracellular DNA indicated the presence of high-molecular-weight fragments that might have contained other gene sequences. This protocol allows investigation of extracellular DNA and its possible participation in natural transformation processes.
Diversity and Distribution of Methanotrophic Archaea at Cold Seeps
Authors: Knittel Katrin , Lösekann Tina , Boetius Antje , Kort Renate , Amann Rudolf 
Published: January 2005

ABSTRACT

In this study we investigated by using 16S rRNA-based methods the distribution and biomass of archaea in samples from (i) sediments above outcropping methane hydrate at Hydrate Ridge (Cascadia margin off Oregon) and (ii) massive microbial mats enclosing carbonate reefs (Crimea area, Black Sea). The archaeal diversity was low in both locations; there were only four (Hydrate Ridge) and five (Black Sea) different phylogenetic clusters of sequences, most of which belonged to the methanotrophic archaea (ANME). ANME group 2 (ANME-2) sequences were the most abundant and diverse sequences at Hydrate Ridge, whereas ANME-1 sequences dominated the Black Sea mats. Other seep-specific sequences belonged to the newly defined group ANME-3 (related to
Methanococcoides
spp.) and to the
Crenarchaeota
of marine benthic group B. Quantitative analysis of the samples by fluorescence in situ hybridization (FISH) showed that ANME-1 and ANME-2 co-occurred at the cold seep sites investigated. At Hydrate Ridge the surface sediments were dominated by aggregates consisting of ANME-2 and members of the
Desulfosarcina-Desulfococcus
branch (DSS) (ANME-2/DSS aggregates), which accounted for >90% of the total cell biomass. The numbers of ANME-1 cells increased strongly with depth; these cells accounted 1% of all single cells at the surface and more than 30% of all single cells (5% of the total cells) in 7- to 10-cm sediment horizons that were directly above layers of gas hydrate. In the Black Sea microbial mats ANME-1 accounted for about 50% of all cells. ANME-2/DSS aggregates occurred in microenvironments within the mat but accounted for only 1% of the total cells. FISH probes for the ANME-2a and ANME-2c subclusters were designed based on a comparative 16S rRNA analysis. In Hydrate Ridge sediments ANME-2a/DSS and ANME-2c/DSS aggregates differed significantly in morphology and abundance. The relative abundance values for these subgroups were remarkably different at
Beggiatoa
sites (80% ANME-2a, 20% ANME-2c) and
Calyptogena
sites (20% ANME-2a, 80% ANME-2c), indicating that there was preferential selection of the groups in the two habitats. These variations in the distribution, diversity, and morphology of methanotrophic consortia are discussed with respect to the presence of microbial ecotypes, niche formation, and biogeography.
Nearly Identical Bacteriophage Structural Gene Sequences Are Widely Distributed in both Marine and Freshwater Environments
Authors: Short Cindy M. , Suttle Curtis A. 
Published: January 2005

ABSTRACT
Primers were designed to amplify a 592-bp region within a conserved structural gene (g20) found in some cyanophages. The goal was to use this gene as a proxy to infer genetic richness in natural cyanophage communities and to determine if sequences were more similar in similar environments. Gene products were amplified from samples from the Gulf of Mexico, the Arctic, Southern, and Northeast and Southeast Pacific Oceans, an Arctic cyanobacterial mat, a catfish production pond, lakes in Canada and Germany, and a depth of ca. 3,246 m in the Chuckchi Sea. Amplicons were separated by denaturing gradient gel electrophoresis, and selected bands were sequenced. Phylogenetic analysis revealed four previously unknown groups of g20 clusters, two of which were entirely found in freshwater. Also, sequences with >99% identities were recovered from environments that differed greatly in temperature and salinity. For example, nearly identical sequences were recovered from the Gulf of Mexico, the Southern Pacific Ocean, an Arctic freshwater cyanobacterial mat, and Lake Constance, Germany. These results imply that closely related hosts and the viruses infecting them are distributed widely across environments or that horizontal gene exchange occurs among phage communities from very different environments. Moreover, the amplification of g20 products from deep in the cyanobacterium-sparse Chuckchi Sea suggests that this primer set targets bacteriophages other than those infecting cyanobacteria.
Monitoring of Antibiotic-Induced Alterations in the Human Intestinal Microflora and Detection of Probiotic Strains by Use of Terminal Restriction Fragment Length Polymorphism
Authors: Jernberg Cecilia , Sullivan Åsa , Edlund Charlotta , Jansson Janet K. 
Published: January 2005

ABSTRACT

Terminal restriction fragment length polymorphism (T-RFLP) was investigated as a tool for monitoring the human intestinal microflora during antibiotic treatment and during ingestion of a probiotic product. Fecal samples from eight healthy volunteers were taken before, during, and after administration of clindamycin. During treatment, four subjects were given a probiotic, and four subjects were given a placebo. Changes in the microbial intestinal community composition and relative abundance of specific microbial populations in each subject were monitored by using viable counts and T-RFLP fingerprints. T-RFLP was also used to monitor specific bacterial populations that were either positively or negatively affected by clindamycin. Some dominant bacterial groups, such as
Eubacterium
spp., were easily monitored by T-RFLP, while they were hard to recover by cultivation. Furthermore, the two probiotic
Lactobacillus
strains were easily tracked by T-RFLP and were shown to be the dominant
Lactobacillus
community members in the intestinal microflora of subjects who received the probiotic.
Conjugal TOL Transfer from
Pseudomonas putida
to
Pseudomonas aeruginosa
: Effects of Restriction Proficiency, Toxicant Exposure, Cell Density Ratios, and Conjugation Detection Method on Observed Transfer Efficiencies
Authors: Arango Pinedo Catalina , Smets Barth F. 
Published: January 2005

ABSTRACT

The effects of restriction proficiency and premating exposure to toxicants on conjugal transfer of the TOL plasmid between
Pseudomonas
spp. was investigated by examinations of filter matings. A
Pseudomonas putida
KT2442-derived strain carrying a
gfp
-tagged variant of the TOL plasmid was used as a donor, and both restriction-deficient (PAO1162N) and -proficient (PAO2002N)
Pseudomonas aeruginosa
strains were used as recipients. The in situ enumeration of conjugation events allowed us to obtain frequency estimates that were unbiased by transconjugant growth or plasmid retransfer. We observed a strong dependence of the plasmid transfer frequency on the initial donor-to-recipient ratio of surface matings, which invalidated the use of mass action-based plasmid transfer kinetic estimators. Careful control of the initial parental cell densities permitted evaluations of the true effects of restriction proficiency and toxicant exposure on TOL transfer. At standard donor-to-recipient ratios (10
−3
for PAO1162N and 2 × 10
1
for PAO2002N) and total cell densities (10
5
cells/mm
2
for PAO1162N and 10
6
cells/mm
2
for PAO2002N), plasmid transfer frequencies without toxicant exposure were approximately 10
−7
(events/mm
2
)
−1
for PAO1162N and 10
−11
(events/mm
2
)
−1
for PAO2002N based on in situ observations of conjugation events. The enumeration of transconjugants via selective plating yielded transfer frequencies that were up to 1 order of magnitude lower. Premating exposure to sodium dodecyl sulfate (1 to 10 mM) significantly increased the transfer frequency for the restriction-proficient strain PAO2002N (
P
< 0.05) but not for the restriction-deficient strain PAO1162N. On the other hand, premating exposure to ethanol, toluene, or phenol had no positive effect on the plasmid transfer frequency. Clearly, restriction proficiency provides a strong barrier to interspecific transfer of the TOL plasmid, and this barrier was only marginally attenuated by recipient exposure to toxicants within the ranges examined.
First Record of the Rare SpeciesAeromonas culicicolafrom a Drinking Water Supply
Authors: Figueras M. J. , Suarez-Franquet A. , Chacón M. R. , Soler L. , Navarro M. , Alejandre C. , Grasa B. , Martínez-Murcia A. J. , Guarro J. 
Published: January 2005

ABSTRACTWe describe the recovery of the rare speciesAeromonas culicicola, so far known only in mosquitoes in India, from a drinking water supply in Spain. Typing, using enterobacterial repetitive intergenic consensus-PCR, revealed that the 27 new isolates belonged to 3 very closely related strains. These strains were genetically identified by 16S rRNA gene sequencing. Spanish strains differed from the mosquito strains in three nucleotide positions. The AHCYTOEN gene was present in these water strains, which may have a public health significance.
Byssochlamys nivea
as a Source of Mycophenolic Acid
Authors: Puel Olivier , Tadrist Souria , Galtier Pierre , Oswald Isabelle P. , Delaforge Marcel 
Published: January 2005

ABSTRACT

Byssochlamys
species are responsible for spoilage and degradation of fruits and silages and can also produce the mycotoxin patulin. We analyzed secondary metabolite production by
Byssochlamys nivea
. Mycophenolic acid and its precursors, 5-methylorsellinic acid and 5,7-dihydroxy-4-methylphthalide, were identified in all of the
B. nivea
strains that we examined.
Purification and Characterization of a Novel Class IIa Bacteriocin, Piscicocin CS526, from Surimi-Associated
Carnobacterium piscicola
CS526
Authors: Yamazaki Koji , Suzuki Minako , Kawai Yuji , Inoue Norio , Montville Thomas J. 
Published: January 2005

ABSTRACT

The bacteriocin piscicocin CS526 was inactivated by proteolytic enzymes, was stable at 100°C for 30 min, had a pH range of 2 to 8, and was active against
Enterococcus
,
Listeria
,
Pediococcus
, and
Leuconostoc
. The N-terminal sequence was YGNG

L

, not the YGNG

V

consensus motif common in class IIa bacteriocins (alternate residues underlined). The molecular mass of piscicocin CS526, which had a bactericidal mode of action, was ∼4,430 Da.