bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decolorization and Detoxification of Textile Dyes with a Laccase from
Trametes hirsuta
Authors: Abadulla Elias , Tzanov Tzanko , Costa Silgia , Robra Karl-Heinz , Cavaco-Paulo Artur , Gübitz Georg M. 
Published: July 2002

ABSTRACT

Trametes hirsuta
and a purified laccase from this organism were able to degrade triarylmethane, indigoid, azo, and anthraquinonic dyes. Initial decolorization velocities depended on the substituents on the phenolic rings of the dyes. Immobilization of the
T. hirsuta
laccase on alumina enhanced the thermal stabilities of the enzyme and its tolerance against some enzyme inhibitors, such as halides, copper chelators, and dyeing additives. The laccase lost 50% of its activity at 50 mM NaCl while the 50% inhibitory concentration (IC
50
) of the immobilized enzyme was 85 mM. Treatment of dyes with the immobilized laccase reduced their toxicities (based on the oxygen consumption rate of
Pseudomonas putida
) by up to 80% (anthraquinonic dyes). Textile effluents decolorized with
T. hirsuta
or the laccase were used for dyeing. Metabolites and/or enzyme protein strongly interacted with the dyeing process indicated by lower staining levels (K/S) values than obtained with a blank using water. However, when the effluents were decolorized with immobilized laccase, they could be used for dyeing and acceptable color differences (ΔE*) below 1.1 were measured for most dyes.
Role of ςBin Heat, Ethanol, Acid, and Oxidative Stress Resistance and during Carbon Starvation inListeria monocytogenes
Authors: Ferreira Adriana , O'Byrne Conor P. , Boor Kathryn J. 
Published: July 2002

ABSTRACTTo determine the contribution of sigma B (ςB) to survival of stationary-phaseListeria monocytogenescells following exposure to environmental stresses, we compared the viability of strain 10403S with that of an isogenic nonpolarsigBnull mutant strain after exposure to heat (50°C), ethanol (16.5%), or acid (pH 2.5). Strain viabilities were also determined under the same conditions in cultures that had been previously exposed to sublethal levels of the same stresses (45°C, 5% ethanol, or pH 4.5). The ΔsigBand wild-type strains had similar viabilities following exposure to ethanol and heat, but the ΔsigBstrain was almost 10,000-fold more susceptible to lethal acid stress than its parent strain. However, a 1-h preexposure to pH 4.5 yielded a 1,000-fold improvement in viability for the ΔsigBstrain. These results suggest the existence inL. monocytogenesof both a ςB-dependent mechanism and a pH-dependent mechanism for acid resistance in the stationary phase. ςBcontributed to resistance to both oxidative stress and carbon starvation inL. monocytogenes. The ΔsigBstrain was 100-fold more sensitive to 13.8 mM cumene hydroperoxide than the wild-type strain. Following glucose depletion, the ΔsigBstrain lost viability more rapidly than the parent strain. ςBcontributions to viability during carbon starvation and to acid resistance and oxidative stress resistance support the hypothesis that ςBplays a role in protectingL. monocytogenesagainst environmental adversities.
Determination of Pyrimidine Dimers in
Escherichia coli
and
Cryptosporidium parvum
during UV Light Inactivation, Photoreactivation, and Dark Repair
Authors: Oguma Kumiko , Katayama Hiroyuki , Mitani Hiroshi , Morita Shigemitsu , Hirata Tsuyoshi , Ohgaki Shinichiro 
Published: July 2002

ABSTRACT

UV inactivation, photoreactivation, and dark repair of
Escherichia coli
and
Cryptosporidium parvum
were investigated with the endonuclease sensitive site (ESS) assay, which can determine UV-induced pyrimidine dimers in the genomic DNA of microorganisms. In a 99.9% inactivation of
E. coli
, high correlation was observed between the dose of UV irradiation and the number of pyrimidine dimers induced in the DNA of
E. coli
. The colony-forming ability of
E. coli
also correlated highly with the number of pyrimidine dimers in the DNA, indicating that the ESS assay is comparable to the method conventionally used to measure colony-forming ability. When
E. coli
were exposed to fluorescent light after a 99.9% inactivation by UV irradiation, UV-induced pyrimidine dimers in the DNA were continuously repaired and the colony-forming ability recovered gradually. When kept in darkness after the UV inactivation, however,
E. coli
showed neither repair of pyrimidine dimers nor recovery of colony-forming ability. When
C. parvum
were exposed to fluorescent light after UV inactivation, UV-induced pyrimidine dimers in the DNA were continuously repaired, while no recovery of animal infectivity was observed. When kept in darkness after UV inactivation,
C. parvum
also showed no recovery of infectivity in spite of the repair of pyrimidine dimers. It was suggested, therefore, that the infectivity of
C. parvum
would not recover either by photoreactivation or by dark repair even after the repair of pyrimidine dimers in the genomic DNA.
Microbial Communities in the Chemocline of a Hypersaline Deep-Sea Basin (Urania Basin, Mediterranean Sea)
Authors: Sass Andrea M. , Sass Henrik , Coolen Marco J. L. , Cypionka Heribert , Overmann Jörg 
Published: July 2002

ABSTRACT

The Urania basin is a hypersaline sulfidic brine lake at the bottom of the eastern Mediterranean Sea. Since this basin is located at a depth of ∼3,500 m below the sea surface, it receives only a small amount of phytoplankton organic carbon. In the present study, the bacterial assemblages at the interface between the hypersaline brine and the overlaying seawater were investigated. The sulfide concentration increased from 0 to 10 mM within a vertical interval of 5 m across the interface. Within this chemocline, the total bacterial cell counts and the exoenzyme activities were elevated. Employing 11 cultivation methods, we isolated a total of 70 bacterial strains. The 16S ribosomal DNA sequences of 32 of the strains were identical to environmental sequences detected in the chemocline by culture-independent molecular methods. These strains were identified as flavobacteria,
Alteromonas macleodii
, and
Halomonas aquamarina
. All 70 strains could grow chemoorganoheterotrophically under oxic conditions. Sixty-six strains grew on peptone, casein hydrolysate, and yeast extract, whereas only 15 strains did not utilize polymeric carbohydrates. Twenty-one of the isolates could grow both chemoorganotrophically and chemolithotrophically. While the most probable numbers in most cases ranged between 0.006 and 4.3% of the total cell counts, an unsually high value of 54% was determined above the chemocline with media containing amino acids as the carbon and energy source. Our results indicate that culturable bacteria thriving at the oxic-anoxic interface of the Urania basin differ considerably from the chemolithoautotrophic bacteria typical of other chemocline habitats.
Prevalence ofCampylobacterspp., Escherichia coli, andSalmonellaSerovars in Retail Chicken, Turkey, Pork, and Beef from the Greater Washington, D.C., Area
Authors: Zhao Cuiwei , Ge Beilei , De Villena Juan , Sudler Robert , Yeh Emily , Zhao Shaohua , White David G. , Wagner David , Meng Jianghong 
Published: July 2002

ABSTRACTA total of 825 samples of retail raw meats (chicken, turkey, pork, and beef) were examined for the presence ofEscherichia coliandSalmonellaserovars, and 719 of these samples were also tested forCampylobacterspp. The samples were randomly obtained from 59 stores of four supermarket chains during 107 sampling visits in the Greater Washington, D.C., area from June 1999 to July 2000. The majority (70.7%) of chicken samples (n= 184) were contaminated withCampylobacter, and a large percentage of the stores visited (91%) hadCampylobacter-contaminated chickens. Approximately 14% of the 172 turkey samples yieldedCampylobacter, whereas fewer pork (1.7%) and beef (0.5%) samples were positive for this pathogen. A total of 722Campylobacterisolates were obtained from 159 meat samples; 53.6% of these isolates wereCampylobacter jejuni, 41.3% wereCampylobacter coli, and 5.1% were other species. Of the 212 chicken samples, 82 (38.7%) yieldedE. coli, while 19.0% of the beef samples, 16.3% of the pork samples, and 11.9% of the turkey samples were positive forE. coli. However, only 25 (3.0%) of the retail meat samples tested were positive forSalmonella. Significant differences in the bacterial contamination rates were observed for the four supermarket chains. This study revealed that retail raw meats are often contaminated with food-borne pathogens; however, there are marked differences in the prevalence of such pathogens in different meats. Raw retail meats are potential vehicles for transmitting food-borne diseases, and our findings stress the need for increased implementation of hazard analysis of critical control point (HACCP) and consumer food safety education efforts.
Sequence Analysis of a 101-Kilobase Plasmid Required for Agar Degradation by aMicroscillaIsolate
Authors: Zhong Zhenping , Toukdarian Aresa , Helinski Donald , Knauf Vic , Sykes Sean , Wilkinson Jane E. , O'Bryne Colleen , Shea Terry , DeLoughery Craig , Caspi Ron 
Published: July 2002

ABSTRACTAn agar-degrading marine bacterium identified as aMicroscillaspecies was isolated from coastal California marine sediment. This organism harbored a single 101-kb circular DNA plasmid designated pSD15. The complete nucleotide sequence of pSD15 was obtained, and sequence analysis indicated a number of genes putatively encoding a variety of enzymes involved in polysaccharide utilization. The most striking feature was the occurrence of five putative agarase genes. Loss of the plasmid, which occurred at a surprisingly high frequency, was associated with loss of agarase activity, supporting the sequence analysis results.
Molecular Typing by Pulsed-Field Gel Electrophoresis of Spanish Animal and HumanListeria monocytogenesIsolates
Authors: Vela A. I. , Fernandez-Garayzabal J. F. , Vazquez J. A. , Latre M. V. , Blanco M. M. , Moreno M. A. , de la Fuente L. , Marco J. , Franco C. , Cepeda A. , Rodriguez Moure A. A. , Suarez G. , Dominguez L. 
Published: July 2002

ABSTRACTA total of 153 strains ofListeria monocytogenesisolated from different sources (72 from sheep, 12 from cattle, 18 from feedstuffs, and 51 from humans) in Spain from 1989 to 2000 were characterized by pulsed-field gel electrophoresis. The strains ofL. monocytogenesdisplayed 55 pulsotypes. The 84 animal, 51 human, and 18 feedstuff strains displayed 31, 29, and 7 different pulsotypes, respectively, indicating a great genetic diversity among the SpanishL. monocytogenesisolates studied.L. monocytogenesisolates from clinical samples and feedstuffs consumed by the diseased animals were analyzed in 21 flocks. In most cases, clinical strains from different animals of the same flock had identical pulsotypes, confirming the existence of a listeriosis outbreak.L. monocytogenesstrains with pulsotypes identical to those of clinical strains were isolated from silage, potatoes, and maize stalks. This is the first study wherein potatoes and maize stalks are epidemiologically linked with clinical listeriosis.
Biological Sensor for Sucrose Availability: Relative Sensitivities of Various Reporter Genes
Authors: Miller William G. , Brandl Maria T. , Quiñones Beatriz , Lindow Steven E. 
Published: July 2002

ABSTRACT

A set of three sucrose-regulated transcriptional fusions was constructed. Fusions p61RYTIR, p61RYlac, and p61RYice contain the
scrR
sucrose repressor gene and the promoterless
gfp,
lacZ,
and
inaZ
reporter genes, respectively, fused to the
scrY
promoter from
Salmonella enterica
serovar Typhimurium. Cells of
Erwinia herbicola
containing these fusions are induced only in media amended with sucrose, fructose, or sorbose. While a large variation in sucrose-dependent reporter gene activity was observed in cells harboring all gene fusions, fusions to the
inaZ
reporter gene yielded a much wider range of activity and were responsive to lower levels of sucrose than either
lacZ
or
gfp
. The
lacZ
reporter gene was found to be more efficient than
gfp
, requiring approximately 300-fold fewer cells for a detectable response over all concentrations of sucrose. Similarly,
inaZ
was found to be more efficient than
lacZ,
requiring 30-fold fewer cells at 1.45 μM sucrose and 6,100-fold fewer cells at 29 mM sucrose for a quantifiable response. The fluorescence of individual cells containing p61RYTIR was quantified following epifluorescence microscopy in order to relate the fluorescence exhibited by populations of cells in batch cultures with that of individual cells in such cultures. While the mean fluorescence intensity of a population of individual cells increased with increasing concentrations of sucrose, a wide range of fluorescence intensity was seen among individual cells. For most cultures the distribution of fluorescence intensity among individual cells was log-normally distributed, but cells grown in intermediate concentrations of sucrose exhibited two distinct populations of cells, one having relatively low fluorescence and another with much higher fluorescence. When cells were inoculated onto bean leaves, whole-cell ice nucleation and
gfp
-based biological sensors for sucrose each indicated that the average concentration of sucrose on moist leaf surfaces was about 20 μM. Importantly, the variation in green fluorescent protein fluorescence of biosensor cells on leaves suggested that large spatial variations in sugar availability occur on leaves.
Changes in Protein Synthesis and Morphology during Acid Adaptation of
Propionibacterium freudenreichii
Authors: Jan Gwénaël , Leverrier Pauline , Pichereau Vianney , Boyaval Patrick 
Published: July 2002

ABSTRACT

Survival of bacteria in changing environments depends on their ability to adapt to abiotic stresses. Microorganisms used in food technology face acid stress during fermentation processes. Similarly, probiotic bacteria have to survive acid stress imposed within the stomach in order to reach the intestine and play a beneficial role. Propionibacteria are used both as cheese starters and as probiotics in human alimentation. Adaptation to low pH thus constitutes a limit to their efficacy. Acid stress adaptation in the probiotic SI41 strain of
Propionibacterium freudenreichii
was therefore investigated. The acid tolerance response (ATR) was evidenced in a chemically defined medium. Transient exposure to pH 5 afforded protection toward acid challenge at pH 2. Protein neosynthesis was shown to be required for optimal ATR, since chloramphenicol reduced the acquired acid tolerance. Important changes in genetic expression were observed with two-dimensional electrophoresis during adaptation. Among the up-regulated polypeptides, a biotin carboxyl carrier protein and enzymes involved in DNA synthesis and repair were identified during the early stress response, while the universal chaperonins GroEL and GroES corresponded to a later response. The beneficial effect of ATR was evident at both the physiological and morphological levels. This study constitutes a first step toward understanding the very efficient ATR described in
P. freudenreichii
.
Effect of Culture Conditions on Ergosterol as an Indicator of Biomass in the Aquatic Hyphomycetes
Authors: Charcosset Jean-Yves , Chauvet Eric 
Published: July 2002

ABSTRACT

Ergosterol is a membrane component specific to fungi that can be used to estimate fungal biomass using appropriate factors of conversion. Our objectives were to determine the limits of use of ergosterol content as a measure of biomass for aquatic hyphomycetes, and to evaluate a previously established ergosterol-to-biomass conversion factor. We varied inoculum quality, growth medium, and degree of shaking of four aquatic hyphomycete species. In cultures inoculated with homogenized mycelium, we found a significant effect of shaking condition and culture age on ergosterol content. In liquid cultures with defined medium, ergosterol content reached 10 to 11 μg/mg of mycelium (dry mass) and varied by factors of 2.2 during exponential growth and 1.3 during stationary phase. The increase in ergosterol content during exponential phase could be attributed, at least in part, to rapid depletion of glucose. Oxygen availability to internal hyphae within the mycelial mass is also responsible for the differences found between culture conditions. Ergosterol concentration ranged from 0.8 to 1.6 μg/mg in static cultures inoculated with agar plugs. Ergosterol content varied by a factor of 4 in two media of different richnesses. For different combinations of these parameters, strong (

r
2

= 0.83 to 0.98) and highly significant (
P
≪ 0.001) linear relationships between ergosterol and mycelial dry mass (up to 110 mg) were observed. Overall, the ergosterol content varied by a factor of 14 (0.8 to 11 mg/g). These results suggest that care must be taken when the ergosterol content is used to compare data generated in different field environments.
Influence of the Natural Microbial Flora on the Acid Tolerance Response of
Listeria monocytogenes
in a Model System of Fresh Meat Decontamination Fluids
Authors: Samelis John , Sofos John N. , Kendall Patricia A. , Smith Gary C. 
Published: July 2002

ABSTRACT

Depending on its composition and metabolic activity, the natural flora that may be established in a meat plant environment can affect the survival, growth, and acid tolerance response (ATR) of bacterial pathogens present in the same niche. To investigate this hypothesis, changes in populations and ATR of inoculated (10
5
CFU/ml)
Listeria monocytogenes
were evaluated at 35°C in water (10 or 85°C) or acidic (2% lactic or acetic acid) washings of beef with or without prior filter sterilization. The model experiments were performed at 35°C rather than lower (≤15°C) temperatures to maximize the response of inoculated
L. monocytogenes
in the washings with or without competitive flora. Acid solution washings were free (<1.0 log CFU/ml) of natural flora before inoculation (day 0), and no microbial growth occurred during storage (35°C, 8 days). Inoculated
L. monocytogenes
died off (negative enrichment) in acid washings within 24 h. In nonacid (water) washings, the pathogen increased (approximately 1.0 to 2.0 log CFU/ml), irrespective of natural flora, which, when present, predominated (>8.0 log CFU/ml) by day 1. The pH of inoculated water washings decreased or increased depending on absence or presence of natural flora, respectively. These microbial and pH changes modulated the ATR of
L. monocytogenes
at 35°C. In filter-sterilized water washings, inoculated
L. monocytogenes
increased its ATR by at least 1.0 log CFU/ml from days 1 to 8, while in unfiltered water washings the pathogen was acid tolerant at day 1 (0.3 to 1.4 log CFU/ml reduction) and became acid sensitive (3.0 to >5.0 log CFU/ml reduction) at day 8. These results suggest that the predominant gram-negative flora of an aerobic fresh meat plant environment may sensitize bacterial pathogens to acid.
Changes in Bacterial Community Composition and Dynamics and Viral Mortality Rates Associated with Enhanced Flagellate Grazing in a Mesoeutrophic Reservoir
Authors: Šimek Karel , Pernthaler Jakob , Weinbauer Markus G. , Hornák Karel , Dolan John R. , Nedoma Jirı́ , Mašı́n Michal , Amann Rudolf 
Published: July 2002

ABSTRACT

Bacterioplankton from a meso-eutrophic dam reservoir was size fractionated to reduce (<0.8-μm treatment) or enhance (<5-μm treatment) protistan grazing and then incubated in situ for 96 h in dialysis bags. Time course samples were taken from the bags and the reservoir to estimate bacterial abundance, mean cell volume, production, protistan grazing, viral abundance, and frequency of visibly infected cells. Shifts in bacterial community composition (BCC) were examined by denaturing gradient gel electrophoresis (DGGE), cloning and sequencing of 16S rDNA genes from the different treatments, and fluorescence in situ hybridization (FISH) with previously employed and newly designed oligonucleotide probes. Changes in bacterioplankton characteristics were clearly linked to changes in mortality rates. In the reservoir, where bacterial production about equaled protist grazing and viral mortality, community characteristics were nearly invariant. In the “grazer-free” (0.8-μm-filtered) treatment, subject only to a relatively low mortality rate (∼17% day
−1
) from viral lysis, bacteria increased markedly in concentration. While the mean bacterial cell volume was invariant, DGGE indicated a shift in BCC and FISH revealed an increase in the proportion of one lineage within the beta proteobacteria. In the grazing-enhanced treatment (5-μm filtrate), grazing mortality was ∼200% and viral lysis resulted in mortality of 30% of daily production. Cell concentrations declined, and grazing-resistant flocs and filaments eventually dominated the biomass, together accounting for >80% of the total bacteria by the end of the experiment. Once again, BCC changed strongly and a significant fraction of the large filaments was detected using a FISH probe targeted to members of the
Flectobacillus
lineage. Shifts of BCC were also reflected in DGGE patterns and in the increases in the relative importance of both beta proteobacteria and members of the
Cytophaga-Flavobacterium
cluster, which consistently formed different parts of the bacterial flocs. Viral concentrations and frequencies of infected cells were highly significantly correlated with grazing rates, suggesting that protistan grazing may stimulate viral activity.
Detection of Toxigenicity by a Probe for the Microcystin Synthetase A Gene (mcyA)of the Cyanobacterial GenusMicrocystis: Comparison of Toxicities with 16S rRNA and Phycocyanin Operon (Phycocyanin Intergenic Spacer) Phylogenies
Authors: Tillett Daniel , Parker Dorothy L. , Neilan Brett A. 
Published: July 2002

ABSTRACTThe relationship between toxigenicity and phylogeny within the cyanobacterial genusMicrocystisis unclear. To investigate this issue, we have designed PCR primers for theN-methyltransferase (NMT) domain of the microcystin synthetase genemcyAand have probed 37Microcystissp. cultures as well as several field samples. The NMT region was present in all 18 laboratory strains that gave positive reactions in the protein phosphatase inhibition assay for microcystin but was absent in 17 nontoxic strains. Two other nontoxic strains, one of which had previously been reported to produce microcystin, possessed the NMT region. Detection of NMT-specific DNA in field samples corresponded to periods of toxicity as assessed by protein phosphatase inhibition. TheMicrocystisstrains formed a monophyletic cluster based on 16S rRNA gene sequences but comprised two groups with respect to phycocyanin intergenic spacer (PC-IGS) sequences. Toxic and nontoxic strains appeared to be erratically distributed within the PC-IGS and 16S rRNA trees. Sequence analysis of the NMT domain revealed two coherent groups. The genomic region immediately downstream of themcyABCcluster in all 20 NMT-positive strains contained an open reading frame of unknown function (uma1) at a conserved distance frommcyC. All nontoxic strains also containeduma1, which is not cotranscribed withmcyABC. The consistent linkage ofmcyCtouma1suggests thatmcyChas not been frequently transferred into nontoxic strains via any mechanism involving insertion at random chromosomal locations. These results are discussed with respect to various mechanisms that could explain the patchy distribution of toxigenicity among the variousMicrocystisclades.