bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cold Shock Induction of Thermal Sensitivity in
Listeria monocytogenes
Authors: Miller Arthur J. , Bayles Darrell O. , Eblen B. Shawn 
Published: July 2002

ABSTRACT

Cold shock at 0 to 15°C for 1 to 3 h increased the thermal sensitivity of
Listeria monocytogenes
. In a model broth system, thermal death time at 60°C was reduced by up to 45% after
L. monocytogenes
Scott A was cold shocked for 3 h. The duration of the cold shock affected thermal tolerance more than did the magnitude of the temperature downshift. The
Z
values were 8.8°C for controls and 7.7°C for cold-shocked cells. The
D
values of cold-shocked cells did not return to control levels after incubation for 3 h at 28°C followed by heating at 60°C. Nine
L. monocytogenes
strains that were cold shocked for 3 h exhibited
D
60
values that were reduced by 13 to 37%. The
D
-value reduction was greatest in cold-shocked stationary-phase cells compared to cells from cultures in either the lag or exponential phases of growth. In addition, cold-shocked cells were more likely to be inactivated by a given heat treatment than nonshocked cells, which were more likely to experience sublethal injury. The
D
values of chloramphenicol-treated control cells and chloramphenicol-treated cold-shocked cells were no different from those of untreated cold-shocked cells, suggesting that cold shock suppresses synthesis of proteins responsible for heat protection. In related experiments, the
D
values of
L. monocytogenes
Scott A were decreased 25% on frankfurter skins and 15% in ultra-high temperature milk if the inoculated products were first cold shocked. Induction of increased thermal sensitivity in
L. monocytogenes
by thermal flux shows potential to become a practical and efficacious preventative control method.
Broad-Host-Range Shuttle Vectors for Screening of Regulated Promoter Activity in Viridans Group Streptococci: Isolation of a pH-Regulated Promoter
Authors: Vriesema Aldwin J. M. , Brinkman René , Kok Jan , Dankert Jacob , Zaat Sebastian A. J. 
Published: July 2002

ABSTRACT

Viridans group streptococci are major constituents of the normal human oral flora and are also identified as the predominant pathogenic bacteria in native valve infective endocarditis. Little information is available regarding the regulation of gene expression in viridans group streptococci, either in response to changes in the oral environment or during development of endocarditis. We therefore constructed a set of broad-host-range vectors for the isolation of promoters from viridans group streptococci that are activated by specific environmental stimuli in vitro or in vivo. A genomic library of
Streptococcus gordonii
strain CH1 was constructed in one of the new vectors, and this library was introduced into a homologous bacterium by using an optimized electroporation protocol for viridans group streptococci. Because viridans group streptococci entering the bloodstream from the oral cavity encounter an increase in pH, we selected promoters upregulated by this specific stimulus. One of the selected promoter sequences showed homology to the promoter region of the
hydA
gene from
Clostridium acetobutylicum
, the expression of which is known to be regulated by the environmental pH. The isolation of this pH-regulated promoter shows that
S. gordonii
can sense an increase in the environmental pH, which serves as a signal for bacterial gene activation. Furthermore, this demonstrates the usefulness of these new selection vectors in research on adaptive gene expression of viridans group streptococci and possibly also of other gram-positive bacteria.
Diversity and Distribution of DNA Sequences with Affinity to Ammonia-Oxidizing Bacteria of the β Subdivision of the Class
Proteobacteria
in the Arctic Ocean
Authors: Bano Nasreen , Hollibaugh James T. 
Published: July 2002

ABSTRACT

The spatial distribution and diversity of ammonia-oxidizing bacteria of the β subdivision of the class
Proteobacteria
(hereinafter referred to as ammonia oxidizers) in the Arctic Ocean were determined. The presence of ammonia oxidizers was detected by PCR amplification of 16S rRNA genes using a primer set specific for this group of organisms (nitA and nitB, which amplifies a 1.1-kb fragment between positions 137 and 1234, corresponding to
Escherichia coli
16S rDNA numbering). We analyzed 246 samples collected from the upper water column (5 to 235 m) during March and April 1995, September and October 1996, and September 1997. Ammonia oxidizers were detected in 25% of the samples from 5 m, 80% of the samples from 55 m, 88% of the samples from 133 m, and 50% of the samples from 235 m. Analysis of nitA-nitB PCR product by nested PCR-denaturing gradient gel electrophoresis (DGGE) showed that all positive samples contained the same major band (band A), indicating the presence of a dominant, ubiquitous ammonia oxidizer in the Arctic Ocean basin. Twenty-two percent of the samples contained additional major bands. These samples were restricted to the Chukchi Sea shelf break, the Chukchi cap, and the Canada basin; areas likely influenced by Pacific inflow. The nucleotide sequence of the 1.1-kb nitA-nitB PCR product from a sample that contained only band A grouped with sequences designated group 1 marine
Nitrosospira
-like sequences. PCR-DGGE analysis of 122 clones from four libraries revealed that 67 to 71% of the inserts contained sequences with the same mobility as band A. Nucleotide sequences (1.1 kb) of another distinct group of clones, found only in 1995 samples (25%), fell into the group 5 marine
Nitrosomonas
-like sequences. Our results suggest that the Arctic Ocean β-proteobacterial ammonia oxidizers have low diversity and are dominated by marine
Nitrosospira
-like organisms. Diversity appears to be higher in Western Arctic Ocean regions influenced by inflow from the Pacific Ocean through the Bering and Chukchi seas.
Design and Evaluation of a
Lactobacillus manihotivorans
Species-Specific rRNA-Targeted Hybridization Probe and Its Application to the Study of Sour Cassava Fermentation
Authors: Ampe Frédéric 
Published: July 2002

ABSTRACT

Based on 16S rRNA sequence comparison, we have designed a 20-mer oligonucleotide that targets a region specific to the species
Lactobacillus manihotivorans
recently isolated from sour cassava fermentation. The probe recognized the rRNA obtained from all the
L. manihotivorans
strains tested but did not recognize 56 strains of microorganisms from culture collections or directly isolated from sour cassava, including 29 species of lactic acid bacteria. This probe was then successfully used in quantitative RNA blots and demonstrated the importance of
L. manihotivorans
in the fermentation of sour cassava starch, which could represent up to 20% of total lactic acid bacteria.
Inactivation of the Glutamate Decarboxylase Gene in
Lactococcus lactis
subsp.
cremoris
Authors: Nomura Masaru , Kobayashi Miho , Ohmomo Sadahiro , Okamoto Takashi 
Published: July 2002

ABSTRACT

Lactococcus lactis
subsp.
lactis
strains show glutamate decarboxylase activity, whereas
L. lactis
subsp.
cremoris
strains do not. The
gadB
gene encoding glutamate decarboxylase was detected in the
L. lactis
subsp.
cremoris
genome but was poorly expressed. Sequence analysis showed that the gene is inactivated by the frameshift mutation and encoded in a nonfunctional protein.
Production and Characterization of Monoclonal Antibodies against Vegetative Cells of
Bacillus cereus
Authors: Charni Nadine , Perissol Claude , Le Petit Jean , Rugani Nathalie 
Published: July 2002

ABSTRACT

Two monoclonal antibodies (MAbs) against
Bacillus cereus
were produced. The MAbs (8D3 and 9B7) were selected by enzyme-linked immunosorbent assay for their reactivity with
B. cereus
vegetative cells. They reacted with
B. cereus
vegetative cells while failing to recognize
B. cereus
spores. Immunoblotting revealed that MAb 8D3 recognized a 22-kDa antigen, while MAb 9B7 recognized two antigens with molecular masses of approximately 58 and 62 kDa. The use of MAbs 8D3 and 9B7 in combination to develop an immunological method for the detection of
B. cereus
vegetative cells in foods was investigated.
Characterization of a Bifunctional Enzyme Fusion of Trehalose-6-Phosphate Synthetase and Trehalose-6-Phosphate Phosphatase of
Escherichia coli
Authors: Seo Hak Soo , Koo Yeon Jong , Lim Jae Yun , Song Jong Tae , Kim Chung Ho , Kim Ju Kon , Lee Jong Seob , Choi Yang Do 
Published: July 2002

ABSTRACT

To test the effect of the physical proximity of two enzymes catalyzing sequential reactions, a bifunctional fusion enzyme, TPSP, was constructed by fusing the
Escherichia coli
genes for trehalose-6-phosphate (T6P) synthetase (TPS) and trehalose-6-phosphate phosphatase (TPP). TPSP catalyzes the sequential reaction in which T6P is formed and then dephosphorylated, leading to the synthesis of trehalose. The fused chimeric gene was overexpressed in
E. coli
and purified to near homogeneity; its molecular weight was 88,300, as expected. The

K
m

values of the TPSP fusion enzyme for the sequential overall reaction from UDP-glucose and glucose 6-phosphate to trehalose were smaller than those of an equimolar mixture of TPS and TPP (TPS/TPP). However, the
k
cat
values of TPSP were similar to those of TPS/TPP, resulting in a 3.5- to 4.0-fold increase in the catalytic efficiency (
k
cat
/

K
m

). The

K
m

and
k
cat
values of TPSP and TPP for the phosphatase reaction from T6P to trehalose were quite similar. This suggests that the increased catalytic efficiency results from the proximity of TPS and TPP in the TPSP fusion enzyme. The thermal stability of the TPSP fusion enzyme was quite similar to that of the TPS/TPP mixture, suggesting that the structure of each enzyme moiety in TPSP is unperturbed by intramolecular constraint. These results clearly demonstrate that the bifunctional fusion enzyme TPSP catalyzing sequential reactions has kinetic advantages over a mixture of both enzymes (TPS and TPP). These results are also supported by the in vivo accumulation of up to 0.48 mg of trehalose per g of cells after isopropyl-β-
d
-thiogalactopyranoside treatment of cells harboring the construct encoding TPSP.
Lon Protease Influences Antibiotic Production and UV Tolerance of
Pseudomonas fluorescens
Pf-5
Authors: Whistler Cheryl A. , Stockwell Virginia O. , Loper Joyce E. 
Published: July 2002

ABSTRACT

Pseudomonas fluorescens
Pf-5 is a soil bacterium that suppresses plant pathogens due in part to its production of the antibiotic pyoluteorin. Previous characterization of Pf-5 revealed three global regulators, including the stationary-phase sigma factor ς
S
and the two-component regulators GacA and GacS, that influence both antibiotic production and stress response. In this report, we describe the serine protease Lon as a fourth global regulator influencing these phenotypes in Pf-5.
lon
mutants overproduced pyoluteorin, transcribed pyoluteorin biosynthesis genes at enhanced levels, and were more sensitive to UV exposure than Pf-5. The
lon
gene was preceded by sequences that resembled promoters recognized by the heat shock sigma factor ς
32
(ς
H
) of
Escherichia coli
, and Lon accumulation by Pf-5 increased after heat shock. Therefore, ς
H
represents the third sigma factor (with ς
S
and ς
70
) implicated in the regulation of antibiotic production by
P. fluorescens
. Lon protein levels were similar in stationary-phase and exponentially growing cultures of Pf-5 and were not positively affected by the global regulator ς
S
or GacS. The association of antibiotic production and stress response has practical implications for the success of disease suppression in the soil environment, where biological control organisms such as Pf-5 are likely to encounter environmental stresses.
Reduction of Pulmonary Toxicity of
Stachybotrys chartarum
Spores by Methanol Extraction of Mycotoxins
Authors: Rao Carol Y. , Brain Joseph D. , Burge Harriet A. 
Published: July 2002

ABSTRACT

The fungus
Stachybotrys chartarum
has been implicated in cases of nonspecific indoor air quality complaints in adults and in cases of pulmonary hemorrhaging in infants. The effects that have been described have been attributed to mycotoxins. Previous dose-effect studies focused on exposure to a single mycotoxin in a solvent, a strategy which is unlikely to accurately characterize the effects of inhaled spores. In this study we examined the role of mycotoxins in the pulmonary effects caused by
S. chartarum
spores and the dose dependency of these effects.
S. chartarum
spores were extracted in methanol to reduce the mycotoxin content of the spores. Then either untreated (toxin-containing) or methanol-extracted
S. chartarum
spores were intratracheally instilled into male 10-week-old Charles River-Dawley rats. After 24 h, the lungs were lavaged, and the bronchoalveolar lavage fluid was analyzed to determine differences in lactic dehydrogenase, albumin, hemoglobin, myeloperoxidase, and leukocyte differential counts. Weight change was also monitored. Our data show that methanol extraction dramatically reduced the toxicity of
S. chartarum
spores. No statistically significant effects were observed in the bronchoalveolar lavage fluids of the animals that were treated with methanol-extracted spores at any dose. Conversely, dose-dependent effects of the toxin-containing spores were observed when we examined the lactic dehydrogenase, albumin, and hemoglobin concentrations, the polymorphonuclear leukocyte counts, and weight loss. Our findings show that a single, intense exposure to toxin-containing
S. chartarum
spores results in pulmonary inflammation and injury in a dose-dependent manner. Importantly, the effects are related to methanol-soluble toxins in the spores.
Sphingomonas alaskensis
Strain AFO1, an Abundant Oligotrophic Ultramicrobacterium from the North Pacific
Authors: Eguchi Mitsuru , Ostrowski Martin , Fegatella Fitri , Bowman John , Nichols David , Nishino Tomohiko , Cavicchioli Ricardo 
Published: July 2002

ABSTRACT

Numerous studies have established the importance of picoplankton (microorganisms of ≤2 μm in length) in energy flow and nutrient cycling in marine oligotrophic environments, and significant effort has been directed at identifying and isolating heterotrophic picoplankton from the world's oceans. Using a method of diluting natural seawater to extinction followed by monthly subculturing for 12 months, a bacterium was isolated that was able to form colonies on solid medium. The strain was isolated from a 10
5
dilution of seawater where the standing bacterial count was 3.1 × 10
5
cells ml
−1
. This indicated that the isolate was representative of the most abundant bacteria at the sampling site, 1.5 km from Cape Muroto, Japan. The bacterium was characterized and found to be ultramicrosized (less than 0.1 μm
3
), and the size varied to only a small degree when the cells were starved or grown in rich media. A detailed molecular (16S rRNA sequence, DNA-DNA hybridization, G+C mol%, genome size), chemotaxonomic (lipid analysis, morphology), and physiological (resistance to hydrogen peroxide, heat, and ethanol) characterization of the bacterium revealed that it was a strain of
Sphingomonas alaskensis
. The type strain, RB2256, was previously isolated from Resurrection Bay, Alaska, and similar isolates have been obtained from the North Sea. The isolation of this species over an extended period, its high abundance at the time of sampling, and its geographical distribution indicate that it has the capacity to proliferate in ocean waters and is therefore likely to be an important contributor in terms of biomass and nutrient cycling in marine environments.
Isolation of Novel Pelagic Bacteria from the German Bight and Their Seasonal Contributions to Surface Picoplankton
Authors: Eilers Heike , Pernthaler Jakob , Peplies Jörg , Glöckner Frank Oliver , Gerdts Gunnar , Amann Rudolf 
Published: July 2002

ABSTRACT

We tested new strategies for the isolation of abundant bacteria from coastal North Sea surface waters, which included reducing by several orders of magnitude the concentrations of inorganic N and P compounds in a synthetic seawater medium. Agar plates were resampled over 37 days, and slowly growing colonies were allowed to develop by repeatedly removing all newly formed colonies. A fivefold increase of colonies was observed on plates with reduced nutrient levels, and the phylogenetic composition of the culture collection changed over time, towards members of the
Roseobacter
lineage and other alpha-proteobacteria. Novel gamma-proteobacteria from a previously uncultured but cosmopolitan lineage (NOR5) formed colonies only after 12 days of plate incubation. A time series of German Bight surface waters (January to December 1998) was screened by fluorescence in situ hybridization (FISH) with isolate-specific and general probes. During spring and early summer, a prominent fraction of FISH-detectable bacteria (mean, 51%) were affiliated with the
Cytophaga-Flavobacterium
group (CF) of the
Bacteroidetes
. One
Cytophaga
sp. lineage with cultured representatives formed almost 20% of the CF group. Members of the
Roseobacter
cluster constituted approximately 50% of alpha-proteobacteria, but none of the
Roseobacter
-related isolates formed populations of >1% in the environment. Thus, the readily culturable members of this clade are probably not representative of
Roseobacter
species that are common in the water column. In contrast, members of NOR5 were found at high abundances (>10
5
cells ml
−1
) in the summer plankton. Some abundant pelagic bacteria are apparently able to form colonies on solid media, but appropriate isolation techniques for different species need to be developed.
Substrate Selectivity of a 3-Nitrophenol-Induced Metabolic System in
Pseudomonas putida
2NP8 Transforming Nitroaromatic Compounds into Ammonia under Aerobic Conditions
Authors: Zhao Jian-Shen , Ward Owen P. 
Published: July 2002

ABSTRACT

The 3-nitrophenol-induced enzyme system in cells of
Pseudomonas putida
2NP8 manifested a wide substrate range in transforming nitroaromatic compounds through to ammonia production. All of the 30 mono- or dinitroaromatic substrates except 4-nitrophenol, 2,4-dinitrophenol, 2,4,6-trinitrophenol, 3-nitroaniline, 2-nitrobenzoic acid, and 2-nitrofuran were quickly transformed. Ammonia production from most nitroaromatic substrates appeared to be stoichiometric.
Case of Localized Recombination in 23S rRNA Genes from Divergent
Bradyrhizobium
Lineages Associated with Neotropical Legumes
Authors: Parker Matthew A. 
Published: July 2002

ABSTRACT

Enzyme electrophoresis and rRNA sequencing were used to analyze relationships of
Bradyrhizobium
sp. nodule bacteria from four papilionoid legumes (
Clitoria javitensis, Erythrina costaricensis, Rhynchosia pyramidalis
, and
Desmodium axillare
) growing on Barro Colorado Island (BCI), Panama. Bacteria with identical multilocus allele profiles were commonly found in association with two or more legume genera. Among the 16 multilocus genotypes (electrophoretic types [ETs]) detected, six ETs formed a closely related cluster that included isolates from all four legume taxa. Bacteria from two other BCI legumes (
Platypodium
and
Machaerium
) sampled in a previous study were also identical to certain ETs in this group. Isolates from different legume genera that had the same ET had identical nucleotide sequences for both a 5′ portion of the 23S rRNA and the nearly full-length 16S rRNA genes. These results suggest that
Bradyrhizobium
genotypes with low host specificity may be prevalent in this tropical forest. Parsimony analysis of 16S rRNA sequence variation indicated that most isolates were related to
Bradyrhizobium japonicum
USDA 110, although one ET sampled from
C. javitensis
had a 16S rRNA gene highly similar to that of
Bradyrhizobium elkanii
USDA 76. However, this isolate displayed a mosaic structure within the 5′ 23S rRNA region: one 84-bp segment was identical to that of BCI isolate Pe1-3 (a close relative of
B. japonicum
USDA 110, based on 16S rRNA data), while an adjacent 288-bp segment matched that of
B. elkanii
USDA 76. This mosaic structure is one of the first observations suggesting recombination in nature between
Bradyrhizobium
isolates related to
B. japonicum
versus
B. elkanii
.
2-Bromoethanesulfonate Affects Bacteria in a Trichloroethene-Dechlorinating Culture
Authors: Chiu Pei C. , Lee Minho 
Published: July 2002

ABSTRACT
Long-term exposure to 2-bromoethanesulfonate (BES), an agent known to inhibit methanogenesis, altered the bacterial community structure of an anaerobic enrichment culture that reductively dechlorinated trichloroethene (TCE). BES did not hinder the dechlorination of TCE or other chlorinated ethenes as previously reported, although different intermediates and end products were observed.
Region-Specific Transcriptional Activity in the Genome of
Streptomyces coelicolor
A3(2)
Authors: Gust Bertolt , Spatz Kerstin , Spychaj Alexander , Redenbach Matthias 
Published: July 2002

ABSTRACT

Transcriptional analysis of microbial genomes is an important component of functional genomics. Strategies such as hybridization of labeled total RNA against ordered clone libraries or differential-display approaches have already been carried out to identify expressed genes. We describe here an additional method which applies subtractive hybridization between genome-specific DNA and total RNA followed by a PCR approach to identify expressed microbial genes. With the new strategy, the expression of genes in the terminal regions of the linear
Streptomyces coelicolor
A3(2) chromosome and the accessory linear plasmid SCP1 was analyzed. The results indicate that the method is useful for the identification of expressed genes in actinomycetes and other microbial systems. We demonstrate for the first time that at least 24 genes in the chromosome end regions (silent regions) of
S. coelicolor
are actively expressed. In addition, several expressed SCP1 genes were identified, including a gene which shows high similarity to microbial
dnaN
genes and which seems to play a role in SCP1 maintenance.
Rapid Evolution of Novel Traits in Microorganisms
Authors: Selifonova Olga , Valle Fernando , Schellenberger Volker 
Published: July 2002

ABSTRACT
The use of natural microorganisms in biotransformations is frequently constrained by their limited tolerance to the high concentrations of metabolites and solvents required for effective industrial production. In many cases, more robust strains have to be generated by random mutagenesis and selection. This process of directed evolution can be accelerated in mutator strains, which carry defects in one or more of their DNA repair genes. However, in order to use mutator strains, it is essential to restore the normal low mutation rate of the selected organisms immediately after selection to prevent the accumulation of undesirable spontaneous mutations. To enable this process, we constructed temperature-sensitive plasmids that temporarily increase the mutation frequency of their hosts by 20- to 4,000-fold. Under appropriate selection pressure, microorganisms transformed with mutator plasmids can be quickly evolved to exhibit new, complex traits. By using this approach, we were able to increase the tolerance of three bacterial strains to dimethylformamide by 10 to 20 g/liter during only two subsequent transfers. Subsequently, the evolved strains were returned to their normal low mutation rate by curing the cells of the mutator plasmids. Our results demonstrate a new and efficient method for rapid strain improvement based on in vivo mutagenesis.