bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Experiments To Examine the Effects of Heating on Vegetative Cells and Spores ofClostridium perfringensIsolates Carrying Plasmid Genes versus Chromosomal Enterotoxin Genes
Authors: Sarker Mahfuzur R. , Shivers Robert P. , Sparks Shauna G. , Juneja Vijay K. , McClane Bruce A. 
Published: July 2002

ABSTRACTClostridium perfringensenterotoxin (CPE) is an important virulence factor for bothC. perfringenstype A food poisoning and several non-food-borne human gastrointestinal diseases. Recent studies have indicated thatC. perfringensisolates associated with food poisoning carry a chromosomalcpegene, while non-food-borne human gastrointestinal disease isolates carry a plasmidcpegene. However, no explanation has been provided for the strong associations between certaincpegenotypes and particular CPE-associated diseases. SinceC. perfringensfood poisoning usually involves cooked meat products, we hypothesized that chromosomalcpeisolates are so strongly associated with food poisoning because (i) they are more heat resistant than plasmidcpeisolates, (ii) heating induces loss of thecpeplasmid, or (iii) heating induces migration of the plasmidcpegene to the chromosome. When we tested these hypotheses, vegetative cells of chromosomalcpeisolates were found to exhibit, on average approximately twofold-higher decimal reduction values (Dvalues) at 55°C than vegetative cells of plasmidcpeisolates exhibited. Furthermore, the spores of chromosomalcpeisolates had, on average, approximately 60-fold-higherDvalues at 100°C than the spores of plasmidcpeisolates had. Southern hybridization and CPE Western blot analyses demonstrated that all survivors of heating retained theircpegene in its original plasmid or chromosomal location and could still express CPE. These results suggest that chromosomalcpeisolates are strongly associated with food poisoning, at least in part, because their cells and spores possess a high degree of heat resistance, which should enhance their survival in incompletely cooked or inadequately warmed foods.
Detection of Oxytetracycline Production byStreptomyces rimosusin Soil Microcosms by Combining Whole-Cell Biosensors and Flow Cytometry
Authors: Hansen Lars Hestbjerg , Ferrari Belinda , Sørensen Anders Hay , Veal Duncan , Sørensen Søren Johannes 
Published: July 2002

ABSTRACTCombining the high specificity of bacterial biosensors and the resolution power of fluorescence-activated cell sorting (FACS) provided qualitative detection of oxytetracycline production byStreptomyces rimosusin soil microcosms. A plasmid containing a transcriptional fusion between thetetR-regulated Ptetpromoter from Tn10and a FACS-optimizedgfpgene was constructed. When harbored byEscherichia coli, this plasmid produces large amounts of green fluorescent protein (GFP) in the presence of tetracycline. This tetracycline biosensor was used to detect the production of oxytetracycline byS. rimosusintroduced into sterile soil. The tetracycline-induced GFP-producing biosensors were detected by FACS analysis, enabling the detection of oxytetracycline encounters by single biosensor cells. This approach can be used to study interactions between antibiotic producers and their target organisms in soil.
Physiological Role of β-Phosphoglucomutase in
Lactococcus lactis
Authors: Levander Fredrik , Andersson Ulrika , Rådström Peter 
Published: July 2002

ABSTRACT

A β-phosphoglucomutase (β-PGM) mutant of
Lactococcus lactis
subsp.
lactis
ATCC 19435 was constructed using a minimal integration vector and double-crossover recombination. The mutant and the wild-type strain were grown under controlled conditions with different sugars to elucidate the role of β-PGM in carbohydrate catabolism and anabolism. The mutation did not significantly affect growth, product formation, or cell composition when glucose or lactose was used as the carbon source. With maltose or trehalose as the carbon source the wild-type strain had a maximum specific growth rate of 0.5 h
−1
, while the deletion of β-PGM resulted in a maximum specific growth rate of 0.05 h
−1
on maltose and no growth at all on trehalose. Growth of the mutant strain on maltose resulted in smaller amounts of lactate but more formate, acetate, and ethanol, and approximately 1/10 of the maltose was found as β-glucose 1-phosphate in the medium. Furthermore, the β-PGM mutant cells grown on maltose were considerably larger and accumulated polysaccharides which consisted of α-1,4-bound glucose units. When the cells were grown at a low dilution rate in a glucose and maltose mixture, the wild-type strain exhibited a higher carbohydrate content than when grown at higher growth rates, but still this content was lower than that in the β-PGM mutant. In addition, significant differences in the initial metabolism of maltose and trehalose were found, and cell extracts did not digest free trehalose but only trehalose 6-phosphate, which yielded β-glucose 1-phosphate and glucose 6-phosphate. This demonstrates the presence of a novel enzymatic pathway for trehalose different from that of maltose metabolism in
L. lactis
.
Iron-Binding Compounds from
Agrobacterium
spp.: Biological Control Strain
Agrobacterium rhizogenes
K84 Produces a Hydroxamate Siderophore
Authors: Penyalver Ramón , Oger Philippe , López Marı́a M. , Farrand Stephen K. 
Published: July 2002

ABSTRACT

Iron-binding compounds were produced in various amounts in response to iron starvation by a collection of
Agrobacterium
strains belonging to the species
A. tumefaciens, A. rhizogenes
, and
A. vitis
. The crown gall biocontrol agent
A. rhizogenes
strain K84 produced a hydroxamate iron chelator in large amounts. Production of this compound, and also of a previously described antibiotic-like substance called ALS84, occurred only in cultures of strain K84 grown in iron-deficient medium. Similarly, sensitivity to ALS84 was expressed only when susceptible cells were tested in low-iron media. Five independent Tn
5
-induced mutants of strain K84 affected in the production of the hydroxamate iron chelator showed a similar reduction in the production of ALS84. One of these mutants, M8-10, was completely deficient in the production of both agents and grew poorly compared to the wild type under iron-limiting conditions. Thus, the hydroxamate compound has siderophore activity. A 9.1-kb fragment of chromosomal DNA containing the Tn
5
insertion from this mutant was cloned and marker exchanged into wild-type strain K84. The homogenote lost the ability to produce the hydroxamate siderophore and also ALS84. A cosmid clone was isolated from a genomic library of strain K84 that restored to strain M8-10 the ability to produce of the siderophore and ALS84, as well as growth in iron-deficient medium. This cosmid clone contained the region in which Tn
5
was located in the mutant. Sequence analysis showed that the Tn
5
insert in this mutant was located in an open reading frame coding for a protein that has similarity to those of the gramicidin S synthetase repeat superfamily. Some such proteins are required for synthesis of hydroxamate siderophores by other bacteria. Southern analysis revealed that the biosynthetic gene from strain K84 is present only in isolates of
A. rhizogenes
that produce hydroxamate-type compounds under low-iron conditions. Based on physiological and genetic analyses showing a correlation between production of a hydroxamate siderophore and ALS84 by strain K84, we conclude that the two activities share a biosynthetic route and may be the same compound.
Nisin Resistance of
Streptococcus bovis
Authors: Mantovani Hilário C. , Russell James B. 
Published: July 2002

ABSTRACT

The growth of
Streptococcus bovis
JB1 was initially inhibited by nisin (1 μM), and nisin caused a more than 3-log decrease in viability. However, some of the cells survived, and these nisin-resistant cells grew as rapidly as untreated ones. To see if the nisin resistance was merely a selection, nisin-sensitive cells were obtained from agar plates lacking nisin. Results indicated that virtually any nisin-sensitive cell could become nisin-resistant if the ratio of nisin to cells was not too high and the incubation period was long enough. Isolates obtained from the rumen were initially nisin sensitive, but they also developed nisin resistance. Nisin-resistant cultures remained nisin resistant even if nisin was not present, but competition studies indicated that nisin-sensitive cells could eventually displace the resistant ones if nisin was not present. Nisin-sensitive, glucose-energized cells lost virtually all of their intracellular potassium if 1 μM nisin was added, but resistant cells retained potassium even after addition of 10 μM nisin. Nisin-resistant cells were less hydrophobic and more lysozyme-resistant than nisin-sensitive cells. Because the nisin-resistant cells bound less cytochrome
c
, it appeared that nisin was being excluded by a net positive (i.e., less negative) charge. Nisin-resistant cells had more lipoteichoic acid than nisin-sensitive cells, and deesterified lipoteichoic acids from nisin-resistant cells migrated more slowly through a polyacrylamide gel than those from nisin-sensitive cells. These results indicated that lipoteichoic acids could be modified to increase the resistance of
S. bovis
to nisin.
S. bovis
JB1 cultures were still sensitive to monensin, tetracycline, vancomycin, and bacitracin, but ampicillin resistance was 1,000-fold greater.
Determination of DNA Content of Aquatic Bacteria by Flow Cytometry
Authors: Button D. K. , Robertson Betsy R. 
Published: July 2002

ABSTRACT

The distribution of DNA among bacterioplankton and bacterial isolates was determined by flow cytometry of DAPI (4′,6′-diamidino-2-phenylindole)-stained organisms. Conditions were optimized to minimize error from nonspecific staining, AT bias, DNA packing, changes in ionic strength, and differences in cell permeability. The sensitivity was sufficient to characterize the small 1- to 2-Mb-genome organisms in freshwater and seawater, as well as low-DNA cells (“dims”). The dims could be formed from laboratory cultivars; their apparent DNA content was 0.1 Mb and similar to that of many particles in seawater. Preservation with formaldehyde stabilized samples until analysis. Further permeabilization with Triton X-100 facilitated the penetration of stain into stain-resistant lithotrophs. The amount of DNA per cell determined by flow cytometry agreed with mean values obtained from spectrophotometric analyses of cultures. Correction for the DNA AT bias of the stain was made for bacterial isolates with known G+C contents. The number of chromosome copies per cell was determined with pure cultures, which allowed growth rate analyses based on cell cycle theory. The chromosome ratio was empirically related to the rate of growth, and the rate of growth was related to nutrient concentration through specific affinity theory to obtain a probe for nutrient kinetics. The chromosome size of a
Marinobacter arcticus
isolate was determined to be 3.0 Mb by this method. In a typical seawater sample the distribution of bacterial DNA revealed two major populations based on DNA content that were not necessarily similar to populations determined by using other stains or protocols. A mean value of 2.5 fg of DNA cell
−1
was obtained for a typical seawater sample, and 90% of the population contained more than 1.1 fg of DNA cell
−1
.
Detection of the Bacteriocin Propionicin PLG-1 with Polyvalent Anti-PLG-1 Antiserum
Authors: Leversee Jay A. , Glatz Bonita A. 
Published: July 2002

ABSTRACT

Polyclonal antibodies against the bacteriocin propionicin PLG-1 were produced in rabbits at high titer (256,000 to 512,000, as determined by indirect enzyme-linked immunosorbent assay [ELISA]). Anti-PLG-1 antiserum neutralized the antimicrobial activity of PLG-1 preparations in a well diffusion assay. Cross-reacting protein was detected using an indirect ELISA of the culture supernatant from a fed-batch fermentation of the producer strain
Propionibacterium thoenii
P127 within the first 24 h of incubation, but bacteriocin activity was not detected in the same culture until 217 h of incubation. Culture supernatants from 156 strains of classical dairy propionibacteria were tested by indirect ELISA at 5 and 12 days of incubation for production of cross-reacting protein and by well diffusion assay for bacteriocin activity. Cross-reacting protein was detected in 52 strains: all of the tested strains of
P. thoenii
, most of the strains of
Propionibacterium jensenii
, and a minority of the
Propionibacterium acidipropionici
and
Propionibacterium freudenreichii
strains. Of these 52 strains, only 4 strains of
P. thoenii
showed bacteriocin activity in a well diffusion assay. Eight bacteriocin-negative mutants of strain P127 were negative in both ELISA and well diffusion assays. Western blot analysis showed that three protein bands bound anti-PLG-1 antibodies in culture supernatants: a 9.1-kDa band that is assumed to be the PLG-1 monomer and 16.2- and 27.5-kDa bands that may be precursors, multimers, or complexes of PLG-1.
Identification of Deoxynivalenol- and Nivalenol-Producing Chemotypes of
Gibberella zeae
by Using PCR
Authors: Lee Theresa , Oh Dae-Woong , Kim Hye-Seon , Lee Jungkwan , Kim Yong-Ho , Yun Sung-Hwan , Lee Yin-Won 
Published: July 2002

ABSTRACT

Gibberella zeae
, a major cause of cereal scab, may be divided into two chemotypes based on production of the trichothecenes deoxynivalenol (DON) and nivalenol (NIV). We cloned and sequenced the gene cluster for trichothecene biosynthesis from each chemotype.
G. zeae
H-11 is a DON producer isolated from corn, and
G. zeae
88-1 is a NIV producer from barley. We sequenced a 23-kb gene cluster from H-11 and a 26-kb cluster from 88-1, along with the unlinked
Tri101
genes. Each gene cluster contained 10
Tri
gene homologues in the same order and transcriptional directions as those of
Fusarium sporotrichioides
. Between H-11 and 88-1 all of the
Tri
homologues except
Tri7
were conserved, with identities ranging from 88 to 98% and 82 to 99% at the nucleotide and amino acid levels, respectively. The
Tri7
sequences were only 80% identical at the nucleotide level. We aligned the
Tri7
genes and found that the
Tri7
open reading frame of H-11 carried several mutations and an insertion containing 10 copies of an 11-bp tandem repeat. The
Tri7
gene from 88-1 carried neither the repeat nor the mutations. We assayed 100
G. zeae
isolates of both chemotypes by PCR amplification with a primer pair derived from the
Tri7
gene and could differentiate the chemotypes by polyacrylamide gel electrophoresis. The PCR-based method developed in this study should provide a simple and reliable diagnostic tool for differentiating the two chemotypes of
G. zeae
.
Degradation of 3-Methylpyridine and 3-Ethylpyridine by
Gordonia nitida
LE31
Authors: Lee Jay J. , Rhee Sung-Keun , Lee Sung-Taik 
Published: July 2002

ABSTRACT

Cells of
Gordonia nitida
LE31 grown on 3-methylpyridine degraded 3-ethylpyridine without a lag time and vice versa. Cyclic intermediates were not detected, but formic acid was identified as a metabolite. Degradation of levulinic acid was induced in cells grown on 3-methylpyridine and 3-ethylpyridine. Levulinic aldehyde dehydrogenase and formamidase activities were higher in cells grown on 3-methylpyridine and 3-ethylpyridine than in cells grown on acetate. These data indicate that 3-methylpyridine and 3-ethylpyridine were degraded via a new pathway involving C-2–C-3 ring cleavage.
Effects of T4 Lysozyme Release from Transgenic Potato Roots on Bacterial Rhizosphere Communities Are Negligible Relative to Natural Factors
Authors: Heuer Holger , Kroppenstedt Reiner M. , Lottmann Jana , Berg Gabriele , Smalla Kornelia 
Published: July 2002

ABSTRACT

Rhizosphere bacterial communities of two transgenic potato lines which produce T4 lysozyme for protection against bacterial infections were analyzed in comparison to communities of wild-type plants and transgenic controls not harboring the lysozyme gene. Rhizosphere samples were taken from young, flowering, and senescent plants at two field sites in three consecutive years. The communities were characterized in a polyphasic approach. Cultivation-dependent methods included heterotrophic plate counts, determination of species composition and diversity based on fatty acid analysis of isolates, and community level catabolic profiling. Cultivation-independent analyses were based on denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments amplified from rhizosphere DNA using primers specific for
Bacteria
,
Actinomycetales
, or α- or β-
Proteobacteria
. Several bands of the DGGE patterns were further characterized by sequence analysis. All methods revealed that environmental factors related to season, field site, or year but not to the T4 lysozyme expression of the transgenic plants influenced the rhizosphere communities. For one of the T4 lysozyme-producing cultivars, no deviation in the rhizosphere communities compared to the control lines was observed. For the other, differences were detected at some of the samplings between the rhizosphere community structure and those of one or all other cultivars which were not attributable to T4 lysozyme production but most likely to differences observed in the growth characteristics of this cultivar.
Comparison of Fecal Coliform Agar and Violet Red Bile Lactose Agar for Fecal Coliform Enumeration in Foods
Authors: Leclercq A. , Wanegue C. , Baylac P. 
Published: July 2002

ABSTRACT

A 24-h direct plating method for fecal coliform enumeration with a resuscitation step (preincubation for 2 h at 37 ± 1°C and transfer to 44 ± 1°C for 22 h) using fecal coliform agar (FCA) was compared with the 24-h standardized violet red bile lactose agar (VRBL) method. FCA and VRBL have equivalent specificities and sensitivities, except for lactose-positive non-fecal coliforms such as
Hafnia alvei
, which could form typical colonies on FCA and VRBL. Recovery of cold-stressed
Escherichia coli
in mashed potatoes on FCA was about 1 log unit lower than that with VRBL. When the FCA method was compared with standard VRBL for enumeration of fecal coliforms, based on counting carried out on 170 different food samples, results were not significantly different (
P
> 0.05). Based on 203 typical identified colonies selected as found on VRBL and FCA, the latter medium appears to allow the enumeration of more true fecal coliforms and has higher performance in certain ways (specificity, sensitivity, and negative and positive predictive values) than VRBL. Most colonies clearly identified on both media were
E. coli
and
H. alvei
, a non-fecal coliform. Therefore, the replacement of fecal coliform enumeration by
E. coli
enumeration to estimate food sanitary quality should be recommended.
Siderophore Typing, a Powerful Tool for the Identification of Fluorescent and Nonfluorescent Pseudomonads
Authors: Meyer Jean-Marie , Geoffroy Valérie A. , Baida Nader , Gardan Louis , Izard Daniel , Lemanceau Philippe , Achouak Wafa , Palleroni Norberto J. 
Published: July 2002

ABSTRACT

A total of 301 strains of fluorescent pseudomonads previously characterized by conventional phenotypic and/or genomic taxonomic methods were analyzed through siderotyping, i.e., by the isoelectrophoretic characterization of their main siderophores and pyoverdines and determination of the pyoverdine-mediated iron uptake specificity of the strains. As a general rule, strains within a well-circumscribed taxonomic group, namely the species
Pseudomonas brassicacearum
,
Pseudomonas fuscovaginae
,
Pseudomonas jessenii
,
Pseudomonas mandelii
,
Pseudomonas monteilii
, “
Pseudomonas mosselii
,” “
Pseudomonas palleronii
,”
Pseudomonas rhodesiae
, “
Pseudomonas salomonii
,”
Pseudomonas syringae
,
Pseudomonas thivervalensis
,
Pseudomonas tolaasii
, and
Pseudomonas veronii
and the genomospecies FP1, FP2, and FP3 produced an identical pyoverdine which, in addition, was characteristic of the group, since it was structurally different from the pyoverdines produced by the other groups. In contrast, 28 strains belonging to the notoriously heterogeneous
Pseudomonas fluorescens
species were characterized by great heterogeneity at the pyoverdine level. The study of 23 partially characterized phenotypic clusters demonstrated that siderotyping is very useful in suggesting correlations between clusters and well-defined species and in detecting misclassified individual strains, as verified by DNA-DNA hybridization. The usefulness of siderotyping as a determinative tool was extended to the nonfluorescent species
Pseudomonas corrugata
,
Pseudomonas frederiksbergensis
,
Pseudomonas graminis
, and
Pseudomonas plecoglossicida
, which were seen to have an identical species-specific siderophore system and thus were easily differentiated from one another. Thus, the fast, accurate, and easy-to-perform siderotyping method compares favorably with the usual phenotypic and genomic methods presently necessary for accurate identification of pseudomonads at the species level.
Enzyme-Linked Immunosorbent Assays Using the Recombinant Dense Granule Antigens GRA6 and GRA1 of
Toxoplasma gondii
for Detection of Immunoglobulin G Antibodies
Authors: Lecordier Laurence , Fourmaux Marie-Pierre , Mercier Corinne , Dehecq Eric , Masy E. , Cesbron-Delauw Marie-France 
Published: July 2002

ABSTRACT

The potential of the dense granule antigens GRA1 and GRA6 of
Toxoplasma gondii
to be used as diagnosis reagents in a recombinant form was evaluated. Both proteins were expressed in
Escherichia coli
as glutathione-
S
-transferase (GST) fusions. The GST-GRA1 fusion comprises the entire GRA1 sequence devoid of its N-terminal signal peptide. Separate expression of the two N- and C-terminal hydrophilic regions of GRA6 showed that only the N-terminal hydrophilic part of the protein was recognized by a pool of positive human sera in an immunoblot. One hundred
T. gondii
-positive and 98 negative human sera were tested in two separate immunoglobulin G (IgG)-direct enzyme-linked immunosorbent assays (ELISAs) using either GST-GRA1 or GST-GRA6-Nt recombinant protein. Whereas the sensitivity of the GST-GRA1 IgG ELISA was low (68%), the GST-GRA6-Nt IgG ELISA reached a sensitivity of 96%. The reactivity to GRA6-Nt was shown to be high even with human sera of low IgG titers. In addition, comparison of the optical density values for each serum revealed that GRA1 may complement GRA6-Nt to reach an overall sensitivity of 98%. Therefore, the GST-GRA6-Nt ELISA could be used together with another antigen like GRA1 for the development of a recombinant antigen-based test for serodiagnosis of toxoplasmosis.