bluuebunny/crossref_metadata_2025_split huggingface dataset:
Classification of Antibiotic Resistance Patterns of Indicator Bacteria by Discriminant Analysis: Use in Predicting the Source of Fecal Contamination in Subtropical Waters
Authors: Harwood Valerie J. , Whitlock John , Withington Victoria 
Published: July 2002

ABSTRACT
The antibiotic resistance patterns of fecal streptococci and fecal coliforms isolated from domestic wastewater and animal feces were determined using a battery of antibiotics (amoxicillin, ampicillin, cephalothin, chlortetracycline, oxytetracycline, tetracycline, erythromycin, streptomycin, and vancomycin) at four concentrations each. The sources of animal feces included wild birds, cattle, chickens, dogs, pigs, and raccoons. Antibiotic resistance patterns of fecal streptococci and fecal coliforms from known sources were grouped into two separate databases, and discriminant analysis of these patterns was used to establish the relationship between the antibiotic resistance patterns and the bacterial source. The fecal streptococcus and fecal coliform databases classified isolates from known sources with similar accuracies. The average rate of correct classification for the fecal streptococcus database was 62.3%, and that for the fecal coliform database was 63.9%. The sources of fecal streptococci and fecal coliforms isolated from surface waters were identified by discriminant analysis of their antibiotic resistance patterns. Both databases identified the source of indicator bacteria isolated from surface waters directly impacted by septic tank discharges as human. At sample sites selected for relatively low anthropogenic impact, the dominant sources of indicator bacteria were identified as various animals. The antibiotic resistance analysis technique promises to be a useful tool in assessing sources of fecal contamination in subtropical waters, such as those in Florida.
Virulence Genes in Environmental Strains of
Vibrio cholerae
Authors: Chakraborty Soumen , Mukhopadhyay Asish K. , Bhadra Rupak Kumar , Ghosh Amar Nath , Mitra Rupak , Shimada Toshio , Yamasaki Shinji , Faruque Shah M. , Takeda Yoshifumi , Colwell Rita R. , Nair G. Balakrish 
Published: July 2002

ABSTRACT

The virulence of a pathogen is dependent on a discrete set of genetic determinants and their well-regulated expression. The
ctxAB
and
tcpA
genes are known to play a cardinal role in maintaining virulence in
Vibrio cholerae
, and these genes are believed to be exclusively associated with clinical strains of O1 and O139 serogroups. In this study, we examined the presence of five virulence genes, including
ctxAB
and
tcpA
, as well as
toxR
and
toxT
, which are involved in the regulation of virulence, in environmental strains of
V. cholerae
cultured from three different freshwater lakes and ponds in the eastern part of Calcutta, India. PCR analysis revealed the presence of these virulence genes or their homologues among diverse serotypes and ribotypes of environmental
V. cholerae
strains. Sequencing of a part of the
tcpA
gene carried by an environmental strain showed 97.7% homology to the
tcpA
gene of the classical biotype of
V. cholerae
O1. Strains carrying the
tcpA
gene expressed the toxin-coregulated pilus (TCP), demonstrated by both autoagglutination analysis and electron microscopy of the TCP pili. Strains carrying
ctxAB
genes also produced cholera toxin, determined by monosialoganglioside enzyme-linked immunosorbent assay and by passage in the ileal loops of rabbits. Thus, this study demonstrates the presence and expression of critical virulence genes or their homologues in diverse environmental strains of
V. cholerae
, which appear to constitute an environmental reservoir of virulence genes, thereby providing new insights into the ecology of
V. cholerae
.
Leaky
Lactococcus
Cultures That Externalize Enzymes and Antigens Independently of Culture Lysis and Secretion and Export Pathways
Authors: Walker Shirley A. , Klaenhammer Todd R. 
Published: July 2002

ABSTRACT

A novel system that leaks β-galactosidase (β-gal) without a requirement for secretion or export signals was developed in
Lactococcus lactis
by controlled expression of integrated phage holin and lysin cassettes. The late promoter of the lytic lactococcal bacteriophage φ31 is an 888-bp fragment (P
15A10
) encoding the transcriptional activator. When a high-copy-number P
15A10
::
lacZ.st
fusion was introduced into
L. lactis
strains C10, ML8, NCK203, and R1/r1t, high levels of the resultant β-gal activity were detected in the supernatant (approximately 85% of the total β-gal activity for C10, ML8, and NCK203 and 45% for R1/r1t). Studies showed that the phenotype resulted from expression of Tac31A from the P
15A10
fragment, which activated a homologous late promoter in prophages harbored by the lactococcal strains. Despite the high levels of β-gal obtained in the supernatant, the growth of the strains was not significantly affected, nor was there any evidence of severe membrane damage as determined by using propidium iodide or transmission electron microscopy. Integration of the holin-lysin cassette of phage r1t, under the control of the phage φ31 late promoter, into the host genome of MG1363 yielded a similar “leaky” phenotype, indicating that holin and lysin might play a critical role in the release of β-gal into the medium. In addition to β-gal, tetanus toxin fragment C was successfully delivered into the growth medium by this system. Interestingly, the X-prolyl dipeptidyl aminopeptidase PepXP (a dimer with a molecular mass of 176 kDa) was not delivered at significant levels outside the cell. These findings point toward the development of bacterial strains able to efficiently release relevant proteins and enzymes outside the cell in the absence of known secretion and export signals.
Occurrence of Tn
4371
-Related Mobile Elements and Sequences in (Chloro)biphenyl-Degrading Bacteria
Authors: Springael Dirk , Ryngaert Annemie , Merlin Christophe , Toussaint Ariane , Mergeay Max 
Published: July 2002

ABSTRACT

Tn
4371
, a 55-kb transposable element involved in the degradation and biphenyl or 4-chlorobiphenyl identified in
Ralstonia eutropha
A5, displays a modular structure including a phage-like integrase gene (
int
), a
Pseudomonas
-like (chloro)biphenyl catabolic gene cluster (
bph
), and RP4- and Ti-plasmid-like transfer genes (
trb
) (C. Merlin, D. Springael, and A. Toussaint, Plasmid 41:40–54, 1999). Southern blot hybridization was used to examine the presence of different regions of Tn
4371
in a collection of (chloro)biphenyl-degrading bacteria originating from different habitats and belonging to different bacterial genera. Tn
4371
-related sequences were never detected on endogenous plasmids. Although the gene probes containing only
bph
sequences hybridized to genomic DNA from most strains tested, a limited selection of strains, all β-proteobacteria, displayed hybridization patterns similar to the Tn
4371 bph
cluster. Homology between Tn
4371
and DNA of two of those strains, originating from the same area as strain A5, extended outside the catabolic genes and covered the putative transfer region of Tn
4371
. On the other hand, none of the (chloro)biphenyl degraders hybridized with the outer left part of Tn
4371
containing the
int
gene. The
bph
catabolic determinant of the two strains displaying homology to the Tn
4371
transfer genes and a third strain isolated from the A5 area could be mobilized to a
R. eutropha
recipient, after insertion into an endogenous or introduced IncP1 plasmid. The mobilized DNA of those strains included all Tn
4371
homologous sequences previously identified in their genome. Our observations show that the
bph
genes present on Tn
4371
are highly conserved between different (chloro)biphenyl-degrading hosts, isolated globally but belonging mainly to the β-proteobacteria. On the other hand, Tn
4371
-related mobile elements carrying
bph
genes are apparently only found in isolates from the environment that provided the Tn
4371
-bearing isolate A5.
Antimicrobial Properties of Garlic Oil against Human Enteric Bacteria: Evaluation of Methodologies and Comparisons with Garlic Oil Sulfides and Garlic Powder
Authors: Ross Z. M. , O'Gara E. A. , Hill D. J. , Sleightholme H. V. , Maslin D. J. 
Published: July 2002

ABSTRACT

The antimicrobial effects of aqueous garlic extracts are well established but those of garlic oil (GO) are little known. Methodologies for estimating the antimicrobial activity of GO were assessed and GO, GO sulfide constituents, and garlic powder (GP) were compared in tests against human enteric bacteria. Test methodologies were identified as capable of producing underestimates of GO activity. Antimicrobial activity was greater in media lacking tryptone or cysteine, suggesting that, as for allicin, GO effects may involve sulfhydryl reactivity. All bacteria tested, which included both gram-negative and -positive bacteria and pathogenic forms, were susceptible to garlic materials. On a weight-of-product basis, 24 h MICs for GO (0.02 to 5.5 mg/ml, 62 enteric isolates) and dimethyl trisulfide (0.02 to 0.31 mg/ml, 6 enteric isolates) were lower than those for a mixture of diallyl sulfides (0.63 to 25 mg/ml, 6 enteric isolates) and for GP, which also exhibited a smaller MIC range (6.25 to 12.5 mg/ml, 29 enteric isolates). Viability time studies of GO and GP against
Enterobacter aerogenes
showed time- and dose-dependent effects. Based upon its thiosulfinate content, GP was more active than GO against most bacteria, although some properties of GO are identified as offering greater therapeutic potential. Further exploration of the potential of GP and GO in enteric disease control appears warranted.
Response of the Endophytic Diazotroph
Gluconacetobacter diazotrophicus
on Solid Media to Changes in Atmospheric Partial O
2
Pressure
Authors: Pan Bo , Vessey J. Kevin 
Published: July 2002

ABSTRACT

Gluconacetobacter diazotrophicus
is an N
2
-fixing endophyte isolated from sugarcane.
G. diazotrophicus
was grown on solid medium at atmospheric partial O
2
pressures (pO
2
) of 10, 20, and 30 kPa for 5 to 6 days. Using a flowthrough gas exchange system, nitrogenase activity and respiration rate were then measured at a range of atmospheric pO
2
(5 to 60 kPa). Nitrogenase activity was measured by H
2
evolution in N
2
-O
2
and in Ar-O
2
, and respiration rate was measured by CO
2
evolution in N
2
-O
2
. To validate the use of H
2
production as an assay for nitrogenase activity, a non-N
2
-fixing (Nif
−
) mutant of
G. diazotrophicus
was tested and found to have a low rate of uptake hydrogenase (Hup
+
) activity (0.016 ±  0.009 μmol of H
2
10
10
cells
−1
h
−1
) when incubated in an atmosphere enriched in H
2
. However, Hup
+
activity was not detectable under the normal assay conditions used in our experiments.
G. diazotrophicus
fixed nitrogen at all atmospheric pO
2
tested. However, when the assay atmospheric pO
2
was below the level at which the colonies had been grown, nitrogenase activity was decreased. Optimal atmospheric pO
2
for nitrogenase activity was 0 to 20 kPa above the pO
2
at which the bacteria had been grown. As atmospheric pO
2
was increased in 10-kPa steps to the highest levels (40 to 60 kPa), nitrogenase activity decreased in a stepwise manner. Despite the decrease in nitrogenase activity as atmospheric pO
2
was increased, respiration rate increased marginally. A large single-step increase in atmospheric pO
2
from 20 to 60 kPa caused a rapid 84% decrease in nitrogenase activity. However, upon returning to 20 kPa of O
2
, 80% of nitrogenase activity was recovered within 10 min, indicating a “switch-off/switch-on” O
2
protection mechanism of nitrogenase activity. Our study demonstrates that colonies of
G. diazotrophicus
can fix N
2
at a wide range of atmospheric pO
2
and can adapt to maintain nitrogenase activity in response to both long-term and short-term changes in atmospheric pO
2
.
In Situ Characterization of
Nitrospira
-Like Nitrite-Oxidizing Bacteria Active in Wastewater Treatment Plants
Authors: Daims Holger , Nielsen Jeppe L. , Nielsen Per H. , Schleifer Karl-Heinz , Wagner Michael 
Published: July 2002

ABSTRACT

Uncultivated
Nitrospira
-like bacteria in different biofilm and activated-sludge samples were investigated by cultivation-independent molecular approaches. Initially, the phylogenetic affiliation of
Nitrospira
-like bacteria in a nitrifying biofilm was determined by 16S rRNA gene sequence analysis. Subsequently, a phylogenetic consensus tree of the
Nitrospira
phylum including all publicly available sequences was constructed. This analysis revealed that the genus
Nitrospira
consists of at least four distinct sublineages. Based on these data, two 16S rRNA-directed oligonucleotide probes specific for the phylum and genus
Nitrospira
, respectively, were developed and evaluated for suitability for fluorescence in situ hybridization (FISH). The probes were used to investigate the in situ architecture of cell aggregates of
Nitrospira
-like nitrite oxidizers in wastewater treatment plants by FISH, confocal laser scanning microscopy, and computer-aided three-dimensional visualization. Cavities and a network of cell-free channels inside the
Nitrospira
microcolonies were detected that were water permeable, as demonstrated by fluorescein staining. The uptake of different carbon sources by
Nitrospira
-like bacteria within their natural habitat under different incubation conditions was studied by combined FISH and microautoradiography. Under aerobic conditions, the
Nitrospira
-like bacteria in bioreactor samples took up inorganic carbon (as HCO
3
−
or as CO
2
) and pyruvate but not acetate, butyrate, and propionate, suggesting that these bacteria can grow mixotrophically in the presence of pyruvate. In contrast, no uptake by the
Nitrospira
-like bacteria of any of the carbon sources tested was observed under anoxic or anaerobic conditions.
Biodegradation of Methyltert-Butyl Ether by a Pure Bacterial Culture
Authors: Hatzinger Paul B. , McClay Kevin , Vainberg Simon , Tugusheva Marina , Condee Charles W. , Steffan Robert J. 
Published: July 2002

ABSTRACTBiodegradation of methyltert-butyl ether (MTBE) by the hydrogen-oxidizing bacteriumHydrogenophaga flavaENV735 was evaluated. ENV735 grew slowly on MTBE ortert-butyl alcohol (TBA) as sole sources of carbon and energy, but growth on these substrates was greatly enhanced by the addition of a small amount of yeast extract. The addition of H2did not enhance or diminish MTBE degradation by the strain, and MTBE was only poorly degraded or not degraded by type strains ofHydrogenophagaor hydrogen-oxidizing enrichment cultures, respectively. MTBE degradation activity was constitutively expressed in ENV735 and was not greatly affected by formaldehyde, carbon monoxide, allyl thiourea, or acetylene. MTBE degradation was inhibited by 1-amino benzotriazole and butadiene monoepoxide. TBA degradation was inducible by TBA and was inhibited by formaldehyde at concentrations of >0.24 mM and by acetylene but not by the other inhibitors tested. These results demonstrate that separate, independently regulated genes encode MTBE and TBA metabolism in ENV735.
Shared Binding Sites in Lepidoptera for
Bacillus thuringiensis
Cry1Ja and Cry1A Toxins
Authors: Herrero Salvador , González-Cabrera Joel , Tabashnik Bruce E. , Ferré Juan 
Published: July 2002

ABSTRACT

Bacillus thuringiensis
toxins act by binding to specific target sites in the insect midgut epithelial membrane. The best-known mechanism of resistance to
B. thuringiensis
toxins is reduced binding to target sites. Because alteration of a binding site shared by several toxins may cause resistance to all of them, knowledge of which toxins share binding sites is useful for predicting cross-resistance. Conversely, cross-resistance among toxins suggests that the toxins share a binding site. At least two strains of diamondback moth (
Plutella xylostella
) with resistance to Cry1A toxins and reduced binding of Cry1A toxins have strong cross-resistance to Cry1Ja. Thus, we hypothesized that Cry1Ja shares binding sites with Cry1A toxins. We tested this hypothesis in six moth and butterfly species, each from a different family:
Cacyreus marshalli
(Lycaenidae),
Lobesia botrana
(Tortricidae),
Manduca sexta
(Sphingidae),
Pectinophora gossypiella
(Gelechiidae),
P. xylostella
(Plutellidae), and
Spodoptera exigua
(Noctuidae). Although the extent of competition varied among species, experiments with biotinylated Cry1Ja and radiolabeled Cry1Ac showed that Cry1Ja and Cry1Ac competed for binding sites in all six species. A recent report also indicates shared binding sites for Cry1Ja and Cry1A toxins in
Heliothis virescens
(Noctuidae). Thus, shared binding sites for Cry1Ja and Cry1A occur in all lepidopteran species tested so far.
Nickel-Resistance-Based Minitransposons: New Tools for Genetic Manipulation of Environmental Bacteria
Authors: Taghavi Safieh , Delanghe Hilde , Lodewyckx Cindy , Mergeay Max , van der Lelie Daniël 
Published: July 2002

ABSTRACT

The
ncc
and
nre
nickel resistance determinants from
Ralstonia eutropha
-like strain 31A were used to construct mini-Tn
5
transposons. Broad host expression of nickel resistance was observed for the
nre
minitransposons in members of the α, β, and γ subclasses of the
Proteobacteria
, while the
ncc
minitransposons expressed nickel resistance only in
R. eutropha
-like strains.
Impact of UV Radiation on Bacterioplankton Community Composition
Authors: Winter Christian , Moeseneder Markus M. , Herndl Gerhard J. 
Published: July 2002

ABSTRACT

The potential effect of UV radiation on the composition of coastal marine bacterioplankton communities was investigated. Dilution cultures with seawater collected from the surface mixed layer of the coastal North Sea were exposed to different ranges of natural or artificial solar radiation for up to two diurnal cycles. The composition of the bacterioplankton community prior to exposure was compared to that after exposure to the different radiation regimes using denaturing gradient gel electrophoresis (DGGE) of 16S rRNA and 16S ribosomal DNA. Only minor changes in the composition of the bacterial community in the different radiation regimes were detectable. Sequencing of selected bands obtained by DGGE revealed that some species of the
Flexibacter-Cytophaga-Bacteroides
(FCB) group were sensitive to UV radiation while other species of the FCB group were resistant. Overall, only up to ≈10% of the operational taxonomic units present in the dilution cultures appeared to be affected by UV radiation. Thus, we conclude that UV radiation has little effect on the composition of coastal marine bacterioplankton communities in the North Sea.
Mobilization of Selenite by
Ralstonia metallidurans
CH34
Authors: Roux Murielle , Sarret Géraldine , Pignot-Paintrand Isabelle , Fontecave Marc , Coves Jacques 
Published: July 2002

ABSTRACT

Ralstonia metallidurans
CH34 (formerly
Alcaligenes eutrophus
CH34) is a soil bacterium characteristic of metal-contaminated biotopes, as it is able to grow in the presence of a variety of heavy metals.
R. metallidurans
CH34 is reported now to resist up to 6 mM selenite and to reduce selenite to elemental red selenium as shown by extended X-ray absorption fine-structure analysis. Growth kinetics analysis suggests an adaptation of the cells to the selenite stress during the lag-phase period. Depending on the culture conditions, the medium can be completely depleted of selenite. Selenium accumulates essentially in the cytoplasm as judged from electron microscopy and energy-dispersive X-ray analysis. Elemental selenium, highly insoluble, represents a nontoxic storage form for the bacterium. The ability of
R. metallidurans
CH34 to reduce large amounts of selenite may be of interest for bioremediation processes targeting selenite-polluted sites.
Spatial Arrangements and Associative Behavior of Species in an In Vitro Oral Biofilm Model
Authors: Guggenheim M. , Shapiro S. , Gmür R. , Guggenheim B. 
Published: July 2002

ABSTRACT

The spatial arrangements and associative behavior of
Actinomyces naeslundii, Veillonella dispar, Fusobacterium nucleatum, Streptococcus sobrinus
, and
Streptococcus oralis
strains in an in vitro model of supragingival plaque were determined. Using species-specific fluorescence-labeled antibodies in conjunction with confocal laser scanning microscopy, the volumes and distribution of the five strains were assessed during biofilm formation. The volume-derived cell numbers of each strain correlated well with respective culture data. Between 15 min and 64 h, populations of each strain increased in a manner reminiscent of batch growth. The microcolony morphologies of all members of the consortium and their distributions within the biofilm were characterized, as were interspecies associations. Biofilms formed 15 min after inoculation consisted principally of single nonaggregated cells. All five strains adhered strongly to the saliva-conditioned substratum, and therefore, coadhesion played no role during the initial phase of biofilm formation. This observation does not reflect the results of in vitro coaggregation of the five strains, which depended upon the nature of the suspension medium. While the possibility cannot be excluded that some interspecies associations observed at later stages of biofilm formation were initiated by coadhesion, increase in bacterial numbers appeared to be largely a growth phenomenon regulated by the prevailing cultivation conditions.
Cold-Adapted β-Galactosidase from the Antarctic Psychrophile
Pseudoalteromonas haloplanktis
Authors: Hoyoux A. , Jennes I. , Dubois P. , Genicot S. , Dubail F. , François J. M. , Baise E. , Feller G. , Gerday C. 
Published: July 2002

ABSTRACT

The β-galactosidase from the Antarctic gram-negative bacterium
Pseudoalteromonas haloplanktis
TAE 79 was purified to homogeneity. The nucleotide sequence and the NH
2
-terminal amino acid sequence of the purified enzyme indicate that the β-galactosidase subunit is composed of 1,038 amino acids with a calculated
M
r
of 118,068. This β-galactosidase shares structural properties with
Escherichia coli
β-galactosidase (comparable subunit mass, 51% amino sequence identity, conservation of amino acid residues involved in catalysis, similar optimal pH value, and requirement for divalent metal ions) but is characterized by a higher catalytic efficiency on synthetic and natural substrates and by a shift of apparent optimum activity toward low temperatures and lower thermal stability. The enzyme also differs by a higher pI (7.8) and by specific thermodynamic activation parameters.
P. haloplanktis
β-galactosidase was expressed in
E. coli
, and the recombinant enzyme displays properties identical to those of the wild-type enzyme. Heat-induced unfolding monitored by intrinsic fluorescence spectroscopy showed lower melting point values for both
P. haloplanktis
wild-type and recombinant β-galactosidase compared to the mesophilic enzyme. Assays of lactose hydrolysis in milk demonstrate that
P. haloplanktis
β-galactosidase can outperform the current commercial β-galactosidase from
Kluyveromyces marxianus
var. lactis, suggesting that the cold-adapted β-galactosidase could be used to hydrolyze lactose in dairy products processed in refrigerated plants.