bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quinolobactin, a New Siderophore of
Pseudomonas fluorescens
ATCC 17400, the Production of Which Is Repressed by the Cognate Pyoverdine
Authors: Mossialos Dimitris , Meyer Jean-Marie , Budzikiewicz Herbert , Wolff Ulrich , Koedam Nico , Baysse Christine , Anjaiah Vanamala , Cornelis Pierre 
Published: July 2002

ABSTRACT

Transposon mutant strain 3G6 of
Pseudomonas fluorescens
ATCC 17400 which was deficient in pyoverdine production, was found to produce another iron-chelating molecule; this molecule was identified as 8-hydroxy-4-methoxy-quinaldic acid (designated quinolobactin). The pyoverdine-deficient mutant produced a supplementary 75-kDa iron-repressed outer membrane protein (IROMP) in addition to the 85-kDa IROMP present in the wild type. The mutant was also characterized by substantially increased uptake of
59
Fe-quinolobactin. The 75-kDa IROMP was produced by the wild type after induction by quinolobactin-containing culture supernatants obtained from the pyoverdine-negative mutant or by purified quinolobactin. Conversely, adding purified wild-type pyoverdine to the growth medium resulted in suppression of the 75-kDa IROMP in the pyoverdine-deficient mutant; however, suppression was not observed when
Pseudomonas aeruginosa
PAO1 pyoverdine, a siderophore utilized by strain 3G6, was added to the culture. Therefore, we assume that the quinolobactin receptor is the 75-kDa IROMP and that the quinolobactin-mediated iron uptake system is repressed by the cognate pyoverdine.
Cyt1A from
Bacillus thuringiensis
Synergizes Activity of
Bacillus sphaericus
against
Aedes aegypti
(Diptera: Culicidae)
Authors: Wirth Margaret C. , Federici Brian A. , Walton William E. 
Published: July 2002

ABSTRACT

Bacillus sphaericus
is a mosquitocidal bacterium recently developed as a commercial larvicide that is used worldwide to control pestiferous and vector mosquitoes. Whereas
B. sphaericus
is highly active against larvae of
Culex
and
Anopheles
mosquitoes, it is virtually nontoxic to
Aedes aegypti
, an important vector species. In the present study, we evaluated the capacity of the cytolytic protein Cyt1A from
Bacillus thuringiensis
subsp.
israelensis
to enhance the toxicity of
B. sphaericus
toward
A. aegypti
. Various combinations of these two materials were evaluated, and all were highly toxic. A ratio of 10:1 of
B. sphaericus
to Cyt1A was 3,600-fold more toxic to
A. aegypti
than
B. sphaericus
alone. Statistical analysis showed this high activity was due to synergism between the Cyt1A toxin and
B. sphaericus
. These results suggest that Cyt1A could be useful in expanding the host range of
B. sphaericus
.
2,4,6-Trinitrotoluene Reduction by Carbon Monoxide Dehydrogenase from
Clostridium thermoaceticum
Authors: Huang Shouqin , Lindahl Paul A. , Wang Chuanyue , Bennett George N. , Rudolph Frederick B. , Hughes Joseph B. 
Published: July 2002

ABSTRACT

Purified CO dehydrogenase (CODH) from
Clostridium thermoaceticum
catalyzed the transformation of 2,4,6-trinitrotoluene (TNT). The intermediates and reduced products of TNT transformation were separated and appear to be identical to the compounds formed by
C. acetobutylicum
, namely, 2-hydroxylamino-4,6-dinitrotoluene (2HA46DNT), 4-hydroxylamino-2,6-dinitrotoluene (4HA26DNT), 2,4-dihydroxylamino-6-nitrotoluene (24DHANT), and the Bamberger rearrangement product of 2,4-dihydroxylamino-6-nitrotoluene. In the presence of saturating CO, CODH catalyzed the conversion of TNT to two monohydroxylamino derivatives (2HA46DNT and 4HA26DNT), with 4HA26DNT as the dominant isomer. These derivatives were then converted to 24DHANT, which slowly converted to the Bamberger rearrangement product. Apparent

K
m

and
k
cat
values of TNT reduction were 165 ± 43 μM for TNT and 400 ± 94 s
−1
, respectively. Cyanide, an inhibitor for the CO/CO
2
oxidation/reduction activity of CODH, inhibited the TNT degradation activity of CODH.
Higher Diversity of
Rhizobium leguminosarum
Biovar viciae Populations in Arable Soils than in Grass Soils
Authors: Palmer K. M. , Young J. P. W. 
Published: July 2002

ABSTRACT

The bacterial genetic diversity after long-term arable cultivation was compared with that under permanent grassland using replicated paired contrasts. Pea-nodulating
Rhizobium leguminosarum
populations were sampled from pairs of arable and grass sites at four locations in Yorkshire, United Kingdom. Isolates were characterized using both chromosomal (16S-23S ribosomal DNA internal transcribed spacer PCR-restriction fragment length polymorphism) and plasmid (group-specific
repC
PCR amplification) markers. The diversities of chromosomal types,
repC
profiles, and combined genotypes were calculated using richness in types (adjusted to equal sample sizes by rarefaction), Shannon-Wiener index, and Simpson's index. The relative differences in diversity within each pair of sites were similar for all three diversity measures. Chromosomal types,
repC
profiles, and combined genotypes were each more diverse in arable soils than in grass soils at two of the four locations. The other comparisons showed no significant differences. We conclude that rhizobial diversity can be affected by differences between these two management regimens. Multiple regression analyses indicated that lower diversity was associated with high potential nitrogen and phosphate levels or with acidity.
Effects of Metal Phytoextraction Practices on the Indigenous Community of Arbuscular Mycorrhizal Fungi at a Metal-Contaminated Landfill
Authors: Pawlowska Teresa E. , Chaney Rufus L. , Chin Mel , Charvat Iris 
Published: July 2002

ABSTRACT

Phytoextraction involves use of plants to remove toxic metals from soil. We examined the effects of phytoextraction practices with three plant species (
Silene vulgaris
,
Thlaspi caerulescens
, and
Zea mays
) and a factorial variation of soil amendments (either an ammonium or nitrate source of nitrogen and the presence or absence of an elemental sulfur supplement) on arbuscular mycorrhizal (AM) fungi (Glomales, Zygomycetes) at a moderately metal-contaminated landfill located in St. Paul, Minn. Specifically, we tested whether the applied treatments affected the density of glomalean spores and AM root colonization in maize. Glomalean fungi from the landfill were grouped into two morphotypes characterized by either light-colored spores (LCS) or dark-colored spores (DCS). Dominant species of the LCS morphotype were
Glomus mosseae
and an unidentified
Glomus
sp., whereas the DCS morphotype was dominated by
Glomus constrictum
. The density of spores of the LCS morphotype from the phytoremediated area was lower than the density of these spores in the untreated landfill soil. Within the experimental area, spore density of the LCS morphotype in the rhizosphere of mycorrhizal maize was significantly higher than in rhizospheres of nonmycorrhizal
S. vulgaris
or
T. caerulescens
. Sulfur supplement increased vesicular root colonization in maize and exerted a negative effect on spore density in maize rhizosphere. We conclude that phytoextraction practices, e.g., the choice of plant species and soil amendments, may have a great impact on the quantity and species composition of glomalean propagules as well as on mycorrhiza functioning during long-term metal-remediation treatments.
Cloning of the Malic Enzyme Gene from
Corynebacterium glutamicum
and Role of the Enzyme in Lactate Metabolism
Authors: Gourdon Pierre , Baucher Marie-France , Lindley Nic D. , Guyonvarch Armel 
Published: July 2002

ABSTRACT

Malic enzyme is one of at least five enzymes, known to be present in
Corynebacterium glutamicum
, capable of carboxylation and decarboxylation reactions coupling glycolysis and the tricarboxylic acid cycle. To date, no information is available concerning the physiological role of the malic enzyme in this bacterium. The
malE
gene from
C. glutamicum
has been cloned and sequenced. The protein encoded by this gene has been purified to homogeneity, and the biochemical properties have been established. Biochemical characteristics indicate a decarboxylation role linked to NADPH generation. Strains of
C. glutamicum
in which the
malE
gene had been disrupted or overexpressed showed no detectable phenotype during growth on either acetate or glucose, but showed a significant modification of growth behavior during lactate metabolism. The wild type showed a characteristic brief period of exponential growth on lactate followed by a linear growth period. This growth pattern was further accentuated in a
malE
-disrupted strain (
ΔmalE
). However, the strain overexpressing
malE
maintained exponential growth until all lactate had been consumed. This strain accumulated significantly larger amounts of pyruvate in the medium than the other strains.
Effect of Dissemination of 2,4-Dichlorophenoxyacetic Acid (2,4-D) Degradation Plasmids on 2,4-D Degradation and on Bacterial Community Structure in Two Different Soil Horizons
Authors: Dejonghe Winnie , Goris Johan , El Fantroussi Saïd , Höfte Monica , De Vos Paul , Verstraete Willy , Top Eva M. 
Published: July 2002

ABSTRACT

Transfer of the 2,4-dichlorophenoxyacetic acid (2,4-D) degradation plasmids pEMT1 and pJP4 from an introduced donor strain,
Pseudomonas putida
UWC3, to the indigenous bacteria of two different horizons (A horizon, depth of 0 to 30 cm; B horizon, depth of 30 to 60 cm) of a 2,4-D-contaminated soil was investigated as a means of bioaugmentation. When the soil was amended with nutrients, plasmid transfer and enhanced degradation of 2,4-D were observed. These findings were most striking in the B horizon, where the indigenous bacteria were unable to degrade any of the 2,4-D (100 mg/kg of soil) during at least 22 days but where inoculation with either of the two plasmid donors resulted in complete 2,4-D degradation within 14 days. In contrast, in soils not amended with nutrients, inoculation of donors in the A horizon and subsequent formation of transconjugants (10
5
CFU/g of soil) could not increase the 2,4-D degradation rate compared to that of the noninoculated soil. However, donor inoculation in the nonamended B-horizon soil resulted in complete degradation of 2,4-D within 19 days, while no degradation at all was observed in noninoculated soil during 89 days. With plasmid pEMT1, this enhanced degradation seemed to be due only to transconjugants (10
5
CFU/g of soil), since the donor was already undetectable when degradation started. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA genes showed that inoculation of the donors was followed by a shift in the microbial community structure of the nonamended B-horizon soils. The new 16S rRNA gene fragments in the DGGE profile corresponded with the 16S rRNA genes of 2,4-D-degrading transconjugant colonies isolated on agar plates. This result indicates that the observed change in the community was due to proliferation of transconjugants formed in soil. Overall, this work clearly demonstrates that bioaugmentation can constitute an effective strategy for cleanup of soils which are poor in nutrients and microbial activity, such as those of the B horizon.
Role of
phaD
in Accumulation of Medium-Chain-Length Poly(3-Hydroxyalkanoates) in
Pseudomonas oleovorans
Authors: Klinke Stefan , de Roo Guy , Witholt Bernard , Kessler Birgit 
Published: July 2002

ABSTRACT

Pseudomonas oleovorans
is capable of producing poly(3-hydroxyalkanoates) (PHAs) as intracellular storage material. To analyze the possible involvement of
phaD
in medium-chain-length (MCL) PHA biosynthesis, we generated a
phaD
knockout mutant by homologous recombination. Upon disruption of the
phaD
gene, MCL PHA polymer accumulation was decreased. The PHA granule size was reduced, and the number of granules inside the cell was increased. Furthermore, mutant cells appeared to be smaller than wild-type cells. Investigation of MCL PHA granules revealed that the pattern of granule-associated proteins was changed and that the predominant protein PhaI was missing in the mutant. Complementation of the mutant with a
phaD
-harboring plasmid partially restored the wild-type characteristics of MCL PHA production and fully restored the granule and cell sizes. Furthermore, PhaI was attached to the granules of the complemented mutant. These results indicate that the
phaD
gene encodes a protein which plays an important role in MCL PHA biosynthesis. However, although its main effect seems to be the stabilization of MCL PHA granules, we found that the PhaD protein is not a major granule-associated protein and therefore might act by an unknown mechanism involving the PhaI protein.
Role of Respiratory Nitrate Reductase in Ability of
Pseudomonas fluorescens
YT101 To Colonize the Rhizosphere of Maize
Authors: Ghiglione Jean-François , Gourbiere François , Potier Patrick , Philippot Laurent , Lensi Robert 
Published: July 2002

ABSTRACT

Selection of the denitrifying community by plant roots (i.e., increase in the denitrifier/total heterotroph ratio in the rhizosphere) has been reported by several authors. However, very few studies to evaluate the role of the denitrifying function itself in the selection of microorganisms in the rhizosphere have been performed. In the present study, we compared the rhizosphere survival of the denitrifying
Pseudomonas fluorescens
YT101 strain with that of its isogenic mutant deficient in the ability to synthesize the respiratory nitrate reductase, coinoculated in nonplanted or planted soil. We demonstrated that under nonlimiting nitrate conditions, the denitrifying wild-type strain had an advantage in the ability to colonize the rhizosphere of maize. Investigations of the effect of the inoculum characteristics (density of the total inoculum and relative proportions of mutant and wild-type strains) on the outcome of the selection demonstrated that the selective effect of the plant was expressed only during the phase of bacterial multiplication and that the intensity of selection was dependent on the magnitude of this phase. Moreover, application of the de Wit replacement series technique to our results suggests that the advantage of the wild-type strain was maximal when the ratio between the two strains in the inoculum was close to 1:1. This work constitutes the first direct demonstration that the presence of a functional structural gene encoding the respiratory nitrate reductase confers higher rhizosphere competence to a microorganism.
Expression of Green Fluorescent Protein in
Streptococcus gordonii
DL1 and Its Use as a Species-Specific Marker in Coadhesion with
Streptococcus oralis
34 in Saliva-Conditioned Biofilms In Vitro
Authors: Aspiras Marcelo B. , Kazmerzak Karen M. , Kolenbrander Paul E. , McNab Roderick , Hardegen Neil , Jenkinson Howard F. 
Published: July 2002

ABSTRACT

Streptococcus gordonii
is one of the predominant streptococci in the biofilm ecology of the oral cavity. It interacts with other bacteria through receptor-adhesin complexes formed between cognate molecules on the surfaces of the partner cells. To study the spatial organization of
S. gordonii
DL1 in oral biofilms, we used green fluorescent protein (GFP) as a species-specific marker to identify
S. gordonii
in a two-species in vitro oral biofilm flowcell system. To drive expression of
gfp
, we isolated and characterized an endogenous
S. gordonii
promoter,
PhppA
, which is situated upstream of the chromosomal
hppA
gene encoding an oligopeptide-binding lipoprotein. A chromosomal chloramphenicol acetyltransferase (
cat
) gene fusion with
PhppA
was constructed and used to demonstrate that
PhppA
was highly active throughout the growth of bacteria in batch culture. A promoterless 0.8-kb
gfp
(′
gfp
) cassette was PCR amplified from pBJ169 and subcloned to replace the
cat
cassette downstream of the
S. gordonii
-derived
PhppA
in pMH109-HPP, generating pMA1. Subsequently, the
PhppA-′gfp
cassette was PCR amplified from pMA1 and subcloned into pDL277 and pVA838 to generate the
Escherichia coli-S. gordonii
shuttle vectors pMA2 and pMA3, respectively. Each vector was transformed into
S. gordonii
DL1 aerobically to ensure GFP expression. Flow cytometric analyses of aerobically grown transformant cultures were performed over a 24-h period, and results showed that GFP could be successfully expressed in
S. gordonii
DL1 from
PhppA
and that
S. gordonii
DL1 transformed with the
PhppA-′gfp
fusion plasmid stably maintained the fluorescent phenotype. Fluorescent
S. gordonii
DL1 transformants were used to elucidate the spatial arrangement of
S. gordonii
DL1 alone in biofilms or with the coadhesion partner
Streptococcus oralis
34 in two-species biofilms in a saliva-conditioned in vitro flowcell system. These results show for the first time that GFP expression in oral streptococci can be used as a species-specific marker in model oral biofilms.
Quantitative Immunocapture PCR Assay for Detection of
Campylobacter jejuni
in Foods
Authors: Waller David F. , Ogata Steven A. 
Published: July 2002

ABSTRACT

The rapid detection of food-borne bacterial pathogens as part of a quality control program is necessary for the maintenance of a safe food supply. In this report, we present our findings for an immunocapture PCR method for the detection of
Campylobacter jejuni
in foods. The method permits direct detection of the pathogen without an enrichment step and can be performed in approximately 8 h. Assay results are quantitative, and one cell in a milliliter sample can be detected. Application of the method to spiked milk samples and chicken skin washes did not affect the sensitivity of the assay.
Anaerobic Mineralization of Toluene by Enriched Sediments with Quinones and Humus as Terminal Electron Acceptors
Authors: Cervantes Francisco J. , Dijksma Wouter , Duong-Dac Tuan , Ivanova Anna , Lettinga Gatze , Field Jim A. 
Published: July 2002

ABSTRACT

The anaerobic microbial oxidation of toluene to CO
2
coupled to humus respiration was demonstrated by use of enriched anaerobic sediments from the Amsterdam petroleum harbor (APH) and the Rhine River. Both highly purified soil humic acids (HPSHA) and the humic quinone moiety model compound anthraquinone-2,6-disulfonate (AQDS) were utilized as terminal electron acceptors. After 2 weeks of incubation, 50 and 85% of added uniformly labeled [
13
C]toluene were recovered as
13
CO
2
in HPSHA- and AQDS-supplemented APH sediment enrichment cultures, respectively; negligible recovery occurred in unsupplemented cultures. The conversion of [
13
C]toluene agreed with the high level of recovery of electrons as reduced humus or as anthrahydroquinone-2,6-disulfonate. APH sediment was also able to use nitrate and amorphous manganese dioxide as terminal electron acceptors to support the anaerobic biodegradation of toluene. The addition of substoichiometric amounts of humic acids to bioassay reaction mixtures containing amorphous ferric oxyhydroxide as a terminal electron acceptor led to more than 65% conversion of toluene (1 mM) after 11 weeks of incubation, a result which paralleled the partial recovery of electron equivalents as acid-extractable Fe(II). Negligible conversion of toluene and reduction of Fe(III) occurred in these bioassay reaction mixtures when humic acids were omitted. The present study provides clear quantitative evidence for the mineralization of an aromatic hydrocarbon by humus-respiring microorganisms. The results indicate that humic substances may significantly contribute to the intrinsic bioremediation of anaerobic sites contaminated with priority pollutants by serving as terminal electron acceptors.
Ecology of
Thioploca
spp.: Nitrate and Sulfur Storage in Relation to Chemical Microgradients and Influence of
Thioploca
spp. on the Sedimentary Nitrogen Cycle
Authors: Zopfi Jakob , Kjær Thomas , Nielsen Lars P. , Jørgensen Bo Barker 
Published: July 2002

ABSTRACT

Microsensors, including a recently developed NO
3
−
biosensor, were applied to measure O
2
and NO
3
−
profiles in marine sediments from the upwelling area off central Chile and to investigate the influence of
Thioploca
spp. on the sedimentary nitrogen metabolism. The studies were performed in undisturbed sediment cores incubated in a small laboratory flume to simulate the environmental conditions of low O
2
, high NO
3
−
, and bottom water current. On addition of NO
3
−
and NO
2
−
,
Thioploca
spp. exhibited positive chemotaxis and stretched out of the sediment into the flume water. In a core densely populated with
Thioploca
, the penetration depth of NO
3
−
was only 0.5 mm and a sharp maximum of NO
3
−
uptake was observed 0.5 mm above the sediment surface. In sediments with only few
Thioploca
spp., NO
3
−
was detectable down to a depth of 2 mm and the maximum consumption rates were observed within the sediment. No chemotaxis toward nitrous oxide (N
2
O) was observed, which is consistent with the observation that
Thioploca
does not denitrify but reduces intracellular NO
3
−
to NH
4
+
. Measurements of the intracellular NO
3
−
and S
0
pools in
Thioploca
filaments from various depths in the sediment gave insights into possible differences in the migration behavior between the different species. Living filaments containing significant amounts of intracellular NO
3
−
were found to a depth of at least 13 cm, providing final proof for the vertical shuttling of
Thioploca
spp. and nitrate transport into the sediment.
Riboprinting and 16S rRNA Gene Sequencing for Identification of Brewery
Pediococcus
Isolates
Authors: Barney Michael , Volgyi Antonia , Navarro Alfonso , Ryder David 
Published: July 2002

ABSTRACT

A total of 46 brewery and 15 ATCC
Pediococcus
isolates were ribotyped using a Qualicon RiboPrinter. Of these, 41 isolates were identified as
Pediococcus damnosus
using
Eco
RI digestion. Three ATCC reference strains had patterns similar to each other and matched 17 of the brewery isolates. Six other brewing isolates were similar to ATCC 25249. The other 18
P. damnosus
brewery isolates had unique patterns. Of the remaining brewing isolates, one was identified as
P. parvulus
, two were identified as
P. acidilactici
, and two were identified as unique
Pediococcus
species. The use of alternate restriction endonucleases indicated that
Pst
I and
Pvu
II could further differentiate some strains having identical
Eco
RI profiles. An acid-resistant
P. damnosus
isolate could be distinguished from non-acid-resistant varieties of the same species using
Pst
I instead of
Eco
RI. 16S rRNA gene sequence analysis was compared to riboprinting for identifying pediococci. The complete 16S rRNA gene was PCR amplified and sequenced from seven brewery isolates and three ATCC references with distinctive riboprint patterns. The 16S rRNA gene sequences from six different brewery
P. damnosus
isolates were homologous with a high degree of similarity to the GenBank reference strain but were identical to each other and one ATCC strain with the exception of 1 bp in one strain. A slime-producing, beer spoilage isolate had 16S rRNA gene sequence homology to the
P. acidilactici
reference strain, in agreement with the riboprint data. Although 16S rRNA gene sequencing correctly identified the genus and species of the test
Pediococcus
isolates, riboprinting proved to be a better method for subspecies differentiation.