bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secondary Metabolites Help Biocontrol Strain
Pseudomonas fluorescens
CHA0 To Escape Protozoan Grazing
Authors: Jousset Alexandre , Lara Enrique , Wall Luis G. , Valverde Claudio 
Published: November 2006

ABSTRACT

In soil ecosystems, bacteria must cope with predation activity, which is attributed mainly to protists. The development of antipredation strategies may help bacteria maintain higher populations and persist longer in the soil. We analyzed the interaction between the root-colonizing and biocontrol strain
Pseudomonas fluorescens
CHA0 and three different protist isolates (an amoeba, a flagellate, and a ciliate). CHA0 produces a set of antibiotics, HCN, and an exoprotease. We observed that protists cannot grow on CHA0 but can multiply on isogenic regulatory mutants that do not produce the extracellular metabolites. The in vitro responses to CHA0 cells and its exoproducts included growth inhibition, encystation, paralysis, and cell lysis. By analyzing the responses of protists to bacterial supernatants obtained from different isogenic mutants whose production of one or more exometabolites was affected and also to culture extracts with antibiotic enrichment, we observed different contributions of the phenolic antifungal compound 2,4-diacetylphloroglucinol (DAPG) and the extracellular protease AprA to CHA0 toxicity for protists and to the encystation-reactivation cycle. The grazing pressure artificially produced by a mixture of the three protists in a microcosm system resulted in reduced colonization of cucumber roots by a regulatory isogenic CHA0 mutant unable to produce toxins. These results suggest that exometabolite production in biocontrol strain CHA0 may contribute to avoidance of protist grazing and help sustain higher populations in the rhizosphere, which may be a desirable and advantageous trait for competition with other bacteria for available resources.
Quantifying Substrate Uptake by Individual Cells of Marine Bacterioplankton by Catalyzed Reporter Deposition Fluorescence In Situ Hybridization Combined with Microautoradiography
Authors: Sintes Eva , Herndl Gerhard J. 
Published: November 2006

ABSTRACT

Catalyzed reporter deposition fluorescence in situ hybridization combined with microautoradiography (MICRO-CARD-FISH) is increasingly being used to obtain qualitative information on substrate uptake by individual members of specific prokaryotic communities. Here we evaluated the potential for using this approach quantitatively by relating the measured silver grain area around cells taking up
3
H-labeled leucine to bulk leucine uptake measurements. The increase in the silver grain area over time around leucine-assimilating cells of coastal bacterial assemblages was linear during 4 to 6 h of incubation. By establishing standardized conditions for specific activity levels and concomitantly performing uptake measurements with the bulk community, MICRO-CARD-FISH can be used quantitatively to determine uptake rates on a single-cell level. Therefore, this approach allows comparisons of single-cell activities for bacterial communities obtained from different sites or growing under different ecological conditions.
Intraspecific Variation in Growth and Morphology of the Bloom-Forming Cyanobacterium
Microcystis aeruginosa
Authors: Wilson Alan E. , Wilson Whitney A. , Hay Mark E. 
Published: November 2006

ABSTRACT

In the laboratory, we documented large variation in the morphology, toxicity, and maximum population growth rates for 32
Microcystis aeruginosa
strains isolated from 12 lakes. Growth rates and mean colony sizes varied significantly across strains and were positively correlated. However, growth rates were unrelated to toxin production.
Increased Abundance of IncP-1β Plasmids and Mercury Resistance Genes in Mercury-Polluted River Sediments: First Discovery of IncP-1β Plasmids with a Complex
mer
Transposon as the Sole Accessory Element
Authors: Smalla Kornelia , Haines Anthony S. , Jones Karen , Krögerrecklenfort Ellen , Heuer Holger , Schloter Michael , Thomas Christopher M. 
Published: November 2006

ABSTRACT

Although it is generally assumed that mobile genetic elements facilitate the adaptation of microbial communities to environmental stresses, environmental data supporting this assumption are rare. In this study, river sediment samples taken from two mercury-polluted (A and B) and two nonpolluted or less-polluted (C and D) areas of the river Nura (Kazakhstan) were analyzed by PCR for the presence and abundance of mercury resistance genes and of broad-host-range plasmids. PCR-based detection revealed that mercury pollution corresponded to an increased abundance of mercury resistance genes and of IncP-1β replicon-specific sequences detected in total community DNA. The isolation of IncP-1β plasmids from contaminated sediments was attempted in order to determine whether they carry mercury resistance genes and thus contribute to an adaptation of bacterial populations to Hg pollution. We failed to detect IncP-1β plasmids in the genomic DNA of the cultured Hg-resistant bacterial isolates. However, without selection for mercury resistance, three different IncP-1β plasmids (pTP6, pTP7, and pTP8) were captured directly from contaminated sediment slurry in
Cupriavidus necator
JMP228 based on their ability to mobilize the IncQ plasmid pIE723. These plasmids hybridized with the
merRT
Δ
P
probe and conferred Hg resistance to their host. A broad host range and high stability under conditions of nonselective growth were observed for pTP6 and pTP7. The full sequence of plasmid pTP6 was determined and revealed a backbone almost identical to that of the IncP-1β plasmids R751 and pB8. However, this is the first example of an IncP-1β plasmid which had acquired only a mercury resistance transposon but no antibiotic resistance or biodegradation genes. This transposon carries a rather complex set of
mer
genes and is inserted between Tra1 and Tra2.
Polyphosphate Stores Enhance the Ability of
Vibrio cholerae
To Overcome Environmental Stresses in a Low-Phosphate Environment
Authors: Jahid Iqbal K. , Silva Anisia J. , Benitez Jorge A. 
Published: November 2006

ABSTRACT

Vibrio cholerae
, the causative agent of Asiatic cholera, has been reported to make large quantities of polyphosphate. Inorganic polyphosphate is a ubiquitous molecule with a variety of functions in prokaryotic and eukaryotic cells. We constructed a
V. cholerae
mutant with a deletion in the polyphosphate kinase (
ppk
) gene. The mutant was defective in polyphosphate biosynthesis. Deletion of
ppk
had no significant effect on production of cholera toxin, hemagglutinin/protease, motility, biofilm formation, and colonization of the suckling mouse intestine. The wild type and mutant had similar growth rates in rich and minimal medium and exhibited similar phosphate uptake and alkaline phosphatase induction. In contrast to
ppk
mutants from other gram-negative bacteria, the
V. cholerae
mutant survived prolonged starvation in LB medium and artificial seawater basal salts. The
ppk
mutant was significantly more sensitive to low pH, high salinity, and oxidative stress when it was cultured in low-phosphate minimal medium.
T
he
ppk
mutant failed to induce catalase when it was downshifted to phosphorus-limiting conditions. Furthermore, the increased sensitivity of the
ppk
mutant to environmental stressors in phosphate-limited medium correlated with a diminished capacity to synthesize ATP from intracellular reservoirs. We concluded that polyphosphate protects
V. cholerae
from environmental stresses under phosphate limitation conditions. It has been proposed that toxigenic
V. cholerae
can survive in estuaries and brackish waters in which phosphorus and/or nitrogen can be a limiting nutrient. Thus, synthesis of large polyphosphate stores could enhance the ability of
V. cholerae
to survive in the aquatic environment.
Effect of Sheep Urine Deposition on the Bacterial Community Structure in an Acidic Upland Grassland Soil
Authors: Rooney Deirdre , Kennedy Nabla , Deering Louise , Gleeson Deirdre , Clipson Nicholas 
Published: November 2006

ABSTRACT

The effect of the addition of synthetic sheep urine (SSU) and plant species on the bacterial community composition of upland acidic grasslands was studied using a microcosm approach. Low, medium, and high concentrations of SSU were applied to pots containing plant species typical of both unimproved (
Agrostis capillaris
) and agriculturally improved (
Lolium perenne
) grasslands, and harvests were carried out 10 days and 50 days after the addition of SSU. SSU application significantly increased both soil pH (
P
< 0.005), with pH values ranging from pH 5.4 (zero SSU) to pH 6.4 (high SSU), and microbial activity (
P
< 0.005), with treatment with medium and high levels of SSU displaying significantly higher microbial activity (triphenylformazan dehydrogenase activity) than treatment of soil with zero or low concentrations of SSU. Microbial biomass, however, was not significantly altered by any of the SSU applications. Plant species alone had no effect on microbial biomass or activity. Bacterial community structure was profiled using bacterial automated ribosomal intergenic spacer analysis. Multidimensional scaling plots indicated that applications of high concentrations of SSU significantly altered the bacterial community composition in the presence of plant species but at different times: 10 days after application of high concentrations of SSU, the bacterial community composition of
L. perenne
-planted soils differed significantly from those of any other soils, whereas in the case of
A. capillaris
-planted soils, the bacterial community composition was different 50 days after treatment with high concentrations of SSU. Canonical correspondence analysis also highlighted the importance of interactions between SSU addition, plant species, and time in the bacterial community structure. This study has shown that the response of plants and bacterial communities to sheep urine deposition in grasslands is dependent on both the grass species present and the concentration of SSU applied, which may have important ecological consequences for agricultural grasslands.
RecombinantEscherichia coliStrain Produces a ZZ Domain Displaying Biopolyester Granules Suitable for Immunoglobulin G Purification
Authors: Brockelbank Jane A. , Peters Verena , Rehm Bernd H. A. 
Published: November 2006

ABSTRACTThe immunoglobulin G (IgG) binding ZZ domain of protein A fromStaphylococcus aureuswas fused to the N terminus of the polyhydroxyalkanoate (PHA) synthase fromCupriavidus necator. The fusion protein was confirmed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and mediated formation of ZZ domain-displaying PHA granules in recombinantEscherichia coli. The IgG binding capacity of isolated granules was assessed using enzyme-linked immunosorbent assay and could be enhanced by the overproduction of the ZZ-PHA synthase. ZZ-PHA granules enabled efficient purification of IgG from human serum.
Enhancement of Chilling Resistance of Inoculated Grapevine Plantlets with a Plant Growth-Promoting Rhizobacterium,Burkholderia phytofirmansStrain PsJN
Authors: Ait Barka Essaid , Nowak Jerzy , Clément Christophe 
Published: November 2006

ABSTRACTIn vitro inoculation ofVitis viniferaL. cv. Chardonnay explants with a plant growth-promoting rhizobacterium,Burkholderia phytofirmansstrain PsJN, increased grapevine growth and physiological activity at a low temperature. There was a relationship between endophytic bacterial colonization of the grapevine plantlets and their growth at both ambient (26°C) and low (4°C) temperatures and their sensitivities to chilling. The major benefits of bacterization were observed on root growth (11.8- and 10.7-fold increases at 26°C and 4°C, respectively) and plantlet biomass (6- and 2.2-fold increases at 26°C and 4°C, respectively). The inoculation with PsJN also significantly improved plantlet cold tolerance compared to that of the nonbacterized control. In nonchilled plantlets, bacterization enhanced CO2fixation and O2evolution 1.3 and 2.2 times, respectively. The nonbacterized controls were more sensitive to exposure to low temperatures than were the bacterized plantlets, as indicated by several measured parameters. Moreover, relative to the noninoculated controls, bacterized plantlets had significantly increased levels of starch, proline, and phenolics. These increases correlated with the enhancement of cold tolerance of the grapevine plantlets. In summary,B. phytofirmansstrain PsJN inoculation stimulates grapevine growth and improves its ability to withstand cold stress.
Degradation of Fluorobenzene by
Rhizobiales
Strain F11 via
ortho
Cleavage of 4-Fluorocatechol and Catechol
Authors: Carvalho Maria F. , Ferreira Maria Isabel M. , Moreira Irina S. , Castro Paula M. L. , Janssen Dick B. 
Published: November 2006

ABSTRACT

The aerobic metabolism of fluorobenzene by
Rhizobiales
sp. strain F11 was investigated. Liquid chromatography-mass spectrometry analysis showed that 4-fluorocatechol and catechol were formed as intermediates during fluorobenzene degradation by cell suspensions. Both these compounds, unlike 3-fluorocatechol, supported growth and oxygen uptake. Cells grown on fluorobenzene contained enzymes for the
ortho
pathway but not for
meta
ring cleavage of catechols. The results suggest that fluorobenzene is predominantly degraded via 4-fluorocatechol with subsequent
ortho
cleavage and also partially via catechol.
A Disulfide Bond-Containing Alkaline Phosphatase Triggers a BdbC-Dependent Secretion Stress Response in
Bacillus subtilis
Authors: Darmon Elise , Dorenbos Ronald , Meens Jochen , Freudl Roland , Antelmann Haike , Hecker Michael , Kuipers Oscar P. , Bron Sierd , Quax Wim J. , Dubois Jean-Yves F. , van Dijl Jan Maarten 
Published: November 2006

ABSTRACT

The gram-positive bacterium
Bacillus subtilis
secretes high levels of proteins into its environment. Most of these secretory proteins are exported from the cytoplasm in an unfolded state and have to fold efficiently after membrane translocation. As previously shown for α-amylases of
Bacillus
species, inefficient posttranslocational protein folding is potentially detrimental and stressful. In
B. subtilis
, this so-called secretion stress is sensed and combated by the CssRS two-component system. Two known members of the CssRS regulon are the
htrA
and
htrB
genes, encoding potential extracytoplasmic chaperone proteases for protein quality control. In the present study, we investigated whether high-level production of a secretory protein with two disulfide bonds, PhoA of
Escherichia coli
, induces secretion stress in
B. subtilis
. Our results show that
E. coli
PhoA production triggers a relatively moderate CssRS-dependent secretion stress response in
B. subtilis
. The intensity of this response is significantly increased in the absence of BdbC, which is a major determinant for posttranslocational folding of disulfide bond-containing proteins in
B. subtilis
. Our findings show that BdbC is required to limit the PhoA-induced secretion stress. This conclusion focuses interest on the BdbC-dependent folding pathway for biotechnological production of proteins with disulfide bonds in
B. subtilis
and related bacilli.
Use of Native Lactococci as Vehicles for Delivery of DNA into Mammalian Epithelial Cells
Authors: Guimarães Valéria Dellaretti , Innocentin Silvia , Lefèvre François , Azevedo Vasco , Wal Jean-Michel , Langella Philippe , Chatel Jean-Marc 
Published: November 2006

ABSTRACT

The use of the food-grade bacterium
Lactococcus lactis
as a DNA delivery vehicle at the mucosal level is an attractive DNA vaccination strategy. Previous experiments showed that recombinant
L. lactis
expressing the
Listeria monocytogenes inlA
gene can deliver a functional gene into mammalian cells. Here, we explored the potential use of noninvasive
L. lactis
strains as a DNA delivery vehicle. We constructed two
Escherichia coli-L. lactis
shuttle plasmids, pLIG:BLG1 and pLIG:BLG2, containing a eukaryotic expression cassette with the cDNA of bovine β-lactoglobulin (BLG). The greatest BLG expression after transfection of Cos-7 cells was obtained with pLIG:BLG1, which was then used to transform
L. lactis
MG1363. The resulting
L. lactis
strain MG1363(pLIG:BLG1) was not able to express BLG. The potential of
L. lactis
as a DNA delivery vehicle was analyzed by detection of BLG in Caco-2 human colon carcinoma cells after 3 h of coincubation with (i) purified pLIG:BLG1, (ii) MG1363(pLIG:BLG1), (iii) a mix of MG1363(pLIG) and purified pLIG:BLG1, and (iv) MG1363. Both BLG cDNA and BLG expression were detected only in Caco-2 cells coincubated with MG1363(pLIG:BLG1). There was a decrease in the BLG cDNA level in Caco-2 cells between 24 and 48 h after coincubation. BLG expression by Caco-2 cells started at 24 h and increased between 24 and 72 h. BLG secretion by Caco-2 cells started 48 h after coincubation with MG1363(pLIG:BLG1). We conclude that lactococci can deliver BLG cDNA into mammalian epithelial cells, demonstrating their potential to deliver in vivo a DNA vaccine.
Analysis of Novel Soluble Chromate and Uranyl Reductases and Generation of an Improved Enzyme by Directed Evolution
Authors: Barak Y. , Ackerley D. F. , Dodge C. J. , Banwari L. , Alex C. , Francis A. J. , Matin A. 
Published: November 2006

ABSTRACT

Most polluted sites contain mixed waste. This is especially true of the U.S. Department of Energy (DOE) waste sites which hold a complex mixture of heavy metals, radionuclides, and organic solvents. In such environments enzymes that can remediate multiple pollutants are advantageous. We report here evolution of an enzyme, ChrR6 (formerly referred to as Y6), which shows a markedly enhanced capacity for remediating two of the most serious and prevalent DOE contaminants, chromate and uranyl. ChrR6 is a soluble enzyme and reduces chromate and uranyl intracellularly. Thus, the reduced product is at least partially sequestered and nucleated, minimizing the chances of reoxidation. Only one amino acid change,
Tyr
128
Asn
, was responsible for the observed improvement. We show here that ChrR6 makes
Pseudomonas putida
and
Escherichia coli
more efficient agents for bioremediation if the cellular permeability barrier to the metals is decreased.
Construction of a Library of Human Glycosyltransferases Immobilized in the Cell Wall ofSaccharomyces cerevisiae
Authors: Shimma Yoh-ichi , Saito Fumie , Oosawa Fumi , Jigami Yoshifumi 
Published: November 2006

ABSTRACTFifty-one human glycosyltransferases were expressed inSaccharomyces cerevisiaeas immobilized enzymes and were assayed for enzymatic activities. The stem and catalytic regions of sialyl-, fucosyl-, galactosyl-,N-acetylgalactosaminyl-, andN-acetylglucosaminyltransferases were fused with yeast cell wall Pir proteins, which anchor glycosyltransferases at the yeast cell wall glucan. More than 75% of expressed recombinant glycosyltransferases retained their enzymatic activities in the yeast cell wall fraction and will be used as a human glycosyltransferase library. In increasing the enzymatic activities of immobilized glycosyltransferases, several approaches were found to be effective. Additional expression of yeast protein disulfide isomerase increased the expression levels and activities of polypeptideN-acetylgalactosaminyltransferases and other glycosyltransferases. PIR3 and/or PIR4 was more effective than PIR1 as a cell wall anchor when the Pir-glycosyltransferase fusions were expressed under the control of the constitutive glyceraldehyde-3-phosphate dehydrogenase promoter. Oligosaccharides such as Lewis x, Lewis y, and H antigen were successfully synthesized using this immobilized glycosyltransferase library, indicating that the Pir-fused glycosyltransferases are useful for the production of various human oligosaccharides.
Biofilm and Nanowire Production Leads to Increased Current in
Geobacter sulfurreducens
Fuel Cells
Authors: Reguera Gemma , Nevin Kelly P. , Nicoll Julie S. , Covalla Sean F. , Woodard Trevor L. , Lovley Derek R. 
Published: November 2006

ABSTRACT

Geobacter sulfurreducens
developed highly structured, multilayer biofilms on the anode surface of a microbial fuel cell converting acetate to electricity. Cells at a distance from the anode remained viable, and there was no decrease in the efficiency of current production as the thickness of the biofilm increased. Genetic studies demonstrated that efficient electron transfer through the biofilm required the presence of electrically conductive pili. These pili may represent an electronic network permeating the biofilm that can promote long-range electrical transfer in an energy-efficient manner, increasing electricity production more than 10-fold.
Genetic Variability of
Spodoptera frugiperda
Smith (Lepidoptera: Noctuidae) Populations from Latin America Is Associated with Variations in Susceptibility to
Bacillus thuringiensis
Cry Toxins
Authors: Monnerat Rose , Martins Erica , Queiroz Paulo , Ordúz Sergio , Jaramillo Gabriela , Benintende Graciela , Cozzi Jorge , Real M. Dolores , Martinez-Ramirez Amparo , Rausell Carolina , Cerón Jairo , Ibarra Jorge E. , Del Rincon-Castro M. Cristina , Espinoza Ana M. , Meza-Basso Luis , Cabrera Lizbeth , Sánchez Jorge , Soberon Mario , Bravo Alejandra 
Published: November 2006

ABSTRACT

Bacillus thuringiensis
strains isolated from Latin American soil samples that showed toxicity against three
Spodoptera frugiperda
populations from different geographical areas (Mexico, Colombia, and Brazil) were characterized on the basis of their insecticidal activity, crystal morphology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of parasporal crystals, plasmid profiles, and
cry
gene content. We found that the different
S. frugiperda
populations display different susceptibilities to the selected
B. thuringiensis
strains and also to pure preparations of Cry1B, Cry1C, and Cry1D toxins. Binding assays performed with pure toxin demonstrated that the differences in the toxin binding capacities of these insect populations correlated with the observed differences in susceptibility to the three Cry toxins analyzed. Finally, the genetic variability of the three insect populations was analyzed by random amplification of polymorphic DNA-PCR, which showed significant genetic diversity among the three
S. frugiperda
populations analyzed. The data presented here show that the genetic variability of
S. frugiperda
populations should be carefully considered in the development of insect pest control strategies, including the deployment of genetically modified maize in different geographical regions.