bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secondary Intracellular Symbiotic Bacteria in Aphids of the GenusYamatocallis(Homoptera: Aphididae: Drepanosiphinae)
Authors: Fukatsu Takema 
Published: July 2002

ABSTRACTA novel secondary intracellular symbiotic bacterium from aphids of the genusYamatocallis(subfamily Drepanosiphinae) was characterized by using molecular phylogenetic analysis, in situ hybridization, and diagnostic PCR detection. In the aphid tissues, this bacterium (tentatively designated YSMS [Yamatocallissecondary mycetocyte symbiont]) was found specifically in large cells surrounded by primary mycetocytes harboringBuchneracells. Of nine drepanosiphine aphids examined, YSMS was detected in only two species of the same genus,Yamatocallis tokyoensisandYamatocallis hirayamae. In natural populations of these aphids, YSMS was present in 100% of the individuals. Phylogenetic analysis based on 16S ribosomal DNA (rDNA) sequences demonstrated that YSMS ofY. tokyoensisandY. hirayamaeconstitute a distinct and isolated clade in the γ subdivision of the classProteobacteria. No 16S rDNA sequences of secondary endosymbionts characterized so far from other aphids showed phylogenetic affinity to YSMS. Based on these results, I suggest that YSMS was acquired by an ancestor of the genusYamatocallisand has been conserved throughout the evolution of the lineage. By using the nucleotide substitution rate for 16S rDNA ofBuchneraspp., the time of acquisition of YSMS was estimated to be about 13 to 26 million years ago, in the Miocene epoch of the Tertiary period.
Pseudomonas stutzeri
Nitrite Reductase Gene Abundance in Environmental Samples Measured by Real-Time PCR
Authors: Grüntzig Verónica , Nold Stephen C. , Zhou Jizhong , Tiedje James M. 
Published: July 2002

ABSTRACT

We used real-time PCR to quantify the denitrifying nitrite reductase gene (
nirS
), a functional gene of biogeochemical significance. The assay was tested in vitro and applied to environmental samples. The primer-probe set selected was specific for
nirS
sequences that corresponded approximately to the
Pseudomonas stutzeri
species. The assay was linear from 1 to 10
6
gene copies (
r
2
= 0.999). Variability at low gene concentrations did not allow detection of twofold differences in gene copy number at less than 100 copies. DNA spiking and cell-addition experiments gave predicted results, suggesting that this assay provides an accurate measure of
P. stutzeri nirS
abundance in environmental samples. Although
P. stutzeri
abundance was high in lake sediment and groundwater samples, we detected low or no abundance of this species in marine sediment samples from Puget Sound (Wash.) and from the Washington ocean margin. These results suggest that
P. stutzeri
may not be a dominant marine denitrifier.
Factors Affecting Catalase Expression in
Pseudomonas aeruginosa
Biofilms and Planktonic Cells
Authors: Frederick Jesse R. , Elkins James G. , Bollinger Nikki , Hassett Daniel J. , McDermott Timothy R. 
Published: July 2002

ABSTRACT

Previous work with
Pseudomonas aeruginosa
showed that catalase activity in biofilms was significantly reduced relative to that in planktonic cells. To better understand biofilm physiology, we examined possible explanations for the differential expression of catalase in cells cultured in these two different conditions. For maximal catalase activity, biofilm cells required significantly more iron (25 μM as FeCl
3
) in the medium, whereas planktonic cultures required no addition of iron. However, iron-stimulated catalase activity in biofilms was still only about one-third that in planktonic cells. Oxygen effects on catalase activity were also investigated. Nitrate-respiring planktonic cultures produced approximately twice as much catalase activity as aerobic cultures grown in the presence of nitrate; the nitrate stimulation effect could also be demonstrated in biofilms. Cultures fermenting arginine had reduced catalase levels; however, catalase repression was also observed in aerobic cultures grown in the presence of arginine. It was concluded that iron availability, but not oxygen availability, is a major factor affecting catalase expression in biofilms.
Bovine Rotavirus Nonstructural Protein 4 Produced by
Lactococcus lactis
Is Antigenic and Immunogenic
Authors: Enouf Vincent , Langella Philippe , Commissaire Jacqueline , Cohen Jean , Corthier Gérard 
Published: July 2002

ABSTRACT

Rotavirus nonstructural protein 4 (NSP4) can induce diarrhea in mice. To get insight into the biological effects of NSP4, production of large quantities of this protein is necessary. We first tried to produce the protein in
Escherichia coli
, but the
nsp4
gene proved to be unstable. The capacity of the generally regarded as safe organism
Lactococcus lactis
to produce NSP4 either intra- or extracellularly was then investigated by using the nisin-controlled expression system. Production of recombinant NSP4 (rNSP4) was observed in
L. lactis
for both locations. In spite of a very low secretion efficiency, the highest level of production was obtained with the fusion between a lactococcal signal peptide and rNSP4. Cultures of the rNSP4-secreting strain were injected into rabbits, and a specific immune response was elicited. The anti-rNSP4 antibodies produced in these rabbits recognized NSP4 in MA104 cells infected by rotavirus. We showed that
L. lactis
is able to produce antigenic and immunogenic rNSP4 and thus is a good organism for producing viral antigens.
Stress and Stress-Induced Neuroendocrine Changes Increase the Susceptibility of Juvenile Oysters (
Crassostrea gigas
) to
Vibrio splendidus
Authors: Lacoste Arnaud , Jalabert Fabienne , Malham Shelagh K. , Cueff Anne , Poulet Serge A. 
Published: July 2002

ABSTRACT

Oysters are permanently exposed to various microbes, and their defense system is continuously solicited to prevent accumulation of invading and pathogenic organisms. Therefore, impairment of the animal's defense system usually results in mass mortalities in cultured oyster stocks or increased bacterial loads in food products intended for human consumption. In the present study, experiments were conducted to examine the effects of stress on the juvenile oyster's resistance to the oyster pathogen
Vibrio splendidus
. Oysters (
Crassostrea gigas
) were challenged with a low dose of a pathogenic
V. splendidus
strain and subjected to a mechanical stress 3 days later. Both mortality and
V.
splendidus
loads increased in stressed oysters, whereas they remained low in unstressed animals. Injection of noradrenaline or adrenocorticotropic hormone, two key components of the oyster neuroendocrine stress response system, also caused higher mortality and increased accumulation of
V. splendidus
in challenged oysters. These results suggest that the physiological changes imposed by stress, or stress hormones, influenced host-pathogen interactions in oysters and increased juvenile
C. gigas
vulnerability to
Vibrio splendidus
.
The
Sinorhizobium meliloti
Nutrient-Deprivation-Induced Tyrosine Degradation Gene
hmgA
Is Controlled by a Novel Member of the
arsR
Family of Regulatory Genes
Authors: Milcamps Anne , Struffi Paolo , de Bruijn Frans J. 
Published: July 2002

ABSTRACT

The regulation of the nutrient-deprivation-induced
Sinorhizobium meliloti
homogentisate dioxygenase (
hmgA
) gene, involved in tyrosine degradation, was examined.
hmgA
expression was found to be independent of the canonical nitrogen regulation (
ntr
) system. To identify regulators of
hmgA, s
econdary mutagenesis of an
S. meliloti
strain harboring a
hmgA-luxAB
reporter gene fusion (N4) was carried out using transposon Tn
1721
. Two independent Tn
1721
insertions were found to be located in a positive regulatory gene (
nitR
), encoding a protein sharing amino acid sequence similarity with proteins of the ArsR family of regulators. NitR was found to be a regulator of
S. meliloti hmgA
expression under nitrogen deprivation conditions, suggesting the presence of a
ntr
-independent nitrogen deprivation regulatory system.
nitR
insertion mutations were shown not to affect bacterial growth, nodulation of
Medicago sativa
(alfalfa) plants, or symbiotic nitrogen fixation under the physiological conditions examined. Further analysis of the
nitR
locus revealed the presence of open reading frames encoding proteins sharing amino acid sequence similarities with an ATP-binding phosphonate transport protein (PhnN), as well as transmembrane efflux proteins.
Identification of Nucleotide Sequences for the Specific and Rapid Detection of
Yersinia pestis
Authors: Radnedge Lyndsay , Gamez-Chin Silvia , McCready Paula M. , Worsham Patricia L. , Andersen Gary L. 
Published: July 2002

ABSTRACT

Suppression subtractive hybridization, a cost-effective approach for targeting unique DNA, was used to identify a 41.7-kb
Yersinia pestis
-specific region. One primer pair designed from this region amplified PCR products from natural isolates of
Y. pestis
and produced no false positives for near neighbors, an important criterion for unambiguous bacterial identification.
Control of Bacterial Motility by Environmental Factors in Polarly Flagellated and Peritrichous Bacteria Isolated from Lake Baikal
Authors: Soutourina O. A. , Semenova E. A. , Parfenova V. V. , Danchin A. , Bertin P. 
Published: July 2002

ABSTRACT

Despite numerous studies on bacterial motility, little is known about the regulation of this process by environmental factors in natural isolates. In this study we investigated the control of bacterial motility in response to environmental parameters in two strains isolated from the natural habitat of Lake Baikal. Morphological characterization, carbon source utilization, fermentation analysis, and sequence comparison of 16S rRNA genes showed that these strains belong to two distinct genera, i.e.,
Enterobacter
and
Pseudomonas
; they were named strains 22 and Y1000, respectively. Both strains swarmed at 25°C and remained motile at low temperatures (4°C), especially the
Pseudomonas
strain, which further supports the psychrotrophic characteristics of this strain. In contrast, a strong inhibition of motility was observed at above 30°C and with a high NaCl concentration. The existence of flagellar regulatory proteins FlhDC and FleQ was demonstrated in
Enterobacter
strain 22 and
Pseudomonas
strain Y1000, respectively, and environmental conditions reduced the expression of the structural genes potentially located at the first level in the flagellar cascade in both organisms. Finally, as in
Enterobacter
strain 22, a strong reduction in the transcription of the master regulatory gene
fleQ
was observed in
Pseudomonas
strain Y1000 in the presence of novobiocin, a DNA gyrase inhibitor, suggesting a link between DNA supercoiling and motility control by environmental factors. Thus, striking similarities observed in the two organisms suggest that these processes have evolved toward a similar regulatory mechanism in polarly flagellated and laterally flagellated (peritrichous) bacteria.
A Second Quorum-Sensing System Regulates Cell Surface Properties but Not Phenazine Antibiotic Production in
Pseudomonas aureofaciens
Authors: Zhang Zhongge , Pierson Leland S. 
Published: July 2002

ABSTRACT

The root-associated biological control bacterium
Pseudomonas aureofaciens
30-84 produces a range of exoproducts, including protease and phenazines. Phenazine antibiotic biosynthesis by
phzXYFABCD
is regulated in part by the PhzR-PhzI quorum-sensing system. Mutants defective in
phzR
or
phzI
produce very low levels of phenazines but wild-type levels of exoprotease. In the present study, a second genomic region of strain 30-84 was identified that, when present in
trans
, increased β-galactosidase activity in a genomic
phzB
::
lacZ
reporter and partially restored phenazine production to a
phzR
mutant. Sequence analysis identified two adjacent genes,
csaR
and
csaI
, that encode members of the LuxR-LuxI family of regulatory proteins. No putative promoter region is present upstream of the
csaI
start codon and no
lux
box-like element was found in either the
csaR
promoter or the 30-bp intergenic region between
csaR
and
csaI
. Both the PhzR-PhzI and CsaR-CsaI systems are regulated by the GacS-GacA two-component regulatory system. In contrast to the multicopy effects of
csaR
and
csaI
in
trans
, a genomic
csaR
mutant (30-84R2) and a
csaI
mutant (30-84I2) did not exhibit altered phenazine production in vitro or in situ, indicating that the CsaR-CsaI system is not involved in phenazine regulation in strain 30-84. Both mutants also produced wild-type levels of protease. However, disruption of both
csaI
and
phzI
or both
csaR
and
phzR
eliminated both phenazine and protease production completely. Thus, the two quorum-sensing systems do not interact for phenazine regulation but do interact for protease regulation. Additionally, the CsaI
N
-acylhomoserine lactone (AHL) signal was not recognized by the phenazine AHL reporter 30-84I/Z but was recognized by the AHL reporters
Chromobacterium violaceum
CV026 and
Agrobacterium tumefaciens
A136(pCF240). Inactivation of
csaR
resulted in a smooth mucoid colony phenotype and formation of cell aggregates in broth, suggesting that CsaR is involved in regulating biosynthesis of cell surface components. Strain 30-84I/I2 exhibited mucoid colony and clumping phenotypes similar to those of 30-84R2. Both phenotypes were reversed by complementation with
csaR-csaI
or by the addition of the CsaI AHL signal. Both quorum-sensing systems play a role in colonization by strain 30-84. Whereas loss of PhzR resulted in a 6.6-fold decrease in colonization by strain 30-84 on wheat roots in natural soil, a
phzR
csaR
double mutant resulted in a 47-fold decrease. These data suggest that gene(s) regulated by the CsaR-CsaI system also plays a role in the rhizosphere competence of
P. aureofaciens
30-84.
Identification and Characterization of the Gene Cluster Involved in Chitin Degradation in a Marine Bacterium,
Alteromonas
sp. Strain O-7
Authors: Tsujibo Hiroshi , Orikoshi Hideyuki , Baba Nao , Miyahara Masahiro , Miyamoto Katsushiro , Yasuda Masahide , Inamori Yoshihiko 
Published: July 2002

ABSTRACT

Alteromonas
sp. strain O-7 secretes chitinase A (ChiA), chitinase B (ChiB), and chitinase C (ChiC) in the presence of chitin. A gene cluster involved in the chitinolytic system of the strain was cloned and sequenced upstream of and including the
chiA
gene. The gene cluster consisted of three different open reading frames organized in the order
chiD
,
cbp1
, and
chiA
. The
chiD
,
cbp1
, and
chiA
genes were closely linked and transcribed in the same direction. Sequence analysis indicated that Cbp1 (475 amino acids) was a chitin-binding protein composed of two discrete functional regions. ChiD (1,037 amino acids) showed sequence similarity to bacterial chitinases classified into family 18 of glycosyl hydrolases. The
cbp1
and
chiD
genes were expressed in
Escherichia coli
, and the recombinant proteins were purified to homogeneity. The highest binding activities of Cbp1 and ChiD were observed when α-chitin was used as a substrate. Cbp1 and ChiD possessed a chitin-binding domain (ChtBD) belonging to ChtBD type 3. ChiD rapidly hydrolyzed chitin oligosaccharides in sizes from trimers to hexamers, but not chitin. However, after prolonged incubation with large amounts of ChiD, the enzyme produced a small amount of (GlcNAc)
2
from chitin. The optimum temperature and pH of ChiD were 50°C and 7.0, respectively.
Morphological Changes of Rhizobia in Peat Cultures
Authors: Feng Lu , Roughley Rodney J. , Copeland Les 
Published: July 2002

ABSTRACT

Morphological changes that take place in peat cultures of several species of rhizobia were examined. These changes seemed to be associated with enhanced survival of cells in peat and after inoculation onto plastic beads, which were used as a model system for seeds. Cell wall changes, in which the periplasmic space appeared to be occluded with electron-dense material, were observed in
Rhizobium
sp. strain SU343 and
Bradyrhizobium lupini
WU425 cells after 7 and 14 days in peat, respectively. Nutrient limitation and low O
2
concentration in peat are suggested to be factors involved in the induction of the morphological changes. Polyhydroxybutyrate reserves, which were present in broth-cultured cells of both species of rhizobia, were mobilized after transfer into peat but did not appear to influence survival after inoculation onto beads. Enhanced expression of an iron-manganese superoxide dismutase was also observed after the cells were transferred into peat. We conclude that cell wall thickening in rhizobia after transfer from broth cultures into peat is an adaptive response for long-term survival under nutrient-limited conditions in peat. Cells with thickened walls may also be more resistant to other types of stress, such as that encountered on a seed surface.
Identification of a Hydrophobin Gene That is Developmentally Regulated in the Ectomycorrhizal Fungus
Tricholoma terreum
Authors: Mankel Angela , Krause Katrin , Kothe Erika 
Published: July 2002

ABSTRACT

The symbiosis between ectomycorrhizal fungi and trees is an essential part of forest ecology and depends entirely on the communication between the two partners for establishing and maintaining the relationship. The identification and characterization of differentially expressed genes is a step to identifying such signals and to understanding the regulation of this process. We determined the role of hydrophobins produced by
Tricholoma terreum
in mycorrhiza formation and hyphal development. A hydrophobin was purified from culture supernatant, and the corresponding gene was identified. The gene is expressed in aerial mycelium and in mycorrhiza. By using a heterologous antiserum directed against a hydrophobin found in the aerial mycelium of
Schizophyllum commune
, we detected a hydrophobin in the symbiosis between
T. terreum
and its native pine host
Pinus sylvestris
. The hydrophobin was found in aerial mycelium of the hyphal mantle and also in the Hartig net hyphae, which form the interface between both partners. Interestingly, this was not the case in the interaction of
T. terreum
with a host of low compatibility, the spruce
Picea abies
. The differential expression with respect to host was verified at the transcriptional level by competitive PCR. The differential protein accumulation pattern with respect to host compatibility seen by immunofluorescence staining can thus be attributed at least in part to transcriptional control of the
hyd1
gene.
Inhibition of Bacterial Growth, Enterotoxin Production, and Spore Outgrowth in Strains of
Bacillus cereus
by Bacteriocin AS-48
Authors: Abriouel Hikmate , Maqueda Mercedes , Gálvez Antonio , Martínez-Bueno Manuel , Valdivia Eva 
Published: July 2002

ABSTRACT

Bacteriocin AS-48 showed high bactericidal activity for mesophilic and psychrotrophic strains of
Bacillus cereus
over a broad pH range. AS-48 inhibition of the enterotoxin-producing strain LWL1 was enhanced by sodium nitrite, sodium lactate, and sodium chloride. The latter also enhanced AS-48 activity against strain CECT 131. Bacterial growth and enterotoxin production by strain LWL1 were completely inhibited at bacteriocin concentrations of 7.5 μg/ml. At subinhibitory bacteriocin concentrations, enterotoxin production decreased markedly and sporulation was delayed. Intact spores were resistant to AS-48 but became gradually sensitive to AS-48 during the course of germination.
Rapid Detection of
Shigella
Species in Environmental Sewage by an Immunocapture PCR with Universal Primers
Authors: Peng Xuanxian , Luo Wen , Zhang Jianying , Wang Sanying , Lin Shengcai 
Published: July 2002

ABSTRACT

In the present study, we developed a quick, highly specific method for detection of
Shigella
species by combining immunocapturing of the bacteria and a universal primer PCR. The method drastically enhances test sensitivity, and it can be used not only for identification of
Shigella
species in the environment but also for rapid detection of other pathogens.
Role of Glucose in Enhancing the Temperature-Dependent Growth Inhibition ofEscherichia coliO157:H7 ATCC 43895 by aPseudomonassp
Authors: Samelis John , Sofos John N. 
Published: July 2002

ABSTRACTGrowth ofEscherichia coliO157:H7 strain ATCC 43895 was monitored at 5, 10, 15, and 25°C in both pure and mixed (1:1) cultures with a gluconate-producingPseudomonassp. found in meat to evaluate the effect of the absence and presence of 1% glucose in broth on temperature-dependent competition. The number of colonies of thePseudomonasstrain exceeded 9 log CFU/ml under all conditions tested. The pathogen grew better as the temperature increased from 10 to 15 and 25°C and grew better in pure culture than in mixed cultures.Pseudomonassp. inhibitedE. coliO157:H7 in cocultures with glucose at 10°C, while at 15°C the pathogen exhibited a biphasic pattern of growth with an intermediate inactivation period. Pathogen inhibition was much weaker in cocultures grown without glucose at 10 to 15°C and, irrespective of glucose, at 25°C. These results indicate that glucose enhances the growth inhibition ofE. coliO157:H7 by somePseudomonasspp., potentially due to its rapid uptake and conversion to gluconate, at low (≤15°C) temperatures.
Characterization of the Oxygen Tolerance of a Hydrogenase Linked to a Carbon Monoxide Oxidation Pathway in
Rubrivivax gelatinosus
Authors: Maness Pin-Ching , Smolinski Sharon , Dillon Anne C. , Heben Michael J. , Weaver Paul F. 
Published: July 2002

ABSTRACT

A hydrogenase linked to the carbon monoxide oxidation pathway in
Rubrivivax gelatinosus
displays tolerance to O
2
. When either whole-cell or membrane-free partially purified hydrogenase was stirred in full air (21% O
2
, 79% N
2
), its H
2
evolution activity exhibited a half-life of 20 or 6 h, respectively, as determined by an anaerobic assay using reduced methyl viologen. When the partially purified hydrogenase was stirred in an atmosphere containing either 3.3 or 13% O
2
for 15 min and evaluated by a hydrogen-deuterium (H-D) exchange assay, nearly 80 or 60% of its isotopic exchange rate was retained, respectively. When this enzyme suspension was subsequently returned to an anaerobic atmosphere, more than 90% of the H-D exchange activity was recovered, reflecting the reversibility of this hydrogenase toward O
2
inactivation. Like most hydrogenases, the CO-linked hydrogenase was extremely sensitive to CO, with 50% inhibition occurring at 3.9 μM dissolved CO. Hydrogen production from the CO-linked hydrogenase was detected when ferredoxins of a prokaryotic source were the immediate electron mediator, provided they were photoreduced by spinach thylakoid membranes containing active water-splitting activity. Based on its appreciable tolerance to O
2
, potential applications of this hydrogenase are discussed.
Rapid Detection of
Escherichia coli
O157:H7 with Multiplex Real-Time PCR Assays
Authors: Jothikumar Narayanan , Griffiths Mansel W. 
Published: July 2002

ABSTRACT

A SYBR Green LightCycler PCR assay using a single primer pair allowed simultaneous detection of
stx1
and/or
stx2
of
Escherichia coli
O157:H7. A distinct sequence of the Shiga-like toxin genes was amplified to yield products of 227 and/or 224 bp, respectively. The two products were distinguished by melting point curve analysis.