Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “AEROMONAS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41Linked to original sources
PubMed1995

A specific PulD homolog is required for the secretion of paracrystalline surface array subunits in Aeromonas hydrophila.

Aeromonas hydrophila is an important pathogen of fish, and its high-virulence strains display a two-dimensional paracrystalline layer (S-layer) on their outermost surfaces. The nucleotide sequence of a 4.1-kb region located 700 bp upstream of the A. hydrophila TF7 S-layer protein gene (ahsA) has been determined. A sequence analysis of the region revealed the presence of three complete open reading frames ending in a gene encoding a 79.8-kDa polypeptide that shows high homology to the PulD family of secretion proteins. The sequenced region displays both organizational and sequence homology to the Xanthomonas campestris pv. campestris Xps secretory system. Insertional inactivation of the spsD (S-protein secretion D) gene showed that the loss of expression of the PulD homolog coincided with the localization of the S-protein in the periplasm and the loss of the S-layer from the surface of the bacterium. However, the secretion of the enzymes hemolysin, amylase, and protease was unaffected in the mutant with the nonfunctional spsD gene, as was the export of flagella and fimbrial proteins. Southern blot analysis showed that the spsD gene was not conserved among all strains of S-protein-producing A. hydrophila or Aeromonas veronii biotype sobria. Use of the promoterless chloramphenicol acetyltransferase gene showed that unlike pulD and its homologs, spsD contains its own promoter. A. hydrophila has been shown to contain the exe operon, which is responsible for the secretion of a number of extracellular enzymes in this bacterium. A fragment of DNA was generated from the exeD gene of A. hydrophilia Ah65 by PCR and was subsequently used in hybridization studies to probe the chromosome of A. hydrophila TF7. The presence of an exeD homolog in A. hydrophila TF7 was found; therefore, the spsD gene encodes a second pulD homolog that displays a high specificity for the secretion of the S-protein. This gene appears to be part of a second terminal branch of the general secretory pathway in A. hydrophila.

Aeromonas hydrophila↗
PubMed1996

Aeromonas salmonicida possesses two genes encoding homologs of the major outer membrane protein, OmpA.

Two homologs of the outer membrane protein OmpA were identified in Aeromonas salmonicida by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, and amino-terminal sequence analyses. An A. salmonicida genomic DNA library was constructed by using lambda GEM-11 and recombinant phage carrying both genes ompAI and ompAII) selected by immunoscreening. A 5.0-kb BamHI fragment containing the two genes in tandem was subcloned in pBluescript and used for further subcloning and sequencing of the genes. The encoded proteins (Mr = 33,564 and 32,536 for mature OmpAI and OmpAII, respectively) had only 64% identity with each other and otherwise had the highest level of homology to OmpA proteins from the members of the family Enterobacteriaceae. Based on the Escherichia coli OmpA model, an eight-stranded amphipathic beta-barrel model for the membrane assembly of the N-terminal half of OmpAI and OmpAII was predicted. Most variation between the two proteins was localized to the predicted surface loops and periplasmic turns, while the transmembrane strands and C-terminals domains were highly conserved. Expression of ompAI and ompAII separately in E. coli indicated that both genes could be independently transcribed from their own promoters and that both gene products were assembled into the E. coli outer membrane. A survey of different Aeromonas spp. by PCR revealed that possession of two tandem ompA genes was widespread among this genus. This is the first report of any bacterial species possessing two genes for homologs of this major outer membrane protein.

Aeromonas↗
PubMed1996

Identification of the catalytic triad of the lipase/acyltransferase from Aeromonas hydrophila.

Aeromonas hydrophila secretes a lipolytic enzyme that has several properties in common with the mammalian enzyme lecithin-cholesterol acyltransferase. We have recently shown that it is a member of a newly described group of proteins that contain five similar blocks of sequence arranged in the same order in their primary structures (C. Upton and J. T. Buckley, Trends Biochem. Sci. 233:178-179, 1995). Assuming that, like other lipases, these enzymes have a Ser-Asp-His catalytic triad, we used these blocks to predict which aspartic acid and histidine would be at the active site of the Aeromonas enzyme. Targeted residues were replaced with other amino acids by site-directed mutagenesis, and the effects on secretion and activity were assessed. Changing His-291 to asparagine completely abolished enzyme activity, although secretion by the bacteria was not affected. Only very small amounts of the D116N mutant appeared in the culture supernatant, likely because it is sensitive to periplasmic proteases it encounters en route. Assays of crude preparations containing this variant showed no detectable enzyme activity. We conclude that, together with Ser-16, which we have identified previously, Asp-116 and His-291 compose the catalytic triad of the enzyme.

Acyltransferases↗
PubMed1997

Expression of the AsbA1, OXA-12, and AsbM1 beta-lactamases in Aeromonas jandaei AER 14 is coordinated by a two-component regulon.

Aeromonas jandaei AER 14 (formerly Aeromonas sobria AER 14) expresses three inducible beta-lactamases, AsbA1, OXA-12 (AsbB1), and AsbM1. Mutant strains that constitutively overexpress all three enzyme simultaneously, suggesting that they share a common regulatory pathway, have been isolated. Detectable expression of the cloned genes of AsbA1 and OXA-12 in some Escherichia coli K-12 laboratory strains is achieved only in the presence of a blp mutation. These mutations map to the cre operon at 0 min, which encodes a classical two-component regulatory system of unknown function. Two regulatory elements from A. jandaei which permit high-level constitutive expression of OXA-12 in E. coli were cloned. Both loci encode proteins with characteristics of response regulator proteins of two-component regulatory systems. One of these loci, designated blrA, bestowed constitutive expression of all three beta-lactamases in A. jandaei AER 14 when present on a multicopy plasmid, confirming its role in the regulatory pathway of beta-lactamase production in this organism.

Aeromonas↗
PubMed2002

Characterization of an ADP-ribosyltransferase toxin (AexT) from Aeromonas salmonicida subsp. salmonicida.

An ADP-ribosylating toxin named Aeromonas salmonicida exoenzyme T (AexT) in A. salmonicida subsp. salmonicida, the etiological agent of furunculosis in fish, was characterized. Gene aexT, encoding toxin AexT, was cloned and characterized by sequence analysis. AexT shows significant sequence similarity to the ExoS and ExoT exotoxins of Pseudomonas aeruginosa and to the YopE cytotoxin of different Yersinia species. The aexT gene was detected in all of the 12 A. salmonicida subsp. salmonicida strains tested but was absent from all other Aeromonas species. Recombinant AexT produced in Escherichia coli possesses enzymatic ADP-ribosyltransferase activity. Monospecific polyclonal antibodies directed against purified recombinant AexT detected the toxin produced by A. salmonicida subsp. salmonicida and cross-reacted with ExoS and ExoT of P. aeruginosa. AexT toxin could be detected in a wild type (wt) strain of A. salmonicida subsp. salmonicida freshly isolated from a fish with furunculosis; however, its expression required contact with RTG-2 rainbow trout gonad cells. Under these conditions, the AexT protein was found to be intracellular or tightly cell associated. No AexT was found when A. salmonicida subsp. salmonicida was incubated in cell culture medium in the absence of RTG-2 cells. Upon infection with wt A. salmonicida subsp. salmonicida, the fish gonad RTG-2 cells rapidly underwent significant morphological changes. These changes were demonstrated to constitute cell rounding, which accompanied induction of production of AexT and which led to cell lysis after extended incubation. An aexT mutant which was constructed from the wt strain with an insertionally inactivated aexT gene by allelic exchange had no toxic effect on RTG-2 cells and was devoid of AexT production. Hence AexT is directly involved in the toxicity of A. salmonicida subsp. salmonicida for RTG-2 fish cells.

ADP Ribose Transferases↗
PubMed2006

Polar flagellum biogenesis in Aeromonas hydrophila.

Mesophilic Aeromonas spp. constitutively express a single polar flagellum that helps the bacteria move to more favorable environments and is an important virulence and colonization factor. Certain strains can also produce multiple lateral flagella in semisolid media or over surfaces. We have previously reported 16 genes (flgN to flgL) that constitute region 1 of the Aeromonas hydrophila AH-3 polar flagellum biogenesis gene clusters. We identified 39 new polar flagellum genes distributed in four noncontiguous chromosome regions (regions 2 to 5). Region 2 contained six genes (flaA to maf-1), including a modification accessory factor gene (maf-1) that has not been previously reported and is thought to be involved in glycosylation of polar flagellum filament. Region 3 contained 29 genes (fliE to orf29), most of which are involved in flagellum basal body formation and chemotaxis. Region 4 contained a single gene involved in the motor stator formation (motX), and region 5 contained the three master regulatory genes for the A. hydrophila polar flagella (flrA to flrC). Mutations in the flaH, maf-1, fliM, flhA, fliA, and flrC genes, as well as the double mutant flaA flaB, all caused loss of polar flagella and reduction in adherence and biofilm formation. A defined mutation in the pomB stator gene did not affect polar flagellum motility, in contrast to the motX mutant, which was unable to swim even though it expressed a polar flagellum. Mutations in all of these genes did not affect lateral flagellum synthesis or swarming motility, showing that both A. hydrophila flagellum systems are entirely distinct.

Aeromonas hydrophila↗
PubMed1964

Proteolytic activity and general characteristics of a marine bacterium, Aeromonas proteolytica sp. N.

Merkel, Joseph R. (Fort Johnson Marine Biological Laboratory, College of Charleston, Charleston, S.C.), Eugene D. Traganza, Barid B. Mukherjee, Travis B. Griffin, and J. M. Prescott. Proteolytic activity and general characteristics of a marine bacterium, Aeromonas proteolytica sp. n. J. Bacteriol. 87:1227-1233. 1964.-A highly proteolytic bacterial species was isolated from the alimentary canal of the marine borer, Limnoria. The morphological and biochemical characteristics of the organism indicated that it was a new Aeromonas species, for which the name A. proteolytica is proposed. When freshly isolated, the organism required seawater for growth; but, upon prolonged culture in the laboratory, it was able to grow in media of greatly reduced salt concentration, provided that relatively large amounts of peptone were supplied. Peptone or hydrolysates of casein were capable of supplying all organic nutrients required for growth and proteinase production. Certain individual amino acids were also able to furnish all energy, carbon, and nitrogen requirements. Inorganic nitrogen was utilized in the presence of citrate, but could not serve as the only source of nitrogen in the presence of glucose. The organism was facultatively anaerobic, but best growth and proteinase production occurred only with vigorous aeration. The amount of growth obtained in 24 hr increased rapidly as the incubation temperature was increased up to a maximum of 40 C, but no growth occurred at 42 C.

Aeromonas↗
PubMed1966

Purification and characterization of the beta-galactosidase of Aeromonas formicans.

Rohlfing, S. R. (Western Reserve University, Cleveland, Ohio), and I. P. Crawford. Purification and characterization of the beta-galactosidase of Aeromonas formicans. J. Bacteriol. 91:1085-1097. 1966.-The beta-galactosidase of Aeromonas formicans was purified by diethylaminoethyl cellulose chromatography and gel filtration on Sephadex G-200. The properties of the enzyme molecule were compared with purified beta-galactosidase from Escherichia coli. The sedimentation coefficients and electrophoretic mobilities of the two enzymes were not significantly different; the electrophoretic mobility of urea-produced subunits of the two enzymes was also similar. The stabilities of the two enzymes to denaturing agents provided measurable differences; E. coli beta-galactosidase is relatively more heat-stable and more resistant to the action of urea. The amino acid compositions of the two proteins revealed significant differences in several amino acids, particularly alanine, arginine, glycine, and leucine. The comparisons cited suggest that A. formicans and E. coli are not completely unrelated, for their beta-galactosidases show considerable structural similarity.

Aeromonas↗
PubMed1967

Electron microscopy of the lysis of Staphylococcus aureus cell walls by Aeromonas lytic factor.

Isolated and purified cell walls of Staphylococcus aureus were treated with a purified fraction of the culture supernatant fluid of a species of Aeromonas. The course of lysis of the cell walls was followed over a period of time by examination of samples under an electron microscope. The undifferentiated cell wall was rapidly digested, but the equatorial rings were more resistant. The undifferentiated cell wall became a very thin sheet before completely dissolving, leaving a series of equatorial rings of various widths. As digestion proceeded, solubilization of the entire cell wall occurred. Analogous findings were obtained with purified S. aureus mucopeptide. It is concluded that the Aeromonas lytic principle is an enzyme, and that susceptible bonds are more concentrated in the undifferentiated cell wall mucopeptide.

Aeromonas↗
PubMed1979

Aeromonas primary wound infection of a diver in polluted waters.

Two separate species of Aeromonas, A. sobria (not listed as a species in Bergey's Manual of Determinative Bacteriology, 8th ed.) and A. hydrophila, were primary pathogens isolated from the leg wound of a diver conducting operations in polluted waters. This is the first recorded instance of a primary infection of soft tissue in a human caused by two species of Aeromonas, one of which was resistant to tetracycline. Because of the very rapid development of this wound infection, cytotoxicity of these organisms was examined in several biological systems. A. sobria was hemolytic for sheep erythrocytes, cytotoxic for Y-1 adrenal cells, and enterotoxic in rabbit ligated intestinal loops, whereas A. hydrophila was hemolytic and cytotoxic. Pertinent clinical, bacteriological, and environmental features of the case are presented.

Adult↗
PubMed1984

Hemagglutination patterns of Aeromonas spp. in relation to biotype and source.

Aeromonas spp. show patterns of hemagglutination with human group O cells in the presence of fucose, galactose, and mannose. These patterns are related to biotype as well as to the source of isolates. There was good correlation between hemagglutination pattern and the presence of diarrhea among strains isolated in Western Australia, which was the only source with adequate data for classification of children with an without diarrhea. Most of the environmental and other nonfecal isolates produced patterns different from those in strains associated with diarrhea. These results suggest that hemagglutinins should be considered with enterotoxins as virulence factors in Aeromonas spp.

Aeromonas↗
PubMed1985

Invasiveness of Aeromonas spp. in relation to biotype, virulence factors, and clinical features.

Of 69 fecal isolates of Aeromonas spp., 18 had the ability to invade HEp-2 cells. Invasiveness correlated with biotype; of the 18 invasive strains, 16 were A. sobria and 2 were A. hydrophila. No invasive strains were found among the A. caviae. Of the 18 invasive strains, 13 were enterotoxigenic. Of the enterotoxigenic and invasive strains, 12 were A. sobria, but enterotoxicity was also more common among noninvasive strains of A. sobria. Fucose-resistant hemagglutination was also more common in A. sobria, but invasive strains were equally divided between fucose-resistant hemagglutination and other patterns. Detailed clinical information was available for 27 of the 69 strains. All 15 strains of A. sobria or A. hydrophila associated with diarrhea were enterotoxigenic; 6 of the 10 strains of A. sobria were also invasive. Blood was present in the stool samples of five of the six patients with invasive A. sobria and in none of the patients with noninvasive strains. Although limited, these observations suggest that dysenteric symptoms may be produced by invasive Aeromonas spp.

Adult↗
PubMed1985

Growth of Aeromonas spp. on cefsulodin-Irgasan-novobiocin agar selective for Yersinia enterocolitica.

Twenty-eight strains of Aeromonas spp. were analyzed for their ability to grow on two different kinds of cefsulodin-Irgasan (triclosan; Ciba-Geigy AG, Basel, Switzerland)-novobiocin (CIN) agar containing 15 or 4 mg of cefsulodin per ml and on inositol-bile salts-brilliant green (IBB) agar. Relative to blood agar, 68% of the strains were inhibited by more than 2 logs (i.e., less than 1% growth) at 37 degrees C (39% at 25 degrees C) on CIN I (high cefsulodin concentration), 7% were inhibited at either temperature on CIN II (low cefsulodin concentration), 4% were inhibited on IBB agar at 37 degrees C, and none were inhibited on IBB agar at 25 degrees C. These results reflect the MICs of cefsulodin on CIN Base: the MIC for 50% of the strains was 8 mg/liter at 37 and 25 degrees C, and the MICs for 90% of the strains were 16 mg/liter at 37 degrees C and 64 mg/liter at 25 degrees C. The MICs of Irgasan and novobiocin were far beyond the concentrations used in CIN media. We argue that CIN agar containing 4 mg of cefsulodin per ml (CIN II) can be used for the simultaneous detection of Aeromonas spp. and Yersinia spp.

Aeromonas↗
PubMed1985

Cephalothin susceptibility as a potential marker for the Aeromonas sobria group.

Fifty-four motile Aeromonas strains, composing the three currently recognizable species, were tested for susceptibility to cephalothin by broth dilution and disk agar diffusion assays. Cephalothin susceptibility was significantly associated with Aeromonas sobria (P less than 0.001) and may be an additional phenotypic marker useful in the identification of this species.

Aeromonas↗
PubMed1986

Evidence for production of an enterotoxin and cholera toxin cross-reactive factor by Aeromonas hydrophila.

The enterotoxins produced by Aeromonas hydrophila were examined for biological activity by the rabbit ileal loop and suckling mouse assays, as well as by elongation of CHO cells. Antigenic evaluation of the culture filtrates from various isolates of A. hydrophila was performed by enzyme-linked immunosorbent assay with anti-cholera toxin and anti-Aeromonas enterotoxin. Heat stability data demonstrated the presence of a heat-labile cholera toxin cross-reactive factor and a heat stable non-cholera toxin cross-reactive enterotoxin. The biological activities of both enterotoxins were heat labile at 56 degrees C for 20 min.

Aeromonas↗
PubMed1990

Detection of the aerolysin gene in Aeromonas hydrophila by the polymerase chain reaction.

Synthetic oligonucleotide primers were used in a polymerase chain reaction (PCR) technique to detect the gene for aerolysin in strains of Aeromonas hydrophila and to screen for identical genes in A. caviae, A. sobria, and A. veronii isolated from patients with diarrheal disease. Primers targeted a 209-bp fragment of the aer gene coding for the beta-hemolysin and detected template DNA only in the PCR using nucleic acid (NA) from hemolytic strains of A. hydrophila which were also cytotoxic to Vero and CHO cells and enterotoxic in suckling-mouse assays. PCR amplification of NA from hemolytic A. sobria or nonhemolytic A. hydrophila and A. caviae strains was consistently negative. Primer specificity was determined in the PCR by using NA extracted from 56 strains of bacteria, including hemolytic Escherichia coli and Listeria monocytogenes as well as several recognized enteric pathogens defined in terms of their toxigenicity. The detection limit for the aerolysin gene by PCR amplification was 1 ng of total NA. The PCR clearly identified aerolysin-producing strains of A. hydrophila and may have application as a species-specific virulence test because other hemolytic Aeromonas species tested were negative.

Aeromonas↗
PubMed1990

Extended serogrouping scheme for motile, mesophilic Aeromonas species.

A total of 1,255 strains of motile, mesophilic Aeromonas species isolated from clinical and environmental specimens in the United Kingdom and 258 strains isolated in Australia, Brazil, Peru, and the United States were examined by using antisera for serogroups O1 to O44 (R. Sakazaki and T. Shimada, Jpn. J. Med. Sci. 37:247-255, 1984) and for unpublished serogroup O45 (R. Sakazaki). The typeability rate for strains isolated in the United Kingdom was 35%; the strains isolated in other countries had typeability rates of between 14 and 43%. A total of 52 provisional new serogroups were identified, and the strains with unidentified O groups were examined by using antisera for these provisional new serogroups. The typeability rate for strains isolated in the United Kingdom was increased to 66% (70% of smooth strains). The typeability rates were 76% for A. hydrophila and 63% for both A. caviae and A. sobria. The 52 antisera for the provisional new serogroups increased the typeability rate for strains isolated outside the United Kingdom to between 43 and 68%. This extended serogrouping scheme would be of value in determining the importance of Aeromonas strains as human intestinal pathogens and in investigating the pathogenic mechanisms that may be involved in the production of diarrheal disease.

Aeromonas↗
PubMed1991

Aerokey II: a flexible key for identifying clinical Aeromonas species.

A small subset (n = 18) of highly discriminatory tests was derived from the feature frequency of 50 tests used in the study of 167 predominantly clinical Aeromonas strains. Seven of these eighteen tests were used to construct a flexible, dichotomous key, Aerokey II, for identifying clinical aerontonads: esculin hydrolysis, gas from glucose, acid from arabinose, indole production, acid from sucrose, Voges-Proskauer reaction, and resistance to cephalothin (30 micrograms). This schema was initially evaluated in a single-blind trial of 60 well-characterized clinical Aeromonas hydrophila (n = 21), A. caviae (n = 19), and A. veronii bv. sobria (n = 20) strains from an independent laboratory. Of the 60 strains tested, 58 (97%) were accurately identified to the species level. Aerokey II was further evaluated with 18 additional American Type Culture Collection and reference strains representing the more recently proposed taxa A. veronii bv. veronii, A. schubertii, A. jandaei, and A. trota and accurately identified all of these strains.

Aeromonas↗