Structure of surface polysaccharides from Aeromonas sp. AMG272, a plant-growth promoting rhizobacterium isolated from rice rhizosphere.

Aeromonas sp. AMG272 is a Gram-negative bacterium that has been isolated from agricultural soil and studied for its plant growth-promoting activities. Structures of the O-specific polysaccharide chain of the AMG272 lipopolysaccharide and its capsular polysaccharide were elucidated using GLC-MS and NMR spectroscopy. The structure of the O-specific polysaccharide, →4)-α-l-Rhap-(1 → 3)-ß-d-GlcpNAc-(1→, has been found in other Aeromonas strains and related bacteria, whereas the structure of the capsular polysaccharide has not been reported before: →6)[ß-d-Fucp3NAc4Ac-(1 → 3)]-α-d-GlcpNAc-(1 → 4)-α-d-Galp-(1 → 3)-α-d-GalpNAc-(1 → 4)-α-d-Galp-(1 → .

Adsorptive removal of silver nanoparticles (SNPs) from aqueous solution by Aeromonas punctata and its adsorption isotherm and kinetics.

Silver nanoparticles (SNPs) are being increasingly used in many consumer products and industrial application. The release of SNPs to the environment is a major concern. Here we have studied the adsorptive removal of SNPs by a SNP resistant bacterial species Aeromonas punctata, isolated from the sewage environment. The influence of zeta potential on adsorption was investigated at acidic, neutral and alkaline pH and with varying salt (NaCl) concentrations. The rate of adsorption and removal of SNPs was decreases with increase in pH and salt concentration. The zeta potential study suggests that, the adsorption of SNPs on the cell surface was related to electrostatic force of attraction. The equilibrium adsorption isotherm and kinetics of adsorption were also studied. The adsorption equilibrium isotherms fitted well to the Langmuir model. The kinetics of adsorption fitted best to pseudo-first-order. A. punctata was able to remove 4.42 and 3.85 mg/L of SNPs at pH 5 and 7 respectively. The present study can be used for the effective removal of SNPs which is released into the environment and sewage treatment systems.

Characterization of Aeromonas caviae and A. veronii by standardized cellular protein electrophoretic patterns.

Aeromonas caviae and A. veronii recovered from clinical and environmental samples were characterized by SDS-PAGE of whole cell proteins. All strains were typable and showed unique banding patterns. A high intra-specific diversity within these two microorganisms was revealed. Separation of the Polish strains from the Hong-Kong isolates was observed. A. caviae and A. veronii were not distinguishable with respect to their ecological origin. However, strains with very similar protein patterns could dominate in a specific habitat.

The development of a matrix-assisted laser desorption/ionization mass spectrometry-based method for the protein fingerprinting and identification of Aeromonas species using whole cells.

This report describes the development of a method to detect the waterborne pathogen Aeromonas using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The genus Aeromonas is one of several medically significant genera that have gained prominence due to their evolving taxonomy and controversial role in human diseases. In this study, MALDI-MS was applied to the characterization of seventeen species of Aeromonas. These seventeen species were represented by thirty-two strains, which included type, reference and clinical isolates. Intact cells from each strain were used to generate a reproducible library of protein mass spectral fingerprints or m/z signatures. Under the test conditions used, peak lists of the mass ions observed in each species revealed that three mass ions were conserved among all the seventeen species tested. These common mass ions having an average m/z of 6301, 12,160 or 12,254, and 13,450, can be potentially used as genus-specific biomarkers to identify Aeromonas in unknown samples. A dendrogram generated using the m/z signatures of all the strains tested indicated that the mass spectral data contained sufficient information to distinguish between genera, species, and strains. There are several advantages of using MALDI-MS based protein mass spectral fingerprinting of whole cells for the identification of microorganisms as well as for their differentiation at the sub-species level: (1) the capability to detect proteins, (2) high throughput, and (3) relatively simple sample preparation techniques. The accuracy and speed with which data can be obtained makes MALDI-MS a powerful tool especially suited for environmental monitoring and detection of biological hazards.

Intestinal cell adhesion and maximum growth temperature of psychrotrophic aeromonads from surface water.

Investigation of 650 Aeromonas strains taken from surface water--used as a source of drinking water--and from the associated drinking water treatment plants has demonstrated that only a small proportion of the strains are endowed with intestinal cell adhesion and growth at 39 degrees C; these characteristics are concurrently encountered in Aeromonas strains from clinical material. The investigations permit the conclusion that even the Aeromonas species, of which certain strains are pathogenic to human, cannot generally be viewed as being potentially pathogenic.

Flagellate predation on a bacterial model community: interplay of size-selective grazing, specific bacterial cell size, and bacterial community composition.

The influence of grazing by the bacterivorous nanoflagellate Ochromonas sp. strain DS on the taxonomic and morphological structures of a complex bacterial community was studied in one-stage chemostat experiments. A bacterial community, consisting of at least 30 different strains, was fed with a complex carbon source under conditions of low growth rate (0.5 day(-1) when nongrazed) and low substrate concentration (9 mg liter(-1)). Before and after the introduction of the predator, the bacterial community composition was studied by in situ techniques (immunofluorescence microscopy and fluorescent in situ hybridization), as well as by cultivation on agar media. The cell sizes of nonspecifically stained and immunofluorescently labeled bacteria were measured by image analysis. Grazing by the flagellate caused a bidirectional change in the morphological structure of the community. Medium-size bacterial cells, which dominated the nongrazed community, were largely replaced by smaller cells, as well as by cells contained in large multicellular flocs. Cell morphological changes were combined with community taxonomic changes. After introduction of the flagellate, the dominating strains with medium-size cells were largely replaced by single-celled strains with smaller cells on the one hand and, on the other hand, by Pseudomonas sp. strain MWH1, which formed the large, floc-like forms. We assume that size-selective grazing was the major force controlling both the morphological and the taxonomic structures of the model community.

Immunological analysis of extracellular products and cell surface components of motile Aeromonas isolated from fish.

The present work describes the characterization of antigens present in the extracellular products (ECP) and cell wall of strains of motile Aeromonas isolated from rainbow trout culture systems. The relationships among virulence for fish, O-serogroup and profile of LPS were also examined. The slide agglutination test showed that most of the virulent strains of motile Aeromonas (72%) were included in the serotypes O3, O6, O11 and O19 (Guinée and Jansen System). However, there were also non-pathogenic strains within these groups. Electrophoretic analysis of lipopolysaccharides (LPS) and proteins from cell envelope and ECP showed heterogeneity not only among the different serogroups but also within the same serotype. Immunoblot assays of cell envelope components, and of LPS present in the ECP demonstrated a close relationship among Aeromonas strains from the same serotype, while strains from different serotypes were not immunologically related. Moreover, this assay showed that motile Aeromonas belonging to distinct serotypes produced extracellular proteins immunologically related. On the other hand, antigenic cross reactivity was observed between the LPS obtained from cell envelope and those obtained from the ECP. The present results point out the need to include strains representative of each of the serotypes which predominates in a particular area and their ECPs in the formation of vaccines against motile Aeromonas septicaemia.

[Studies on motile-Aeromonas infection: 2). Development of a bacteriophage typing system for motile Aeromonas].

We succeeded in isolating Aeromonas-susceptible phages from river water and mud after a few years (1983-1985) of painstaking effort. For the first time in Japan, we investigated phagetypes of the bacterial strains isolated. The results obtained are summarized as follows: 1) Aeromonas-susceptible phages were isolated from 82 (40.1%) of 195 samples of river water and from 23 (25.6%) of 90 samples of river mud. By the cross-matching test of the phages isolated from the 105 samples, these were classified into 13 type groups (Groups I-XIII). 2) When 594 Aeromonas strains isolated from river water, lake water, river mud and fresh-water fish were examined using the phage group patterns developed by us, 129 (21.7%) strains classified into these phagetypes. Phagetyping was possible for 11 (15.5%) of the 71 strains isolated from river and lake water, for 29 (35.4%) of the 82 strains from river mud and for 89 (20.2%) of the 441 strains from fresh-water fish. By bacterial species, phagetyping was possible for 53 (51.5%) of the 103 strains of A. hydrophila. 21 (7.2%) of the 292 strains of A. sobria, 13 (8.8%) of the 148 strains of A. caviae and 42 (82.4%) of the 51 strains of Aeromonas spp.. Especially the phages classified as Groups I, IV and VI amounted to the majority. Thus we succeeded in isolating Aeromonas-susceptible phages which could be classified into Groups I-XIII. The results suggested the possibility of utilizing this phagetyping for analysis of the ecological distribution of genus Aeromonas.

Phenotypic characteristics of Aeromonas species isolated from adult humans.

The phenotypic characteristics of 89 Aeromonas strains, most of which had been isolated from feces, were examined. Eighty-two percent of the isolates could be placed into one of four groups on the basis of five tests. The relationship of these groups to the three motile species of Aeromonas (Aeromonas caviae, A. hydrophila, and A. sobria) that have been isolated from humans is unclear. Because the means for identification of Aeromonas strains to the species level appear to be imprecise and because the role of each of these species in human diarrhea is unclear at this time, we recommend that identification of enteric Aeromonas isolates to the species level not be done routinely.

Unusual fermentative, gram-negative bacilli isolated from clinical specimens. II. Characterization of Aeromonas species.

Morphological and physiological characterization of 12 Aeromonas strains isolated from clinical specimens demonstrated several important diagnostic features. These included polar arrangement of the flagella; production of oxidase, deoxyribonuclease, amylase, gelatinase, and lipase; lack of ornithine decarboxylase; and sensitivity to polymyxin. Awareness of these features should result in more frequent differentiation of aeromonads from the physiologically similar members of the genus Plesiomonas and the late- or non-lactose-fermenting species of Enterobacteriaceae.

Morphological and biochemical characteristics of Aeromonas punctata (hydrophila, liquefaciens) isolated from human sources.

The isolation of Aeromonas punctata (hydrophila, liquefaciens) from feces, throat, and sputum cultures is presented as further evidence that aeromonads are found in man. Morphological and biochemical studies of these strains indicate that the chief differences between the aeromonads and physiologically similar members of the Enterobacteriaceae are found in the polar arrangement of the flagella and in the production of oxidase by the former. The oxidase test should be performed on all paracolon-like bacteria, and a flagella stain should be employed when an oxidase-positive, gram-negative bacillus is isolated. Application of these tests will undoubtedly result in more frequent identification of Aeromonas species from human sources.