Maltophilia Strain Research Articles

Isolation and characterization of an extracellular proteinase produced by a soil strain ofXanthomonas maltophilia

An extracellular proteinase from aXanthomonas maltophilia strain isolated from soil was purified by ammonium sulfate precipitation, gel exclusion, and ion exchange gel chromatography. The enzyme appeared homogeneous upon polyacrylamide-gel electrophoresis. Its molecular weight was estimated to be 36,000 by the gel filtration assay and 40,000 by polyacrylamidegel electrophoresis after denaturation: it was a monomeric protein. Highly active at alkaline pH with casein as the substrate, it was inactivated by serine-site inhibitors, such as phenylmethylsulfonyl fluoride and diisopropylfluorophosphate. Like serine proteases, it hydrolyzed esters such as the β-naphthyl acetate. Moreover, like metalloproteases, the enzyme was rapidly inactivated by ethylene diamine tetraacetate, and the activity was partially restored by calcium. These original characteristics have not often been reported among other gram-negative bacteria.

Effect of ampicillin-induced alterations in murine intestinal microbiota on the survival and competition of environmentally released pseudomonads

The environmental release of genetically altered microorganisms has prompted the investigation of their potential health effects by the employment of other-than-human models. Although direct health effects are addressed, this investigation examines primarily some potential indirect health effects associated with environmentally released microorganisms. Indirect effects examined include colonization of the gastrointestinal tract, competition with the resident microbiota, and translocation of the dosed microorganisms to other organs. Pseudomonads used in this study were isolated from a commercial product marketed for environmental PCB degradation. When mice were dosed by gavage with approximately 10 9 ampicillin-resistant pseudomonads, an increase in recovery from the intestinal tract, as compared to untreated animals, was observed 48 hr after dosing. Intestinal survival of Pseudomonas aeruginosa strain BC 16 was enhanced 1000-fold and that of P. maltophila strain BC6, 10-fold. Strains BC17 and BC18 were unaffected. Ampicillin treatment had a significant effect on the relative number of microbiota in the intestine, by selecting primarily for the facultative species. The lactose-fermenting enterobacteria, obligately anaerobic predominantly Gram-negative rods, and total aerobic and anaerobic populations were monitored in the presence and absence of the PCB-degrading pseudomonad. P. aeruginosa strain BC17 and P. maltophilia strain BC6 had a dose effect ( p < 0.05) on the total aerobic and anaerobic populations as well as the lactose-fermenting enterobacteria. These results are similar to those for the mouse isolate control, strain PAMG. P. aeruginosa strain BC18 had a dose effect ( p < 0.05) on the total anaerobic population, including the obligately anaerobic Gram-negative bacilli. No translocation of the dosed strains to the liver, spleen, or lung was observed 48 hr after dosing.

Polychlorinated biphenyl-degrading pseudomonads: Survival in mouse intestines and competition with normal flora

Although naturally occurring and mutant organisms, historically, have been released into the environment for various purposes, health concerns associated with the release of microorganisms have recently resurfaced. Federal agencies have been given the task of reassuring society that any released organisms are not likely to produce adverse health effects. Methods, therefore, for evaluating the potential health effects due to environmental release of mutant and genetically engineered microorganisms are under investigation. A mouse model was developed that examines morbidity, mortality, and more indirect effects such as colonization potential of the intestinal tract, as well as competition with and alteration of the intestinal microbiota populations. The Pseudomonas spp. used in this study were isolated from a commercial product and used for degrading polychlorinated biphenyls. Mice were dosed individually with 10(3), 10(6), and 10(9) colony-forming units of each microorganism. At specific time intervals the intestines were removed and examined for the presence of the dosed microorganism. At the two higher doses, 10(6) and 10(9) colony-forming units, P. maltophilia strain BC6 and two P. aeruginosa strains, BC16 and BC18, were recoverable 48 h after dosing. The naturally occurring P. aeruginosa strain, PAMG, isolated from a mouse intestinal homogenate produced a similar response. Statistical analysis indicated that in some of the dosed animals, an alteration in the distribution of normal intestinal microflora occurred. Pseudomonas maltophilia strain BC6 and P. aeruginosa strains BC16 and BC17 caused a change in the obligately anaerobic predominantly gram-negative rod counts, and P. aeruginosa strain BC17 produced a dose effect on the total anaerobic count at the 10% confidence level. The total aerobic count was unaffected by the presence of the dosed pseudomonads.

Analysis of the lipopolysaccharide of Pseudomonas maltophilia 555.

The phenol phase soluble lipopolysaccharide of Pseudomonas maltophilia strain 555, obtained from cells by the hot aqueous phenol method, was of the smooth type. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, hydrolysis, methylation, and 13C and 1H nuclear magnetic resonance analyses showed that this lipopolysaccharide has an O-chain polysaccharide composed of a repeating pentasaccharide unit, containing D-rhamnose (D-Rha, one part), 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc, one part), and 4-acetamido-4,6-dideoxy-D-mannose (D-Rha4NAc, three parts) and having the structure (formula; see text) The serological cross-reactions between P. maltophilia 555 and Brucella species can now be related to the occurrence of N-acyl derivatives of 4-amino-4,6-dideoxy-D-mannopyranosyl residues in the O-chains of their respective lipopolysaccharide components.

Occurrence of selenium in poisonous plants

A bacterial strain (SeITE02), related to the species Stenotrophomonas maltophilia and resistant to selenite (SeIV) up to 50 mM in the growth medium, was isolated from rhizospheric soil of a selenium hyperaccumulator plant, the legume Astragalus bisulcatus. The influence of SeIV on the active growth of this Se-tolerant bacterial strain has been investigated in oxic conditions, along with the isolate's ability to reduce selenite to elemental selenium (Se0). Interestingly, concentrations of 0.5 mM SeIV were wholly reduced by strain SeITE02 in liquid culture within 52 h. Moreover, 87% of SeIV added to the growth medium at the initial concentration of 2.0 mM underwent again reduction in 120 h. Actually, a selenite-mediated induction of a sort of adaptive response to detrimental SeIV effects magnified the efficiency of SeITE02 in reducing this toxic oxyanion. Furthermore, the SeIV influence on cell morphology of strain SeITE02 was evidenced by phase-contrast and electron microscopy analyses. In particular, transmission electron microscopy (TEM)–energy-dispersive X-ray (EDX) analysis of S. maltophilia strain SeITE02, grown in presence of SeIV, showed electron-dense Se0 granules either in the cell cytoplasm or in the extracellular space. Therefore, the capability of strain SeITE02 to quickly reduce soluble and harmful SeIV to insoluble and unavailable Se0 may be looked at as a promising exploitable option for the setup of low-cost biological treatments tailored to manage contamination in selenium-laden effluents.