Cyanotrophic and arsenic oxidizing activities of Pseudomonas mendocina P6115 isolated from mine tailings containing high cyanide concentration.

Mine tailings and wastewater generate man-made environments with several selective pressures, including the presence of heavy metals, arsenic and high cyanide concentrations, but severe nutritional limitations. Some oligotrophic and pioneer bacteria can colonise and grow in mine wastes containing a low concentration of organic matter and combined nitrogen sources. In this study, Pseudomonas mendocina P6115 was isolated from mine tailings in Durango, Mexico, and identified through a phylogenetic approach of 16S rRNA, gyrB, rpoB, and rpoD genes. Cell growth, cyanide consumption, and ammonia production kinetics in a medium with cyanide as sole nitrogen source showed that at the beginning, the strain grew assimilating cyanide, when cyanide was removed, ammonium was produced and accumulated in the culture medium. However, no clear stoichiometric relationship between both nitrogen sources was observed. Also, cyanide complexes were assimilated as nitrogen sources. Other phenotypic tasks that contribute to the strain's adaptation to a mine tailing environment included siderophores production in media with moderate amounts of heavy metals, arsenite and arsenate tolerance, and the capacity of oxidizing arsenite. P. mendocina P6115 harbours cioA/cioB and aoxB genes encoding for a cyanide-insensitive oxidase and an arsenite oxidase, respectively. This is the first report where P. mendocina is described as a cyanotrophic and arsenic oxidizing species. Genotypic and phenotypic tasks of P. mendocina P6115 autochthonous from mine wastes are potentially relevant for biological treatment of residues contaminated with cyanide and arsenic.

Efficient production of polyhydroxyalkanoates (PHAs) from Pseudomonas mendocina PSU using a biodiesel liquid waste (BLW) as the sole carbon source.

Conditions for the optimal production of polyhydroxyalkanoate (PHA) by Pseudomonas mendocina PSU using a biodiesel liquid waste (BLW) were determined by response surface methodology. These were an initial carbon to nitrogen ratio (C/N) of 40 (mole/mole), an initial pH of 7.0, and a temperature of 35 °C. A biomass and PHA concentration of 3.65 g/L and about 2.6 g/L (77% DCW), respectively, were achieved in a growth associated process using 20 g/L glycerol in the BLW after 36 h of exponential growth. The PHA monomer compositions were 3HB (3-hydroxybutyrate), a short-chain-length-PHA, and the medium-chain-length-PHA e.g. 3-hydroxyoctanoate and 3-hydroxydecanoate. Both the phbC and phaC genes were characterized. The phbC enzyme had not been previously detected in a Pseudomonas mendocina species. A 2.15 g/L of an exopolysaccharide, alginate, was also produced with a similar composition to that of other Pseudomonas species.

Genome sequence of Pseudomonas mendocina DLHK, isolated from a biotrickling reactor.

Pseudomonas mendocina DLHK is an aerobic bacterium isolated from a biotrickling reactor which can remove nitric oxide, a common air pollutant from combustion exhaust gas. Here, we present the draft genome of Pseudomonas mendocina DLHK.

Heavy-metal resistance of a France vineyard soil bacterium, Pseudomonas mendocina strain S5.2, revealed by whole-genome sequencing.

Here we present the draft genome of Pseudomonas mendocina strain S5.2, possessing tolerance to a high concentration of copper. In addition to being copper resistant, the genome of P. mendocina strain S5.2 contains a number of heavy-metal-resistant genes known to confer resistance to multiple heavy-metal ions.

[Screening, denitrification characteristics, and anaerobic ammonium oxidation ability of denitrifying bacterium aHD7].

A highly efficient denitrifying bacterium aHD7 was screened from activated sludge. After static culture at 30 degrees C for 3 days, the denitrification rate of the aHD7 reached 91.7%, and during denitrification, nitrite had lower accumulation, with its concentration basically maintained at 1.8 mg x L(-1). The microscopy observation demonstrated that the aHD7 was a gram-negative bacillus, with an average size of 0.5 microm x (1.5-2.5) microm. Based on its biochemical/morphological characteristics and homologic analysis of 16S rDNA sequence, the aHD7 was identified as Pseudomonas mendocina. The investigation on the factors affecting the denitrification capacity of aHD7 showed that at the initial concentration of nitrate nitrogen being less than 276.95 mg x L(-1), the denitrification rate was almost 100%, and when the initial concentration of nitrate nitrogen was as high as 553.59 mg x L(-1), the denitrification rate could reach 66.8%, with little nitrite accumulated. Ethanol was the most suitable carbon source. C/N ratio 6-8 and pH value 6-9 benefited the denitrification. The aHD7 had a good ability of anaerobic ammonium oxidation, and its average ammonium utilization rate reached 4.56 mg x L(-1) x d(-1).

[Isolation, identification and soil remediation of fomesafen-degrading strain FB8].

OBJECTIVE: In order to find new strains to degrade fomesafen in contaminated soil, we isolated and identified a high-efficiency degrading bacterium from polluted soil. The degrading characteristics and remediation ability of the strain were also studied. METHODS: Characteristics of morphological, physiological, biochemical and 16S rRNA sequence were applied to identify the strain. The optimum growth conditions were obtained by studying the effect of environmental factors such as fomesafen concentration, primary pH and temperature on the strain. The strain's remediation ability to fomesafen-polluted soil was verified by sensitive crop and target weeds bioassay in pot soil. RESULTS: A high-efficiency degrading strain FB8 that used fomesafen as sole carbon source was isolated from soybean field suffering fomesafen in Heilongjiang province. It was initially identified as a member of the genus Pseudomonas. The strain could degrade 86.75% of 500 mg/L fomesafen within 96 h. Its optimal growth conditions were determined as follows: 500 mg/L fomesafen, primary pH between 6.0 and 8.0, and at 35 to 37 degrees C. The strain could remedy the sensitive crop maize and sorghum biomass after treating for 30 d for soil contaminated with 5 mg/kg of fomesafen. CONCLUSION: A fomesafen-degrading strain FB8 was selected from fomesafen-contaminated soil in Heilongjiang Province. The strain was closely related to Pseudomonas mendocina. The strain was a suitable candidate for bioremediation of fomesafen-contaminated soil.

Comparative genetic diversity of Pseudomonas stutzeri genomovars, clonal structure, and phylogeny of the species.

A combined phylogenetic and multilocus DNA sequence analysis of 26 Pseudomonas stutzeri strains distributed within the 9 genomovars of the species has been performed. Type strains of the two most closely related species (P. balearica, former genomovar 6, and P. mendocina), together with P. aeruginosa, as the type species of the genus, have been included in the study. The extremely high genetic diversity and the clonal structure of the species were confirmed by the sequence analysis. Clustering of strains in the consensus phylogeny inferred from the analysis of seven nucleotide sequences (16S ribosomal DNA, internally transcribed spacer region 1, gyrB, rpoD, nosZ, catA, and nahH) confirmed the monophyletic origin of the genomovars within the Pseudomonas branch and is in good agreement with earlier DNA-DNA similarity analysis, indicating that the selected genes are representative of the whole genome in members of the species.