Pseudomonas composti sp. nov., isolated from compost samples.

Two unusual, Gram-negative, catalase- and oxidase-positive rods, designated C2(T) and C5, were isolated from compost samples. Comparative 16S rRNA gene sequencing studies demonstrated that both isolates were members of the genus Pseudomonas and belonged to the Pseudomonas aeruginosa group. Strain C2(T) was most closely related to Pseudomonas cuatrocienegasensis 1N(T) and Pseudomonas borbori R-20821(T) (97.9 and 97.8% 16S rRNA gene sequence similarity, respectively). However, phylogenetic analysis based on rpoD gene sequences revealed that both isolates could be discriminated from members of the P. aeruginosa group that exhibited >97% 16S rRNA gene sequence similarity. The DNA G+C content of strain C2(T) was 61.5 mol%. The major fatty acids of strain C2(T) were a summed feature (C(16:1)ω7c and/or iso-C(15:0) 2-OH), C(18:1)ω7c/12t/9t, C(16:0) and C(12:0), which supported the isolates' affiliation with the genus Pseudomonas. Moreover, strain C2(T) could be distinguished from its closest phylogenetic neighbours of the genus Pseudomonas by DNA-DNA hybridization studies and biochemical tests. On the basis of both phenotypic and phylogenetic findings, it is proposed that the isolates be classified as a novel species, with the name Pseudomonas composti sp. nov. The type strain is C2(T) (=CECT 7516(T)=CCUG 59231(T)).

Application of fluorescence in situ hybridization technique to detect simazine-degrading bacteria in soil samples.

We propose a new approach to evaluate the natural attenuation capacity of soil by using fluorescence in situ hybridization (FISH). A specific oligonucleotide probe AtzB1 was designed based on the sequence data of the atzB gene involved in the hydrolytic deamination of s-triazines; this gene, located in a multiple copy plasmid was detected by the optimized FISH protocol. Two agricultural soils (Lodi and Henares) with a history of simazine treatments, and two natural soils (Soto and Monza), without previous exposure to simazine, were studied. AtzB1 probe-target cells were found only in the agricultural soils and, in a greater percentage, in the Lodi soil, compared to the Henares one. Moreover, the greatest percentage of AtzB1 probe-target cells in Lodi was accompanied by a greater mineralization rate, compared to the Henares soil. The FISH method used in this study was suitable for the detection of simazine-degrading bacteria and could be a useful indicator of the potential of soil bioremediation.

Biodegradation of oxadiazon by a soil isolated Pseudomonas fluorescens strain CG5: Implementation in an herbicide removal reactor and modelling.

An oxadiazon-degrading bacterial, Pseudomonas strain CG5, was isolated from an agricultural contaminated soil. This strain CG5 was able to grow on 10mg of oxadiazon per l, yielding 5.18+/-0.2 mg of protein biomass mol(-1). GC-MS analyses of the metabolites from oxadiazon catabolism revealed its dehalogenation and degradation to form non-toxic end-products, cells were then immobilized by adsorption on a ceramic support to be used as biocatalysts in herbicide removal biofilm-reactor processes. Seventy-two per cent of the oxadiazon was removed, and the maximum specific substrate uptake rate was 10.63+/-0.5 microg h(-1) mg(-1) prot. A new mathematical model was developed to interpret and predict the behaviour of the bacteria and pollutants in a biofilm-reactor system, to consider biofilm structural and morphological properties.

Klebsiella planticola strain DSZ mineralizes simazine: physiological adaptations involved in the process.

We examined the ability of a soil bacterium, Klebsiella planticola strain DSZ, to degrade the herbicide simazine (SZ). Strain DSZ is metabolically diverse and grows on a wide range of s-triazine and aromatic compounds. DSZ cells grown in liquid medium with SZ (in 10 mM ethanol) as carbon source mineralized 71.6+/-1.3% of 0.025 mM SZ with a yield of 4.6+/-0.3 microg cell dry weight mmol(-1) carbon. The metabolites produced by DSZ during SZ degradation included ammeline, cyanuric acid, N-formylurea and urea. We studied the physiological adaptations which allow strain DSZ to metabolize SZ. Using scanning electron microscopy, we detected DSZ cells covering the surfaces of SZ crystals when the herbicide was used at high concentrations (0.1 mM). The membrane order observed by FTIR spectroscopy showed membrane activity at low temperature (4 degrees C) to assimilate the herbicide. Membrane fatty acid analysis demonstrated that strain DSZ adapted to grow on SZ by increasing the degree of saturation of membrane lipid fatty acid; and the opposite effect was detected when both SZ and ethanol were used as carbon sources. This confirms the modulator effect of ethanol on membrane fluidity.