Pseudoxanthomonas Mexicana Research Articles

Molecular Characterization of an Oil-Degrading Cyanobacterial Consortium

Recent studies have shown that the cyanobacterium Microcoleus chthonoplastes forms a consortium with heterotrophic bacteria present within the cyanobacterial sheath. These studies also show that this consortium is able to grow in the presence of crude oil, degrading aliphatic heterocyclic organo-sulfur compounds as well as alkylated monocyclic and polycyclic aromatic hydrocarbons. In this work, we characterize this oil-degrading consortium through the analysis of the 16S rRNA gene sequences. We performed the study in cultures of Microcoleus grown in mineral medium and in cultures of the cyanobacterium grown in mineral medium supplemented with crude oil. The results indicate that most of the clones found in the polluted culture correspond to well-known oil-degrading and nitrogen-fixing microorganisms, and belong to different phylogenetic groups, such as the Alpha, Beta, and Gamma subclasses of Proteobacteria, and the Cytophaga/Flavobacteria/Bacteroides group. The control is dominated by one predominant organism (88% of the clones) closely affiliated to Pseudoxanthomonas mexicana (similarity of 99.8%). The presence of organisms closely related to well-known nitrogen fixers such as Rhizobium and Agrobacterium suggests that at least some of the cyanobacteria-associated heterotrophic bacteria are responsible for nitrogen fixation and degradation of hydrocarbon compounds inside the polysaccharidic sheath, whereas Microcoleus provides a habitat and a source of oxygen and organic matter.

Degradation of simazine by microorganisms isolated from soils of Spanish olive fields

The capability of the microbial flora isolated from an olive field soil from Andalusia to mineralize simazine has been analyzed. From this soil, a group of bacteria capable of degrading 60 mg simazine litre(-1) in less than a week has been isolated. These microorganisms showed a low capacity for degrading this herbicide to carbon dioxide. When total DNA was isolated from this group of bacteria, we were able to detect by PCR the presence of only the atzC and the trzN genes. Some components of this bacterial population have been identified by sequencing of specific fragments from bacterial 16S rDNA, including Variovorax sp, Pseudoxanthomonas mexicana Thierry et al, Acidovorax sp and Methylopila capsulata Doronina et al. These data suggest that this consortium of bacteria performs an incomplete degradation of the simazine

Pseudoxanthomonas koreensis sp. nov. and Pseudoxanthomonas daejeonensis sp. nov.

Gram-negative, non-spore-forming, rod-shaped bacteria, T7-09(T) and TR6-08(T), were isolated from soil from a ginseng field in South Korea and characterized to determine their taxonomic position. 16S rRNA gene sequence analysis showed that the two isolates shared 99.5 % sequence similarity. Strains T7-09(T) and TR6-08(T) were shown to belong to the Proteobacteria and showed the highest levels of sequence similarity to Pseudoxanthomonas broegbernensis DSM 12573(T) (98.1 %), Pseudoxanthomonas mexicana AMX 26B(T) (97.4-97.5 %), Pseudoxanthomonas japonensis 12-3(T) (96.5-96.6 %), Pseudoxanthomonas taiwanensis ATCC BAA-404(T) (95.7 %) and Xanthomonas campestris ATCC 33913(T) (96.3-96.5 %). The sequence similarity values with respect to any species with validly published names in related genera were less than 96.5 %. The detection of a quinone system with Q-8 as the predominant compound and a fatty acid profile with C(15 : 0) iso as the predominant acid supported the assignment of the novel isolates to the order 'Xanthomonadales'. The two isolates could be distinguished from the established species of the genus Pseudoxanthomonas by the presence of quantitative unsaturated fatty acid C(17 : 1) iso omega9c and by their unique biochemical profiles. The results of DNA-DNA hybridization clearly demonstrated that T7-09(T) and TR6-08(T) represent separate species. On the basis of these data, it is proposed that T7-09(T) (=KCTC 12208(T)=IAM 15116(T)) and TR6-08(T) (=KCTC 12207(T)=IAM 15115(T)) be classified as the type strains of two novel Pseudoxanthomonas species, for which the names Pseudoxanthomonas koreensis sp. nov. and Pseudoxanthomonas daejeonensis sp. nov., respectively, are proposed.

Pseudoxanthomonas mexicana sp. nov. and Pseudoxanthomonas japonensis sp. nov., isolated from diverse environments, and emended descriptions of the genus Pseudoxanthomonas Finkmann et al. 2000 and of its type species

Pseudoxanthomonas mexicana sp. nov. and Pseudoxanthomonas japonensis sp. nov., isolated from diverse environments, and emended descriptions of the genus Pseudoxanthomonas Finkmann et al. 2000 and of its type species

Pseudoxanthomonas mexicana sp. nov. and Pseudoxanthomonas japonensis sp. nov., isolated from diverse environments, and emended descriptions of the genus Pseudoxanthomonas Finkmann et al. 2000 and of its type species

Three mesophilic bacteria (strains AMX 26B(T), UR374_02 and 12-3(T)) isolated respectively from an anaerobic digester, human urine and urban riverside soil were characterized. Cells were Gram-negative, motile, non-sporulating, straight to curved rods with one polar flagellum and had a strictly respiratory metabolism with O(2) as the preferential terminal electron acceptor. Phylogenetic analysis based on 16S rRNA gene sequences revealed that all strains clustered within the Xanthomonadaceae branch of the Proteobacteria. Isolates AMX 26B(T) and UR374_02 exhibited 100 % 16S rRNA gene sequence similarity and both were related to strain 12-3(T) (99.6 % similarity). The closest relative of all the isolates was Pseudoxanthomonas broegbernensis DSM 12573(T) (similarity 97.1-97.5 %), and they were equidistantly related to Xanthomonas species (95.4-96.6 %), Stenotrophomonas species (95.3-96.1 %) and Pseudoxanthomonas taiwanensis ATCC BAA-4040(T) (95.3-95.4 %). Chemotaxonomic and biochemical data (branched-chain cellular fatty acid pattern without C(13 : 0) iso 3-OH, ubiquinone with eight isoprenoid units, limited range of substrates used, ability to reduce nitrite but not nitrate with the production of N(2)O) supported their affiliation to the genus Pseudoxanthomonas. The results of DNA-DNA hybridization and/or phenotypic analysis allowed them to be differentiated from the two Pseudoxanthomonas species with validly published names and showed that strain 12-3(T) was genomically and phenotypically distinct from the other two isolates. On the basis of these results, two novel species of the genus Pseudoxanthomonas are proposed: Pseudoxanthomonas mexicana sp. nov., consisting of strains AMX 26B(T) (=ATCC 700993(T)=CIP 106674(T)=JCM 11524(T)) (type strain) and UR374_02 (=DSM 15133), and Pseudoxanthomonas japonensis sp. nov., consisting of strain 12-3(T) (=CCUG 48231(T)=CIP 107388(T)=JCM 11525(T)). The report of these two novel species leads to the emendation of the description of the genus Pseudoxanthomonas and the re-evaluation of the phenotype of P. broegbernensis DSM 12573(T) necessitates the emendation of its description.