Study On Managanese Oxidation And Radioresistant PAHs Degradation Bacteria In The Desert Of Xinjiang, And Polyphasic Taxonomy Of Three Novel Species

Taklamakan Desert, the world’s second largest desert in Xinjiang is generally recognized as a harsh and nutrition-poor environment. Surprisingly, there is rich microbial diversity in this region based on previous labratory studies. It is interested in the physiological mechanisms of microorganisms how they survive with Environmental stresses. This study selected manganese oxidation and PAH (poly aromatic hydrocarbons) degradation processes as the targets for understanding the relation of microorganisms to the desert environmental conditions. Some isolated novel species with potential value in applications and theory were also characterized in detail based on taxonomic properties.First of all, Mn oxidation process was studied. Manganese oxidation bacteria are widespread in natural environment, but their diversity and distribution are poorly understood. In this study, It was found that a lot of bacteria species can oxidize manganese ions. Besides dominant Bacillus strains, there is a large number of Actinobacteria, mainly in the Micrococcal section and Nocardia division together with their related genera. A single strain Flavoibacterium sp 12-2 with manganese oxidation ability was also isolated from the same area. These strains harbor a diversity of manganese oxidation phenomena.By using biochemical method, the dependence on Cu2+ of catalytic process was evaluated. It was found that the corresponding phenomenon is not stereotyped, suggesting that the mechanism of manganese oxidation may be complex and diverse. By Fourier Transform InfraRed spectrometry analysis, we hypothesized that cells interaction with the Mn ions obtained four major types, all of which are related with MnOx formation, synthesis of biological molecules as well as their direct interaction with Mn. By electron microscopy combined with EDS (Dispersive X-Ray Fluoresence Spectrometer), bacteriogenic MnOx always coated cells, but some MnOx are present in the cells, some between cells, and some products are also capsulated by excellular molecules such as polysacharides. X-ray diffraction results showed that most MnOx don’t have clear crystal structure, but Mn5O8 like structures were found from the products of three newly discovered strains. Using Biolog system, the influences of high concentrations of Mn ions on the bacterial metabolism was determined. The effect seems complex, but some obvious rules were discovered. All of the above results indicate that the manganese oxidizing bacteria in desert environment has complex manganese related behavior.Followed by the traditional screening and enrichment culture techniques, phylogenetically diverse strains with potential polycyclic aromatic hydrocarbons degradation ability were isolated. Some of these strains possess moderate or strong resistance to radiation. Gamma radiation experiment was utilized to determine the resistance of three representative strains in Deinococcus, Kocuria and Rhodococcus. Their ability to degrade polycyclic aromatic hydrocarbons was determined by Gas Chromatography with mass spectrometry (GC-MS) analysis. These new radiation-resistant strains with potential degradation ability may offer us new research resources for bioremediation in radioactive mixed wasted environmentFinally, three new taxa, including strains XM-003T,1-2T and 1-4, and 13-25T were discovered during microbial resources investigation. Strain 1-2T and 1-4 with 100% 16S rDNA sequence similarity showed the highest similarity with the type strain of P. daechungensis (94.2%), followed by P. Lentus 93.2%. Sequence similarity to other Pedobacter species was less than 93%. Based on polyphasic taxonomic study,1-2T and 1-4 were determined as a novel species of the genus and named Pedobacter glucosidilyticus sp. nov. XM-003T and Mucilaginibacter kameinonensis shared the highest sequence similarity of 96.0%. Phenotypic characterization showed that the strain belongs to Mucilanginibacter but well differentiated with other published species. Thus a new species of the genus was proposed and named Mucilaginibacter ximonensis sp. nov.. Strain 13-25T and C. panacarvi posessed high 16S rDNA sequence similarity (96.9%). However its phenotype is obviously different with C. panacarvi, especially in mobility and Carbon source utilization. In addition, it also obtained clear phenotypic differences with other species of this genus. In conclusion, 13-25T should be named as a novel species Cohnella damuensis sp. nov., which contains xylanolytic activity that may be valuable for application.