Study On Systematic Taxonomy Of The Genus Myxococcus

In this study, Myxobacteria were isolated from 80 different samples, which were collected from Xinjiang, Yunnan, Neimenggu and Hainan. Some of strains were used to study on systematic taxonomy. 16S rDNA sequence analysis, morphological, physiological and biochemical characteristics tests, chemical taxonomy, and G+C mol% were used to study systematic taxonomy of genus Myxococcus.Rabbit dung, filter paper and YWCX were used to induce the fruiting bodies of myxobacteria from different samples. 133 myxobacteria strains were obtained from 80 samples. The highest efficiency of obtaining strains was“rabbit dung inducing methods”. The 16S rDNA sequence analysis showed that 105 strains belong to Myxococcus and the sequence similarities of the test strains and related strains are between 99.4% and 100%. The other 2 strains belong to Corallococcus and the sequence similarities of the test strains and related strains are 98.6% and 98.7%, repectively. The genomic DNA G+C mol% range from 64.93% to 73.78%. Meanwhile, by comparing the genomic DNA G+C mol% of the test strains and related strains, the difference are all below 5% except that of the strain HBUM 93102, whose value is 65.4%, which is lower than that of the related strain Myxococcus fulvus DSM 16525T by 6.3%. Therefore, the genomic DNA G+C mol% can be the verification of phylogenetic analysis of myxobacteria.The analysis of signature nucleotide showed that the pattern of 16S rRNA signatures consists of nucleotides at the 590:649(G-U), 592(G), 593:646(A-U). The comparison of the 16S rRNA secondary structures indicated that 5 species in Myxococcus could be discriminated into 4 types: Myxococcus fulvus, Myxococcus stipitatus, Myxococcus macrospores and the group of Myxococcus virescens and Myxococcus xanthus. Myxococcus virescens and Myxococcus xanthus have the same secondary structures.The dendrogram of numerical taxonomy indicated that test strains of Myxococcus and 6 reference strains were clustered into 5 groups at the similarity of 81%, while all reference strains divided by different speices. Most of results of numerical taxonomy agreed with that of sequences analysis of 16S rDNA.In conclusion, the characters of the genus Myxococcus are: The pattern of 16S rRNA signatures consists of nucleotides at the 590: 649(G-U), 592(G), 593: 646(A-U). The genomic DNA G+C content range from 64.93% to 73.78%(HPLC). Menaquinone type is MK-8(H0). They do not utilize sorbose, glucose, inositol, L-glutamine, L-histidine. They do not utilize inorganic nitrogen source. Gelatin is hydrolyzed. Colonies can adsorb Congo red. Cellulose and csculin are not degraded. Catalase result is positive.All strains could grow on plate with 0.75% NaCl.Their temperature range for optimal growth is between 20℃and 37℃. The pH range for growth is 6-9.All strains are sensitive to 100μg/mL kannamycin and resistant to 5μg/mL neomycin, to 5μg/mL streptomycin, to 5U/mL penicillin, to 2μg/mL erythromycin, to 5μg/mL tetracycline, to 250μg/mL cycloheximide and to 16,700U/mL nystatin.The position of 105 strains is: Bacteria, Proteobacteria, Deltaproteobacteria, Myxococcales, Cystobacterineae, Myxococcaceae, Myxococcus.