Collection and investigation on asymbiotic nitrogen-fixing microbial resources from 13 provinces over China

One hundred and eighty one asymbiotic nitrogen-fixing bacterial strains were isolated from 70 soil samples collected from 13 provinces over China. Results based on the determination of morphology, physiology and chemical properties, together with 16S rDNA sequencing, indicated that these strains belong to 66 species of 24 genera, which account for about a half of currently reported genera of asymbiotic nitrogen-fixing bacteria. Taxonomic distribution of these strains was relative converging, 65 strains belongs to Paenibacillus, 52 strains belongs to Bacillus and 19 strains belongs to Arthrobacter, which accounts for 36%, 29% and 11% of gross resource, respectively. Strains of these 3 groups make up 76% of gross resource. Strains of Paenibacillus and Bacillus showed significant diversity on the distribution regarding to geography and crops. Namely strains of these 2 groups could be isolated from almost every sample collected from root area of crops all over China.