No abstract

A Gram-stain-positive, endospore-forming, rod-shaped bacterium, designated 1ZS3-5 T , was isolated from rice rhizosphere in Hunan Province, PR China. The isolate was identified as a member of the genus Paenibacillus on the basis of phenotypic characteristics and phylogenetic inference analysis. The 16S rRNA and rpoB gene (b-subunit of bacterial RNA polymerase) sequences were closely related to those of Paenibacillus taihuensis CGMCC 1.10966T with similarities of 97.2 % and 89.7 %, respectively. The DNA-DNA hybridization value between 1ZS3-5 T and P. taihuensis CGMCC 1.10966 T was 33.4 %. The DNA G+C content of 1ZS3-5 T was 47.5 mol%. The major polar lipids were diphosphatidylglycerol,

Bacterial strains ZYY136 T and ZYY9 were isolated from surface-sterilized rice roots from a long-term experiment of rice-rice-Astragalus sinicus rotation. The 16S rRNA gene sequences of strains ZYY136 T and ZYY9 showed the highest similarity, of 97.0 %, to Rhizobium tarimense PL-41 T . Sequence analysis of the housekeeping genes recA, thrC and atpD clearly differentiated the isolates from currently described species of the genus Rhizobium. The DNA-DNA relatedness value between ZYY136 T and ZYY9 was 82.3 %, and ZYY136 T showed 34.0 % DNA-DNA relatedness with the most closely related type strain, R. tarimense PL-41 T . The DNA G+C content of strain ZYY136 T was 58.1 mol%. The major cellular fatty acids were summed feature 8 (C 18 : 1 v7c and/or C 18 : 1 v6c), C 16 : 0 and C 16 : 0 3-OH. Strains ZYY136 T and ZYY9 could be differentiated from the previously defined species of the genus Rhizobium by several phenotypic characteristics. Therefore, we conclude that strains ZYY136 T and ZYY9 represent a novel species of the genus Rhizobium, for which the name Rhizobium oryzicola sp. nov. is proposed (type strain ZYY136 T 5ACCC 05753 T 5KCTC 32088 T ).Rhizobium (Frank, 1889) was the first and the only described rhizobial genus, named for its symbiotic association with members of the Leguminosae. However, in recent years, a variety of rhizobia have been isolated from roots of cereal crop plants, soil and water, rather than nodules on leguminous plants (García-Fraile et al., 2007;Quan et al., 2005;Singh et al. 2006;Sullivan et al., 1996;Zhang et al. 2011Zhang et al. , 2012. Endogenous rhizobia have been isolated from different varieties of rice in different areas, mainly including Rhizobium leguminosarum, Rhizobium loti, Rhizobium oryzae, Bradyrhizobium elkanii, Bradyrhizobium japonicum, Azorhizobium caulinodans, Ensifer (Sinorhizobium) meliloti, Mesorhizobium huakuii and former species of the genus Agrobacterium (Mano & Morisaki, 2008). Rhizobia colonize root, stem and leaf tissue of rice but do not form real nodules (Dakora, 2003). At the time of writing, the genus of Rhizobium contained at least 71 recognized species (www.bacterio.net). In this paper, we report on the taxonomy of two novel rice growth-promoting rhizobial strains, ZYY136 T and ZYY9, which were isolated from rice roots during studies of the effects of long-term winter-growing green manure plants on microbial diversity.Samples were taken from a 30-year long-term experiment in the Key Field Monitoring Experimental Station for Red Soil Eco-environment of Ministry of Agriculture, located at Qiyang County of Hunan Province, China. Surface disinfection of rice roots was performed according to the methods of Sun et al. (2008): the samples were washed with tap water, then immersed in 70 % alcohol for 3 min, washed with fresh sodium hypochlorite solution (2.5 % available Cl 2 ) for 5 min, rinsed with 70 % alcohol for 30 s, and finally washed 5-7 times with sterile water. Aliquots of the final rinsing water were spread on R2A (Difco) and tryptic soy agar 3These auth...