Identification Of A Novel Species Of Bacillus PS06 Isolated From The Rhizosphere Soil Of Stipa Breviflora And Its Growth-promoting Effect

Rhizosphere soil is an important link connecting plants and soil,and rhizosphere microorganisms have a ctitical influence on the growth and development of plants.At present,research on rhizosphere microorganisms is mainly focused on crops,and there are few studies related to rhizosphere microorganisms of grassland pastures.Desert grassland is an important part of temperate grassland in China,and its vegetation type is single.Stipa breviflora is the main established population and dominant forage grass in desert grassland.However,there are few studies on its rhizosphere bacterial isolation has been reported.In this study,Stipa breviflora,a dominant constructive species in the desert grassland of Siziwang Banner,Inner Mongolia,was used as the research object.The bacteria of rhizosphere soil of Stipa breviflora were isolated and screened using phosphorus,nitrogen fixation,and potassium-resolving media,and the novel species PS06 was identified and determine its effect on the growth of Stipa breviflora.The main results are as follows:(1)A total of 39 bacterial isolates were isolated from the rhizosphere soil of Stipa breviflora,which belonged to Proteobacteria(46%),Actinobacteria(33%)and Firmicutes(21%)using phylogenetic analysis.At the genus level,Bacillus(18%)of Firmicutes was the most dominant.The 16S rRNA gene sequence similarity between the strain PS06 and its known most closely related type strain Bacillus salsus A24~T is 97.7%,which was suttested potential new species.(2)The results of phenotypic,genotypic,chemotaxonomic,and phylogenetic analyses of strain PS06 showed that there is an obviously difference between strain PS06 and its relatives.Therefore,the strain PS06 is proposed as a new species of Bacillus and named Bacillus pratensis PS06.At the same time,the genome sequencing results showed that the strain has no related genes of both nitrogen fixation and phosphorus solubilization.(3)The results of the inoculation experiment of the strain PS06showed that the strain PS06 promoted the germination of Stipa breviflora seeds in the early growth stage,and the promotion effect was weakened with the extension of the germination time;At the 28th day,the germination rate of the seeds could reach about 90%.At 25 days after the seedling emergence of Stipa breviflora,the strain had a significant promotion effect on the plant height,root length and belowground fresh weight.In this study,we successfully isolated new species bacterium with growth-promoting effects from the rhizosphere of Stipa breviflora by traditional isolation approach,which provided a bacterial resource for the application of biotechnology in the restoration of degraded grasslands.