AUTHOR=Li Hui-Ping , Gan Ya-Nan , Yue Li-Jun , Han Qing-Qing , Chen Jia , Liu Qiong-Mei , Zhao Qi , Zhang Jin-Lin 

TITLE=Newly Isolated Paenibacillus monticola sp. nov., a Novel Plant Growth-Promoting Rhizobacteria Strain From High-Altitude Spruce Forests in the Qilian Mountains, China

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.833313

DOI=10.3389/fmicb.2022.833313

ISSN=1664-302X

ABSTRACT=<p>Species in the genus <italic>Paenibacillus</italic> from special habitats have attracted great attention due to their plant growth-promoting traits. A novel plant growth-promoting rhizobacteria (PGPR) species in the genus <italic>Paenibacillus</italic> was isolated from spruce forest at the height of 3,150 m in the Qilian Mountains, Gansu province, China. The phylogenetic analysis based on 16S rRNA, <italic>rpoB</italic>, and <italic>nifH</italic> gene sequences demonstrated that strain LC-T2<italic><sup>T</sup></italic> was affiliated in the genus <italic>Paenibacillus</italic> and exhibited the highest sequence similarity with <italic>Paenibacillus donghaensis</italic> KCTC 13049<italic><sup>T</sup></italic> (97.4%). Average nucleotide identity (ANIb and ANIm) and digital DNA–DNA hybridization (dDDH) between strain LC-T2<italic><sup>T</sup></italic> and <italic>P. donghaensis</italic> KCTC 13049<italic><sup>T</sup></italic> were 72.6, 83.3, and 21.2%, respectively, indicating their genetic differences at the species level. These differences were further verified by polar lipids profiles, major fatty acid contents, and several distinct physiological characteristics. Meanwhile, the draft genome analysis provided insight into the genetic features to support its plant-associated lifestyle and habitat adaptation. Subsequently, the effects of volatile organic compound (VOC) emitted from strain LC-T2<italic><sup>T</sup></italic> on the growth of <italic>Arabidopsis</italic> were evaluated. Application of strain LC-T2<italic><sup>T</sup></italic> significantly improved root surface area, root projection area, and root fork numbers by 158.3, 158.3, and 241.2%, respectively, compared to control. Also, the effects of LC-T2<italic><sup>T</sup></italic> on the growth of white clover (<italic>Trifolium repens</italic> L.) were further assessed by pot experiment. Application of LC-T2<italic><sup>T</sup></italic> also significantly improved the growth of white clover with root fresh weight increased over three-folds compared to control. Furthermore, the viable bacterial genera of rhizosphere soil were detected in each treatment. The number of genera from LC-T2<italic><sup>T</sup></italic>-inoculated rhizosphere soil was 1.7-fold higher than that of control, and some isolates were similar to strain LC-T2<italic><sup>T</sup></italic>, indicating that LC-T2<italic><sup>T</sup></italic> inoculation was effective in the rhizosphere soil of white clover. Overall, strain LC-T2<italic><sup>T</sup></italic> should be attributed to a novel PGPR species within the genus <italic>Paenibacillus</italic> based on phylogenetic relatedness, genotypic features, and phenotypic and inoculation experiment, for which the name <italic>Paenibacillus monticola</italic> sp. nov. is proposed.</p>