Endophytic Bacterium <i>Flexivirga meconopsidis</i> sp. nov. with Plant Growth-Promoting Function, Isolated from the Seeds of <i>Meconopsis integrifolia</i>

Strain Q11^T of an irregular coccoid Gram-positive bacterium, aerobic and non-motile, was isolated from <i>Meconopsis integrifolia</i> seeds. Strain Q11^T grew optimally in 1% (<i>w</i>/<i>v</i>) NaCl, pH 7, at 30 °C. Strain Q11^T is most closely related to <i>Flexivirga</i>, as evidenced by 16S rRNA gene analysis, and shares the highest similarity with <i>Flexivirga aerilata</i> ID2601S^T (99.24%). Based on genome sequence analysis, the average nucleotide identity and digital DNA–DNA hybridization values of strains Q11^T and D2601S^T were 88.82% and 36.20%, respectively. Additionally, strain Q11^T showed the abilities of nitrogen fixation and indole acetic acid production and was shown to promote maize growth under laboratory conditions. Its genome contains antibiotic resistance genes (the vanY gene in the vanB cluster and the vanW gene in the vanI cluster) and extreme environment tolerance genes (ectoine biosynthetic gene cluster). Shotgun proteomics also detected antibiotic resistance proteins (class A beta-lactamases, D-alanine ligase family proteins) and proteins that improve plant cold tolerance (multispecies cold shock proteins). Strain Q11^T was determined to be a novel species of the genus <i>Flexivirga</i>, for which the name <i>Flexivirga meconopsidis</i> sp. nov. is proposed. The strain type is Q11^T (GDMCC 1.3002^T = JCM 36020 ^T).