Chryseobacterium amylolyticum sp. nov., a potential plant growth-promoting bacterium isolated from the rind of Hami melon.

A novel Gram-stain-negative, aerobic, non-spore-forming, non-motile, golden-yellow pigmented, rod-shaped bacterium with starch-degrading ability, designated RRHN12T, was isolated from the rind of Hami melon with bacterial fruit blotch collected from Hainan Province, PR China. The novel strain exhibits the ability to produce siderophores and indole acetic acid, as well as to inhibit the hyphae growth and sporangia germination of Peronophythora litchii. The 16S rRNA gene sequence analysis showed that strain RRHN12T belonged to the genus Chryseobacterium with the highest similarities to Chryseobacterium aquifrigidense CW9T (99.1%) and Chryseobacterium gleum ATCC 35910T (99.0%). Phylogenomic analysis based on 92 core genes clearly showed that strain RRHN12T was most closely related to C. gleum ATCC 35910T. Genome-derived average nucleotide identity and digital DNA-DNA hybridization values between the novel strain and the closely related type strains were 87.14-92.68% and 32.49-49.40%, respectively, which are below the threshold values for species delineation. The major fatty acids were identified as iso-C15 : 0, iso-C17 : 0 3-OH, summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c) and summed feature 9 (10-methyl C16 : 0 and/or iso-C17 : 1  ω9c). Menaquinone-6 (MK-6) was the predominant respiratory quinone. The major polar lipids contained phosphatidylethanolamine and several unidentified aminolipids. The genomic DNA G+C content of strain RRHN12T was 37.5 mol%. Based on genomic, phenotypic and chemotaxonomic analyses, it should be considered as a novel species of the genus Chryseobacterium, for which the name Chryseobacterium amylolyticum sp. nov. was proposed, with RRHN12T (=GDMCC 1.4744T=JCM 37545T) as the type strain.