A yellow-pigmented strain (JM-1081T) isolated from healthy stem tissue of Zea mays was taxonomically characterized. Cells of the strain were rod-shaped and Gram-stain-negative. Comparative 16S rRNA gene sequence analysis revealed closest relationship to the type strains of Sphingobacterium multivorum (98.1 % similarity), Sphingobacterium mucilaginosum (97.9 %) and Sphingobacterium siyangense (97.8 %). 16S rRNA gene sequence similarities to the type strains of all other Sphingobacterium species were below 97.8 %. Fatty acid analysis of whole-cell hydrolysates of the strain resulted in a pattern typical of the genus Sphingobacterium with iso-C15 : 0 2-OH and/or C16 : 1ω7c, iso-C15 : 0, iso-C17 : 0 3-OH and C16 : 0 and as major compounds. The polyamine pattern contained predominantly sym-homospermidine. The major quinone was menaquinone MK-7 and the only identified lipids in the polar lipid profile were phosphatidylethanolamine and phosphatidylserine. In addition, 15 unidentified lipids were detected in moderate to major amounts. Sphingolipid was detected. The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid. DNA-DNA hybridizations with two of the closely related type strains, those of S. multivorum and S. siyangense, as well as Sphingobacterium canadense resulted in values below 70 %. In addition to the genotypic differences, differential biochemical and chemotaxonomic properties confirmed that the isolate JM-1081T represents a novel species, for which the name Sphingobacterium zeae sp. nov. is proposed. The type strain is JM-1081T (=LMG 29191T=CCM 8652T).
Keywords: Sphingobacterium zeae; endophyte; plant associated; taxonomy.