Lysobacter lactosilyticus sp. nov., a Novel β-Galactosidase Producing Bacterial Strain Isolated from Farmland Soil Applied with Amino Acid Fertilizer.

To isolate β-galactosidase producing bacterial resources, a novel Gram-stain-negative, strictly aerobic bacterial strain designated as A6T was obtained from a farmland soil sample. Cells of the strain were rod-shaped (0.4-0.7 μm × 1.8-2.2 μm) without flagella and motility. Strain A6T grew optimally at 30 °C, pH 7.0 with 0% (w/v) NaCl. Based on phylogenetic analysis, strain A6T clustered within the genus Lysobacter clade and branched with Lysobacter dokdonensis KCTC 12822T (99.5%, 16S rRNA gene sequence similarity) and Lysobacter caseinilyticus KACC 19816T (98.5%). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain A6T and Lysobacter dokdonensis KCTC 12822T were 82.7% and 26.2%, and the values for strain A6T and KACC 19816T were 81.4% and 23.8%, respectively. Iso-C16:0, iso-C15:0, summed feature 9 (C17:1 iso ω9c and/or C16:0 10-methyl) and summed feature 3 (C16:1ω7c and/or C16:1 ω6c) were the major fatty acids, diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine were the major polar lipids, and ubiquinone 8 (Q-8) was the major ubiquinone. The genomic DNA G+C content was 67.2 mol%. Furthermore, under the condition of 30 °C, pH 7.0, 4% inoculation with 10.0 g L-1 lactose, the β-galactosidase activity produced by strain A6T was highest, reaching 95.3 U mL-1, indicating that this strain could be applied as a potential strain for β-galactosidase production. Strain A6T represents a novel species of the genus Lysobacter, and Lysobacter lactosilyticus sp. nov. is proposed on the basis of phenotypic, genotypic, and chemotaxonomic analysis. The type strain is A6T (=KCTC 82184T=CGMCC 1.18582T).