Chryseobacterium caseinilyticum sp. nov., a casein hydrolyzing bacterium isolated from rice plant and emended description of Chryseobacterium piscicola

Abstract

A novel Gram-stain-negative, aerobic, asporogenous, catalase-positive and oxidase-negative, non-motile, golden-yellow pigmented, rod-shaped bacterium with casein-degrading ability, designated strain GCR10T, was isolated from roots of rice plants collected from a paddy field near Dongguk University, Republic of Korea. The results of subsequent 16S rRNA gene sequence analysis indicated that GCR10T shares the highest sequence identity with Chryseobacterium piscicola VQ-6316sT (98.3%). Strain GCR10T grew at 2–32 °C (optimum, 25 °C), at pH 6.0–8.0 (optimum, pH 7.0) and in the presence of 0–2.0% (w/v) NaCl (optimum in the absence of NaCl). The novel strain was able to produce carotenoid and flexirubin-type pigments. The predominant menaquinone was MK-6 and the major fatty acids were identified as iso-C15 : 0, iso-C17 : 0 3-OH and iso-C17 : 1ω9c. The polar lipids were phosphatidylethanolamine, four unidentified aminoglycolipids, two unidentified aminolipids and two unidentified glycolipids. The genome of GCR10T is 4.3 Mb in length with a DNA G+C content of 36.5 mol%. Average nucleotide identity, digital DNA–DNA hybridization and average amino acid identity values between GCR10T and Chryseobacterium piscicola VQ-6316sT were 82.1, 25.2 and 84.3 %, respectively, which clearly indicates that the novel strain is distinct from its closest relative. The demand for natural biodegradable pigments isolated frominsects, plants or microorganisms is increasing day by day because of their beneficial pharmacological properties. Here, we describe a novel strain that produces two types of pigment, carotenoid and flexirubin. On the basis of the results from phenotypic, genotypic and chemotaxonomic analyses, strain GCR10T represents a novel species of the genus Chryseobacterium , and the name Chryseobacterium caseinilyticum sp. nov. is proposed. The type strain is GCR10T (=KACC 21707T=NBRC 114715T).