Flavobacterium baculatum sp. nov., a carotenoid and flexirubin-type pigment producing species isolated from flooded paddy field

Abstract

A Gram-stain-negative, aerobic, asporogenous, motile by gliding, dull-yellow, long rod-shaped bacterial strain, designated SNL9^T, was isolated from a flooded paddy field near Dongguk University, Republic of Korea. The results of phylogenetic analyses based on 16S rRNA gene sequences indicated that SNL9^T represents a member of the genus <i>Flavobacterium</i> and is most closely related to <i>Flavobacterium ummariense</i> DS-12^T (96.2%) and <i>Flavobacterium viscosum</i> YIM 102796^T (96.3%). The average nucleotide identity and <i>in silico</i> DNA-DNA hybridization (DDH) values with <i>F. ummariense</i> DS-12^T and <i>F. viscosum</i> YIM 102796^T were 89.3/39.1 and 87.1/33 %, respectively. The major fatty acids of SNL9^T were identified as iso-C_{15 : 0}, summed feature 3 (comprising C_{16 : 1}ω6<i>c</i> and/or C_{16 : 1}ω7<i>c</i>) and summed feature 9 (comprising iso-C_{17 : 1}ω9<i>c</i> and/or 10 methyl C_{16 : 0}). SNL9^T contained MK-6 as the major respiratory quinone. The polar lipids were phoshatidylethanolamine, one unidentified aminophosphoglycolipid, three unidentified aminoglycolipids, two unidentified glycolipids and one unidentified phosphoglycolipid. The DNA G+C content was 34.2 mol%. SNL9^T produces carotenoid and flexirubin-type pigments. Among them, carotenoids are particularly valuable for the biotechnological and pharmaceutical industries due to their antioxidant activity. Aryl polyenes (APE) pigments were also found in SNL9^T which are responsible for yellow pigment in bacteria. They are stored in the bacterial membrane and protect the bacteria from oxidative stress, particularly from reactive oxygen species. In this paper, we describe a novel isolate, SNL9^T, which protect itself from the attack of free radicals using specific natural products in the membrane. Because of their anti-oxidation properties, aryl polyenes may also be of interest to the cosmetic industry. On the basis of the results of phenotypic, genotypic and chemotaxonomic analyses, SNL9^T represents a novel species of the genus <i>Flavobacterium</i>, for which the name <i>Flavobacterium baculatum</i> sp. nov. is proposed. The type is SNL9^T (=KACC 21170^T=NBRC 113746^T).