Tamlana laminarinivorans sp. nov. and Tamlana sargassicola sp. nov., two novel species isolated from Sargassum, show genomic and physiological adaptations for a Sargassum-associated lifestyle

The genus Tamlana from the Bacteroidota currently includes six validated species. Two strains designated PT2-4 T and 62-3 T were isolated from Sargassum abundant at the Pingtan island coast in the Fujian Province of China. 16S rRNA gene sequence analysis showed that the closest described relative of strains PT2-4 T and 62-3 T is Tamlana sedimentorum JCM 19808 T with 98.40 and 97.98% sequence similarity, respectively. The 16S rRNA gene sequence similarity between strain PT2-4 T and strain 62-3 T was 98.68 %. Furthermore, the highest average nucleotide identity values were 87.34 and 88.97 % for strains PT2-4 T and 62-3 T , respectively. The highest DNA–DNA hybridization (DDH) value of strain PT2-4 T was 35.2 % with strain 62-3 T , while the DDH value of strain 62-3 T was 37.7 % with T. sedimentorum JCM 19808 T . Growth of strains PT2-4 T and 62-3 T occurs at 15–40 °C (optimum, 30 °C) with 0–4 % (w/v) NaCl (optimum 0–1 %). Strains PT2-4 T and 62-3 T can grow from pH 5.0 to 10.0 (optimum, pH 7.0). The major fatty acids of strains PT2-4 T and 62-3 T are iso-C 15 : 0 and iso G-C 15 : 1 . MK-6 is the sole respiratory quinone. Genomic and physiological analyses of strains PT2-4 T and 62-3 T showed corresponding adaptive features. Significant adaptation to the growth environment of macroalgae includes the degradation of brown algae-derived diverse polysaccharides (alginate, laminarin and fucoidan). Notably, strain PT2-4 T can utilize laminarin, fucoidan and alginate via specific carbohydrate-active enzymes encoded in polysaccharide utilization loci, rarely described for the genus Tamlana to date. Based on their distinct physiological characteristics and the traits of utilizing polysaccharides from Sargassum , strains PT2-4 T and 62-3 T are suggested to be classified into two novel species, Tamlana laminarinivorans sp. nov. and Tamlana sargassicola sp. nov. (type strain PT2-4 T =MCCC 1K04427 T =KCTC 92183 T and type strain 62-3 T =MCCC 1K04421 T =KCTC 92182 T ).