Flavobacterium potami sp. nov., a multi-metal resistance genes harbouring bacterium isolated from shallow river silt

Environmental pollution by heavy metals is becoming an increasing problem and has become a matter of great concern due to the adverse effects worldwide. In this study, we report a novel strain of multi-metal resistant bacteria. A Gram-stain-negative, strictly aerobic, non-motile, yellow, rod-shaped strain 17A(T), was isolated from the shallow silt of Fuyang River located in Longdian town, Hengshui city, Hebei province, China. Strain 17A(T) grew at 20-35 degrees C (optimum, 30 degrees C), pH 5-10 (optimum, pH 7) and 0-2% (w/v) NaCl (optimum, 1%). Phylogenetic analyses of 16S rRNA gene sequences showed that strain 17A(T) was closely related to members of the genus Flavobacterium, and had the highest 16S rRNA gene sequence similarity with 'Flavobacterium panacis' DCY106(T) (97.5%), followed by Flavobacterium johnsoniae subsp. johnsoniae UW101(T) (97.3%), Flavobacterium cutihirudinis E89(T) (97.2%), Flavobacterium limi THG-AG6.4(T) (97.2%), Flavobacterium hibisci THG-HG1.4(T) (97.2%) and Flavobacterium johnsoniae subsp. aurantiacum DSM 6792(T) (97.1%). The genome size of strain 17A(T) was 5.4 Mb and the DNA G + C content was 34.0%. The average nucleotide identity, digital DNA-DNA hybridization and average amino acid identity values among strain 17A(T) and reference strains were in the ranges of 79.8-86.1%, 24.1-31.4% and 80.5-88.6%, respectively, lower than the threshold values for species delineation. Strain 17A(T) contained iso-C-15:0 and C-16:0 3-OH as the predominant fatty acids (>= 10%). The main isoprenoid quinone of strain 17A(T) was identified as MK-6. The polar lipids consisted of phosphatidylethanolamine, three unidentified aminolipids, two unidentified aminophospholipids and six unidentified lipids. Comparative genomics analysis between strain 17A(T) and its reference type strains revealed that there are a number of metal-resistant genes in strain 17A(T), which are located in 15 gene clusters responsible for the copper homeostasis, cobalt-zinc-cadmium resistance, copper resistance, and arsenic/antimony resistance, with the copper resistance protein NlpE being unique to 17A(T). Combined data from phenotypic, phylogenetic and chemotaxonomic studies demonstrated that strain 17A(T) is a representative of a novel species within the genus Flavobacterium, for which the name Flavobacterium potami sp. nov. is proposed. The type strain is 17A(T) (= GDMCC 1.2723(T) = JCM 34833(T)).