Phylogenetic diversity of cultivable bacteria associated with Atrina pectinata collected from the tidal flat of Naozhou Island in the South China Sea

Abstract:

[Objective] To understand the diversity of cultivable bacteria associated with Atrina pectinata collected from the tidal flat of Naozhou Island (20°52′–20°56′N, 110°33′–110°38′E) in the South China Sea. [Methods] Bacteria strains were isolated from homogenates of the sample by using the conventional culture-dependent method and then investigated by using phylogenetic analyses based on 16S rRNA gene sequence comparisons. [Results] We isolated 125 bacteria strains from the sample on MA (marine agar), MH (moderate halophilic medium agar) and NA (nutrient agar) supplemented with 0–25% (W/V) NaCl. Based on partial morphological, physiological and biochemical characteristics, out of them, 90 strains were selected and subjected to a molecular systematic study based on 16S rRNA gene sequences. The results showed that the 90 isolates were members of 10 genera (Marinobacter, Chromohalobacter, Halomonas, Salinivibrio, Vibrio, Bacillus, Halobacillus, Virgibacillus, Staphylococcus, Micrococcus) of 6 families (Alteromonadaceae, Halomonadaceae, Vibrionaceae, Bacillaceae, Staphylococcaceae, Micrococcaceae) in 3 phylogenetic groups (Gamma-proteobacteria, Firmicutes, Actinobacteria). The most abundant and diverse isolates were within the phylum Firmicutes (56 strains, 62.2%) and the subphylum Gamma-proteobacteria (31 strains, 34.5%). The results of phylogenetic analyses suggested that there were obvious genetic divergences between most isolates and their closestly related type strains (16S rRNA gene sequence similarities ranging from 95.7%–99.9%). The results also showed that, out of the 90 isolates, at least 5 JSM strains (112019, 112024, 114045, 114058, 114083) should represent potential new taxa. Strain JSM 112024 could represent a novel genus in the family Halomonadaceae, and strains JSM 112019, JSM 114045, JSM 114058 and JSM 114083 could represent four novel species with in 4 characterized genera Salinivibrio, Bacillus, Halomonas and Virgibacillus, respectively. [Conclusion] There are abundant bacterial species diversity and phylogenetic diversity in the Atrina pectinata.