Abstract

Tidal-flat sediments harbor a diverse array of sulfate-reducing bacteria. To isolate novel sulfate-reducing bacteria and determine their abundance, a tidal-flat sediment sample collected off Ganghwa Island (Korea) was investigated using cultivation-based and culture-independent approaches. Two Gram-stain-negative, strictly anaerobic, rod-shaped, sulfate-reducing bacteria, designated IMCC35004T and IMCC35005T, were isolated from the sample. The two strains reduced sulfate, sulfite, elemental sulfur, thiosulfate, Fe(III) citrate, and Mn(IV) oxide by utilizing several carbon sources, including acetate. The 16S rRNA gene amplicon sequencing revealed that the tidal-flat sediment contained diverse members of the phylum Desulfobacterota, and the phylotypes related to IMCC35004T and IMCC35005T were < 1%. The two strains shared 97.6% similarity in 16S rRNA gene sequence and were closely related to Desulfopila aestuarii DSM 18488T (96.1–96.5%). The average nucleotide identity, level of digital DNA–DNA hybridization, average amino acid identity, and percentages of conserved proteins determined analyzing the whole-genome sequences, as well as the chemotaxonomic data showed that the two strains belong to two novel species of a novel genus. Additionally, genes related to dissimilatory sulfate reduction were detected in the genomes of the two strains. Unlike the genera Desulfopila and Desulfotalea, IMCC35004T and IMCC35005T contained menaquinone-5 as the major respiratory quinone. Collectively, IMCC35004T and IMCC35005T were concluded to represent two novel species of a novel genus within the family Desulfocapsaceae, for which the names Desulfosediminicola ganghwensis gen. nov., sp. nov. (IMCC35004T = KCTC 15826T = NBRC 114003T) and Desulfosediminicola flagellatus sp. nov. (IMCC35005T = KCTC 15827T = NBRC 114004T) are proposed.

Highlights

  • Sulfate-reducing bacteria (SRB) are defined by their ability to use sulfate as a terminal electron acceptor during anaerobic respiration, and they are known to be universally found in anoxic habitats, including marine sediments, soil, groundwater, active sludge, and animal ­guts[1,2,3,4,5]

  • This study reports the isolation of two sulfate-reducing bacterial strains of the family Desulfocapsaceae from a tidal-flat sediment of the Yellow Sea

  • The two strains were found to share 97.6% similarity in 16S rRNA gene sequence, which is less than the proposed cut-off value of 98.7% for bacterial species ­demarcation[23,24], suggesting that these strains belong to two separate species

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Summary

Introduction

Sulfate-reducing bacteria (SRB) are defined by their ability to use sulfate as a terminal electron acceptor during anaerobic respiration, and they are known to be universally found in anoxic habitats, including marine sediments, soil, groundwater, active sludge, and animal ­guts[1,2,3,4,5]. The coastal area of the Yellow Sea is characterized by the presence of vast tidal-flat sediments, where the families Desulfobulbaceae and Desulfocapsaceae have been abundantly detected via culture-independent analyses, but the members of the family have rarely been i­solated[20,21,22]. This study reports the isolation of two sulfate-reducing bacterial strains of the family Desulfocapsaceae from a tidal-flat sediment of the Yellow Sea. Based on the distinct genomic and phenotypic characteristics, the two strains were considered to belong to two novel species of a new genus in the family Desulfocapsaceae

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