Reclassification of Algibacter wandonensis as a Later Heterotypic Synonym of Algibacter lectus Based on Whole-Genome Sequence Analysis.

The genus Algibacter belongs to the family Flavobacteriaceae of the Bacteroidetes, and all members of this genus were isolated from marine environments. Among the Algibacter species, two members, Algibacter lectus KMM 3902 and Algibacter wandonensis WS-MY22, were isolated from green algae and sediment around a brown algae respectively. The 16S rRNA gene sequences of these two type strains possess 99.4% sequence similarity. In this study, further studies were undertaken to clarify the taxonomic assignments of the two species. Whole-genome sequence analysis showed that the similarities for other phylogenetic markers are also very high (i.e. 99.9% for gyrB, 99.6% for recA and 99.9% for rpoD). Average nucleotide identity, average amino acids identity and digital DNA-DNA hybridization value between A. lectus KMM 3902 and A. wandonensis WS-MY22 are 98.3%, 98.6% and 89.4% respectively, all clearly exceed suggested species delineation thresholds. Furthermore, phylogenetic trees based on sequences of 16S rRNA gene and up-to-date bacterial core gene set (UBCG) consisting of 92 genes provided additional evidence that A. lectus KMM 3902 and A. wandonensis WS-MY22 are very closely related. In addition, a review of their profiles indicated that A. lectus KMM 3902 and A. wandonensis WS-MY22 did not present pronounced differences at phenotypic and chemotaxonomic levels. Based on these evidence, we propose that A. wandonensis should be reclassified as later heterotypic synonyms of A. lectus.