Until now, a large number of isolates of this genus were obtained from diverse marine environments and preliminarily identified by 16S rRNA gene sequencing. At the time of writing, the genus Thioclava consisted of the five published species, including the type species Thioclava pacifica ( Sorokin et al., 2005), along with Thioclava dalianensis ( Zhang et al., 2013), Thioclava atlantica ( Lai et al., 2014a), Thioclava indica ( Liu et al., 2015a), and the newly described Thioclava nitratireducens ( Liu et al., 2017b). Thioclava is a genus consisting of Gram-staining-negative, moderately halophilic and facultatively aerobic bacteria belonging to the family Rhodobacteraceae within the class Alphaproteobacteria ( Sorokin et al., 2005). Taken together, the newly established MLSA in this study first described the variability and phylogeny of the genus Thioclava which contributes to better understanding its ecology and evolution. (type strain 11.10-0-13 T = MCCC 1A03502 T = LMG 29618 T) by using a polyphasic taxonomic approach. (type strain TAW-CT134 T = MCCC 1A10143 T = LMG 29615 T) and Thioclava marinus sp. Two of the four new species were identified as Thioclava sediminum sp. The digital DNA-DNA hybridization and average nucleotide identity analyses based on genome sequences of the representative strains reconfirmed the validity of the MLSA analysis, and recommended a 97.3% MLSA similarity as the soft species threshold and nine species representing the five known and four putative novel species. In contrast to 16S rRNA gene-based tree that was unable to separate some species within this genus, each tree based on a single housekeeping gene and MLSA had consistently defined seven clades, corresponding to the five established ones and two novel ones. The study was based on sequences of 16S rRNA gene and five protein-coding housekeeping genes, gyrB, rpoD, dnaK, trpB, and recA. 2State Key Laboratory Breeding Base of Marine Genetic Resources, Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, State Oceanic Administration, Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resources, Key Laboratory of Marine Genetic Resources of Fujian Province, Xiamen, ChinaĪ multilocus sequence analysis (MLSA) was established and performed on the genus Thioclava, including 23 strains isolated from diverse marine environments, with the aim of better differentiation of strains and species within this genus.1School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, China.
Yang Liu 1,2, Qiliang Lai 2 and Zongze Shao 1,2 *
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