Neochroococcus gongqingensis gen. Et sp. nov., a new member of coccoid cyanobacteria from a watercourse, eastern China

Abstract

The taxonomy of coccoid cyanobacteria has been largely revised in recent years. In this study, a novel coccoid cyanobacterial strain was isolated from a watercourse at the Poyang Lake Model Research Base, Jiangxi province, Eastern China. A polyphasic approach combining morphological and molecular testing was used to characterize this strain referred to as CHAB 4018. Regarding colonial form and cellular spatial arrange-ment, this strain was morphologically similar to strains of the genus Eucapsis. The maximum 16S rRNA gene sequence similarity of this strain to the currently described cyanobacteria genera was 93.40%, exceeding the cutoff for genus delimitation in bacteriology. Furthermore, a phylogenetic tree based on 16S rRNA gene sequences indicated that strain CHAB 4018 formed a unique clade in the family Chroococcaceae and was phylogeneti-cally close to the recently established genus Cryptococcum but distant from the Chroococcus ‘sensu stricto’ clade and from Eucapsis. Thus, a novel coccoid cyanobacterial genus with a new species is here described as Neochroococcus gongqingensis. A large phylogenetic tree using more strains suggested phylogenetic intermixture of Chroococcus–like and Eucapsis–like cyanobacteria, suggesting the need for further studies on the phylogeny and taxonomy of coccoid cyanobacteria.