Chelatococcus thermostellatus sp. nov., a new thermophile for bioplastic synthesis: comparative phylogenetic and physiological study

The poly(3-hydroxybutyrate), PHB, accumulating thermophilic strain MW9(T), isolated from an aerobic organic waste treatment plant, was characterized by detailed physiological and phylogenetic studies. The strain is a Gram-stain-negative, rod shaped, non-spore forming member of Alphaproteobacteria. It shows optimum growth at 50 °C. Based on 16S rRNA gene sequence similarity, the strain together with five very similar isolates, was affiliated to the genus Chelatococcus (Ibrahim et al. in J Appl Microbiol 109:1579-1590, 2010). Rep-PCR genomic fingerprints and partial dnaK gene sequence also revealed that these isolates are very similar, but differ from other Chelatococcus type strains. The major fatty acids were similar to those of other strains of the genus Chelatococcus. DNA-DNA hybridization of strain MW9(T) with Chelatococcus species type strains revealed 11.0-47.7 % relatedness. G+C content of DNA was 67.1 mol%, which is comparable with the other strains of Chelatococcus species. The physiological and phenotypic characteristics of the new strain MW9(T) are sufficient to differentiate it from previously described species in the genus Chelatococcus. Strain MW9(T) is considered to represent a novel species of the genus Chelatococcus, for which the name Chelatococcus thermostellatus is proposed. The type strain is MW9(T) (=LMG 27009(T) = DSM 28244(T)). Compared to known Chelatococcus strains, strain MW9(T) could be a potent candidate for bioplastic production at elevated temperature.