Citricoccus lacusdiani sp. nov., an actinobacterium promoting Microcystis growth with limited soluble phosphorus

A novel actinobacterium, designated strain JXJ CY 21^T, was isolated from the culture mass of Microcystis sp. FACHB-905 collected from Lake Dianchi, South-west China. Polyphasic taxonomic study revealed that the isolate should be a member of the genus Citricoccus. Comparison of the 16S rRNA gene sequence of strain JXJ CY 21^T with the available sequences in the GenBank database showed that the strain is closely related to Citricoccus zhacaiensis FS24^T (97.8 % similarity), Citricoccus parietis 02-Je-010^T (97.7 %), Citricoccus terreus V3M1^T (97.6 %), Citricoccus nitrophenolicus PNP1^T (97.2 %), Citricoccus alkalitolerans YIM 70010^T (97.2 %) and Citricoccus muralis 4-0^T (97.0 %). The DNA-DNA hybridization values between strain JXJ CY 21^T and the related type strains C. zhacaiensis FS24^T and C. parietis 02-Je-010^T were 16.0 ± 2.6 and 5.4 ± 1.7 %, respectively. The peptidoglycan in the cell wall was A4α type containing lysine-glutamic acid-glycine. The major respiratory menaquinone was found to be MK-8 (H₂) (98.5 %), while the major cellular fatty acids (>10 %) were anteiso-C_15:0, iso-C_16:0, iso-C_15:0 and iso-C_14:0. The polar lipids detected were diphosphatidylglycerol, phosphatidylinositol, phosphatidylglycerol, an unidentified phospholipid and an unidentified glycolipid. The DNA G + C content was determined to be 62.7 mol%. Strain JXJ CY 21^T can solubilize both insoluble inorganic and organic phosphates up to 24.7 and 1.7 mg/l respectively. This property of the novel actinobacterium acts as a modulator for enhancement of growth of Microcystis sp. FACHB-905 in the lake ecosystem where the amount of soluble phosphate is limited. On the basis of the above taxonomic data, strain JXJ CY 21^T represents a novel species of the genus Citricoccus, for which the name Citricoccus lacusdiani sp. nov. is proposed. The type strain is JXJ CY 21^T (=KCTC 29653^T = DSM 29160^T).