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

A novel actinobacterium, designated strain JXJ CY 21, 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 with the available sequences in the GenBank database showed that the strain is closely related to Citricoccus zhacaiensis FS24 (97.8 % similarity), Citricoccus parietis 02-Je-010 (97.7 %), Citricoccus terreus V3M1 (97.6 %), Citricoccus nitrophenolicus PNP1 (97.2 %), Citricoccus alkalitolerans YIM 70010 (97.2 %) and Citricoccus muralis 4-0 (97.0 %). The DNA-DNA hybridization values between strain JXJ CY 21 and the related type strains C. zhacaiensis FS24 and C. parietis 02-Je-010 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 (H) (98.5 %), while the major cellular fatty acids (>10 %) were anteiso-C, iso-C, iso-C and iso-C. 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 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 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 (=KCTC 29653 = DSM 29160).