Modestobacter lacusdianchii sp. nov., a Phosphate-Solubilizing Actinobacterium with Ability to Promote Microcystis Growth

A novel actinobacterium, designated strain JXJ CY 19(T), was isolated from a culture mat of Microcystis aeruginosa FACHB-905 collected from Dianchi Lake, South-west China. 16S rRNA gene sequences comparison of strain JXJ CY 19(T) and the available sequences in the GenBank database showed that the strain was closely related to Modestobacter marinus 42H12-1(T) (99.1% similarity) and Modestobacter roseus KLBMP 1279(T) (99.0%). The isolate had meso-diaminopimelic in the cell wall with whole-cell sugars of mannose, rhamnose, ribose, glucose, galactose, and arabinose. The menaquinone detected was MK-9(H(4)), while the major cellular fatty acids include C(17:1) ω8c, C(15:0) iso, C(15:1) iso G and C(16:0) iso. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and an unidentified phospholipid. The DNA-DNA hybridization values between strains JXJ CY 19(T) and the closely related type strains Modestobacter marinus CGMCC 4.5581(T) and Modestobacter roseus NBRC 108673(T) were determined to be 50.8 ± 0.8% and 44.1 ± 1.7%, respectively. The DNA G+C content was 71.9 mol%. On the basis of the above taxonomic data and differences in physiological characters from the closely related type strains, strain JXJ CY 19(T) was recognized as a novel species of the genus Modestobacter, for which the name Modestobacter lacusdianchii sp. nov. (JXJ CY 19(T) = KCTC 39600(T) = CPCC 204352(T)) is proposed. The type strain JXJ CY 19(T) can solubilize calcium phosphate tribasic (Ca(3)(PO(4))(2)), phytin and (L)-α-phosphatidylcholine. The phosphate-solubilizing property of the novel actinobacterium could be a possible factor for the increase in growth of Microcystis aeruginosa FACHB-905 in ecosystem where the amount of available soluble phosphate is limited such as Dianchi Lake.