Mycolicibacterium lacusdiani sp. nov., an Attached Bacterium of Microcystis aeruginosa

In eutrophic water, attached bacteria of Microcystis play an important role in the formation, development, and degradation of Microcystis blooms. A novel actinobacterium, designated as JXJ CY 35(T), was isolated from the culture mass of Microcystis aeruginosa FACHB-905 (Maf) collected from Lake Dianchi, Yunnan Province, China. Strain JXJ CY 35(T) was gram-positive, acid-fast staining, aerobic, with short rod-shaped cells, positive for catalase, and negative for oxidase. The isolate was able to grow at 10.0–36.0°C, pH 4.0–10.0, and tolerate up to 5.0% (w/v) NaCl, with optimal growth at 28°C, pH 7.0–8.0, and 0% (w/v) NaCl. Cell-wall peptidoglycan contains aspartic acid, glutamic acid, glycine, and alanine, with mannose, ribose, galactose, and arabinose as whole-cell sugars. Polar lipids consist of diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), glycolipid (GL1-3), phosphoglycolipid (PGL), phosphatidylinositol (PI), and unidentified lipid (L1). The predominant menaquinone was MK-9. Major fatty acids (>10%) were C(17:1)ω7c (37.0%) and C(18:1)ω9c (18.9%). The complete genome sequence of strain JXJ CY 35(T) was 6,138,096 bp in size with a DNA G + C content of 68.3%. Based on 16S rRNA gene sequences, it has 98.2% similarity to Mycolicibacterium arabiense JCM 18538(T). The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain JXJ CY 35(T) and the closest five type strains M. arabiense JCM 18538(T), M. goodii ATCC 700504(T), M. mageritense DSM 44476(T), M. austroafricanum DSM 44191(T), and Mycobacterium neglectum CECT 8778(T) were 52.1, 20.3, 20.3, 20.6, and 19.8%, and 92.7, 75.5, 75.6, 76.0, and 75.2%, respectively. On the basis of the above taxonomic data and differences in physiological characteristics from the closely related type strain, strain JXJ CY 35(T) was determined to represent a novel species of genus Mycolicibacterium, for which the name Mycolicibacterium lacusdiani sp. nov., is proposed. The type strain is JXJ CY 35(T) (=KCTC 49379(T) = CGMCC 1.17501(T)). Different inoculation dosages of the type strain JXJ CY 35(T) could exhibit different effects on the growth of Maf and its toxin synthesis and release. Strain JXJ CY 35(T) could promote the growth of Maf by providing it with available phosphorus, nitrogen, probably vitamins, and plant growth hormones.