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A novel actinobacterium, designated strain JXJ CY 01 T , was isolated from a mucilaginous sheath of Microcystis aeruginosa FACHB-905 collected from Lake Dianchi, south-west China. Taxonomic position of the isolate was determined by polyphasic approaches. Strain JXJ CY 01 T shared 16S rRNA sequence similarities of 98.9 and 98.0% with Microbacterium marinilacus YM11-607 T and Microbacterium paludicola US15 T , and less than 98% with other members of the genus Microbacterium. The DNA-DNA relatedness values between strains JXJ CY 01 T and M. marinilacus JCM 16546 T and M. paludicola JCM 14308 T were 53.5±1.4 and 53.8±2.1%, respectively. l-Ornithine was detected in the cell wall, and rhamnose, galactose, glucose, arabinose, fucose and mannose as signature sugars in the whole-cell hydrolysates. Other chemotaxonomic characteristics determined were MK-12 and MK-11 as predominant menaquinones, anteiso-C 15:0 , iso-C 16:0 , anteiso-C 17:0 and iso-C 17:0 as major cellular fatty acids (>10%), and diphosphatidylglycerol, phosphatidylglycerol, an unidentified glycolipid and two unidentified phospholipids as the polar lipids. The DNA G+C content was 70.4 mol%. On the basis of the above taxonomic data, strain JXJ CY 01 T is determined to represent a novel species of the genus Microbacterium, for which the name Microbacterium lacusdiani sp. nov. is proposed. The type strain is JXJ CY 01 T (= KCTC 29655 T =DSM 29188 T ). The type strain JXJ CY 01 T can solubilize both insoluble inorganic (calcium phosphate) and organic phosphate (l-α-phosphatidylcholine) and is possibly one of the mechanism for enhancement of growth of M. aeruginosa FACHB-905.

A novel actinobacterium, designated strain JXJ CY 19T, 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 19T and the available sequences in the GenBank database showed that the strain was closely related to Modestobacter marinus 42H12-1T (99.1% similarity) and Modestobacter roseus KLBMP 1279T (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(H4), while the major cellular fatty acids include C17:1 ω8c, C15:0 iso, C15:1 iso G and C16:0 iso. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and an unidentified phospholipid. The DNA-DNA hybridization values between strains JXJ CY 19T and the closely related type strains Modestobacter marinus CGMCC 4.5581T and Modestobacter roseus NBRC 108673T 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 19T was recognized as a novel species of the genus Modestobacter, for which the name Modestobacter lacusdianchii sp. nov. (JXJ CY 19T = KCTC 39600T = CPCC 204352T) is proposed. The type strain JXJ CY 19T can solubilize calcium phosphate tribasic (Ca3(PO4)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.

Three Gram-stain-positive, aerobic, motile actinobacterial strains designated as CPCC 205119T, CPCC 205215, and CPCC 205251 were isolated from different biological soil crust samples collected from Tengger Desert, China. The 16S rRNA gene sequence comparison of these three strains showed they had almost identical 16S rRNA genes, which were closely related to members of the family Geodermatophilaceae , with the highest similarities of 96.3–97.3% to the species of Modestobacter. In the phylogenetic tree based on 16S rRNA gene sequences, these isolates clustered into a subclade next to the branch containing the species of Modestobacter lapidis and Modestobacter multiseptatus , within the lineage of the genus Modestobacter. The comparative genomic characteristics (values of ANI, dDDH, AAI, and POCP) and the phenotypic properties (morphological, physiological, and chemotaxonomic characteristics) of these isolates readily supported to affiliate them to the genus Modestobacter as a single separate species. For which, we proposed that the isolates CPCC 205119T, CPCC 205215, and CPCC 205251 represent a novel species of the genus Modestobacter as Modestobacter deserti sp. nov. CPCC 205119T (=I12A-02624=NBRC 113528T=KCTC 49201T) is the type strain. The genome of strain CPCC 205119T consisted of one chromosome (4,843,235bp) containing 4,424 coding genes, 48 tRNA genes, five rRNA genes, three other ncRNA genes, and 101 pseudogenes, with G+C content of 74.7%. The whole-genome sequences analysis indicated that this species contained alkaline phosphatase genes (phoA / phoD), phosphate transport-related genes (phoU , phnC , phnD , phnE , phoB , phoH , phoP , phoR , pitH , ppk , pstA , pstB , pstC , and pstS), trehalose-phosphate synthase gene (otsA), trehalose 6-phosphate phosphatase gene (otsB) and other encoding genes for the properties that help the microorganisms to adapt to harsh environmental conditions prevalent in deserts. Strains of this species could solubilize tricalcium phosphate [Ca3(PO4)2] and phytin, assimilate pyrophosphate, thiophosphate, dithiophosphate, phosphoenol pyruvate, 2-deoxy-d-glucose-6-phosphate, and cysteamine-S-phosphate. [ABSTRACT FROM AUTHOR]