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).
To identify lipase LipA (PFL_0617) from Pseudomonas protegens Pf-5, a lipA deletion mutant (Pf0617) and a complementary strain (Pf0617lipA) were constructed, and their effects on the lipase production were examined. Pf0617 remarkably decreased its whole-cell lipase activity, whereas Pf0617lipA made its whole-cell lipase activity not only restore to wild-type level but also get a further increment. However, the deletion and overexpression of lipA did not affect the extracellular lipase activity. In addition, the unbroken whole cells of these strains were able to catalyze the hydrolysis of membrane-permeable p-nitrophenyl esters, but could not hydrolyze the membrane-impermeable olive oil. These results confirmed that LipA was an intracellular lipase and Pf-5 could also be used as a natural whole-cell biocatalyst. To evaluate the potential of Pf-5 as a whole-cell biocatalyst and separately characterize the whole-cell LipA, the properties of the whole-cell lipases from Pf-5 and Top10lipA were characterized. The results demonstrated that both Pf-5 and Top10lipA exhibited high tolerance to alkaline condition, high temperature, heavy metal ions, surfactants, and organic solvents. Taken together, lipA can realize functional expression in E. coli Top10, and Pf-5 and Top10lipA as whole-cell biocatalysts may have enormous potential in applications.
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