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Objectives: Developing a counterselective system for efficient markerless gene deletions in biocontrol strain P. protegens Pf-5. Results: We successfully implemented a markerless deletion of upp in Pf-5 to obtain the 5-FU resistant strain Pf5139. With this strain, we performed markerless gene deletions for each component of Gac/Rsm system and a 17 kb DNA fragment with the deletion ratio of 20 to 50%, and efficiently constructed a strain with triple deletions based on the suicide plasmid pJQ200UPP. In addition, there is no obvious connection between the deleted fragment length and the deletion ratio. Conclusion: The upp-based counterselective system in this study is efficient and valuable for markerless gene deletions in Pf-5, indicating that it has great potential in the study of gene function and in the application of genome reduction for Pseudomonas strains. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

An antialgal compound was isolated from the cultured broth of Streptomyces jiujiangensis JXJ 0074 by using bioassay methods. Based on the data of H-NMR, C-NMR, ESI-MS, and thin layer chromatography, the active compound was identified as L-valine, which showed antialgal activity mainly against Microcystis. L-valine exhibited greater antialgal activities than both L-lysine and copper sulfate (CuSO) did on Microcystis aeruginosa lawn. However, M. aeruginosa recovered growth earlier with higher growth rate in L-valine treatment than in L-lysine treatment. L-valine dissipated completely within 2 days, much quicker than L-lysine (6 days), which resulted in the lysing of more than 80 % M. aeruginosa cells and the release of amount of intracellular microcystin-LR (MC-LR) within 2 days. As a resultant, the extracellular MC-LR content was more than twice of the control from day 1 to 5. Exposure to L-valine significantly promoted the synthesis of MC-LR. L-lysine also promoted the release and synthesis of MC-LR with much lesser efficiency than L-valine. L-valine could damage Microcystis severely, causing perforation and collapse of M. aeruginosa cells and decrease of the chlorophyll. The superoxide dismutase (SOD) activity in L-valine-treated cells of M. aeruginosa initially increased with 32.94 ± 3.37 % higher than the control after 36 h and then decreased quickly. However, the increase rate of superoxide anion radical (O) was much higher than that of SOD, which resulted in serious lipid peroxidation and accumulation of malondialdehyde (MDA). To our knowledge, this is the first report showing L-valine active against cyanobacteria. [ABSTRACT FROM AUTHOR]