Identification of five strains of antarctic bacteria producing low-temperature lipase

Five strains of antarctic bacteria producing extracellular low-temperature lipase are screened from seawater collectedby CTD during the Chinese 18th Antarctic Scientific Expedition. Their phylogenetic positions on the basis ofamplification, comparison and analysis of almost complete 16S rDNA sequence are determined by neighbor-joininganalysis. Phylogenetic analysis indicates that all of these five strains belong to g-proteobacteria. The strains 11102 and 92 are classified as genus Pseudoalteromonas sp. and genus Psychrobacter sp. respectively. The strains 25101, 2221 and 1281 are classified as genus Moritella sp.

Antarctic Psychrophile Bacteria Screening for Oil Degradation and Their Degrading Characteristics

Two hydrocarbon degrading bacteria NJ276 and NJ341 were screened from 385 Antarctic marine bacteria and their degrading characteristics were studied. Diesel oil as sole carbon source was used in this study. The results showed that the oil degradation rates of Antarctic psychrophile bacteria NJ276 and NJ341 were 23.47 % and 32.15 %, respectively, after 20 days culturation at 5 ℃, and the rates were 43.95 % and 62.47 % respectively after 20 days culturation at 15 ℃. The oil degradation abilities were enhanced remarkably with the increasing culture temperature. GC - MSs indicated the residual oil contained C15 - C21 7 alkyls after degradation by NJ276, and C16, C17 and C18 3 alkyls after degradation by NJ341. The 16S rDNA gene sequences homology and phylogenetic analysis of the two Antarctic psychrophile bacteria showed that NJ276 belonged to the described genus Pseudoalteromonas and NJ341 belonged to the genus Colwellia.

Production and characterization of an extracellular polysaccharide of antarctic marine bacteria Pseudoalteromonas sp. S-15-13

Twenty-seven antarctic bacteria producing extracellular polysaccharide （EPS） were selected from 57 strains by staining technology. The effects of major environmental factors on the growth and EPS production of Pseudoalteromonas sp. S - 15 - 13 were investigated, and the EPS was separated and purified for characterization analysis. The results showed that the optimal conditions for the EPS production were culture period, 56 h; growth temperature, 8 ℃ ; carbon source, 1.0% glucose; NaCI concentration, 3.0% ; pH 6.0 - 7.0. The EPS was purified by cold ethanol precipitation, proteins removal, ion exchange chromatography and gel chromatography technology. The molecular mass of EPS - H was 62 kDa as determined by the high performance gel permeation chromatography. Its sugar composition was a homopolymer of marmose analyzed by gas chromatograph spectroscopy. After repeated freezing and thawing of the bacteria hiomass in the presence of EPS, the bacterial growth was much higher than that observed after freezing in the absence of EPS and the difference augmented with the increase of freeze-thaw cycles. It is hypothesized that the adaptation of Pseudoalteromonas sp. S- 15 - 13 to the antarctic marine conditions, characterized by low temperature, high NaCl concentration and repeated freeze-thaw cycles, might be related to the EPS production ability.

Optimization of Fermentation Medium and Conditions of Antibiotic Active Substances Produced by Antarctic Psychrotrophic Bacterium Rheinheimera sp. 97

[Objective] The aim was to optimize the fermentation medium and conditions of antibiotic active substances produced by Antarctic psychrotrophic bacterium Rheinheimera sp.97.[Method] Single-factor experiment and orthogonal test were adopted to optimize the fermentation medium of antibiotic active substances produced by Antarctic psychrotrophic bacterium R.sp.97,while the fermentation conditions were optimized by single-factor experiment.[Result] The optimum fermentation medium for the antibiotic active substances production was as follows：tryptone 3.0 g/L,ammonium sulfate 1.0 g/L,starch 2.0 g/L,NaCl 15.0 g/L.The optimized fermentation conditions were as follows：the starting pH of medium was 8.0,fermentation temperature was 10 ℃,liquid volume in Erlenmeyer flask was 30 %（V/V）and inoculation amount was 1%（V/V）.Under the optimized fermentation medium and conditions,the antibacterial activity of R.sp.97 was increased by 18.1%.[Conclusion] This study had provided basis for the antibiotic active substances produced by Antarctic psychrotrophic bacterium R.sp.97.

Isolation and Phylogenetic Analysis of Plant Pathogen-Inhibiting Strains from Southern Ocean

[Objective] The aim was to isolate the strains resistant to plant pathogenic fungi from Southern Ocean and study their phylogenetic relationship and antimicrobial spectrum. [Method] Agar diffusion method was adopted to screen antimicrobial strains and determine the antimicrobial spectrum. Phylogenetic relationship of the strains was analyzed by neighbor-joining method of the Mega 4.0 software. [Result] Twenty antimicrobial strains were screened from seawater of Southern Ocean collected during the 27^th Chinese Antarctic Scientific Expedition. Molecular identification and phyloge- netic analysis indicated that two antimicrobial strains were members of Pseu- domonas, two strains were members of Psychrobacter, and the other 16 trains were members of Pseudoalteromonas. The antimicrobial spectrum of four strains which had higher antimicrobial activity indicated that the strains 312, 83-1 and 195 greatly inhibited the growth of Fusarium oxysporum, Rhizoctonia solani K（Jhn, Phytophthora capsici Leonian, Verticillium dahliae, Alternaria solani, Thanatephoru scucumeris and Phomopsis asparagi （Sacc）; strain 312-1 had obvious antimicrobial effect on the six of the plant pathogens except R. solani. [Conclusion] Four strains which had higher antimicrobial effect were obtained and should be further studied for development and application.