Bioprospecting And Antibacterial Studies On Actinobacteria Of Salt Lakes From Two Sub-areas

Salt lake,as a special ecological environment with high salt concentration,is rich in actinobacteria,and these actinobacteria have the potential to produce new structural active compounds,and are an important source of drugs such as antibiotics.In this study,an exploration on actinobacterial diversity,novelty and antibacterial activity of soil or sediment samples from salt lakes were carried out.The diversity,novelty,as well as antimicrobial activity of culturable actinobacteria were investigated to provide a foundation for new antibiotic discovery.Totally,8 salt lake soil samples,collected from 4 salt lakes in the Nenjiang sub-area of Tongliao,Inner Mongolia,China and 7 salt lake soil samples,collected from 5 salt lakes in the Tibet sub-area,were studied.The studies methods were listed as follows: Pure culture methods using 5 kinds of isolation media and 2 kinds of p H were employed.Actinobacterial strains were then purified from air dried soil samples using the dilution spread and streaking methods.2)The 16 S r RNA gene of the pure strain was obtained by PCR amplification,and homology comparison was conducted to analyze the diversity of the actinobacterial genus.3)The representative strains were selected for 24-deep-well plate fermentation by Automatically Detect Duplic,and the fermentation liquid was centrifuged to obtain supernatant;4)Six kinds of pathogenic bacteria were selected as the testing bacteria,and the antibacterial activity evaluation of the fermentation broth of actinobacterial strains was carried out by the Oxford cup method.The results were as follows: 1)A total of 324 actinobacterial strains were isolated and purified from 8 soil samples collected from the Tongliao Nenjiang sub-area,they distributed in 9 orders,16 families and 25 genera.A total of 86 strains of Streptomyces,as dominant genera were isolated,which accounts for 27 % of all the strains;The second was 48 Nocardiopsis strains,which accounting for 15 %;There are 43 Nesterenkonia strains,accounting for 13 %;2)A total of 523 strains of actinobacterial strains were isolated and purified from 7 soil samples collected from the Tibet sub-area,which distributed in 6 orders,13 families and 27 genera.A total of 169 strains of Streptomyces as dominant genera,accounting for 32 % of all the strains;The second was 64 Kocuria strains,which account for12 %;There are 61 strains of Arthrobacter,accounting for 12 %;3)In terms of the number and species diversity isolated,PYG medium was the best among the five isolation media;4)The similarity of 16 S r RNA gene sequence of the 12 strains was low(<98.70 %),among which the rate of potential new species was high.Two strains with low similarity were selected for cloning,and their phylogenetic tree was constructed.It was found that strain T17a6-2 was most likely to be a new species in Citricoccus,and strain S24c1-8 was most likely to be a new genus in Oerskoviaceae.5)72 strains were selected from Nenjiang Salt Lake sub-region in Tongliao for fermentation culture and antibacterial activity evaluation.Among them,the fermentation products of 17 strains showed antibacterial activity against at least one tested strain,with a positive rate of 23.6 %.90 actinobacteria were selected from the subregion of salt lake in Xizang province for antibacterial activity evaluation.Among them,the fermentation products of 33 strains showed antibacterial activity against at least one tested strain,with a positive rate of 36.7 %.The above results show that there are not only a large number of actinobacteria in Tongliao Nenjiang Salt Lake sub-region and Tibet Salt Lake sub-region,but also a high probability of finding and obtaining rare and novel actinobacteria,which has the potential to discover new antibiotics from them.