| Objective:Lactic acid bacteria shows great potential application value in biological preservation fortheir low temperature adaption.In this study, the strains are isloted from intestinal and mucous ofcold-water fish in Xinjiang. This study is meaningful in mining the diversity of species and heredity of Lactic acid bacteria providing excellent strains for the development of biotechnology and further refining Lactic acid bacteria resource in China.Methods: With the MRS, Elliker, Bile Esculin Azide Agar, M17Aga, Lactobacillius selective agar,Bifidobacterium BS Medium and tomato juice agar (modified) medium, microorganisms in18kinds of cold water fish’s intestine and mucosa from Xinjiang were isolated. By the size of colony, shape, catalase and gram stain test to preliminary identification the low temperature tolerance strain.The phylogenetic of those low temperature resistant strains were identified based on16S rRNA gene sequence. And then Lactic acid bacteria with low temperature tolerance were screened out andthe optimum growth temperature and physiology biochemistry experiments were also measured. Apreliminary study on the susceptibility of the isolated strains were also preformed with the papermethod.Results:1. With the MRS, Elliker, Bile Esculin Azide Agar, M17Agar, Lactobacillius selective agar, Bifidobacterium BS Medium and tomato juice agar (modified) medium,161bacterial strains with low temperature tolerance were isolated in this study.161isolated strains were suspected as lactic acid bacteria with the Gram test and catalase experiment.2. Physiology biochemistry experiments and homologous of16S rRNA were preformed to invastaged those strains: the161isolated strains belonged to10categories. Among them,12belongedto Antarctic bacterium;1belonged to Bacillus;1belonged to Enterococcus;12belonged to Burkholderia;49belonged to Carnobacterium;2belonged to Hafnia;67belonged to Lactobacillus;7belonged to Leuconostoc;1belonged to Vagococcus and the others belonged to Pseudomonas. Lactobacillus is the largest, accounting for41%.3. Temperature tolerance test show that among the43isolated strains,19were psychrophile and24were psychrotrophs. The temperature is stay with the water which the fish grow up. Salt resistance experiments suggest that most of the strains can grow up at6%NaCl concentration. Theyare belongs to the micro well salt bacteria, but a few of strains such as E-XLC-1, BS-XLC-5, E-XLC-2, FQ-SLM-7, M17-HLM-4, M-JGM-4and M-CYC-3, can still grow when the salt concentration at8%, but growth slowly or even stop when the salt concentration higher than10%.4. Physiological and biochemical experiments about the43isolated strains showed: Only E-HLM-5and E-ZLYM-2are positive the others are negative in the contact enzyme experiment; All the strains were negative except E-HLM-5, BS-JYC-1, M-HBGC-1, E-ZLYM-2, M17-HLM-4and M-CYC-1in the M.R experiments; In V-P test showed that55.8%is positive. Except3is positive in Arginine experiment; Only9of the strains are positive the others are negative in the nitrate red uction experiments. Enterococcus M17-JYC-3are all negative except for the V-P test.5.12different carbon source test results show that all the low temperature strains can use Mannose, Rhamnose and Sorbose as carbon source. The strain of E-XLC-2can use all the sugar, alcohol as carbon source. We can speculation according to our experimental results of carbon sourceutilization: different strains of the carbon source utilization is likely related to fish species.6.43low temperature tolerance strains were isolated from different kinds of cold water fish of intestinal and mucous. The testing results of11kinds commonly used antibiotics showed that streptomycin had the highest drug resistance rate (100%); AMP had the highest antibiotic sensitive rate (100%); penicillin had the highest mediation rate (81.39%); In addition, different strains have different drug sensitivity. |
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