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The Investigation of Halophilic and Halotolerant Actinomycetes Resource in Yushuihe, Qinghai

Author: ZhuHua
Tutor: LaiHangXian;XueQuanHong
School: Northwest University of Science and Technology
Course: Microbiology
Keywords: Yushuihe salt lake isolation method halophilic and halotolerant actinomycetes taxonomic identification
CLC: Q938
Type: Master's thesis
Year: 2009
Downloads: 48
Quote: 0
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Abstract


Actinomycete in high salty environments has become an important research topic in recent years. There are numerous salt lakes in the Tsaidam Basin, Qinghai Province, but little is known about actinomycete populations in the lakes. The objectives of this study were to (1) develop effective methods for separating and screening actnomycetes from saline environments such as salt lakes and mines and (2) to identify halophilic and halotolerant actinomycetes, thus increase our knowledge about actinomycete resources.The total water-soluble salt content, pH value and salt ion content of test samples from Yushuihe were determined. The effect of different types of culture medium, different salt concentrations, and different sample pretreatments on actinomycetes was determined in order to determine the optimum conditions for the isolation of halophilic and halotolerant actinomycetes. Some strains were identified taxonomically with polyphasic taxonomy techniques. The main conclusions were as follows:1. The pH value of all test samples were alkaline. The water-soluble salt contents of the sediment、sand and river water were 158.67 g/kg、90.43 g/kg and 3.1 g/L respectively. The concentration of Na+ and K+ were similar and higher than the concentration of any other cation. The main anion was Cl-. This indicates that NaCl and KCl were the main salts in these samples. This has important implications for designing effect isolation methods.2. We isolated 89 actinomycete strains using three types of culture medium, four salt concentrations, and three sample pretreatments. There were significant differences in actinomycetes species and populations among the treatments. Separation efficiency was highest when a modified starch-casein medium with a 14% salt concentration was used to isolate actinomyces..3. The tolerance of actinomycetes for NaCL was different than their tolerance to KCl. Specifically, the highest NaCl conenctration that actinomycetes could tolerate was 14.63% whereas they could tolerate KCl concentrations as high as 30.4%. This suggested that K+ may be the essential growth factor for the actinomycete strains isolated in this study. In addition, nine actinomycete strains could not survive in a saline medium without NaCl. This indicates that they may be Na-addicted actinomycetes.4. Eight halophilic actinomycetes were obtained. Tests with NaCl indicated that among these strains, one was weakly halophilic, three were moderately halophilic, and three were extremely halophilic. In comparison, tests with KCl indicated one weakly halophilic strain and seven extremely halophilic strains. Strain QL026 may be an extreme K-addicted actinomycetes. All the strains had strong salt tolerance and the level of salt-tolerance was moderate or higher. There were twenty-two strains with extreme salt tolerance and seven strains with high salt tolerance5. Eleven actinomycete strains were identified by polyphasic taxonomy. Distinctions between the strains were based on morphological, physiological and biochemical characteristics, cell chemistry, and 16S rDNA sequence analysis. Strains QL048, QL009, QL007, QL060, QL010, QL057, QL019, QL052, and QL077 were identified as Streptomyces, whereas strains QL073 and QL071 belonged to Nocardia. Strains QL048, QL009, QL007, QL060, QL010, QL057, QL019, QL052 and QL073 are likely to be new species.

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