Effect of inorganic salts on the conjugation and heterologous expression of actinorhodin in Streptomyces avermitilis
无机盐对阿维链霉菌接合转移及异源表达放线紫红素的影响

Abstract: Objective] Streptomyces avermitilis NRRL8165 could serve as a good host for heterlogous expression of antibiotics biosynthetic gene clusters. However, it needs to improve its conjugation frequency to accept large plasmids. Methods] We chose MgCl2 , NaCl, Ca(NO3)2 and CaCl2, to test whether they affected the conjugation frequency of large plasmids at salt concentration from 0-200 mmol/L. A complete random experiment was designed for optimization. Results] We found that CaCl2 promoted conjugation dramatically, and MgCl2 did significantly too. The complete random experiment led to diclosure of an optimal combination of MgCl2 and CaCl2 by which the conjugation frequency was improved by 11 fold. In addition, a supplemented medium was found to lead to successful heterologous expression of actinorhodin in S. avermitilis. Conclusion] Some inorganic salts can not only significantly improve the conjugation frequency of Streptomyces avermitilis NRRL8165 but also promote the expression of actinorhodin in Streptomyces avermitilis NRRL8165.