Mutagenic effects of sodium azide in a cold tolerant Streptomyces spp.

(Published in The fifth National conference on Science and Technology, Nov. 10-12, 2008 Kathmandu pp.185)

K. B. Tiwari1, K Bhattarai2, U. T. Shrestha1 and V. P. Agrawal1
1Research Laboratory for Biotechnology and Biochemistry (RLABB)
Maitidevi, Kathmandu, Nepal
2Universal Science College
Maitidevi, Kathmandu, Nepal

Streptomyces spp. produces most of the known antibiotics that has therapeutic importance. The work explores the sodium azide induced beneficial mutations in a Streptomyces strain isolated from Khumbu, Everest region. A Streptomyces strain was isolated from a soil sample and purified at the Research Laboratory for Agricultural Biotechnology and Biochemistry (RLABB), Kathmandu, Nepal. The bacterium was then grown separately on plates containing 12.5, 25, 37.5 or 50ppm sodium azide. Subcultured colonies from plates containing sublethal concentrations of sodium azide were more brittle, irregular, smaller in size, yellowish in color, and asporogenic in comparison to the wild strain. Treatment of Streptomyces with 12.5ppm of sodium azide enabled bacteria to utilize nitrate, whereas alternate carbon sources (sucrose, mannitol and salicin) could be metabolized by those bacteria treated with 37.5ppm of the chemical. To explore possible mutations a RAPD primer (sequence CTGGCGTGAC; GC 70%; mp 34ºC) was used to investigate the DNA polymorphisms. Compared to that of the wild strain with five bands on a 1% agarose gel, two bands from a mutant were missing. Although point mutations on the primer binding site most likely resulted in the loss of bands, the RAPD-PCR technique can not reveal mutations in sequence between flanking ends. While this study explored loss-of-function (LOF) and gain-of-function (GOF) mutations, the GOF changes are more likely to result in strain improvement.