The Antibacterial Activity Of Endophytic Fungi From Rhodiola Sp. And Effects Of Se⁴⁺、Pb²⁺ On Its Physiological Activity

Rhodiola.L is a rare medicinal plants with adaptogen activity, and the research of endophytic fungi is still blank. This study mainly studied antimicrobial activity and biological activity of 168 endophytic fungi from three main Rhodiola species, which provided theory bases for exploring endophytic fungi in host responsed to stress, and help host to selecting absorption of inorganic element. It also offers the help for searching fungal resources of antibacterial activity and selective element absorption activity in practice.Agar diffusion method was adopted to screening the antimicrobial activity of 168 endophytic fungi of Rhodiola plants in vitro by using the eight kinds of pathogenic microorganisms as indicator bacteria. The results showed that 70 fungal endophytes of Rhodiola crenulata,50 strains of R. sachalinensis,48 strains of R. angusta, had at least one of the endophytic fungi inhibiting antimicrobial activity, which were accounted for 41.4%, 17.4%,21.1% of the total fungi. zpRs-S-12 and Rc-R-5.With high antibacterial activity were to futher optimizing their fermentation conditions. The results show that soluble starch was the best carbon source, yeast powder was the best nitrogen source. The optimal conditions of the bacteriostatic activity of the Rc-R-5 to ordinary Proteus vulgaris was loaded with 40 mL in 100-mL triangular flask,4 pieces of 5 mm diameter inoculation quantity, 25 ℃, pH8.0,6 d continuous fermentation, etc. The optimized conditions of the zpRs-S-12 to Bacillus subtilis:40 mL/100 mL liquid volume, inculune size was 4 pieces of 5 mm diameter,20 ℃, pH 8.0,4 d continuous fermentation cultivation, etc. The optimized fermention conditions of the zpRs-S-12 to Penicillium chrysogenum:30 mL/100 mL loaded liquid volume, inculune size was 4 pieces of 5 mm diameter,20 ℃, pH 8.0,4 d continuous fermentation cultivation, etc.Se4+、Pb2+ were selected to study the effect on antimicrobial activity physiological activity and of zpRs-S-12 and Rc-R-5. Results showed that high levels of Se4+ and Pb2+ significantly inhibited antimicrobial activities of zpRs-S-12 and Rc-R-5, and induced increasing of the content of MDA in bacteria body, decreasing of content of soluble protein, the content of GSH, but content of proline, antioxidant activity enzyme SOD、CAT activity increased significantly. It showed that oxygen free radicals produced under the environmental stress, which was not only causing cell damage by membranous peroxide, but also affecting secondary metabolism growth of the fungi.This study further researched the role of endophytic fungi in absorption of Se4+ and Pb2+ in Rhodiola responsing to stress. The results showed that endophytic fungi help host absorbing Se4+ and resistanting the stress of Pb2+. In the former course, the time of concentration decreasing of vitial signal NO was retarded, and the later was extended. Both the positive ion were increasly absorbed by host plant inoculated with endophytic fungi, which indicated that endophytic fungi were beneficial for elements absorption during the development of host plants.The research results show that endophytic fungi from Rhodiola were unique resources of natural products, which have important research value in the search for exploring bio-active endophytic fungi and novel antimicrobial natural products.