Lichen-Associated Endophytes from Helan Mountains: Insight into Microbial Diversity and Application

The secondary metabolites produced by endophytic bacteria in lichens exhibit a wide range of bioactivities, including antibacterial, anti-inflammatory, and anti-tumor properties. In this study, 17 strains with distinct morphologies were isolated and identified from lichens collected in the Helan Mountains. Results show that the isolated strains included 13 Streptomyces strains, 1 Niallia strain, 1 Acinetobacter strain, 1 Peribacillus strain, and 1 Pseudarthrobacter strain. The antibacterial activity tests revealed that the secondary metabolites of 14 strains inhibited Staphylococcus aureus, 8 inhibited Proteus vulgaris, and 6 inhibited Candida albicans. In the salt and alkali resistance tests, three strains grew at NaCl concentrations of 25, 50, 75, and 100 g/l, respectively. Additionally, 14 strains exhibited robust alkali tolerance, growing at pH 8, 9, 10, and 11. These results highlight the remarkable biological and environmental adaptability of the strains isolated from lichens in the Helan Mountains, providing a solid foundation for subsequent exploration and research into novel structural compounds.