Lichen is a complex model of symbiosis including not only fungi and algae but other bacteria such as Actinobacteria. Of note, Actinobacteria are renowned for capacity to produce various antibiotics. Recently, with discovery of some new secondary metabolites from lichen, lichen-associated actinomycetes have attracted extensive attention. In Vietnam, as of this time, no research has been made regarding the actinomycetes associated with lichen. In this research we carried out isolating lichen-associated Actinobacteria from samples collected in Vietnam.

Five lichen samples collected on stems in Bao Loc City and Ben Tre City. After pre-treatment with four methods, they were isolated on agar surface with cycloheximide as an antifungal agent. Isolates were tested antimicrobial activity by perpendicular streak method. The potent isolates selected from antimicrobial assay were characterized by morphological, biochemical and physiological methods, and 16S rRNA gene sequences.

We has been collected 105 actinomycete isolates of Actinobacteria in which 65 strains survived through secondary culture. Ten isolates displayed significant antimicrobial activity on perpendicular streak method, in which 4VH3 showed good results on both Gram positive and negative bacteria. Morphology, biological characteristics and 16S rRNA sequences of 4VH3 were identify. In addition, the crude extract of 4VH3, having red color, was analysed by TLC-bioautography and determined the MIC on bacteria and yeast. Especially, the extract indicated considerable capacity against Enterococcus faecalis, Staphyloccocus aureus MRSA to be 0.06 and 0.25 µg/mL, respectively. Streptomyces sp. 4VH3 has high potential to discover anti-MRSA compounds in an chemical composition research.

Fig 1. Inhibitory zone of Actinobacterial isolates against bacteria and yeast
Fig 2. TLC-Bioautography of 4VH3’s crude extract

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