MYXOBACTERIA FROM VIETNAM: ISOLATION, PHYLOGENETIC ANALYSIS AND BIOPROSPECTION

Abstract Forty-three myxobacterial strains were isolated and identified from 20 soil samples collected in Vietnam. The information on morphological characteristics and 16S ribosomal gene sequencing showed that these strains were designated to seven genera belonging to Angiococcus, Archangium, Chondromyces, Corallococcus, Cystobacter, Melittangium, and Myxococcus, in suborder Cystobacterineae and Sorangiineae. The phylogenetic tree was constructed to clarify the genetic relationship between myxobacterial isolates. Myxobacteria were cultured, and crude extracts were obtained after 10-day fermentation in P-medium in the presence of the Amberlite XAD 16N adsorbent resin. Elution was carried out with acetone and methanol to obtain the crude extracts. Evaluation of antioxidant activity used the DPPH and ABTS assay, the minimum inhibitory concentration values were determined by the microdilution method. The total extract from CT21 had the highest total antioxidant activity (IC 50 = 52.34 ± 1.47 µg/mL, 30.28 ± 0.74 µg/mL for DPPH and ABTS assays, respectively). The other potential strain was TG131 and GL41 that IC 50 values were 40.28 ± 1.13 and 57.24 ± 1.52 µg/mL, respectively (by the DPPH method), and 48.35 ± 0.58 and 42.76 ± 0.50 µg/mL, respectively (by the ABTS method). Interestingly, 100% isolated myxobacterial strains show inhibitory activity against at least one of the tested microorganisms. The potential antimicrobial strain was GL41, which inhibited all tested microorganisms, and the MIC values were 1 µg/mL against MRSA, MSSA, S. faecalis, C. albicans , and A. niger . The highest active strains were members of Myxococcus sp. genus.