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 (IC50 = 52.34 +/- 1.47 mcg/mL, 30.28 +/- 0.74 mcg/mL for DPPH and ABTS assays, respectively). The other potential strain was TG131 and GL41 that IC50 values were 40.28 +/- 1.13 and 57.24 +/- 1.52 mcg/mL, respectively (by the DPPH method), and 48.35 +/- 0.58 and 42.76 +/- 0.50 mcg/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 mcg/mL against MRSA, MSSA, S. faecalis, C. albicans, and A. niger. The highest active strains were members of Myxococcus sp. genus.

Myxobacteria have been considered microbial factories for producing secondary metabolites that have a variety of potential biological actions for discovering and isolating new biological molecules. Forty-three myxobacterial strains were isolated and identified from 20 soil samples collected in Vietnam. The information on morphological characteristics and phylogenetic analysis inferred from 16S ribosomal gene showed that the newly isolated myxobacterial strains were classified into seven genera of Angiococcus, Archangium, Corallococcus, Cystobacter, Melittangium, and Myxococcus. Antioxidant activity was measured with the DPPH and ABTS assays; the minimum inhibitory concentration values were determined by the microdilution method. The extract from CT21 strain had the highest total antioxidant activity (IC50 = 52.34 ± 1.47 and 30.28 ± 0.74 μg/mL for the DPPH and ABTS, respectively). Interestingly, all strains isolated myxobacterial strains show inhibitory activity against at least one of the tested microorganisms. The most potent 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. Almost all active strains were members of the Myxococcus genus, among of which, GL41 strain was identified as Myxococcus stipitatus. Myxobacteria strains isolated from soil are a potent source of bioactive metabolite production.