Evaluation of the antimicrobial and antifungal activity of endophytic bacterial crude extracts from medicinal plant Ajuga turkestanica (Rgl.) Brig (Lamiaceae)

Ajuga turkestanica (Lamiaceae) is an endemic species of flora of Uzbekistan and is widely used in traditional medicine from its aboveground and root parts. In the course of a scientific study strains of endophytic bacteria with antimicrobial activity were isolated from the underground and upper parts of the plant. Twelve bacterial strains were selected to obtain crude extracts with methanol and ethyl acetate. The was studied pathogenic test of crude extracts of selected endophytic bacterial strains against bacterial strains and plant phytopathogenic fungi. It has been established that crude extracts isolated from strains of endophytic bacteria are effective against pathogenic test microbes. All extracts have an inhibitory effect pathogen test strains against gram-positive Staphylococcus aureus-91, Bacillus subtilis-5, gram-negative Escherichia coli - 221, Pseudomonas aeruginosa - 225 and Candida albicans-247. The crude extracts showed a minimum inhibitory concentration of 3.125 mu g/mL - 50 mu g/mL, inhibiting the growth of test strains of the pathogen. The range of action of all extracts at the minimum inhibitory concentration was as follows: E. coli 6.25 mu g/mL - 25 mu g/mL, B. subtilis 12.5 mu g/mL - 50 mu g/mL, S. aureus -3.122 mu g/mL - 50 mu g/mL, P. aeruginosa 12.5 mu g/mL -50 mu g/mL. The inhibitory effect of all endophytic bacterial strains on plant phytopathogenic fungi was as follows: Fusarium oxysporium: 3-5 cm, 44% -70% and Fusarium proliferatum: 4.1-7 cm, 27.8% - 56%. Our findings provide new insights into the antimicrobial activities of B. mojavensis (M11) and B. amyloliquefaciens (M13) natural endophytes, suggest this species may a promising candidate as a biocontrol agent to confer resistance to F. oxysporium and F. proliferatum disease and other phytopathogens in medicinal plants. (C) 2023 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.