Assessing the Antagonistic Potential and Antibiotic Resistance of Actinomycetes Isolated from Two Zheltozems of Southeastern China

Abstract

Forty streptomycete strains have been isolated into pure culture from two eroded zheltozems (yellow soils) of the Fujian province. Their antagonistic activities and contributions to the formation of soil resistome have been characterized. The estimation of the antimicrobial effect of natural isolates allowed revealing 6 strains simultaneously inhibiting the growth of the fungi Fusarium oxisporum, Alternaria alternata, Paecilomyces sp., Trichoderma sp., and Candida albicans. One strain (Streptomyces aburaviensis F2-6) with a wide range of antifungal actions was also active against the bacteria Pseudomonas putuda, P. fluorescens, P. sepacia, Streptococcus sp., and Escherichia coli. It has been shown that the share of isolates with a wide range of antimicrobial effects (44%) and a high antagonistic activity (77%) in zheltozem of the urban Zhangzhou district is significantly higher than in the soil of the village of Hongkeng (22 and 39%, respectively). According to the resistome concept, determinants of resistance to antibiotics first appeared in their producers; they can be transmitted to other bacteria in the soil due to horizontal drift. Tests of streptomycetes for resistance to antibiotics with different acting mechanisms (inhibitors of the synthesis of cytoderm, protein, and metabolic pathways) has shown that the share of cultures with multiple resistance in zheltozems does not exceed 25–31%. No resistance to all of the studied antibiotics is characteristic of 15–16% of the strains isolated from zheltozems. The obtained data can be used for assessing the risks related to the transfer of antibiotic resistance genes from the environment to clinically valuable pathogenic species.