Caracterização micromorfológica e potencial antimicrobiano de actinobactérias isoladas de solo do município de Cambé, Paraná

Abstract

Soil is one of the most complex and biologically active natural systems, harboring a high microbial diversity and playing a key role in ecological and biogeochemical processes. Soil physicochemical heterogeneity directly influences microbial communities, favoring the development of microorganisms capable of producing secondary metabolites of biotechnological interest. Among soil types, Red Nitisols stand out for their high natural fertility, clay content, and intense biological activity, which support metabolically active microbial populations. In this context, actinobacteria are particularly relevant due to their recognized capacity to produce bioactive compounds, especially antibacterial agents. This study aimed to isolate, characterize, and evaluate the antibacterial potential of actinobacteria obtained from soil samples collected in the municipality of Cambé, Paraná, Brazil. Isolation was performed using the surface plating method on Casein Dextrose Agar supplemented with nystatin, resulting in 27 bacterial isolates, of which 18 remained viable for subsequent analyses and were organized into the CPR collection (Cambé–Paraná). Micromorphological characterization by microculture indicated a predominance of the genus Streptomyces (11 strains), as well as the presence of Micrococcus (4 isolates), Microbispora (2 isolates), and Streptosporangium (1 isolate). Antibacterial activity was assessed using the cross-streak method on ISP-2 medium against Klebsiella pneumoniae, Salmonella enterica, and Staphylococcus aureus. The results demonstrated variable antibacterial activity among the isolates and indicator microorganisms, reflecting a pattern of differential susceptibility under the experimental conditions. Some strains showed activity against all tested bacteria, while S. aureus exhibited lower overall sensitivity compared to the Gram-negative indicators. Overall, the findings reinforce soil as an important source of actinobacteria with antibacterial potential and highlight the relevance of Streptomyces in the search for new bioactive compounds.