Atividade antimicrobiana de bactérias isoladas do tecido de Palythoa caribaeorum dos recifes costeiros de Carapibus, Paraíba

Abstract

The antimicrobial activity presented by coral-associated bacteria, besides promoting the health of their host, also represents a source for obtaining new bioactive compounds. Under this perspective, the present study aimed to analyze the antimicrobial activity of bacteria associated to the zoanthid Palythoa caribaeorum from the coral reefs of Carapibus, Paraiba, Brazil. The phylogenetic analysis was conducted based on partial sequences of the 16S rRNA gene using bioinformatics tools. The bacterial isolates obtained, 84% belonged to the Firmicutes phylum and the Proteobacteria phylum with 84 and 16% of isolates, respectively. Among the 49 isolates, five genera could be found: Bacillus, Vibrio, Pseudomonas, Staphylococcus and Alteromonas. The antimicrobial activity of the isolates was tested against four bacterial strains and one yeast strain: Bacillus cereus (CCT0198), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa (P1R14) and Candida albicans (ATCC 10231), using antibiosis and antibiogram assays. The Minimal Inhibitory Concentration (MIC) was determined with the microdilution method. A total of 19 isolates showed antimicrobial activity, with the Bacillus genus being responsible for the largest number of antagonist bacteria, with 12 positive isolates in the antibiosis assay and four positive results in the antibiogram assay. In the antibiosis assay, the Vibrio genus presented three antagonistic isolates and the Pseudomonas genus only one isolate. The NC8 isolate, which was classified as Bacillus sp., inhibited all reference strains in the antibiosis assay and the B. cereus, S. aureus and C. albicans strains in the antibiogram assay. The lyophilized material of the NC8 isolate showed bacteriostatic activity against B. cereus, with a MIC value of 125 μg/ml. In the cytotoxicity assay, the hemolysis degree was 4,8% for the lyophilized material at tested concentrations, indicating its low cytotoxicity. The results showed the antimicrobial potential of some marine bacterial isolates, which deserve further studies in order to develop novel therapeutic agents.