Characterization of microflora composition and antimicrobial activity of algal extracts from italian thermal muds

摘要

Aim: Fine granular clay, the so-called “peloids,” allowed to ripen for several months in contact with mineral thermal water and the organic substances derived from metabolic activities, represents the basis of thermal mud therapy. A complex microalgal community (Cyanophyceae, Chlorophyceae and Bacillariophyceae) is responsible for the therapeutic effects of thermal muds. Biological components of peloids produce bioactives, possessing anti-inflammatory, antirheumatic and antioxidant properties; for this reason, such matrix is widely used in thermal spas. The research reports results of a preliminary study aimed to characterize the microflora biodiversity of mature and nonmature thermal mud. Algal components were further extracted in order to test the antimicrobial activity of produced bioactive compounds. Materials and Methods: Microscopic, microbiological and molecular techniques were employed (DNA extraction, polymerase chain reaction and sequencing). For antimicrobial activity of algal extracts, Kirby–Bauer disck method was employed. Results: Results show a significant microfloral diversity in samples and a great number of taxa belonging to widely diffused genera such as Leptolyngbya sp., Nostoc sp., Scenedesmus sp., Navicula sp., and Amphora sp. Microbial communities indicate an absolute prevalence of a nonpathogenic flora, mostly composed of Bacillaceae. Conclusion: The association between the microbial and algal composition and the different maturation stages of thermal clay could represent an essential tool to identify markers of proper ripening. This ensures the best product quality and its beneficial properties. The extension of the study, characterizing the components of mud at different ripening times, consents the standardization of ripening process. Antimicrobial activity assay represents a preliminary step for subsequent analysis for the isolation of single component, employing analytical chemistry techniques, characterizing and identifying bioactive compounds of interest.