GNPS_Fractionation of strain 142 and 5

Extracts of two most promising strains were subjected to activity-guided fractionation and determination of the fraction minimum inhibitory concentration (MIC) against selected bacterial and fungal isolates. Multiple fractions were responsible for their antimicrobial effect with MIC reaching low-micromolar concentrations and in some of them high level of specificity was recorded. Twenty-six bioactive fractions analyzed on LC-HRMS/MS and Global Natural Product Social Molecular Networking (GNPS) online workflow using dereplication resulted in identification of only forty-nine peptide spectrum matches (PSMs) with eleven unique metabolites spectrum matches (MSMs). Interestingly only three fractions from Nostoc calcicola Lukesova 3/97 and strain 5 and four fractions from Desmonostoc sp. Cc2 strain 142 showed the presence of unique MSMs suggesting the presence of unknown antimicrobial metabolites among majority of bioactive fractions from both the strains.