Abstract Authors
Jo-Marie Vreulink - Applied Microbial and Health Biotechnology Institute, Cape Peninsula University of Technology
Alaric Prins - Applied Microbial and Health Biotechnology Institute, Cape Peninsula University of Technology
Rosemary Dorrington - Antimicrobial Drug Discovery (ADD) Hub, Department of Biochemistry, Microbiology and Bioinformatics, Rhodes University
Marilize Le Roes-Hill - Applied Microbial and Health Biotechnology Institute, Cape Peninsula University of Technology
Abstract Description
The emerging global health threat of infections caused by Candida spp. is intensified by antifungal resistance. Therefore, there is an urgent need for the discovery of new antifungal drugs. Marine actinobacteria have been considered as an underexplored reservoir of novel bio-active compounds. Preliminary screening of actinobacteria strains isolated from marine sponges indicated that nine strains have anti-Candida activity. As such, this study aims to find novel antifungal compounds produced by these nine actinobacteria isolates. The genomes of the nine isolates were sequenced at CAF on the Ion Torrent GeneStudio TM S5 system using 200 bp chemistry. The assembled genomes were analysed by antiSMASH (https://antismash.secondarymetabolites.org/) to identify biosynthetic gene clusters (BGCs) potentially linked to anti-Candida activity. The genome sequences were also submitted to the Type Strain Genome Server (TYGS; https://tygs.dsmz.de/) to determine the phylogenomic positioning of the isolates. The isolates were tested for anti-Candida activity using the cross-streak method on International Streptomyces Project medium 2 (ISP2), starch-glucose-glycerol (SGG) and Medium 19 (M19), as well as these media supplemented with Red Sea Salt (RSS). The isolates were also cultivated in the same media for extract preparation. The extracts were screened for anti-Candida activity using the disk diffusion and Resazurin dye-based liquid assays. Eight isolates contained a BGC showing homology to the candicidin cluster. Submission of the genome sequences to TYGS indicated that these isolates potentially represent novel species belonging to the genus Streptomyces. The nine isolates displayed varied anti-Candida activity with the cross-streak method. In some cases the anti-Candida activity was enhanced by the supplementation of the media with RSS. The extracts prepared from the different liquid cultures also displayed anti-Candida activity. The anti-Candida activity displayed by the isolates may be as a result of the production of candicidin. Since the isolates represent novel species belonging to the genus Streptomyces, these isolates also have the potential to produce novel antifungal compounds. Future studies will be aimed at isolating and identifying the compounds responsible for the anti-Candida activity.
