Antimicrobial Activity and Enzymatic Production of Aquatic Invertebrate-Associated Bacteria

Epibiosis represents a close association with direct or indirect interactions between a substrate and sessile organisms. Here, we studied the microepibionts associated with aquatic invertebrates and their antimicrobial potential and enzymatic activities. Thus, jellyfish (Rhizotoma pulmo), ascidians (Phallusia mammillata), aplysia (Aplysia fasciata) and sea cucumber (Holothuria tubulosa) were sampled from the Gulf of Tunis region, and their bacterial epibionts from different organs were isolated and identified. A total collection of 123 isolates was identified and studied for its antimicrobial potential, antibiotic resistance, production of exoenzymes and molecular 16S ribosomal DNA sequencing. The results showed mostly Gram- specified as Enterobacter hormaechei (97%) and Shewanella baltica (96%) from Rhizostoma pulmo, Gammaproteobacterium (92%), Shewanella livingstonensis (95%), Shewanella putrefaciens (98%) and Shewanella sp (98%) from Aplysia fasciata, two Citrobacter freundii (95% and 87%) from Holothuria tubulosa, Pseudomonas sp (88%) and Shewanella putrefaciens (98%) from Phallusia mammillata. The agar overlay inhibition method revealed an antagonistic potential for 22 isolates with large spectrum of inhibition. Besides, these isolates produced various extracellular hydrolytic enzymes including: chitinase, hemolysis, lecithinase, gelatinase, amylase, lipase and cellulase. These results suggested the importance of bacteria epibionts associated with aquatic invertebrates, given their antimicrobial potential and their high capacity to produce hydrolytic enzymes and their roles in biological and ecological survey of the invertebrate remain to be explored previously in their biotechnological uses.