Katodinium dorsalisulcum and Nitzschia closterium studies in ectocrinic compounds and their antimicrobial properties.

The object of this study was to determine antibiotic activity produced by the extracellular extracts of axenic cultures of marine algae. Research has shown that seawater itself is known to have antimicrobial activity which is attributed to the bactericidal compounds produced by marine organisms. In this study, two marine phytoplanktons were used in order to determine whether their extracellular polymeric substances (EPS) possessed antimicrobial properties. The species were the marine dinoflagellate Katodinium dorsalisulcum and the marine diatom Nitzschia closterium. The organisms were isolated from axenic cultures that were grown in an artificial sea water medium, (ASP8). The material was precipitated and purified by several chemical procedures. The purified extracts were tested for antimicrobial properties using the Kirby Bauer (1966), disk diffusion method of analysis. In this method, paper disks were impregnated with the extract obtained and incubated with known bacterial species on two different media; Mueller Hinton agar and Tryptic Soy agar. The zones of inhibition obtained were analyzed in order to determine the type of microorganism on which he extract would have the most pronounced effect. These tests were conducted on the liquid extract, 100% solid extract and the 50% diluted solid extract of the phytoplankton cultures. The results were compared with other standard antibiotics that address the four main methods of antibiotic action: inhibition of cell wall synthesis, inhibition of cell membrane synthesis, inhibition of nucleic acid synthesis, inhibition of protein synthesis. In addition to this, carbohydrate and amino acid tests were conducted on the extracts in order to determine the percent concentration of carbohydrate and amino acids present and to determine whether this contributed to the antimicrobial properties of these organisms.