Phylogenetics and antibacterial properties of exopolysaccharides from marine bacteria isolated from Mauritius seawater

Abstract

Purpose The marine environment harbours diverse bacterial species which can be exploited for the production of valuable compounds such as exopolysaccharides (EPS) which hold promises for biotechnological applications. The coastal waters of Mauritius is a relatively underexplored marine environment and in this study, isolated bacterial species were tested for the production of EPS exhibiting antibacterial properties against human bacterial pathogens from the genera Acinetobacter, Bacillus, Campylobacter, Enterobacter, Enterococcus, Escherichia, Proteus, Pseudomonas, Salmonella, Streptococcus and Staphylococcus. Methods Bacteria were first isolated from seawater samples. Using the disc diffusion method, their EPS were tested for antibacterial effects through two screenings, with each involving a different set of arbitrarily chosen group of pathogens. The microorganisms producing antibacterial EPS were subsequently identified by morphological, biochemical and 16S rRNAbased phylogenetic analyses. Those EPS exhibiting broadest antibacterial activities were eventually characterised by Fouriertransform infrared spectroscopy (FTIR) and thin-layer chromatography (TLC). Results Eight EPS were found to display antibacterial effects against more than half of the pathogens and the microorganisms producing them were identified as Bacillus, Halomonas, Psychrobacter and Alcaligenes species. However, only two of these EPS were found to be the most active, with their MIC values ranging between 62.5 and 500 μg/ml. FTIR and TLC analyses revealed the presence of carboxyl, hydroxyl and amide as well as sulphate for the EPS, with glucose or fructose being the main sugar. Conclusion The results suggest that Mauritius seawater can be a source of biotechnologically useful microorganisms, producing EPS having potential as antimicrobial agents. DNA sequence data also suggest possible novel bacterial species.

Molecular Characterization and Biocompatibility of Exopolysaccharide Produced by Moderately Halophilic Bacterium Virgibacillus dokdonensis from the Saltern of Kumta Coast

“…Importantly, glucose, ribose, fructose, and xylose sugars are commonly found in various bacterial EPSs along with a few other monosaccharides [ 9 ]. For instance, the EPS produced by Halomonas venusta and Alcaligenes faecalis isolated from the seawater of Mauritius consists of mainly fructose and glucose sugars [ 52 ]. The EPS from Bacillus licheniformis T14 consists of fructose, fucose, and glucose as major monosaccharides [ 53 ].…”

Blue Biotechnology: Marine Bacteria Bioproducts

“…Low yields in nature are because EPS production requires 70% of cellular energy, e.g., in some cases, such as with Halomonas alkaliantarctica [81][82][83]. The production of EPSs is in competition with the formation of cell membrane components due to the metabolic pathways used to produce both compounds and their raw materials [74,84].…”

“…Within the medical field, EPSs have been used for treatments against arthritis [77], obesity, and colitis [72], as antivirals, antibacterials [84], and antioxidants, and some against certain types of cancer such as breast cancer, where it has been shown that they increase apoptosis in cancer cells [89].…”

Recent Antimicrobial Responses of Halophilic Microbes in Clinical Pathogens

“…Raffinose carbohydrate was significantly present in the HPLC analysis for the aforementioned EPS with a significant peak at a retention time of 3.910. Halophilic species such as Bacillus, Halomonas, Psychrobacter, and Alcaligenes produced eight EPS compounds with antimicrobial efficacies, and E15 strains were reported to be more active against B. cereus, S. aureus, S. saprophyticus, Enterobacter cloacae, Proteus mirabilis, MRSA, Enterococcus faecalis, Streptococcus pneumonia, Acinetobacter sp, and Campylobacter jejuni with MICs ranging between 250 and 500 µg/mL [120]. E37 also exhibited a wide antimicrobial activity with 250, 62.5, 125, and 500 µg/mL MICs, respectively, against the same pathogens mentioned above.…”