Identification of antibacterial metabolites produced by a marine bacterium Halobacillus marinus HMALI004

Abstract

Aims: This study examined and characterized the extract for metabolites of Halobacillus marinus HMALI004 to understand their antibacterial activities against opportunistic marine pathogens, that is, Vibrio parahaemolyticus and Vibrio cholerae. Methods and Results:The bacterial strain HMALI004 was characterized as H. marinus, and an antibacterial spectral test revealed its inhibition against two opportunistic marine pathogens (V. parahaemolyticus and V. cholera). Fermentation broth of strain HMALI004 was subjected to column chromatography and highperformance liquid chromatography to separate antibacterial substances. Two compounds were successfully isolated and identified as 1H-pyrrole-2-carboxylic acid and 4-chloro-1H-pyrrole-2-carboxylic acid by mass spectrometry (MS) and nuclear magnetic resonance. The minimal inhibition concentration (MIC) values of 1H-pyrrole-2-carboxylic acid and 4-chloro-1H-pyrrole-2-carboxylic acid for V. parahaemolyticus were 25 μg/ml, while their MIC values for V. cholerae were 50 and 100 μg/ml, respectively. The reactive oxygen species (ROS) production of two pathogen strains treated with 1H-pyrrole-2-carboxylic acid and 4-chloro-1H-pyrrole-2-carboxylic acid were detected to investigate the antimicrobial mechanism. The results suggested that 4-chloro-1H-pyrrole-2-carboxylic acid exerted enhanced ROS production in V. parahaemolyticus, whereas 1H-pyrrole-2-carboxylic acid had a weaker effect. Both compounds caused a significant rise in ROS production in V. cholerae, causing severe damage to the cell wall and cytoplasm, leading to cell death. Conclusions:The bacterium H. marinus HMALI004 was isolated from a shrimp pond and was found to produce antimicrobial compounds, which could inhibit the growth of opportunistic marine pathogens V. parahaemolyticus and V. cholerae by increasing ROS.Significance and Impact of the Study: Successfully isolated antibacterialproducing strain, H. marinus HMALI004, and its antimicrobial compounds could be used as biological control agents for marine pathogens.

Contribution of the Types of Tropical Coastal Aquaculture Ponds to the Differential Distribution of the Family Bacillaceae Bacterial Community

“…B. hwajinpoensis was frst isolated from sea water from Hwajinpo Beach, East Sea in Korea [30], and its heterotrophic nitrifcation-aerobic denitrifcation efects on water purifcation by removing inorganic nitrogen and total nitrogen were subsequently reported [31]. Halobacillus as a major ecosystem-adapted microbial component could survive from extreme environments due to its stronger survivability and fexible adaptability, such as salt lakes, hypersaline sediments and soils [32][33][34]. Some reporters have reported its outstanding capacity of inhibiting fungi activity thereby promoting the growth of plants [34,35], while some reporters have reported that Halobacillus from a shrimp pond exhibited antibacterial potencies against the opportunistic marine pathogens of Vibrio parahaemolyticus and Vibrio cholerae by producing antimicrobial compounds [32].…”

“…Halobacillus as a major ecosystem-adapted microbial component could survive from extreme environments due to its stronger survivability and fexible adaptability, such as salt lakes, hypersaline sediments and soils [32][33][34]. Some reporters have reported its outstanding capacity of inhibiting fungi activity thereby promoting the growth of plants [34,35], while some reporters have reported that Halobacillus from a shrimp pond exhibited antibacterial potencies against the opportunistic marine pathogens of Vibrio parahaemolyticus and Vibrio cholerae by producing antimicrobial compounds [32]. Meanwhile, although some unique Bacillaceae genera was presented in the earthen ponds, such as Talassobacillus, Paenibacillus, Fictibacillus, Ornithinibacillus, Oceanobacillus, Solibacillus, Lysinibacillus, Virgibacillus, and Brevibacillus, the concentration of these bacteria was not high.…”

Metagenomic assembled genomes indicated the potential application of hypersaline microbiome for plant growth promotion and stress alleviation in salinized soils

“…In addition to assisting the hypersaline microflora in maintaining regular metabolic processes and osmotic balance maintenance, the compatible solutes also prevent microbial proteins from denaturation, increasing their capacity to withstand significant changes in the surrounding saline environment ( 7 ). Since hypersaline microflora are well adapted to extreme salt conditions, they have garnered significant interest in various biotechnological applications ( 8 – 11 ). Their diverse metabolic capabilities and resilience to extreme environments have made them valuable candidates.…”