Identification and characterization of antibacterial compounds produced by Zymomonas mobilis .

Abstract

Antimicrobial resistance has emerged as a global threat, rendering many previously effective antibiotics ineffective against multidrug-resistant (MDR) microorganisms. The misuse and overuse of antibiotics in human healthcare and agriculture have contributed to the development of antibiotic-resistant bacteria. Although Zymomonas mobilis has been well studied for bioethanol production from lignocellulosic biomass. The specific compounds involved in the antibiotic activity of this bacterium remain unclear. So, this study focuses on the identification and characterization of antibacterial compounds produced by Z. mobilis. To evaluate the antibacterial activity, three strains of Z. mobilis were fermented in RM broth, and the resulting supernatants were tested against gram-positive, gram-negative, and multidrug-resistant bacteria. To do so, disk diffusion screening assays, the determination of minimum inhibitory concentrations, and the identification of antibacterial compounds through high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrophotometry (GC-MS) were carried out. In the crude extract phase, all three strains of Z. mobilis show antibacterial activity against marine fish pathogens such as Vibrio parahaemolyticus, Vibrio anguillarum, and Vibrio damsela. However, for the butanol crude extract, Z. mobilis strains gave antibacterial activity to all the marine fish pathogens and human pathogens, and even to Escherichia coli multi-drug resistance. Among both crude extracts, the ZM6 strain exhibited the highest antibacterial activity compared to the other strains. For the determination of minimum inhibitory concentration (MIC), V. parahaemolyticus was used and tested. The values of MIC of water phase crude extracts from all Z. mobilis strains tested were at 10 mg ml-1, in contrasts from the butanol crude extract, all the strains showed the same MIC value at 5 mg ml-1. Around 81 compounds were identified in both crude extracts using gas chromatography-mass spectrometry (GC-MS) analysis. Among those compounds, 17 compounds were potential active compounds that were responsible for antibiotic activity against V. parahaemolyticus. Then, two potential active compounds identified as secondary metabolite compounds, were further investigated for investigation of their synthetic pathways and associated genes using various bioinformatic tools. In conclusion, this study demonstrates the potential of Z. mobilis as a valuable resource for both bioethanol production and the discovery of active antibacterial compounds.