Abstract
Antibiotic resistance is a global crisis and antimicrobial peptides or bacteriocins are the ascending alternatives. This study is reporting a potential bacteriocin from B. subtilis (MK733983) of ethnomedicinal origin showing significant activity with Mycobacterium smegmatis as an indicator organism on spot-on-lawn assay. Production optimization with suitable physical parameters such as modified lysogeny broth [1.5% peptone; 0.75% salt; 0.75% yeast], temperature [35 °C], pH [7], inoculum size [1%] and time course [24 h] has enhanced the activity up to 20%. This study also observed that supplements like minimal essential medium amino acids and B complex vitamins individually has further enhanced the bacteriocin activity by 13% (total 33%), biomass by 43%, total protein and activity by 17% and 22% respectively. However, addition of some common growth supplements like multivitamins with trace elements, CaCl2 and MgSO4 had shown inhibitory effect on bacteriocin activity. Molecular weight of the bacteriocin was estimated to be below 14kDa and bioassay guided TLC techniques showed distinctive antibacterial activity. The bacteriocin completely lost its activity with Trypsin, α-Chymotrypsin, Proteinase K but not with Amylase, and showed up to 40% activity with Papain. It showed heat stability up to 70°C with a wide antibacterial spectrum against standard strains of Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Chromobacterium violaceum with minimal inhibitory concentrations ranging between 0.325±0.02-0.75±0.02mg/mL, suggesting the bacteriocin may have wide application prospects.
Highlights
Antimicrobial resistance (AMR) has become an escalating global burden with an increase in the microbial resistance endangering the efficacy of antibiotics across all socio-economic backgrounds, with other complicated risks such as drug-drug interactions, hospital acquired infections and others posing a serious challenge (Ventola, 2017)
Present study was focused on optimizing B. subtilis (MK733983) strain capable of producing a potential antimycobacterial bacteriocin with M. smegmatis as an indicator microorganism (IMO)
The bacteriocin preparation is described in detail by Santhi & Aranganathan (2019) and production optimization was determined step-by-step, advancing to parameter with already optimal factors and their bacteriocin activity was determined by 30 μL of each of bacteriocin (1mg/mL) loaded into 6 mm wide wells made in LB agar plates pre-swabbed with 100 μL of M. smegmatis (106 CFU/mL) as an indicator and zone of inhibition (ZOI) in mm was taken as a measure of antimicrobial activity (Tagg & McGiven, 1971)
Summary
Antimicrobial resistance (AMR) has become an escalating global burden with an increase in the microbial resistance endangering the efficacy of antibiotics across all socio-economic backgrounds, with other complicated risks such as drug-drug interactions, hospital acquired infections and others posing a serious challenge (Ventola, 2017). Some bacterial species produce biologically active proteins or peptides known as peptide antibiotics, known as bacteriocins (Zhang et al, 2018). Many of these ribosomally synthesized peptides or proteins are known to have narrow spectrum, inhibiting the bacteria that are taxonomically close, but a few others are known to be broad spectrum (Silva et al, 2018). Characterization of the biologically active compounds like bacteriocins is pivotal for comprehensive understanding of their scope in their future potential as therapeutic agents, preservatives, or other uses. Antibacterial Inhibition spectrum of the bacteriocin was tested against some standard strains of gram positive and negative bacteria that fall under WHO critical and high priority pathogen list (WHO report, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
