Antimicrobial Activities of Bacteriocin-Like Extracellular Metabolites Produced by Soil Bacteria

Abstract

In an attempt to competitively inhibit other organisms within the same environment, microbial cells produce a wide range of bioactive bacteriocins and bacteriocin-like extracellular metabolites (BLEM). Bacterial species (Bacillus and Pseudomonas) were isolated from soil samples, screened for BLEM production and the crude activity of cell free metabolites determined by agar diffusion assay. Partial purification of metabolites was achieved by protein precipitation with ammonium sulfate and BLEM sensitivities to temperature, pH, surfactant and ultraviolet radiation along with the mode of action of partially purified BLEM on indicator strains and other pathogens were characterized. Bacillus subtilis SF8 and Pseudomonas aeruginosa SF4 produced BLEM inhibitory to closely related strains with partially purified activity units of 768 and 2048AU/mL respectively. BLEMs retained large percentages of their inhibitory activities over a wide range of temperature and pH, 71%, 92% and 80% activity was retained by BLEM from B. subtilis SF8 while 91%, 81% and 89% activity was retained by BLEM from P. aeruginosa SF4 after 60 minutes of BLEM preincubation at 90 0 C, pH 4 and 10, respectively. Ultraviolet radiation enhanced BLEM production in P. aeruginosa SF4 but not in B. subtilis SF8. Fourier Transformed Infrared (FTIR) spectroscopy revealed that BLEMs from both B. subtilis SF8 and P. aeruginosa SF4 interfered with cell membrane components of B. macerans SF2 and P. fluorescence BS2 respectively. The BLEM also had a broad inhibitory range on test bacterial and fungal pathogens.

Overview of Global Trends in Classification, Methods of Preparation and Application of Bacteriocins

“…A characteristic feature of the saposin fold is the presence of a V-shaped segment formed by three spirals. The cationic surface charge of bacteriocins of this subgroup provides interaction with target bacterial membranes with subsequent pore formation [ 48 ]. Acidocin B belonging to subgroup II is four helices connected by a hydrophobic core.…”

“…It is considered that the receptor of this group of peptides is the mannose-phosphotransferase transport complex (Man-PTS). The IIC Man-PTS enzyme contains extracellular loops that interact with bacteriocins, resulting in the penetration of the peptide into the membrane and the formation of pores with subsequent cell death [ 48 , 63 ].…”

Characterization and statistical optimization of γ-PGA produced by Bacillus megaterium UP47 isolated from Pentaclethra macrophylla

“…All samples (10 g or 10 mL) were heated in a boiling GFL 1083 shaker water bath (GFL Technology, Senden, Germany) for 15 min to kill off non-sporulating microbial cells and thus enhance the isolation of more Bacillus species, mixed with 90 mL sterile distilled water, vortexed vigorously and serially diluted. Different dilutions (1 mL) from each sample were aseptically transferred into 90 mm sterile disposable Petri dishes, plated out on nutrient agar and solidified PPM agar, and incubated at 30°C for 24-48 h. 19 Morphologically distinct bacteria from inoculated Petri dishes were subcultured onto nutrient agar plates to obtain pure cultures. The pure cultures were stored on nutrient agar slants in a refrigerator and in 25% glycerol nutrient broth at −20°C.…”