Babar, TKGlare, TravisHampton, JohnHurst, MRHNarciso, JOBeattie, A2022-12-072022-09-252022-102022-09-215T6JF (isidoc)https://hdl.handle.net/10182/15710Brevibacillus laterosporus (Bl) is a Gram-positive and spore-forming bacterium belonging to the Brevibacillus brevis phylogenetic cluster. Globally, insect pathogenic strains of the bacterium have been isolated, characterised, and some activities have been patented. Two isolates, Bl 1821L and Bl 1951, exhibiting pathogenicity against the diamondback moth and mosquitoes, are under development as a biopesticide in New Zealand. However, due to the suspected activity of putative antibacterial proteins (ABPs), the endemic isolates often grow erratically. Various purification methods, including size exclusion chromatography, sucrose density gradient centrifugation, polyethylene glycol precipitation, and ammonium sulphate precipitation employed in this study, enabled the isolation of two putative antibacterial proteins of ∼30 and ∼48 kD from Bl 1821L and one putative antibacterial protein of ∼30 kD from Bl 1951. Purification of the uninduced cultures of Bl 1821L and Bl 1951 also yielded protein bands of ∼30 and ∼48 kD on SDS-PAGE, which indicated their spontaneous induction. A disc diffusion assay was used to determine the antagonistic activities of the putative ABPs. Subsequent transmission electron microscope (TEM) examination of a purified putative antibacterial protein-containing solution showed the presence of encapsulin (∼30 kD) and polysheath (∼48 kD)-like structures. Although only the ∼30 kD protein was purified from Bl 1951, both structures were seen in this strain under TEM. Furthermore, while assessing the antibacterial activity of some fractions of Bl 1951 against Bl 1821L in the size exclusion chromatography method, the population of Bl 1821L persister cells was noted. Overall, this work added a wealth of knowledge about the purification of the high-molecular-weight (HMW) proteins (bacteriocins) of Gram-positive bacteria including Bl.16 pagesen© 2022 by the authors. Licensee MDPI, Basel, Switzerland.antibacterial proteinsencapsulating proteinhigh molecular-weight bacteriocinsinsect pathogenic bacteriumphage tail-like proteinpurification methodsJournal Article10.3390/pr101019322227-97172022-11-21ANZSRC::310510 Molecular evolutionANZSRC::300409 Crop and pasture protection (incl. pests, diseases and weeds)ANZSRC::310701 BacteriologyANZSRC::310799 Microbiology not elsewhere classifiedANZSRC::300103 Agricultural molecular engineering of nucleic acids and proteinsANZSRC::4004 Chemical engineeringhttps://creativecommons.org/licenses/by/4.0/Attribution