Molecular Physiological Characterization of a High Heat Resistant Spore Forming Bacillus subtilis Food Isolate

Abstract

Bacterial endospores (spores) are among the most resistant living forms on earth. Spores of Bacillus subtilis A163 show extremely high resistance to wet heat compared to spores of laboratory strains. In this study, we found that spores of B. subtilis A163 were indeed very wet heat resistant and released dipicolinic acid (DPA) very slowly during heat treatment. We also determined the proteome of vegetative cells and spores of B. subtilis A163 and the differences in these proteomes from those of the laboratory strain PY79, spores of which are much less heat resistant. This proteomic characterization identified 2011 proteins in spores and 1901 proteins in vegetative cells of B. subtilis A163. Surprisingly, spore morphogenic protein SpoVM had no homologs in B. subtilis A163. Comparing protein expression between these two strains uncovered 108 proteins that were differentially present in spores and 93 proteins differentially present in cells. In addition, five of the seven proteins on an operon in strain A163, which is thought to be primarily responsible for this strain’s spores high heat resistance, were also identified. These findings reveal proteomic differences of the two strains exhibiting different resistance to heat and form a basis for further mechanistic analysis of the high heat resistance of B. subtilis A163 spores.

Resistance properties and the role of the inner membrane and coat of Bacillus subtilis spores with extreme wet heat resistance

“…In addition to the factors noted above, an additional factor important in spore wet heat resistance was reported recently (Berendsen, Krawczyk, et al, 2015a; Berendsen, Zwietering, et al, 2015b; Berendsen, Boekhorst, et al, 2016a; Berendsen, Konings, et al, 2016b; den Besten et al, 2018; Tu et al, 2021). This factor is a transposable genetic element in spores with extremely high wet heat resistance, such that B .…”

What’s new and notable in bacterial spore killing!

“…The α/β-type SASP also protect DNA against wet heat damage, and CaDPA may assist in protecting DNA from some damage by immobilizing it (Setlow et al 2006 ), although generally not against radiation induced damage. Notably, recent work has found an additional factor capable of protecting spores against wet heat, which is genes expressed from a transposon found in spores of some Bacillus species making extremely wet heat-resistant spores (Krawczyk et al 2016 , 2017 ; Luo et al 2021 ; Tu et al 2021 ). The same transposon is also associated with enhanced resistance against high pressure (Li et al 2019 ).…”

“…A final area of concern going forward is the appearance of new strains that make spores with much greater resistance properties. Indeed, this is the case for spores of some Bacillus strains that can resist normal food processing temperatures used for wet heat (Krawczyk et al 2016 , 2017 ; Li et al 2019 ; Tu et al 2021 ). It seems even likely that food processing regimens have selected for the highly resistant spores.…”

Soybean Oil Regulates the Fatty Acid Synthesis II System of Bacillus amyloliquefaciens LFB112 by Activating Acetyl-CoA Levels

“…Bacillus species have been used as probiotics for at least 50 years and are commonly employed as growth promoters and competitive exclusion agents in animal production [ 9 ]. This is attributed to their high-temperature resistance [ 10 , 11 ], acid and alkali resistance [ 12 , 13 ], ease of culture, storage stability, and low processing loss [ 13 , 14 , 15 ]. Amongst these species, Bacillus subtilis is a typical representative; its subordinate strain, Bacillus amyloliquefaciens, can secrete various protein-active substances.…”