Abstract
The bacterium Moorella thermoacetica produces the most heat-resistant spores of any spoilage-causing microorganism known in the food industry. Previous work by our group revealed that the resistance of these spores to wet heat and biocides was lower when spores were produced at a lower temperature than the optimal temperature. Here, we used electron microcopy to characterize the ultrastructure of the coat of the spores formed at different sporulation temperatures; we found that spores produced at 55 °C mainly exhibited a lamellar inner coat tightly associated with a diffuse outer coat, while spores produced at 45 °C showed an inner and an outer coat separated by a less electron-dense zone. Moreover, misarranged coat structures were more frequently observed when spores were produced at the lower temperature. We then analyzed the proteome of the spores obtained at either 45 °C or 55 °C with respect to proteins putatively involved in the spore coat, exosporium, or in spore resistance. Some putative spore coat proteins, such as CotSA, were only identified in spores produced at 55 °C; other putative exosporium and coat proteins were significantly less abundant in spores produced at 45 °C. Altogether, our results suggest that sporulation temperature affects the structure and protein composition of M. thermoacetica spores.
Highlights
Published: 4 January 2022Endosporulation is an ancient mechanism, first appearing about 2 billion years ago, that allows Gram-positive bacteria to adapt to harsh environmental conditions
Spores of M. thermoacetica ATCC 39073 were produced on agar plates at either optimal growth temperature (55 ◦ C) or suboptimal temperature (45 ◦ C), with four batches of each
Coat Layers of Moorella thermoacetica Differ According to Sporulation Temperature
Summary
Published: 4 January 2022Endosporulation is an ancient mechanism, first appearing about 2 billion years ago, that allows Gram-positive bacteria to adapt to harsh environmental conditions. The structure of a spore differs greatly from that of vegetative cells, with the chromosome in a dehydrated core, surrounded by several concentric layers: the inner forespore membrane, the germ cell wall, the cortex, the outer forespore membrane, the coat layers, and an outer layer structure, called the crust in Bacillus subtilis and the exosporium in other species of Bacillus and Clostridium [2] This particular structure has been shown to provide the spores some ability to adhere to biotic and abiotic surfaces, as well as protection against various types of stress [1,2]. The cortex appears to play an important role in reducing the water content of the spore during spore formation, together with the accumulation of dipicolinic acid (DPA), a specific component of spores that complexes with
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