Moorella thermoacetica spores are the most heat-resistant so far retrieved in food industry and we previously showed that the resistance properties of these spores to wet- heat and biocides were lower when spores were produced at low limit temperature than at optimal temperature. By electron microcopy, we observed that the ultrastructure of the spore coat differed according to the sporulation temperature, with spores produced at 55 °C mainly exhibiting lamellar inner coat tightly associated to diffuse outer coat, while spores produced at 45 °C showing an inner and outer coat separated by a less electron- dense zone. Moreover, misarranged coat structures were more frequently observed when spores were produced at low limit temperature. We analyzed the proteome of spore ob- tained at 45° and 55 °C and focused our data analysis on putative spore coat, exosporium proteins or proteins playing a role in spore resistance. Some putative spore coat proteins, such as CotSA, were only identified in spores produced at 55 °C, while some other puta- tive 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 the protein composition of M. thermoacetica spores.