As　the　optimal　growth　temperature　of　Bacillus　licheniformis　is　relatively　higher　than　many　other　industrial　bacteria,　its　use　for　industrial　production　can　reduce　contamination　and　minimize　cooling　and　product　recovery　costs　during　fermentation　processes.　However,　little　is　known　about　the　thermotolerance　of　this　important　bacterial　species.　To　investigate　the　underlying　mechanism,　strains　B.　licheniformis　ATCC　14580　and　B186　were　cultivated　at　their　own　optimal　growth　temperature　(42　°C　and　50　°C)　and　higher　temperature　(60　°C),　respectively,　and　tandem　mass　tags　(TMT)-based　quantitative　proteome　analysis　and　bioinformatics　tools　were　employed　to　identify　differentially　expressed　proteins.　A　total　of　21　differential　proteins　were　identified　and　shown　to　participate　in　a　wide　range　of　biological　processes,　including　protein　refolding,　amino　acid　and　fatty　acid　metabolism,　etc.　Hence,　the　ability　of　B.　licheniformis　to　exhibit　optimal　growth　at　high　temperatures　may　depend　on　invoking　its　intrinsic　“heat-against”　proteomic　mechanism　for　long-term　viability.　Our　results　may　assist　the　genetic　improvement　of　industrial　strains　of　this　important　Bacillus　specie.　©　2017,　Springer-Verlag　Berlin　Heidelberg　and　the　University　of　Milan.