Among the soil bacteria of the spore former genus Bacillus, the human pathogens mostly belong to the B. cereus group. This species is divided in seven phylogenetic groups, with particular traits in virulence, and particular growth temperature ranges, where each of these seven phylogenetic groups corresponds to a specific ‘thermotype’, showing clear differences in ability to grow at low or high temperatures. After a temperature downshift, changes that occur in the bacterial cell include a decrease of the membrane fluidity, a stabilization of secondary structures of nucleic acids which consequently causes a decreased efficiency in transcription and translation, a misfolding of some proteins, etc. The bacterial cell response involves various mechanisms which, among the Bacillus genus, have been mostly studied in Bacillus subtilis. This chapter focuses on current research about B. cereus low-temperature adaptation, compared to what is well described in B. subtilis.