Short-Chain and Unsaturated Fatty Acids Increase Sequentially From the Lag Phase During Cold Growth of Bacillus cereus

Fatty acids of two mesophilic and one psychrotrophic strains of the foodborne pathogen Bacillus cereus were analyzed by gas chromatography coupled to mass spectrometry during growth at cold (10 and 12?degrees C) vs. optimal (30?degrees C) temperatures and during the whole growth process (6-7 sampling times) from lag to stationary phase. In all these strains, a sequential change of fatty acids during cold growth was observed. Fatty acids were modified as soon as the end of lag, with an increase of the short-chain fatty acids (less than 15 carbons), particularly i13. These short-chain fatty acids then reached a maximum at the beginning of growth and eventually decreased to their initial level, suggesting their importance as a rapid cold adaptation mechanism for B. cereus. In a second step, an increase in delta???????(5,10) di-saturated fatty acids and in monounsaturated fatty acids in delta???????(5) position, at the expense of unsaturation in delta(10), started during exponential phase and continued until the end of stationary phase, suggesting a role in growth consolidation and survival at cold temperatures. Among these unsaturated fatty acids, those produced by unsaturation of n16 increased in the three strains, whereas other unsaturated fatty acids increased in some strains only. This study highlights the importance of kinetic analysis of fatty acids during cold adaptation.

Automated summary

The study observed sequential changes of fatty acids in Bacillus cereus during cold growth process, with short-chain fatty acids increasing rapidly in the early growth stage and then decreasing, followed by an increase in saturated and monounsaturated fatty acids, contributing to growth consolidation and survival at cold temperatures. Unsaturated fatty acids, particularly those from unsaturation of n16, increased in all three strains, highlighting the importance of kinetic analysis of fatty acids during cold adaptation.