Insights into lactic acid bacteria cryoresistance using FTIR microspectroscopy

Area of Science:

• Microbiology
• Biophysics
• Analytical Chemistry

Background:

• Bacterial cell preservation using freezing is common, but cryoresistance varies significantly.
• Understanding the cellular basis of freezing tolerance is crucial for optimizing preservation techniques.

Purpose of the Study:

• To identify cellular markers of cryoresistance in lactic acid bacteria (LAB).
• To compare the freeze-tolerance of three distinct LAB strains: Carnobacterium maltaromaticum, Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, and Lactobacillus delbrueckii subsp. bulgaricus CFL1.

Main Methods:

• Cytoplasmic membrane properties (fatty acid composition, fluidity, lipid phase transition) were analyzed.
• Vitrification temperatures were quantified using differential scanning calorimetry.
• Fourier transform infrared (FTIR) microspectroscopy was employed for biochemical characterization of live bacteria.

Main Results:

• Multivariate analysis of FTIR spectra differentiated LAB strains based on lipid, protein, and peptidoglycan components.
• Freezing induced modifications in these components, particularly in freeze-sensitive L. bulgaricus strains, increasing cellular heterogeneity.
• Freeze-resistant C. maltaromaticum showed no observable cellular damage.

Conclusions:

• FTIR microspectroscopy can discriminate between LAB strains with different freezing tolerances.
• Specific infrared spectral band absorbance changes are potential novel markers for bacterial freeze-sensitivity.
• FTIR offers a rapid, non-invasive method for evaluating LAB freeze-sensitivity.