The fatty acid composition and freeze–thaw resistance of eight strains of
thermophilic lactobacilli were studied. Seven of these contained the same polar and
neutral lipids, the five major components making up 90% of the cellular fatty acid
pool being 14[ratio ]0, 16[ratio ]0, 16[ratio ]1, 18[ratio ]1 and C19 cyclopropane (cyc19[ratio ]0). Strain comparison
by means of cluster analysis based on the fatty acid ratios using the overlap
coefficient revealed two well defined clusters. One was formed by three strains of
species Lactobacillus delbrueckii subsp. lactis and Lb. delbrueckii subsp. delbrueckii,
the other included five strains of the species Lb. delbrueckii subsp. bulgaricus, Lb.
acidophilus and Lb. helveticus. Resistance of strains with a high content of
unsaturated fatty acids (66–70%) decreased with increasing cyc19[ratio ]0 concentrations.
In contrast, in strains with a low concentration of unsaturated fatty acids (42–49%),
increasing cyc19[ratio ]0 levels were associated with increased freeze–thaw resistance.