Genetic evaluation of bile salt resistance and sensitivity in a subculture of Escherichia coli K-12 substrain JC3272

Abstract

Though most Escherichia coli strains are adapted to survival in environments with high concentrations of bile salts, some mutant strains lack this ability. Prior work has reported that a spontaneous mutant of the K-12 strain JC3272 is sensitive to bile salts. To test this, cultures of this mutant (JC3272I) and a non-mutant strain (JC3272F) were evaluated on both solid and liquid media containing bile salts. Amplification of the lapA and lapB genes—which are hypothesized to affect bile salt sensitivity—was achieved in both strains via polymerase chain reaction. A combination of Sanger and Illumina sequencing was then used to compare the amplified genes and to produce whole-genome sequences. Culturing confirmed a difference in sensitivity to bile salts between the two strains. However, sequencing did not reveal any differences between the strains in the lapAB region. Furthermore, no mutations found via whole-genome sequencing had known roles in bile salt resistance. These results may imply the existence of an unpublished mechanism of bile salt resistance in E. coli.