Capsule Formation is Necessary for Kanamycin Tolerance in Escherichia coli K-12

Capsules play an important role in protecting bacteria from harmful substances such as antibiotics, by hindering entry into the cell and ability to reach the bacterial cytosol. The study investigated the effects of sucrose non-ionic osmotic stress on kanamycin tolerance in E. coli K-12 through the induction of capsule formation. Through the use of rcsB deletion mutant strain of E. coli deficient in capsule formation pathway, we explored the protective effects of capsular presence against kanamycin under sucrose osmotic stress conditions. Presence of functional capsule allowed for higher tolerance to bacteriocidal effects of kanamycin in E. coli, relative to the strains unable to form capsules. No notable induction of kanamycin tolerance was observed within wild type E. coli between the different sucrose osmotic treatments used. Ultimately, the results suggested that though the presence of a capsule is necessary for some tolerance to kanamycin, at the treatment concentrations used, sucrose osmotic stress does not result in additional tolerance to kanamycin.