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Abstract
Bacterial capsules can regulate the passage of molecules into cells, however it is not known whether they confer antibiotic resistance, and if this potential resistance is directed at specific classes of antibiotics. This study examined whether the Escherichia coli K12 capsule provides resistance to the antibiotics streptomycin and tetracycline. This potential resistance was investigated by comparing a strain with a deletion of the wza gene, which encodes a capsular polysaccharide transport protein, to wildtype cells. The amount of capsular polysaccharides produced by o o the ∆wza mutant was reduced compared to wildtype cells at 21 C, but not 37 C. A broth minimal inhibitory concentration (MIC) assay determined antibiotic susceptibility, and no difference between wildtype and the ∆wza mutant was observed. Additionally, both cell types were four times more susceptible to both antibiotics at 21°C relative to 37ºC. Taken together, these results indicate that the E. coli K12 capsule does not play a role in conferring resistance to either streptomycin or tetracycline.