Cross-resistance between bacteriophages and colicins in Escherichia coli K-12

Cross-resistance between bacteriophages and colicins was studied using collections of bacteriophage- and colicin-resistant mutants of Escherichia coli K-12. No new examples were found of highly specific one-to-one cross-resistance of the type suggestive of common receptors. However, several groups of mutants showed tolerance to colicins and resistance to bacteriophages. Mutants known to be very defective in lipopolysaccharides composition were found to commonly show tolerance to certain colicins in addition to their bacteriophage resistance. Another group of mutants showed varying patterns of resistance to colicins E2, E3, K, L, A, S4, N, and X and bacteriophages E4, K2, K20, K21, K29, and H+. However, many bacteriophage-resistant mutants were fully colicin sensitive, and most colicin-resistant mutants were fully sensitive to bacteriophages.