The lysogenization of the non-O157 Escherichia coli strains by
stx-converting bacteriophage phi24B is associated with the O antigen
loss and reduced fitness
Abstract
Acquisition of new prophages that are able to increase the bacterial
fitness by lysogenic conversion is believed to be important strategy of
bacterial adaptation to changing environment. However, in contrast to
the factors determining the range of bacteriophage lytic activity,
little is known about the factors that define the lysogenization host
range. Bacteriophage phi24B is the paradigmal model of stx-converting
phages, encoding the toxins of the Shiga-toxigenic E. coli (STEC). This
virus has been shown to lysogenize the wide range of E. coli strains
that is much broader than the range of the strains supporting its lytic
growth. Therefore, phages produced by the STEC population colonizing the
small intestine are potentially able to lysogenize symbiotic E. coli in
the hindgut, and these secondary lysogens may contribute to the overall
patient toxic load and to lead to the emergence of new pathogenic STEC
strains. We demonstrate, however, that O antigen effectively limit the
lysogenization of the wild E. coli strains by phi24B phage. The lysogens
are formed from the spontaneous rough mutants and therefore have
increased sensitivity to other bacteriophages and to the bactericidal
activity of the serum if compared to their respective parental strains.