The book of Lambda does not tell us that naturally occurring lysogens of Escherichia coli are likely to be resistant as well as immune

Abstract

The most significant difference between bacteriophages functionally and ecologically is whether they are purely lytic (virulent) or temperate. Virulent phages can only be transmitted horizontally by infection, most commonly with the death of their hosts. Temperate phages can also be transmitted horizontally, but upon infection of susceptible bacteria, their genomes can be incorporated into that of their host’s as a prophage and be transmitted vertically in the course of cell division by their lysogenic hosts. From what we know from studies with the temperate phage Lambda and other temperate phages, in laboratory culture, lysogenic bacteria are protected from killing by the phage coded for by their prophage by immunity; where upon infecting lysogens, the free temperate phage coded by their prophage is lost. Why are lysogens not only resistant but also immune to the phage coded by their prophage since immunity does not confer protection against virulent phages? To address this question, we used a mathematical model and performed experiments with temperate and virulent mutants of the phage Lambda in laboratory culture. Our models predict and experiments confirm that selection would favor the evolution of resistant and immune lysogens, particularly if the environment includes virulent phage that shares the same receptors as the temperate. To explore the validity and generality of this prediction, we examined 10 lysogenic Escherichia coli from natural populations. All 10 were capable of forming immune lysogens, but their original hosts were resistant to the phage coded by their prophage.

Bacterial resistance to temperate phage is influenced by the frequency of lysogenic establishment

“…used model-based and in vitro experiments to show that temperate λ phage leads to similarly high levels of lysogenic and phage-resistant non-lysogenic E. coli after one day, whereas the presence of virulent λ phage results in a numerical dominance of the latter. 46 Not only are our results consistent with these observations, but we also show that even an increased frequency of lysis by temperate phages can lead to elevated phage resistance, reaching levels similar to those seen with a strictly lytic phage. For a greater understanding of this relationship between lysis/lysogeny by temperate phages and phage resistance in the host bacterium, more detailed genetic studies will be needed.…”

Valp1, a Newly Identified Temperate Phage Facilitating Coexistence of Lysogenic and Non-Lysogenic Populations of Vibrio anguillarum

“…A noteworthy aspect of our results is the persistence of the PF4 strain in co-culture with the lysogenic strain P1.1 in the presence of the Valp1 phage. This phenomenon has been explored by other authors in E. coli and the lambda phage, where it was observed that under similar conditions, a predominance of lysogenic bacteria and non-lysogenic strains resistant to the phage also occurred [ 40 ]. However, in that case, both bacterial population maintained a similar proportion.…”

Bacterial Virus Forcing of Bacterial O-Antigen Shields: Lessons from Coliphages

“…To my knowledge, the OPS protective efficiency has never been assessed on E. coli grown anaerobically and/or on starved cells that would better mimic the conditions in the human gut than actively growing aerobic cultures. Interestingly, the environmental E. coli isolates that were lysogenic by phages closely related to the phage lambda or by P2-like phages were not only immune to the phages encoded by their own prophages but also resistant to (unable to adsorb) these viruses [65]. The authors explain this finding by expected evolution of the resistance in lysogens that initially were only immune to phages.…”

“…I, however, speculate that the tested strains could be completely protected by the O antigen or rendered almost non-penetrable for lambda-like or P2-like phages. Unfortunately, the mechanism of the resistance observed [65] was not analyzed in the study.…”