Reversible bacteriophage resistance by shedding the bacterial cell wall

Abstract

Phages are highly abundant in the environment and pose a major threat for bacteria. Therefore, bacteria have evolved sophisticated defence systems to withstand phage attacks. Here, we describe a previously unknown mechanism by which mono- and diderm bacteria survive infection with diverse lytic phages. Phage exposure leads to a rapid and near-complete conversion of walled cells to a cell-wall-deficient state, which remains viable in osmoprotective conditions and can revert to the walled state. While shedding the cell wall dramatically reduces the number of progeny phages produced by the host, it does not always preclude phage infection. Altogether, these results show that the formation of cell-wall-deficient cells prevents complete eradication of the bacterial population and suggest that cell wall deficiency may potentially limit the efficacy of phage therapy, especially in highly osmotic environments or when used together with antibiotics that target the cell wall.

A Flexible and Efficient Microfluidics Platform for the Characterization and Isolation of Novel Bacteriophages

“…3B and C ). This resembles our previously reported observations that described a phage-induced escape mechanism that allows the bacterial cell to shed its cell wall and thereby evade phage predation ( 12 , 19 ). By exposing these spherical cells to water, we observed that the majority of cells were lysed, which indicates that these are likely not spores but indeed cell wall-deficient cells as described in Ongenae et al ( 12 , 19 ) (Fig.…”

“…The thin glass bottom ( 26 , 27 ), fixation of motile bacteria in a matrix, and barrier-free separation of bacteria and phages by the phaseguide allow for improved long-term imaging that can capture small details such as a change in bacterial cell shape. This is illustrated by the observation of the formation of cell wall-deficient cells in response to phage predation ( 12 ). Likely, this behavior went unnoticed previously due to the limited imaging quality possible with a 96-well plate setup.…”

“… B. subtilis is capable of producing spores in conditions of environmental stress ( 30 ). However, the striking similarity in size and appearance to the wall-less cells that form under phage attack makes this interpretation possible but less likely ( 12 ). In either case, the setup allows not only for the isolation of new phages but simultaneously allows for the study of the host response.…”

“…In an initial application, we have previously tested the application of a versatile plate-based platform to study bacteria-phage interactions ( 12 ). Here, we thoroughly test, expand, and describe this setup to allow the screening of bacteriophage activity in a spatially efficient and high-throughput manner without the need for external pumps or tubing.…”

L-form conversion in Gram-positive bacteria enables escape from phage infection

“…Therefore, L-form research has mostly addressed their possible role as persisters in chronic or recurrent infections [16][17][18][19] . While it has been pointed out previously that L-forms or wall-deficient cells may also confer resistance to phage infection [20][21][22][23] , the biological relevance of this phenomenon remained elusive because no clear link between phage infection and L-form emergence has yet been demonstrated. Here we investigate the effects of phage infection on the emergence of bacterial L-forms, using Listeria monocytogenes and phage A006.…”