Abstract
The cell wall plays a central role in protecting bacteria from some environmental stresses, but not against all. In fact, in some cases, an elaborate cell envelope may even render the cell more vulnerable. For example, it contains molecules or complexes that bacteriophages recognize as the first step of host invasion, such as proteins and sugars, or cell appendages such as pili or flagella. In order to counteract phages, bacteria have evolved multiple escape mechanisms, such as restriction-modification, abortive infection, CRISPR/Cas systems or phage inhibitors. In this perspective review, we present the hypothesis that bacteria may have additional means to escape phage attack. Some bacteria are known to be able to shed their cell wall in response to environmental stresses, yielding cells that transiently lack a cell wall. In this wall-less state, the bacteria may be temporarily protected against phages, since they lack the essential entities that are necessary for phage binding and infection. Given that cell wall deficiency can be triggered by clinically administered antibiotics, phage escape could be an unwanted consequence that limits the use of phage therapy for treating stubborn infections.
Highlights
Bacteriophages, or phages, are viruses that infect bacteria
We will start with discussing the detailed structure of the bacterial cell envelope and its specific components that enable phage attachment to their hosts
We discuss the ability of several bacteria to shed their cell wall under influence of stressors and the consequences of a cell wall-deficient (CWD) lifestyle
Summary
Bacteriophages, or (in short) phages, are viruses that infect bacteria. It has been estimated that they outnumber bacteria in the biosphere by a factor of 10 and are present in almost all natural environments [1,2]. As phages are non-motile microorganisms, it is presumed that the initial contact between a phage and a suitable host occurs via random collisions as a result of free diffusion [3] Phages recognize their host species by interacting with specific receptors, especially sugars and proteins, exposed on the bacterial cell surface. We propose that the ability of bacteria to shed their wall may be an underappreciated mechanism to evade phage infection, as phages may no longer be able to recognize their host. In this perspective review, we will start with discussing the detailed structure of the bacterial cell envelope and its specific components that enable phage attachment to their hosts. Since cell wall-less states have been reported to occur in pathogenic species [4,5], this evasion mechanism may be highly relevant for the development of phage therapy treatments
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