About this Research Topic
Bacterial cells are encased in a cell wall, which is required to maintain cell shape and to confer physical strength to the cell. The cell wall allows bacteria to cope with osmotic and environmental challenges and to secure cell integrity during all stages of bacterial growth and propagation, and thus has to be sufficiently rigid. Moreover, to accommodate growth processes, the cell wall at the same time has to be a highly dynamic structure: During cell enlargement, division, and differentiation, bacteria continuously remodel, degrade, and resynthesise their cell wall, but pivotally need to assure cell integrity during these processes. Finally, the cell wall is also adjusted according to both environmental constraints and metabolic requirements. However, how exactly this is achieved is not fully understood.
The structural component of the bacterial cell wall is peptidoglycan (PG), a mesh-like polymer of glycan chains interlinked by short-chain peptides, constituting a net-like macromolecular structure that has historically also termed murein or murein sacculus. Although the basic structure of PG is conserved among bacteria, considerable variations occur regarding cross-bridging, modifications, and attachments. Moreover, different structural arrangements of the cell envelope exist within bacteria: a thin peptidoglycan layer sandwiched between an inner and outer membrane is present in Gram-negative bacteria, and a thick peptidoglycan layer decorated with secondary glycopolymers including teichoic acids, is present in Gram-positive bacteria. Furthermore, even more complex envelope structures exist, such as those found in corynebacteria or mycobacteria.
Crucially, all bacteria possess a multitude of often redundant lytic enzymes, termed “autolysins”, and other cell wall modifying and synthesizing enzymes, allowing to degrade and rebuild the various structures covering the cells. However, how cell wall turnover and cell wall biosynthesis are coordinated during different stages of bacterial growth is currently unclear. The mechanisms that prevent cell lysis during these processes are also unclear.
This Research Topic focuses on the dynamics of the bacterial cell wall, its modifications, and structural rearrangements during cell growth and differentiation. It pays particular attention to the turnover of peptidoglycan, its breakdown and recycling, as well as the regulation of these processes. Other structures, for example, secondary polymers such as teichoic acids, which are dynamically changed during bacterial growth and differentiation, are also covered.
In recent years, our view on the bacterial cell envelope has undergone a dramatic change that challenged old models of cell wall structure, biosynthesis, and turnover. This collection of articles aims to contribute to new understandings of bacterial cell wall structure and dynamics.
Keywords: microbial glycobiology, peptidoglycan turnover, cell wall recycling, cell wall remodelling, autolysins and autolysis, amino sugar metabolism, carbohydrate-active enzymes