The role of hydrolases in bacterial cell-wall growth

• Peptidoglycan hydrolases cleave bonds in the bacterial cell wall, causing expansion.
• Hydrolase activity can be a major determinant of growth rate and wall architecture.
• Sets of hydrolases essential for growth have been identified in several organisms.
• It is unknown how hydrolases are coordinated with PG synthesis and insertion.
• Hydrolysis drives membrane migration during forespore engulfment in B. subtilis.

Although hydrolysis is known to be as important as synthesis in the growth and development of the bacterial cell wall, the coupling between these processes is not well understood. Bond cleavage can generate deleterious pores, but may also be required for the incorporation of new material and for the expansion of the wall, highlighting the importance of mechanical forces in interpreting the consequences of hydrolysis in models of growth. Critically, minimal essential subsets of hydrolases have now been identified in several model organisms, enabling the reduction of genetic complexity. Recent studies in Bacillus subtilis have provided evidence for both the presence and absence of coupling between synthesis and hydrolysis during sporulation and elongation, respectively. In this review, we discuss strategies for dissecting the relationship between synthesis and hydrolysis using time-lapse imaging, biophysical measurements of cell-wall architecture, and computational modeling.