Peptidoglycan hydrolysis and Cortex-lytic enzymes

Maintenance of the relatively low water content of the spore protoplast - which is crucial to the spore's properties of heat resistance and metabolic dormancy - appears to be the major role of the conspicuously thick layer of structurally-unique peptidoglycan (cortex) that surrounds the primordial cell-wall and spore core.  Subsequent to germinant-receptor initiated events, which includes the movement of various analytes out of the spore core and an initial influx of water, the spore must degrade the cortex - via the activation of cortex-lytic enzymes (CLEs) - to permit complete hydration of the core, resumption of metabolic activity and eventual emergence of a new vegetative cell.

Construct Isik Ustok; Image Jamie Walters

Research conducted by the Molecular Microbiology group to date has focused upon the combined application of molecular genetic, HPLC and mass spectrometry techniques to investigate structural changes that occur at the molecular level to the spore cortical peptidoglycan during germination.  Additionally, the assignment of putative hydrolytic and/or peptidoglycan modification properties associated with several defined CLEs, and associated proteins, that are involved in the germination of spores of the model-spore former Bacillus megaterium, has been achieved also.

Currently we are using fluorescence microscopy to assist with in vivo localisation studies, plus various biophysical techniques to investigate the molecular mechanisms responsible for the maintenance of spore CLEs in an inactive state during dormancy, and the means by which they are activated during germination.

Peptidoglycan fragments generated by spore CLEs during germination of B. megaterium spores