Study of cell wall permeability of bacteria from the order Actinomycetales with special emphasis on structure and function of cell wall channels

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The cell walls of gram-positive bacteria including those from the order Actinomycetales were believed to be freely permeable to small hydrophilic solutes. Several years ago we were able to demonstrate the presence of channels in the cell walls of two members of the grampositive mycolata (suborder Corynebacteriaceae or Coryneform bacteria), Mycobactehum chelonae and Mycobacterium smegmatis (Trias et al., 1992; Benz and Trias, 1993; 1994), These cell wall channels define the mycolic acid layer of the mycolata as a permeability barrier and suggest that it shares certain similarities to the outer membrane of gram-negative bacteria. The role of cell wall channels in the physiology of the mycolata is now widely accepted. A still open question is their role in non-mycolic acid containing relatives of mycolata. The project will deal with the translation, structure and assembly of cell wall channels of mycolata with special emphasis on the investigation of those of different Corynebacterium species, such as Corynebacterium glutamicum, Corynebacterium callunae and Corynebacterium efficiens that are able to produce amino acids at a technical scale. Of particular interest is the role of the different cell wall channel proteins PorA/H/B/C in the permeability properties of the cell wall and mutations of the proteins to alter the permeability properties of the channels. The study of the cell wall channels from other gram-positive bacteria, which belong to the order Actinomycetales will also be continued. Of special interest is the definition of the permeability properties of the cell wall of bacteria that that do not contain mycolic acids, such as species from the genera Streptomycetes and Corynebacterium, Here the structure of the lipids that form the permeability barrier should be elucidated and characterized. The primary structure of the cell wall channels of these bacteria is absolutely unknown. The genes of the channel-forming proteins will be cloned and sequenced. Attempts will be made to crystallize cell wall channels from different organisms.