Streptomyces are multicellular, Gram-positive bacteria in the phylum of actinobacteria which produce a high amount of bioactive natural products of which the expression is tightly coordinated with... Show moreStreptomyces are multicellular, Gram-positive bacteria in the phylum of actinobacteria which produce a high amount of bioactive natural products of which the expression is tightly coordinated with the life cycle. This thesis shows the identification of S. roseifaciens, a novel species with an uncommon, verticillate spore morphology and a unique household of SsgA-like proteins. Analyses of the peptidoglycan composition show that S. coelicolor show a pattern of 3-3 cross-linking befitting a tip-growing organism and change in composition between vegetative mycelium and spores. Kitasatosporae carry meso-DAP in the peptidoglycan of vegetative mycelium and LL-DAP in the peptidoglycan of spores. In line with this difference, the peptidoglycan architecture of these two growth stages undergoes such radical changes that they would seem to be from different species. S. coelicolor is naturally vancomycin resistant, but the addition of D-alanine and disruption in a single gene increases vancomycin sensitivity by a thousandfold. A knockout mutant of the alanine racemase, alr, requires exogenous addition of D-alanine. The Alr crystal structure of S. coelicolor and the D-cycloserine producer S. lavendulae were compared as to look for possible mechanisms for D-cycloserine resistance. Show less
Saccharomyces cerevisiae is one of the few yeast species that can grow equally well without molecular oxygen (anaerobic) as with this compound present (aerobic). This property has made it one of... Show moreSaccharomyces cerevisiae is one of the few yeast species that can grow equally well without molecular oxygen (anaerobic) as with this compound present (aerobic). This property has made it one of the most abundantly used yeasts in industry, since anaerobic incubation plays a major part in alcohol and bread industry. With the experiments described in this thesis it has been shown that apart from metabolic changes, an adaptation of the cell wall and the plasma membrane is very important for anaerobic growth. There seems to be a connection between this adaptation and the import of sterols, which are essential when no molecular oxygen is present. The importance of these adaptations becomes clear when the genomes of the facultative anaerobic Saccharomyces cerevisiae and the obligatory aerobic Kluyveromyces lactis are compared. K. lactis does not have any genes that encode for a sterol import system.The adaptation of the cell wall and the plasma membrane to anaerobic conditions is extensive and regulated in a complex way, as is apparent from the transcriptome data. Our experiments show that Snf7 is, at least in part, responsible for these changes. Show less
