Studies on Bacterial Membrane Biogenesis Using Glycerol Auxotrophs

Abstract

Proteins and lipids are the major components of biological membranes. Other amphipathic molecules such as lipopolysaccharides and sulfolipids also occur, but they are restricted to only certain types of membranes. The composition of specific membrane systems seems to be regular and constant;¹ however, under conditions of morphogenetic change or development, the composition of membranes can vary. During these periods of change it has been noted in many systems that as the protein content of the membrane increases, so do the lipids at a similar rate. For example, in the case of Rhodopseudomonas spheroides, a photosynthetic bacterium, the synthesis of chlorophyll and carotenoids is induced upon lowering the partial pressure of oxygen in the medium. Concomitant with this induction of pigment synthesis is an increase in the rate of lipid synthesis as well.² During the synthesis of the endoplasmic reticulum in hepatocytes of newborn rats, the development of new and increased enzymatic activities is accompanied by an increase in the phospholipid content of the membrane.³ The induction of thylakoid formation in mutants of Chlamydomonas has also been shown to involve the concurrent synthesis of thylakoid proteins and lipids.³