Akinobu Okabe

Alteration in phospholipid composition of Staphylococcus aureus during formation of autoplast

The phospholipid composition of autoplasts (protoplasts made by autolysis of Staphylococcus aureus 209P was examined. The autoplasts were prepared by incubation of 209P cells in 1.2 M sucrose--0.33 M acetate buffer (pH 5.8). Cardiolipin comprised nearly half the total phospholipid in these autoplasts. Autoplasts had a lower phosphatidylglycerol content than intact cells but similar lysylphosphatidylglycerol content. The increase in cardiolipin content during release of autoplasts was not affected by pH or temperature. The result indicates that removal of the cell wall caused the increase in cardiolipin content. The total amount of phospholipids increased slightly during autoplast formation, but there was no significant increase in fatty acids or diglycerides. The changes of phospholipid composition during formation of the autoplast was due to de novo synthesis of cardiolipin from phosphatidylglycerol.

Lipid Composition of Staphylococcus aureus and Its Derived L-forms

Two strains of Staphylococcus aureus (Newman and Tazaki) and their derived L‐forms were cultured in serum‐containing broth and the differences in their lipid compositions were analyzed. Cardiolipin accounted for more than 50% of the total phospholipid phosphorus in L‐forms, but for less than 25% in parent bacteria. The cardiolipin content of L‐forms was very high through all growth phases, although it increased gradually as growth proceeded. Significant amounts of cholesterol and its esters were present in parent strains and L‐forms, all of which incorporated serum cholesterol into the cell membrane. On the other hand, they could be detected in the L‐forms but not in the parent strains when they were cultured in serum‐free broth. To examine the ability of L‐forms to synthesize cholesterol, the cholesterol content of L‐forms cultured in serum‐free broth was compared with that of the medium. The results indicated that staphylococcal L‐forms could synthesize cholesterol and its esters. These differences in lipid composition suggested that modification of membrane lipids may occur as an adaptation‐al change in response to the disappearance of the cell wall.

Lambda toxin (Clostridium perfringens)

Publisher Summary This chapter discusses the structural chemistry and the biological aspects of lambda toxin. The deduced protein sequence of λ-toxin comprises three portions which include a signal sequence, a pro sequence, and the mature enzyme. Four enzymes belonging to the same M4 peptidase family, Bacillus thermoproteolyticus thermolysin, Bacillus cereus neutral protease, Pseudomonas aeruginosa elastase, have been shown to have closely related tertiary structures. Each enzyme consists of two domains in common which include an N-terminal domain rich in antiparallel β strands, and a C-terminal domain rich in a helices. There is a deep cleft between these domains, and the first two α helices of the C-terminal domain form the bottom of the cleft and act as ligands for a zinc ion and a substrate water molecule. λ-Toxin can degrade immunoglobulin G, complement C3 component, fibrinogen, fibronectin and α2-macroglobulin, which contribute to innate or adaptive immune defense against infection. This implies a pathogenic role, as suggested for many proteases produced by pathogenic bacteria. Intradermal injection of the purified λ-toxin into mice causes hemorrhagic edema by increasing vascular permeability.