Effects of penicillin on synthesis and excretion of lipid and lipoteichoic acid from Streptococcus mutans BHT

Abstract

Cultures of Streptococcus mutans BHT grown for at least eight generations in a chemically defined medium containing [1(3)-14C]glycerol, when treated with growth-inhibitory concentrations (0.2 micrograms/ml) of benzylpenicillin (Pen G), produced and excreted increased amounts of lipid and lipoteichoic acid per unit of cells. Cellular lysis was not observed. Compared with untreated controls, lipid excretion increased 15-fold, and lipoteichoic acid excretion increased 6-fold, 4 h after the addition of Pen G. All lipid species showed increased synthesis and excretion after exposure to Pen G. Although the same lipid types were found in both the Pen G-treated and the untreated cultures, the percent composition was altered after treatment with Pen G. The most dramatic example of this was the percentage of intracellular diphosphatidylglycerol found in the Pen G-treated cultures, 22.6%, in contrast to 5.3% found in the untreated cultures.

Products of phospholipid metabolism in Bacillus stearothermophilus

“…Once released from the membrane, the LTA appeared to be rapidly released from the cell. In terms of the suggested role of LTA as an inhibitor of cell wall autolysins (3,7,9,24), this LTA deficiency may contribute to the unusual sensitivity ofB. stearothermophilus to autolysis and to lysozyme treatment (20).…”

The ability to sensitize host cells for destruction by autologous complement is a general property of lipoteichoic acid

“…However, a variety of data indicate that these molecules extend through the cell wall to the bacterial surface (28). In addition, bacteria are known to secrete these amphipathic molecules in both the fully acylated and unacylated forms (15,22); these events are greatly influenced by environmental factors (28), including enhancement of release by exposure to antibiotics (1,5). Once released from bacteria, LTA can bind to a variety of mammalian cells (2,19,24), including erythrocytes (3), and retain their antigenic activity (9,16,21,27).…”