Modification of the structure and activity of lipid A in Yersinia pestis lipopolysaccharide by growth temperature

Yeisinia pestis strain Yreka was grown at 27 or 37degreesC, and the lipid A structures (lipid A-27degreesC and lipid A-37degreesC) of the respective lipopolysaccharides (LPS) were investigated by matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry. Lipid A-27degreesC consisted of a mixture of tri-acyl, tetra-acyl, penta-acyl, and hexa-acyl lipid A's, of which tetra-acyl lipid A was most abundant. Lipid A-37degreesC consisted predominantly of tri- and tetra-acylated molecules, with only small amounts of penta-acyl lipid A; no hexa.-acyl lipid A was detected. Furthermore, the amount of 4-amino-arabinose was substantially higher in lipid A-27degreesC than in lipid A-37degreesC. By use of mouse and human macrophage cell lines, the biological activities of the LPS and lipid A preparations were measured via their abilities to induce production of tumor necrosis factor alpha (TNF-alpha). In both cell lines the LPS and the lipid A from bacteria grown at 27degreesC were stronger inducers of TNF-a than those from bacteria grown at 37degreesC. However, the difference in activity was more prominent in human macrophage cells. These results suggest that in order to reduce the activation of human macrophages, it may be more advantageous for Y. pestis to produce less-acylated lipid A at 37degreesC.