ANALYSIS OF PROTEINS SYNTHESIZED BY SALMONELLA-TYPHIMURIUM DURING GROWTH WITHIN A HOST MACROPHAGE

Salmonella typhimurium is a facultative intracellular pathogen, able b oth to invade and to survive within eukaryotic cells and to grow in va rious extracellular environments. To compare the bacterial responses t o these disparate environments and to shed light on the nature of the intracellular environment, we have examined the pattern of protein syn thesis by two-dimensional polyacrylamide gel electrophoresis. The leve ls of approximately 40 proteins were observed to increase during growt h within macrophage-like U937 cells, while approximately 100 proteins exhibited levels that were repressed relative to those of an extracell ular control culture. To aid in the interpretation of these results, t he patterns of proteins made by S. typhimurium exposed to various envi ronmental conditions in the laboratory were determined. The intracellu lar protein pattern was then compared with each of these benchmark pro tein patterns. This analysis revealed that, as expected, the intracell ular environment appears to impose numerous stresses on the bacteria, but unexpectedly, the macrophage-induced response was not a simple sum of the individual stress responses displayed during extracellular gro wth.