FIG. 4.

Summary showing the dependency of heterologous secretion on the bacterial context in which the xcp genes are expressed and on the growth conditions. Rectangular and oval symbols represent cells, Xcp machineries, or exoproteins from P. aeruginosa and P. alcaligenes, respectively. When xcp genes are expressed in the natural host (A and B), both endogenous and heterologous exoproteins are secreted. However, when the P. alcaligenes xcp genes are expressed in P. aeruginosa, efficient secretion of either P. alcaligenes lipase or P. aeruginosa elastase occurs only when the strain is grown on a plate (C), not in liquid medium (D), possibly because of a secreton assembly problem in the latter conditions.