STARVATION YIELDS A DRASTIC DECREASE IN OUTER-MEMBRANE PERMEABILITY TO A PERIPLASMIC FOREIGN PROTEIN IN MYXOCOCCUS-XANTHUS

A recombinant Myxococcus xanthus strain was constructed that constitut ively produces two proteins from Escherichia coli, the cytoplasmic bet a-galactosidase and the periplasmic ph 2.5 acid phosphatase (AppA prot ein). We have previously shown that during vegetative growth, AppA pro tein is partly accumulated in the periplasm of M. xanthus and partly r eleased into the medium. We demonstrate here that during starvation-in duced development, release of periplasmic AppA protein to the medium d id not occur over a period of 20 h. This was coincident with, but not caused by, the arrest of the synthesis of the foreign proteins. We hav e shown that this lack of secretion could be attributed to starvation per se and did not depend on the ability of the cells to undergo devel opment. Our findings suggest that protein secretion which occurs durin g the first hours of starvation-induced development might therefore ta ke place via a different route from that which occurs in vegetative ce lls.