Decrease in D. discoideum mitochondrial mRNAs during L. pneumophila infection.

(A) D. discoideum cells were infected with L. pneumophila (JR32) at an M.O.I. of 10 and RNA was extracted at the indicated times and analyzed on northern blots. Substantial cell death occurred after 8 hours in this experiment (data not shown). Messenger RNA for the mitochondrial-encoded genes examined displayed two modes of decline; rapid (nad5 and atp6) and gradual (cobA and cox3). As controls, cells were also exposed to avirulent L. pneumophila (icmT mutant) or the food bacteria K. aerogenes. (B) The mRNA levels of these genes were also examined under conditions that kill D. discoideum cells by oxidative stress (hydrogen peroxide), inhibition of protein synthesis (G418, an aminoglycoside), inhibition of DNA synthesis (Etoposide, a topoisomerase II inhibitor).