Synthesis of guanosine tetra- and pentaphosphates by the obligately anaerobic bacterium Bacteroides thetaiotaomicron in response to molecular oxygen

Abstract

Guanosine 5'-diphosphate 3'-diphosphate (ppGpp) and guanosine 5'-triphosphate 3'-diphosphate (pppGpp) were detected in formic acid extracts of air-exposed culutres of Bacteroides thetaiotaomicron. The identification of ppGpp and pppGpp in B. thetaiotaomicron was based on the following results: (i) cochromatography of 32P-labeled hyperphosphorylated nucleotides in two different two-dimensional solvent systems with authentic ppGpp and pppGpp; (ii) incorporation of [3H]guanosine into the putative ppGpp and pppGpp; (iii) alkaline lability; and (iv) resistance, to periodate oxidation. There was a marked increase in the concentration of ppGpp and pppGpp after shift from anaerobic to aerobic conditions, and accumulation of both ppGpp and pppGpp was blocked under these conditions by pretreatment of the culture with rifampin or tetracycline. Growth and incorporation of [3H]guanosine, [3H]tymidine, [14C]succinate, and L-[35S]methionine into macromolecules were inhibited immediately upon exposure to air. The accumulation of ppGpp and pppGpp in B. thetaiotaomicron upon exposure to air may represent a novel signal for synthesis of these compounds.