LACK OF PRODUCTION OF (P)PPGPP IN HALOBACTERIUM-VOLCANII UNDER CONDITIONS THAT ARE EFFECTIVE IN THE EUBACTERIA

The stringent halobacterial strain Haloferax volcanii was subjected to a set of physiological conditions different from amino acid starvatio n that are known to cause production of guanosine polyphosphates [(p)p p Gpp] in eubacteria via the relA-independent (spoT) pathway. The cond itions used were temperature upshift, treatment with cyanide, and tota l starvation, Under none of these conditions were detectable levels of (p)ppGpp observed, This result, in conjunction with our previous find ing that (p)ppGpp synthesis does not occur under amino acid starvation , leads to the conclusion that in halobacteria both growth rate contro l and stringency are probably governed by mechanisms that operate in t he absence of ppGpp. During exponential growth, a low level of phospho rylated compounds with electrophoretic mobilities similar, but not ide ntical, to that of (p)ppGpp were observed, The intracellular concentra tion of these compounds increased considerably during the stationary p hase of grow th and with all of the treatments used, The compounds wer e identified as short-chain polyphosphates identical to those found un der similar conditions in Saccharomyces cerevisiae.