Abstract
We have controlled the rates at which three different amino acids were available to auxotrophs of Bacillus subtilis by avoiding active transport of the respective substrate. The active transport of oxomethylvalerate, a precursor of isoleucine, was prevented by a kauA mutation, the uptake of L-aspartate was competed by 20 mM L-glutamate, and D-methionine was used instead of L-methionine. When in this way conditions of partial amino acid deprivation were achieved, a partial "stringent response" occurred which included the increase of ppGpp and pppGpp, and the decrease of GTP; such conditions initiated sporulation. In the corresponding relaxed (relA) mutants, the changes of guanine nucleotides were greatly reduced and no sporulation was observed at any substrate concentration; but addition of decoyinine produced a further decrease of GTP and caused sporulation.
Highlights
Aprecursor of isoleucine, was prevented by a kauA,we wanted to determine whether partial limitation mutation, the uptake of L-aspartate was competed by of an amino acid would initiate sporulation
We found that partial limitation ammonium ions, and phosphate
We show that partial limitation of the amino acid substrate synthesis for sporulation was not recognized at the supply caused a rapid increase of ppGpp and pppGpp, a time, the leakiness of these mutants corresponding decrease of GTP, and extensive sporulation in in the absence of the knowngrowth requirement was not the stringent but notthe relaxed strains
Summary
Sporulation of Bacillussubtilis usually starts when the acid by another amino acid taken up by the same transport bacilliare in a medium that contains only slowlymetabolizable system. We show that partial limitation of the amino acid substrate synthesis for sporulation was not recognized at the supply caused a rapid increase of ppGpp and pppGpp, a time, the leakiness (or residual growth rate) of these mutants corresponding decrease of GTP, and extensive sporulation in in the absence of the knowngrowth requirement was not the stringent but notthe relaxed strains. The plate had been washed cells were collected into synthetic medium and inoculated at low ODm (0.0005 to 0.002) into flasks containing (%o volume 00 synthetic medium plus excess of any required compounds (0.25 m~ L-tryptophan, 10 mM L-aspartate, 1 mM L-isoleucine, 2 mM DL-valine, 0.14 mM L-methionine, or 3.4 mM D-methionine). Supplement to be starved for, and the filters with cells were quickly transferred to 1-liter flasks containing 100 ml of the stated medium
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