Separation of two functional roles of L-alanine in the initiation of Bacillus subtilis spore germination

Abstract

Spores of the standard transformable Marburg strain of Bacillus subtilis can be initiated to germinate by l-alanine alone. We isolated mutants which required for this process, in addition to l-alanine, the combination of d-glucose + d-fructose + K(+) or NH(4) (+) ions. In place of fructose, autoclaved or caramelized glucose could be used. Even the standard type strain required the addition of these three agents when d-alanine was present or when the temperature was raised. These findings show that l-alanine normally performs two functions during initiation, one of which is absent in the mutants or is blocked by d-alanine or elevated temperature. One of our mutants was not absolutely dependent on the addition of external l-alanine, because it could be initiated at a reduced rate by the sole addition of glucose + K(+) or NH(4) (+). When K(+) or NH(4) (+) was replaced by Na(+), the initiation rate was greatly reduced. The divalent metal ions Mg(++), Mn(++), and Ca(++) could not satisfy the cation requirement.