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High concentrations of intracellular Ap4A and/or Ap5A in developing Myxococcus xanthus cells inhibit sporulation
Abstract
Diadenosine polyphosphates (Ap n A) are thought to act as signalling molecules regulating stress responses and biofilm formation in prokaryotes. However, Ap n A function in Myxococcus xanthus remains unknown. Here, we investigated the role of Ap n A in M. xanthus, using the wild-type and Ap n A hydrolase (apaH) mutant strains exposed to various stress conditions. In both wild-type and apaH mutant cells cultured on starvation medium (CF agar), the levels of intracellular diadenosine tetraphosphate (Ap4A) and pentaphosphate (Ap5A) increased several fold during the first 16 h of development and decreased gradually thereafter. The levels of Ap4A and Ap5A in the apaH mutant were about 5- and 11-fold higher than those in the wild-type strain at 16 h, respectively. Ap n A hydrolase activity of the wild-type strain increased 1.5-fold during the first 8 h of development, and it then gradually decreased. The apaH mutant formed spores 1–2 days after the wild-type strain did, and the yield of viable spores was 5.5 % of that in the wild-type strain 5 days after inoculation onto CF agar. These results suggest the possibility that high intracellular levels of Ap4A and/or Ap5A may inhibit M. xanthus sporulation at the early stage of development and that the bacteria reduce intracellular Ap4A and Ap5A accumulation through Ap n A hydrolase activity.
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- Accepted:
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Keyword(s):
ApnA hydrolase
,
diadenosine pentaphosphate
,
diadenosine tetraphosphate
and
Myxococcus xanthus
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