The Myxococcus xanthus developmental program can be delayed by inhibition of DNA replication

Section of Microbiology, The University of California, Davis, Davis CA 95616

^* To whom correspondence should be addressed. Email: mhsinger{at}ucdavis.edu.

	Abstract

Under conditions of nutrient deprivation, Myxococcus xanthus undergoes a developmental process that results in the formation of a fruiting body containing environmentally resistant myxospores. We have shown that myxospores contain two copies of the genome, suggesting that cells must replicate the genome prior to or during development. To further investigate the role of DNA replication in development, a temperature-sensitive dnaB mutant, DnaB^A116V, was isolated from M. xanthus. Unlike in E. coli dnaB mutants, where DNA replication immediately halts upon shift to the non-permissive temperature, the M. xanthus mutant ceased growth and DNA replication after one cell doubling at the non-permissive temperature of 37°C. We demonstrate that at the non-permissive temperature that the DnaB^A116V mutant arrests as a population of 1n cells, implying that these cells can complete one round of the cell cycle, but fail to initiate new rounds of DNA replication. In developmental assays, the DnaB^A116V mutant was unable to develop into fruiting bodies and produced fewer myxospores than wild type at the non-permissive temperature. However, the mutant was able to undergo development when the mutant was shifted to the permissive temperature, suggesting that cells have the capacity to undergo DNA replication during development and allow for the formation of myxospores.