Journal of Bacteriology, September 1998, p. 4628-4637, Vol. 180, No. 17
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Section of Microbiology, University of California, Davis, Davis, California 95616,1 and Department of Biochemistry, Stanford Medical School, Stanford, California 943062
Received 25 November 1997/Accepted 16 June 1998
Myxococcus xanthus cells carrying the
4408
Tn5lac insertion at the sde locus show defects
in fruiting body development and sporulation. Our analysis of
sde expression patterns showed that this locus is induced
early in the developmental program (0 to 2 h) and that expression
increases approximately fivefold after 12 h of development.
Further studies showed that expression of sde is induced as
growing cells enter stationary phase, suggesting that activation of the
sde locus is not limited to the developmental process.
Because the peak levels of sde expression in both an sde+ and an sde mutant background
were similar, we conclude that the sde locus is not
autoregulated. Characterization of the sde locus by DNA
sequence analysis indicated that the
4408 insertion occurred within
the sdeK gene. Primer extension analyses localized the 5'
end of sde transcript to a guanine nucleotide 307 bp
upstream of the proposed start for the SdeK coding sequence. The DNA
sequence in the
12 and
24 regions upstream of the sde
transcriptional start site shows similarity to the
54
family of promoters. The results of complementation studies
suggest that the defects in development and sporulation caused by the
4408 insertion are due to an inactivation of sdeK. The
predicted amino acid sequence of SdeK was found to have similarity to
the sequences of the histidine protein kinases of two-component
regulatory systems. Based on our results, we propose that SdeK may be
part of a signal transduction pathway required for the activation and propagation of the early developmental program.
Present address: Stanford Human Genome Center, Department of
Genetics, Stanford Medical School, Stanford, CA 94306
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