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Journal of Bacteriology, December 1998, p. 6215-6223, Vol. 180, No. 23
Department of Microbiology and Molecular
Genetics, The University of Texas Medical School, Houston, Texas 77030
Received 13 August 1998/Accepted 1 October 1998
Myxococcus xanthus multicellular fruiting body
development is initiated by nutrient limitation at high cell density.
Five clustered point mutations (sasB5, -14,
-15, -16, and -17) can bypass the
starvation and high-cell-density requirements for expression of the
4521 developmental reporter gene. These mutants express 4521 at high levels during growth and development in an
asgB background, which is defective in generation of the
cell density signal, A signal. A 1.3-kb region of the sasB
locus cloned from the wild-type chromosome restored the
SasB+ phenotype to the five mutants. DNA sequence analysis
of the 1.3-kb region predicted an open reading frame, designated SasN.
The N terminus of SasN appears to contain a strongly hydrophobic region and a leucine zipper motif. SasN showed no significant sequence similarities to known proteins. A strain containing a newly constructed sasN-null mutation and
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Myxococcus xanthus sasN Encodes a
Regulator That Prevents Developmental Gene Expression during
Growth
4521 Tn5lac in
an otherwise wild-type background expressed 4521 at a high
level during growth and development. A similar sasN-null
mutant formed abnormal fruiting bodies and sporulated at about 10% the
level of wild type. These data indicate that the wild-type
sasN gene product is necessary for normal M. xanthus fruiting body development and functions as a critical regulator that prevents 4521 expression during growth.
*
Corresponding author. Mailing address: Department of
Microbiology and Molecular Genetics, The University of Texas Medical School, 6431 Fannin, 1.765 JFB, Houston, TX 77030. Phone: (713) 500-5448. Fax: (713) 500-5499. E-mail:
hkaplan{at}utmmg.med.uth.tmc.edu.
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