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Journal of Bacteriology, May 2000, p. 2624-2628, Vol. 182, No. 9
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

The GacS Sensor Kinase Regulates Alginate and Poly-beta -Hydroxybutyrate Production in Azotobacter vinelandii

Miguel Castañeda, Josefina Guzmán, Soledad Moreno, and Guadalupe Espín*

Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca Morelos 62250, México

Received 11 November 1999/Accepted 14 February 2000

Azotobacter vinelandii produces two polymers: the extracellular polysaccharide alginate and the intracellular polyester poly-beta -hydroxybutyrate (PHB). A cosmid clone (pSMU588) from an A. vinelandii gene library diminished alginate production by A. vinelandii mucoid strain ATCC 9046. The nucleotide sequence and predicted amino acid sequence of the locus responsible for the mucoidy suppression revealed 65% identity to Pseudomonas GacS, a transmembrane sensor kinase of the two-component regulators, whose cognate response regulator, GacA, is a global activator regulating several products and virulence factors. Plasmid pMC15, harboring gacS, and a strain carrying a gacS nonpolar mutation were constructed. Either pMC15 or the gacS mutation significantly reduced alginate production and transcription of algD, the gene coding for the key enzyme GDP-mannose dehydrogenase of the alginate biosynthetic pathway. We found that the gacS mutation also reduced PHB accumulation and impaired encystment. Taken together, these data indicate that in A. vinelandii the gacSA global system regulates polymer synthesis.

* Corresponding author. Mailing address: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apd. Postal 510-3, Cuernavaca Morelos 62250, México. Phone: 52-73-291644. Fax: 52-73-172388. E-mail: espin{at}ibt.unam.mx.

Journal of Bacteriology, May 2000, p. 2624-2628, Vol. 182, No. 9
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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