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Journal of Bacteriology, September 2000, p. 4829-4835, Vol. 182, No. 17
Departamento de Microbiología
Molecular, Instituto de Biotecnología, Universidad Nacional
Autónoma de México, Cuernavaca Morelos 62250, México
Received 7 March 2000/Accepted 1 June 2000
Transcription of algD, encoding GDP-mannose
dehydrogenase, the key enzyme in the alginate biosynthetic pathway, is
highly regulated in Azotobacter vinelandii. We describe
here the characterization of a Tn5 insertion mutant (AC28)
which shows a higher level of expression of an
algD::lacZ fusion. AC28 cells were
morphologically abnormal and unable to encyst. The cloning and
nucleotide sequencing of the Tn5-disrupted locus in AC28
revealed an operon homologous to the Escherichia coli ampDE
operon. Tn5 was located within the ampD gene,
encoding a cytosolic
N-acetyl-anhydromuramyl-L-alanine amidase that
participates in the intracellular recycling of peptidoglycan fragments.
The ampE gene encodes a transmembrane protein, but the
function of the protein is not known. We constructed strains carrying
ampD or ampE mutations and one with an
ampDE deletion. The strain with a deletion of the
ampDE operon showed a phenotype similar to that of mutant
AC28. The present work demonstrates that both alginate production and
bacterial encystment are greatly influenced by the bacterial ability to
recycle its cell wall.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Inactivation of the ampDE Operon
Increases Transcription of algD and Affects Morphology and
Encystment of Azotobacter vinelandii
*
Corresponding author. Mailing address: Departamento de
Microbiología Molecular, Instituto de Biotecnología,
Universidad Nacional Autónoma de México, Apdo Postal 510-3, Cuernavaca Morelos 62250, México. Phone: 52-73-114692. Fax:
52-73-172388. E-mail: espin{at}ibt.unam.mx.
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