The Azotobacter vinelandii alg8 and alg44 genes are essential for alginate synthesis and can be transcribed from an algD-independent promoter

Mejı́a-Ruı́z, Humberto; Guzmán, Josefina; Moreno, Soledad; Soberón‐Chávez, Gloria; Espı́n, Guadalupe

doi:10.1016/s0378-1119(97)00380-6

Cited by 38 publications

(29 citation statements)

References 23 publications

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“…Effect of mucA, mucABCD, and mucC mutations on algD transcription. Most of the molecular genetics analysis of alginate production in A. vinelandii has been carried out in the highly mucoid strain ATCC 9046 (6,7,24,26,30,31,34,35,36). The detailed analysis of the structure of the regulatory region of the AEIV algD gene is currently being performed.…”

Section: Resultsmentioning

confidence: 99%

“…In A. vinelandii, the biosynthetic gene cluster is arranged in three operons, one of which transcribes the algD gene alone (6,24,30), while in the latter bacterium, this gene cluster is transcribed as a single operon, whose transcription is started from a promoter upstream of the algD gene (9). The alternative sigma factor E (also known as AlgU or AlgT) is responsible for the transcription of the algD gene in P. aeruginosa (44), as well as in Pseudomonas syringae (21).…”

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Role of Azotobacter vinelandii mucA and mucC Gene Products in Alginate Production

et al. 2000

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Azotobacter vinelandii produces the exopolysaccharide alginate, which is essential for its differentiation to desiccation-resistant cysts. In different bacterial species, the alternative sigma factor E regulates the expression of functions related to the extracytoplasmic compartments. In A. vinelandii and Pseudomonas aeruginosa, the E factor (AlgU) is essential for alginate production. In both bacteria, the activity of this sigma factor is regulated by the product of the mucA, mucB, mucC, and mucD genes. In this work, we studied the transcriptional regulation of the A. vinelandii algU-mucABCD gene cluster, as well as the role of the mucA and mucC gene products in alginate production. Our results show the existence of AlgU autoregulation and show that both MucA and MucC play a negative role in alginate production.

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Role of Azotobacter vinelandii mucA and mucC Gene Products in Alginate Production

et al. 2000

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“…Alg8 and Alg44 have been found to be membrane proteins necessary for alginate production (26,29) and, based on sequence alignment studies, Alg8 is proposed to be the polymerase (29). AlgX has also been shown to be necessary for alginate FIG.…”

Section: Discussionmentioning

confidence: 99%

The Pseudomonas fluorescens AlgG Protein, but Not Its Mannuronan C-5-Epimerase Activity, Is Needed for Alginate Polymer Formation

et al. 2003

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Bacterial alginates are produced as 1-4-linked ␤-D-mannuronan, followed by epimerization of some of the mannuronic acid residues to ␣-L-guluronic acid. Here we report the isolation of four different epimerizationdefective point mutants of the periplasmic Pseudomonas fluorescens mannuronan C-5-epimerase AlgG. All mutations affected amino acids conserved among AlgG-epimerases and were clustered in a part of the enzyme also sharing some sequence similarity to a group of secreted epimerases previously reported in Azotobacter vinelandii. An algG-deletion mutant was constructed and found to produce predominantly a dimer containing a 4-deoxy-L-erythro-hex-4-enepyranosyluronate residue at the nonreducing end and a mannuronic acid residue at the reducing end. The production of this dimer is the result of the activity of an alginate lyase, AlgL, whose in vivo activity is much more limited in the presence of AlgG. A strain expressing both an epimerase-defective (point mutation) and a wild-type epimerase was constructed and shown to produce two types of alginate molecules: one class being pure mannuronan and the other having the wild-type content of guluronic acid residues. This formation of two distinct classes of polymers in a genetically pure cell line can be explained by assuming that AlgG is part of a periplasmic protein complex.

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“…vinelandii has been shown to posses an alginate biosynthetic gene cluster organized in three operons (5,25,29,30,49), one of which transcribes algD, which encodes GDP-mannose dehydrogenase, the key enzyme of the alginate biosynthetic pathway. The algUmucABCD cluster has been characterized in A. vinelandii and in Pseudomonas aeruginosa and has been shown to control alginate production (28,34,37,44,45,53).…”

Section: Azotobacter Vinelandii Is a Nitrogen-fixing Soil Bacterium Tmentioning

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The Global Regulators GacA and ς ^S Form Part of a Cascade That Controls Alginate Production in Azotobacter vinelandii

et al. 2001

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Transcription of the Azotobacter vinelandii algD gene, which encodes GDP-mannose dehydrogenase (the rate-limiting enzyme of alginate synthesis), starts from three sites: p1, p2, and p3. The sensor kinase GacS, a member of the two-component regulatory system, is required for transcription of algD from its three sites during the stationary phase. Here we show that algD is expressed constitutively throughout the growth cycle from the p2 and p3 sites and that transcription from p1 started at the transition between the exponential growth phase and stationary phase. We constructed A. vinelandii strains that carried mutations in gacA encoding the cognate response regulator of GacS and in rpoS coding for the stationary-phase S factor. The gacA mutation impaired alginate production and transcription of algD from its three promoters. Transcription of rpoS was also abolished by the gacA mutation. The rpoS mutation impaired transcription of algD from the p1 promoter and increased it from the p2 E promoter. The results of this study provide evidence for the predominant role of GacA in a regulatory cascade controlling alginate production and gene expression during the stationary phase in A. vinelandii.

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The Azotobacter vinelandii alg8 and alg44 genes are essential for alginate synthesis and can be transcribed from an algD-independent promoter

Cited by 38 publications

References 23 publications

Role of Azotobacter vinelandii mucA and mucC Gene Products in Alginate Production

Role of Azotobacter vinelandii mucA and mucC Gene Products in Alginate Production

The Pseudomonas fluorescens AlgG Protein, but Not Its Mannuronan C-5-Epimerase Activity, Is Needed for Alginate Polymer Formation

The Global Regulators GacA and ς ^S Form Part of a Cascade That Controls Alginate Production in Azotobacter vinelandii

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The Azotobacter vinelandii alg8 and alg44 genes are essential for alginate synthesis and can be transcribed from an algD-independent promoter

Cited by 38 publications

References 23 publications

Role of Azotobacter vinelandii mucA and mucC Gene Products in Alginate Production

Role of Azotobacter vinelandii mucA and mucC Gene Products in Alginate Production

The Pseudomonas fluorescens AlgG Protein, but Not Its Mannuronan C-5-Epimerase Activity, Is Needed for Alginate Polymer Formation

The Global Regulators GacA and ς S Form Part of a Cascade That Controls Alginate Production in Azotobacter vinelandii

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The Global Regulators GacA and ς ^S Form Part of a Cascade That Controls Alginate Production in Azotobacter vinelandii