Genetic analysis of the transcriptional arrangement of Azotobacter vinelandii alginate biosynthetic genes: identification of two independent promoters

Lloret, Lourdes; Barreto, R.; León, Renato; Moreno, Soledad; Martínez-Salazar, Jaime M.; Espı́n, Guadalupe; Soberón‐Chávez, Gloria

doi:10.1111/j.1365-2958.1996.tb02554.x

Cited by 46 publications

(37 citation statements)

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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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confidence: 99%

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

et al. 2000

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“…All genes involved in bacterial alginate biosynthesis, except algC (20), are clustered on the chromosome and are transcribed in one or several units (6,8,34,36). Polymerization of the sugar monomers takes place in the cytoplasmic membrane, using GDP-mannuronic acid as a precursor.…”

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Identification and Characterization of anAzotobacter vinelandiiType I Secretion System Responsible for Export of the AlgE-Type Mannuronan C-5-Epimerases

et al. 2006

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Alginate is a linear copolymer of ␤-D-mannuronic acid and its C-5-epimer, ␣-L-guluronic acid. During biosynthesis, the polymer is first made as mannuronan, and various fractions of the monomers are then epimerized to guluronic acid by mannuronan C-5-epimerases. The Azotobacter vinelandii genome encodes a family of seven extracellular such epimerases (AlgE1 to AlgE7) which display motifs characteristic for proteins secreted via a type I pathway. Putative ATPase-binding cassette regions from the genome draft sequence of the A. vinelandii OP strain and experimentally verified type I transporters from other species were compared. This analysis led to the identification of one putative A. vinelandii type I system (eexDEF). The corresponding genes were individually disrupted in A. vinelandii strain E, and Western blot analysis using polyclonal antibodies against all AlgE epimerases showed that these proteins were present in wild-type culture supernatants but absent from the eex mutant supernatants. Consistent with this, the wild-type strain and the eex mutants produced alginate with about 20% guluronic acid and almost pure mannuronan (<2% guluronic acid), respectively. The A. vinelandii wild type is able to enter a particular desiccation-tolerant resting stage designated cyst. At this stage, the cells are surrounded by a rigid coat in which alginate is a major constituent. Such a coat was formed by wild-type cells in a particular growth medium but was missing in the eex mutants. These mutants were also found to be unable to survive desiccation. The reason for this is probably that continuous stretches of guluronic acid residues are needed for alginate gel formation to take place.

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“…Considering the enzymatic treatment of infections caused by biofilm-forming bacteria, a search was carried out for a new algL from soil bacteria [19] . Moreover, genetic studies on algL-producing microorganisms have revealed that the algL genes are clustered with other alginate biosynthetic gene loci [20] . Hence, in the present study and based on the presence of algL gene, an algL-producing bacterium named Bacillus sp.…”

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confidence: 99%

Screening of Alginate Lyase-Producing Bacteria and Optimization of Media Compositions for Extracellular Alginate Lyase Production

Tavafi¹,

Ali²,

Ghadam³

et al. 2017

IBJ

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Background: Alginate is a linear polysaccharide consisting of guluronate (polyG) and mannuronate (polyM) subunits. Methods: In the initial screening of alginate-degrading bacteria from soil, 10 isolates were able to grow on minimal medium containing alginate. The optimization of cell growth and alginate lyase (algL) production was carried out by the addition of 0.8% alginate and 0.2-0.3 M NaCl to the culture medium. Of 10 isolates, one was selected based on its fast growth rate on minimal 9 medium containing 0.4% sodium alginate. The selected bacterium, identified based on morphological and biochemical characteristics, as well as 16S rDNA sequence data, was confirmed to be an isolate belonging to the genus Bacillus and designated as Bacillus sp. TAG8. Results: The results showed the ability of Bacillus sp. TAG8 in utilizing alginate as a sole carbon source. Bacillus sp. TAG8 growth and algL production were augmented with an increase in sodium alginate concentration and also by the addition of 0.2-0.3 M NaCl. Molecular analysis of TAG8 algL gene showed 99% sequence identity with algL of Pseudomonas aeruginosa PAO1. The algL produced by Bacillus sp. TAG8 cleaved both polyM and polyG blocks in alginate molecule, as well as acetylated alginate residues, confirming the bifunctionality of the isolated lyase. Conclusion: The identification of novel algL genes from microbial communities constitutes a new approach for exploring lyases with specific activity against bacterial alginates and may thus contribute to the eradication of persistent biofilms from clinical samples.

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Genetic analysis of the transcriptional arrangement of Azotobacter vinelandii alginate biosynthetic genes: identification of two independent promoters

Cited by 46 publications

References 46 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

Identification and Characterization of anAzotobacter vinelandiiType I Secretion System Responsible for Export of the AlgE-Type Mannuronan C-5-Epimerases

Screening of Alginate Lyase-Producing Bacteria and Optimization of Media Compositions for Extracellular Alginate Lyase Production

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