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Expression of alginases and alginate polymerase genes in response to oxygen, and their relationship with the alginate molecular weight in Azotobacter vinelandii

Paper ID Volume ID Publish Year Pages File Format Full-Text
17034 42635 2013 7 PDF Available
Title
Expression of alginases and alginate polymerase genes in response to oxygen, and their relationship with the alginate molecular weight in Azotobacter vinelandii
Abstract

•Low dissolved oxygen increased transcription of alginate polymerase complex genes.•Alginases genes expression was a function of dissolved oxygen and the growth phase.•Dissolved oxygen regulates alginase activity, both intracellular and extracellular.•Alginase activity remains in a basal level at low dissolved oxygen.•Mechanisms determining alginate molecular weight depending on oxygen, are proposed.

The transcription of genes involved in alginate polymerization and depolymerization, as well as the alginase activity (extracellular and intracellular) under oxygen-limited and non oxygen-limited conditions in cultures of A. vinelandii, was studied. Two levels of dissolved oxygen tension (DOT) (1% and 5%, oxygen-limited and non-oxygen-limited, respectively) strictly controlled by gas blending, were evaluated in a wild type strain. In cultures at low DOT (1%), in which a high molecular weight alginate (1200 kDa) was synthesized, the transcription levels of alg8 and alg44 (genes encoding alginate polymerase complex), and algX (encoding a protein involved in polymer transport through periplasmic space) were considerably higher as compared to cultures conducted at 5% DOT, under which an alginate with a low MW (42 kDa) was produced. In the case of genes encoding for intracellular and extracellular alginases, the levels of these transcripts were higher at 1% DOT. However, intracellular and extracellular alginase activity were lower (0.017 and 0.01 U/mg protein, respectively) in cultures at 1% DOT, as compared with the activities measured at 5% DOT (0.027 and 0.052 U/mg protein for intracellular and extracellular maximum activity, respectively). The low alginase activity measured in cultures at 1% DOT and the high level of transcription of genes constituting alginate polymerase complex might be mechanisms by which oxygen regulates the production of alginates with a high MW.

Keywords
Dissolved oxygen; Alginate polymerization; Transcription; Alginase activity; Azotobacter vinelandii
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Expression of alginases and alginate polymerase genes in response to oxygen, and their relationship with the alginate molecular weight in Azotobacter vinelandii
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Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volume 53, Issue 2, 10 July 2013, Pages 85–91
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us