Next Article in Journal
Role of Electrostatic Interactions on Supramolecular Organization in Calf-Thymus DNA Solutions under Flow
Next Article in Special Issue
Application of Adzuki Bean Starch in Antioxidant Films Containing Cocoa Nibs Extract
Previous Article in Journal
Injectable and Gellable Chitosan Formulations Filled with Cellulose Nanofibers for Intervertebral Disc Tissue Engineering
Previous Article in Special Issue
Bioreactor Operating Strategies for Improved Polyhydroxyalkanoate (PHA) Productivity
Article Menu

Export Article

Open AccessArticle
Polymers 2018, 10(11), 1203; https://doi.org/10.3390/polym10111203

Polyhydroxyalkanoate (PHA) Polymer Accumulation and pha Gene Expression in Phenazine (phz-) and Pyrrolnitrin (prn-) Defective Mutants of Pseudomonas chlororaphis PA23

1
Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada
2
Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 5V6, Canada
*
Author to whom correspondence should be addressed.
Received: 26 September 2018 / Revised: 19 October 2018 / Accepted: 25 October 2018 / Published: 27 October 2018
(This article belongs to the Special Issue Recent Advances in Bioplastics)
Full-Text   |   PDF [2785 KB, uploaded 3 November 2018]   |  

Abstract

Pseudomonas chlororaphis PA23 was isolated from the rhizosphere of soybeans and identified as a biocontrol bacterium against Sclerotinia sclerotiorum, a fungal plant pathogen. This bacterium produces a number of secondary metabolites, including phenazine-1-carboxylic acid, 2-hydroxyphenazine, pyrrolnitrin (PRN), hydrogen cyanide, proteases, lipases and siderophores. It also synthesizes and accumulates polyhydroxyalkanoate (PHA) polymers as carbon and energy storage compounds under nutrient-limited conditions. Pseudomonads like P. chlororaphis metabolize glucose via the Entner-Doudoroff and Pentose Phosphate pathways, which provide precursors for phenazine production. Mutants defective in phenazine (PHZ; PA23-63), PRN (PA23-8), or both (PA23-63-1) accumulated higher concentrations of PHAs than the wild-type strain (PA23) when cultured in Ramsay’s Minimal Medium with glucose or octanoic acid as the carbon source. Expression levels of six pha genes, phaC1, phaZ, phaC2, phaD, phaF, and phaI, were compared with wild type PA23 by quantitative real time polymerase chain reaction (qPCR). The qPCR studies indicated that there was no change in levels of transcription of the PHA synthase genes phaC1 and phaC2 in the phz- (PA23-63) and phz- prn- (PA23-63-1) mutants in glucose medium. There was a significant increase in expression of phaC2 in octanoate medium. Transcription of phaD, phaF and phaI increased significantly in the phz- prn- (PA23-63-1) mutant. Mutations in regulatory genes like gacS, rpoS, and relA/spoT, which affect PHZ and PRN production, also resulted in altered gene expression. The expression of phaC1, phaC2, phaF, and phaI genes was down-regulated significantly in gacS and rpoS mutants. Thus, it appears that PHZ, PRN, and PHA production is regulated by common mechanisms. Higher PHA production in the phz- (PA23-63), prn- (PA23-8), and phz- prn- (PA23-63-1) mutants in octanoic medium could be correlated with higher expression of phaC2. Further, the greater PHA production observed in the phz- and prn- mutants was not due to increased transcription of PHA synthase genes in glucose medium, but due to more accessibility of carbon substrates and reducing power, which were otherwise used for the synthesis of PHZ and PRN. View Full-Text
Keywords: Pseudomonas chlororaphis PA23; Biocontrol; Phenazine; Pyrrolnitrin; phz- and prn- mutants; Regulatory mutants; gacS; rpoS; relA/spoT; Polyhydroxyalkanoates; pha gene expression Pseudomonas chlororaphis PA23; Biocontrol; Phenazine; Pyrrolnitrin; phz- and prn- mutants; Regulatory mutants; gacS; rpoS; relA/spoT; Polyhydroxyalkanoates; pha gene expression
Figures

Graphical abstract

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
SciFeed

Share & Cite This Article

MDPI and ACS Style

Sharma, P.K.; Munir, R.I.; Plouffe, J.; Shah, N.; de Kievit, T.; Levin, D.B. Polyhydroxyalkanoate (PHA) Polymer Accumulation and pha Gene Expression in Phenazine (phz-) and Pyrrolnitrin (prn-) Defective Mutants of Pseudomonas chlororaphis PA23. Polymers 2018, 10, 1203.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Polymers EISSN 2073-4360 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top