A proteomic approach to understand the role of the outer membrane porins in the organic solvent-tolerance of Pseudomonas aeruginosa PseA.

R Hemamalini,John R Battista,Sunil Khare

doi:10.1371/journal.pone.0103788

R Hemamalini, John R Battista + Show 1 more

Open Access

https://doi.org/10.1371/journal.pone.0103788

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Journal: PloS one	Publication Date: Aug 4, 2014
Citations: 39	License type: CC BY 4.0

Affiliation: Indian Institute of Technology Delhi

Abstract

Solvent-tolerant microbes have the unique ability to thrive in presence of organic solvents. The present study describes the effect of increasing hydrophobicity (log Pow values) of organic solvents on the outer membrane proteome of the solvent-tolerant Pseudomonas aeruginosa PseA cells. The cells were grown in a medium containing 33% (v/v) alkanes of increasing log Pow values. The outer membrane proteins were extracted by alkaline extraction from the late log phase cells and changes in the protein expression were studied by 2-D gel electrophoresis. Seven protein spots showed significant differential expression in the solvent exposed cells. The tryptic digest of the differentially regulated proteins were identified by LC-ESI MS/MS. The identity of these proteins matched with porins OprD, OprE, OprF, OprH, Opr86, LPS assembly protein and A-type flagellin. The reported pI values of these proteins were in the range of 4.94–8.67 and the molecular weights were in the range of 19.5–104.5 kDa. The results suggest significant down-regulation of the A-type flagellin, OprF and OprD and up-regulation of OprE, OprH, Opr86 and LPS assembly protein in presence of organic solvents. OprF and OprD are implicated in antibiotic uptake and outer membrane stability, whereas A-type flagellin confers motility and chemotaxis. Up-regulated OprE is an anaerobically-induced porin while Opr86 is responsible for transport of small molecules and assembly of the outer membrane proteins. Differential regulation of the above porins clearly indicates their role in adaptation to solvent exposure.

Highlights

Organic solvents have been in use as disinfectants and microbicidal agents for a long time
Strains of Pseudomonas putida tolerant to toluene, Clostridium acetobutylicum to butanol, Escherichia coli to ethanol are known among the Gram-negative bacteria [3]
Microorganisms adapt to organic solvents by (i) partitioning the solvent in the lipid layer, (ii) isomerisation of cis- unsaturated fatty acids to trans- unsaturated fatty acids leading to denser membranes, (iii) changing the saturated-to-unsaturated fatty acid ratio (iv) changes in length of the acyl-chains and (v) changes in the phospholipid head groups [6]

Summary

Introduction

Organic solvents have been in use as disinfectants and microbicidal agents for a long time. The present work aims at evaluating the effect of alkanes of increasing hydrophobicity (log Pow) such as n-hexane, cyclohexane, n-heptane, n-octane, n-decane, n-dodecane and n-tetradecane on the proteome profile of a solvent-tolerant Pseudomonas strain, especially to see which proteins get differentially expressed in response to solvent exposure and play a role in the cellular adaptation. The cells grown in the medium containing high amount of alkanes were studied for the changes in the outer membrane proteome using two-dimensional gel electrophoresis followed by identification of the differentially expressed proteins by ESI-Mass.

Results

Conclusion