Cellular responses during morphological transformation in Azospirillum brasilense and Its flcA knockout mutant

Xingsheng Hou; Mary McMillan; Joëlle V F Coumans; Anne Poljak; Mark J Raftery; Lily Pereg

doi:10.1371/journal.pone.0114435

Cellular responses during morphological transformation in Azospirillum brasilense and Its flcA knockout mutant

PLoS One. 2014 Dec 12;9(12):e114435. doi: 10.1371/journal.pone.0114435. eCollection 2014.

Authors

Xingsheng Hou¹, Mary McMillan², Joëlle V F Coumans³, Anne Poljak⁴, Mark J Raftery⁵, Lily Pereg²

Affiliations

¹ School of Science and Technology, University of New England, Armidale, New South Wales, Australia; Department of Microbiology and Immunology, Shanxi Medical University, Taiyuan, Shanxi, China.
² School of Science and Technology, University of New England, Armidale, New South Wales, Australia.
³ School of Science and Technology, University of New England, Armidale, New South Wales, Australia; School of Rural Medicine, University of New England, Armidale, New South Wales, Australia.
⁴ Bioanalytical Mass Spectrometry Facility, Analytical Centre, University of New South Wales, Sydney, New South Wales, Australia; The School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
⁵ Bioanalytical Mass Spectrometry Facility, Analytical Centre, University of New South Wales, Sydney, New South Wales, Australia.

Abstract

FlcA is a response regulator controlling flocculation and the morphological transformation of Azospirillum cells from vegetative to cyst-like forms. To understand the cellular responses of Azospirillum to conditions that cause morphological transformation, proteins differentially expressed under flocculation conditions in A. brasilense Sp7 and its flcA knockout mutant were investigated. Comparison of 2-DE protein profiles of wild-type (Sp7) and a flcA deletion mutant (Sp7-flcAΔ) revealed a total of 33 differentially expressed 2-DE gel spots, with 22 of these spots confidently separated to allow protein identification. Analysis of these spots by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and MASCOT database searching identified 48 proteins (≥10% emPAI in each spot). The functional characteristics of these proteins included carbon metabolism (beta-ketothiolase and citrate synthase), nitrogen metabolism (Glutamine synthetase and nitric oxide synthase), stress tolerance (superoxide dismutase, Alkyl hydroperoxidase and ATP-dependent Clp protease proteolytic subunit) and morphological transformation (transducer coupling protein). The observed differences between Sp7 wild-type and flcA- strains enhance our understanding of the morphological transformation process and help to explain previous phenotypical observations. This work is a step forward in connecting the Azospirillum phenome and genome.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Azospirillum brasilense / cytology*
Azospirillum brasilense / genetics*
Azospirillum brasilense / metabolism
Azospirillum brasilense / physiology
Bacterial Proteins / genetics*
Carbohydrate Metabolism / genetics
Congo Red / metabolism
Flocculation
Gene Expression Profiling
Gene Knockout Techniques*
Mutation*
Nitrogen Fixation / genetics
Phenotype
Plant Roots / microbiology
Proteomics
Stress, Physiological / genetics
Transcription Factors / deficiency*
Transcription Factors / genetics*

Substances

Bacterial Proteins
FlcA protein, Azospirillum brasilense
Transcription Factors
Congo Red

Grants and funding

L.P. received a Faculty of the Sciences Internal Research Grant, from the University of New England. X.H. was supported by a UNERA International Fee & Stipend Scholarship from the University of New England. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Dr. Xingsheng Hou received funding under the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province (No. 2014-95) for the period 01/2014 to 12/2015.