Molecular insights into bacteroid development during Rhizobium-legume symbiosis

Andreas F Haag, Markus F F Arnold, Kamila K Myka, Bernhard Kerscher, Sergio Dall'angelo, Matteo Zanda, Peter Mergaert, Gail P Ferguson

Research output: Contribution to journalArticlepeer-review

96 Citations (Scopus)


Soil bacteria, termed rhizobia can form a symbiosis with legumes in which the bacteria fix atmospheric nitrogen into ammonia that can be utilised by the host. The plant in turn supplies the rhizobia with a carbon source. After infecting the host cell, the bacteria differentiate into a distinct bacteroid form, which is able to fix nitrogen. The bacterial BacA protein is essential for bacteroid differentiation in legumes producing nodule-specific cysteine-rich peptides (NCR), which induce the terminal differentiation of the bacteria into bacteroids. NCRs are antimicrobial peptides similar to mammalian defensins, which are important for the eukaryotic response to invading pathogens. The BacA protein is essential for rhizobia to survive the NCR peptide challenge. Similarities of the lifestyle of intracellular pathogenic bacteria suggest that host factors might also be important for inducing chronic infections in Brucella abortus and Mycobacterium tuberculosis infections. Moreover, rhizobial LPS is modified with an unusual fatty acid, which plays an important role in protecting the bacteria from environmental stresses. Mutants defective in the biosynthesis of this fatty acid display bacteroid development defects within the nodule. In this review, we will focus on these key components, which affect rhizobial bacteroid development and survival. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)364-383
Number of pages20
JournalFEMS Microbiology Reviews
Issue number3
Early online date2 Apr 2013
Publication statusPublished - May 2013

Bibliographical note

This review is dedicated to the memory of Gail P. Ferguson who passed away on 27 December 2011. A.F.H. was and B.K. is funded by an Institute of Medical Sciences, University of Aberdeen PhD studentship, M.F.F.A. and K.K.M. are funded by SULSA PhD studentships, and P.M. is supported by the Agence Nationale de la Recherche, grant ANR-09-BLAN-0396-01.


  • Rhizobium–legume symbiosis
  • antimicrobial peptides
  • nodule-specific
  • cysteine-rich peptides
  • bacteroid differentiation
  • BacA
  • lipopolysaccharide


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