【根瘤菌】Andreas F. Haag Markus F. F. Arnold Kamila K. Myka Bernhard Kerscher Sergio Dall'Angelo Matteo Zanda Peter Mergaert Gail P. Ferguson. Molecular insights into bacteroid development duringRhizobium–legume symbiosis. FEMS Microbiology Reviews
Abstract
Rhizobial soil bacteria can form a symbiosis with legumes in which the bacteria fix atmospheric nitrogen into ammonia that can be utilized 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 (NCRs) 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 in the lifestyle of intracellular pathogenic bacteria suggest that host factors might also be important for inducing chronic infections associated with Brucella abortus and Mycobacterium tuberculosis. Moreover rhizobial lipopolysaccharide 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.
【微生物互养】Brandon E.L. Morris Ruth Henneberger Harald Huber Christine Moissl-Eichinger. Microbial syntrophy: interaction for the common good. FEMS Microbiology Reviews
Abstract
Classical definitions of syntrophy focus on a process performed through metabolic interaction between dependent microbial partners such as the degradation of complex organic compounds under anoxic conditions. However examples from past and current scientific discoveries suggest that a new simple but wider definition is necessary to cover all aspects of microbial syntrophy. We suggest the term ‘obligately mutualistic metabolism’ which still focuses on microbial metabolic cooperation but also includes an ecological aspect: the benefit for both partners. By the combined metabolic activity of microorganisms endergonic reactions can become exergonic through the efficient removal of products and therefore enable a microbial community to survive with minimal energy resources. Here we explain the principles of classical and non-classical syntrophy and illustrate the concepts with various examples. We present biochemical fu