Abstract
Plants interact with a large number of microorganisms that greatly influence their growth and health. Among the beneficial microorganisms, rhizosphere bacteria known as Plant Growth Promoting Bacteria increase plant fitness by producing compounds such as phytohormones or by carrying out symbioses that enhance nutrient acquisition. Nitrogen-fixing bacteria, either as endophytes or as endosymbionts, specifically improve the growth and development of plants by supplying them with nitrogen, a key macro-element. Survival and proliferation of these bacteria require their adaptation to the rhizosphere and host plant, which are particular ecological environments. This adaptation highly depends on bacteria response to the Reactive Oxygen Species (ROS), associated to abiotic stresses or produced by host plants, which determine the outcome of the plant-bacteria interaction. This paper reviews the different antioxidant defense mechanisms identified in diazotrophic bacteria, focusing on their involvement in coping with the changing conditions encountered during interaction with plant partners.
Highlights
Diazotrophic rhizobacteria that interact positively with plants involve endophytic bacteria and rhizobial endocellular symbionts
During S. meliloti/M.sativa interaction, ohr transcripts were detected in nodules and ohr inactivation affects the efficiency of A. caulinodans/ S. rostrata symbiosis, suggesting that the sensing of organic peroxides by OhrR plays a role in the adaptation to the host environment [70,115]
The characterization of many redox regulatory systems has shown the importance of redox regulation in the plant-bacteria symbiotic recognition and the functioning of the symbiotic interactions
Summary
Diazotrophic rhizobacteria that interact positively with plants involve endophytic bacteria and rhizobial endocellular symbionts. Their benefit on plant growth has been attributed to a variety of single or combined mechanisms, including phosphate solubilization, siderophore synthesis, production, and secretion of several phytohormones as well as biological nitrogen (N2 ) fixation (BNF), leading to enhanced plant nutrition [1]. The BNF is exclusively performed by prokaryotes, archaea, and bacteria, collectively known as diazotrophs. Diazotrophic bacteria encode a specific protein complex, the nitrogenase that reduces the atmospheric N2 to ammonia (NH3 ). The diazotrophs such as Azotobacter sp., Azospirillum sp., Bacillus sp., Cyanobacteria sp., and Clostridum sp.
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