Nitric Oxide in Azospirillum and Related Bacteria: Production and Effects

Abstract

Azospirillum and other related plant growth-promoting rhizobacteria produce several phytohormones and signaling molecules. Among them, nitric oxide is now recognized as a key second messenger in plants and in benefi cial and pathological plant-microorganism interactions switching on and off different processes. Nitric oxide has been associated to the signaling cascades leading to lateral and adventitious root development induced by Azospirillum in tomato, in the Azospirillum biofi lm formation, and in the nodule development in rhizobia-legume symbiosis. As a central component of N cycle, nitric oxide is produced and consumed in different metabolic pathways such as denitrifi cation and nitrifi cation, and it is closely related to other N compound like nitrate and nitrite. The emerging importance of nitric oxide in the biology of bacteria-plant relation is a challenge for understanding the molecular and chemical basis underpinning the nitric oxide actions in the association of plant growth-promoting bacteria with roots. In this chapter we describe several techniques that allow detecting and quantifying endogenously produced and exogenously applied nitric oxide in bacteria cultures and inoculated plants, including real-time and/or in situ nitric oxide production. The most used methods-Griess assay, electron paramagnetic resonance, fl uorescent probes, and electrochemical sensors-are described with detailed protocols, discussing their advantages and drawbacks. In addition, we remark factors affecting nitric oxide production like growth conditions, metabolic inhibitors, and others. Finally, pharmacological, genetic, and histochemical strategies to study the role of nitric oxide in the association of Azospirillum with plant roots are presented with examples and methodological procedures.

Nitric Oxide Detection Using a Chemical Trap Method for Applications in Bacterial Systems

“…The Griess method was performed according to the procedures described in the literature [ 34 ], and samples were analyzed after 24, 48, and 72 h of growth in liquid media. The observed NO values were standardized for the bacterial growth using the total protein concentration by the Bradford method [ 35 ].…”

Bactérias diazotróficas em <i>Guzmania monostachia</i> (Bromeliaceae): identificação, sinalização e colonização dos tecidos foliares

“…Além disso, nos últimos anos, tem se verificado que o NO também é produzido pelas bactérias para comunicação com as plantas (Creus et al, 2005). Foi demonstrado que a rizobactéria promotora de crescimento vegetal Azospirillum brasilense produz NO e este participa na sinalização para indução de raízes laterais e adventícias em tomate (Amenta et al, 2015 (Carvalho et al, 2014).…”