Chemotaxis in Azospirillum

Abstract

The ability of Azospirillum to colonize the roots of plants depends on motility and chemotaxis. Azospirillum cells are motile and capable of chemotaxis toward organic acids, sugars, and some aminoacids. Azospirillum is also able to navigate gradients of oxygen, alternative electron acceptors, and redox active compounds. Most attractants and repellents described thus far for this bacterial genus include compounds that affect intracellular metabolism, leading to the suggestion that most taxis responses correspond to energy taxis in Azospirillum spp. Several spatial and temporal gradient assays that can be implemented as quantitative methods are available to characterize taxis responses in Azospirillum species. The analysis of complete sequence genomes of several Azospirillum species reveals that taxis responses are coordinated by multiple chemotaxis pathways. All genomes also possess a chemotaxis pathway that is predicted to regulate alternative cellular functions other than fl agellar motility. Genome analyses indicate that all Azospirillum spp. sequenced to date encode for an extremely large repertoire of putative chemotaxis receptors, which is likely contributing to explaining their ubiquitous distribution.

Impact of plant growth-promoting bacteria on grain yield, protein content, and urea-15 N recovery by maize in a Cerrado Oxisol

“…Factors explaining the different responses of maize to inoculants carrying different PGPB (strains of A. brasilense compared to H. seropedicae) include the ability of these bacteria to fix N 2 from the atmosphere (Alves et al 2015;Ambrosini et al 2016) and produce plant regulators (Radwan et al 2004) as well as the bacteria-genotype interaction (Garcia de Salamone et al 1996;Alexandre 2015;Pereg et al 2016;Scharf et al 2016). In addition, previous studies have indicated that Azospirillum develop better in soils with lower contents of organic matter (Fallik et al 1988) and clay (Ferreira et al 2013) and these two factors might have maximized the effects of the A. brasilense inoculants in the sandy Oxisol of the present study (Table 4 and Fig.…”