Inoculation of axenic black mangrove seedlings in seawater for 8 days with either the terrestrial halotolerant plant growthpromoting bacterium Azospirillum halopraeferens or with Azospirillum brasilense produced heavy colonization of the root surface. The colonization pattern was different for the two strains. A. halopraeferens yielded mainly single cells embedded in a thick sheath, whereas A. ...

Azospirillum brasilense Sp 7 grew rapidly in AZO medium containing reduced nitrogen and succinate as an energy source, with a doubling time of 43 min. No growth was measured with glucose as the sole carbon source. In contrast, Azospirillum lipoferum Sp 59b could grow in media containing either succinate or glucose with a doubling time of 69 min and 223 min, respectively. Warburg-Barcroft respir...

The colonization of wheat roots by Azospirillum brasilense was used as a model system to evaluate the utility of whole-cell hybridization with fluorescently labeled, rRNA-targeted oligonucleotide probes for the in situ monitoring of rhizosphere microbial communities. Root samples of agar- or soil-grown 10- and 30-day-old wheat seedlings inoculated with different strains of A. brasilense were hy...

This study measured the relations between tryptophan production, the phytohormone indole-3-acetic acid (IAA) and the metabolism and accumulation of starch during synthetic mutualism between the microalgae Chlorella sorokiniana and the microalgae growth-promoting bacteria Azospirillum brasilense, created by co-immobilization in alginate beads. Experiments used two wild-type A. brasilense strains...

Azospirillum brasilense is a nitrogen fixing bacterium that has been shown to have various beneficial effects on plant growth and yield. Under normal conditions A. brasilense exists in a motile flagellated form, which, under starvation or stress conditions, can undergo differentiation into an encapsulated, cyst-like form. Quantitative RT-PCR can be used to analyse changes in gene expression dur...

It has previously been reported that the alpha-proteobacterium Azospirillum brasilense undergoes methylation-independent chemotaxis; however, a recent study revealed cheB and cheR genes in this organism. We have constructed cheB, cheR, and cheBR mutants of A. brasilense and determined that the CheB and CheR proteins under study significantly influence chemotaxis and aerotaxis but are not essent...

The mechanism for "NH4+ switch-off/on" of nitrogenase activity in Azospirillum brasilense and A. lipoferum was investigated. A correlation was established between the in vivo regulation of nitrogenase activity by NH4Cl or glutamine and the reversible covalent modification of dinitrogenase reductase. Dinitrogenase reductase ADP-ribosyltransferase (DRAT) activity was detected in extracts of A. br...

Azospirillum brasilense is a diazotroph found in association with important agricultural crops. In this organism, the regulation of nitrogen fixation by ammonium ions involves several proteins including the uridylyltransferase/uridylyl-removing enzyme, GlnD, which reversibly uridylylates the two PII proteins, GlnB and GlnZ, in response to the concentration of ammonium ions. In the present study...

The capacity of Azospirillum brasilense to enhance the accumulation of K, P, Ca, Mg, S, Na, Mn, Fe, B, Cu, and Zn in inoculated wheat and soybean plants was evaluated by using two different analytical methods with five A. brasilense strains originating from four distinct geographical regions. A Pseudomonas isolate from the rhizosphere of Zea mays seedlings was included as a control. All A. bras...

A medium for consistent induction of aggregation of Azospirillum brasilense cells was developed and used to study the effects of chemical and physical factors as well as extracellular components involved in this phenomenon. Growth of A. brasilense strain Cd in a high C:N medium using fructose and ammonium chloride as C and N sources, respectively, resulted in flocculation visible to the naked e...