Endophytic Nitrogen-fixing Bacteria Research Articles

A putative new endophytic nitrogen-fixing bacterium Pantoea sp. from sugarcane.

To isolate and identify endophytic nitrogen-fixing bacteria in sugarcane growing in Cuba without chemical fertilizers. Two N2-fixing isolates, 9C and T2, were obtained from surface-sterilized stems and roots, respectively, of sugarcane variety ML3-18. Both isolates showed acetylene reduction and H2 production in nitrogen-free media. Nitrogenase activity measured by H2 production was about 15 times higher for isolate 9C than for T2 or for Gluconoacetobacter diazotrophicus (PAL-5 standard strain, ATCC 49037). The nifH gene segment was amplified from both isolates using specific primers. Classification of both T2 and 9C was made on the basis of morphological, biochemical, PCR tests and 16S rDNA sequence analysis. Isolate 9C was identified as a Pantoea species from its 16S rDNA, but showed considerable differences in physiological properties from previously reported species of this genus. For example, 9C can be cultured over a wide range of temperature, pH and salt concentration, and showed high H2 production (up to 67.7 nmol H2 h(-1) 10(10) cell(-1)). Isolate T2 was a strain of Gluconacetobacter diazotrophicus. A new N2-fixing endophyte, i.e. Pantoea, able to produce H2 and to grow in a wide range of conditions, was isolated from sugarcane stem tissue and characterized. The strain with these attributes may well be valuable for agriculture.

Review: A brief story of nitrogen fixation in sugarcane - reasons for success in Brazil.

Sugarcane was first introduced into Brazil in 1532, in São Vicente (São Paulo State) by the Portuguese. Since the first cane selection and breeding programs started in Brazil, both local and introduced material were used. In none of the breeding programs were large amounts of nitrogen fertilizer utilized, and this may be the reason why today the best materials have little demand for nitrogen fertilizer, and an effective association has developed between endophytic nitrogen-fixing bacteria and the plant. In some cases high inputs of associated biological nitrogen fixation have been observed. The oil crisis also played a role in the sugarcane story, since the alcohol-from-cane-juice (PRO-ÁLCOOL) program installed to find a substitute for gasoline in cars, stimulated the selection of highly efficient varieties with low nitrogen fertilizer input. The recent promising results involving the inoculation of micropropagated sugarcane plants with endophytic diazotrophic bacteria, along with the ongoing Brazilian sugarcane plant and bacterial genome programs, suggest that the success of the Brazilian sugarcane business may continue for many years to come, considering the potential to be exploited.

Enhancing the internal plant colonization rate with endophytic nitrogen-fixing bacteria

Enhancing the internal plant colonization rate with endophytic nitrogen-fixing bacteria

Colonization of sugarcane by Acetobacter diazotrophicus is inhibited by high N-fertilization

Acetobacter diazotrophicus is a nitrogen-fixing endophytic bacterium, originally isolated from sugarcane. Its colonizing ability was evaluated in high and low N-fertilized sugarcane plants by inoculating stem-cuts with a β-glucuronidase marked A. diazotrophicus strain. Bacterial quantification by the most probable number technique showed a severe decrease of A. diazotrophicus cells in plants fertilized with high levels of nitrogen. The inoculated strain was detected inside low N-fertilized sugarcane plants by histochemical staining of β-glucuronidase and scanning electron microscopy. A. diazotrophicus was found mainly inside cortical cells of stems and inside xylem vessels. No β-glucuronidase activity was observed in non-inoculated plants. High nitrogen fertilization of fields might be a threat to maintaining naturally occurring endophytic associations.

Colonization of sugarcane by Acetobacter diazotrophicus is inhibited by high N-fertilization

Acetobacter diazotrophicus is a nitrogen-fixing endophytic bacterium, originally isolated from sugarcane. Its colonizing ability was evaluated in high and low N-fertilized sugarcane plants by inoculating stem-cuts with a β-glucuronidase marked A. diazotrophicus strain. Bacterial quantification by the most probable number technique showed a severe decrease of A. diazotrophicus cells in plants fertilized with high levels of nitrogen. The inoculated strain was detected inside low N-fertilized sugarcane plants by histochemical staining of β-glucuronidase and scanning electron microscopy. A. diazotrophicus was found mainly inside cortical cells of stems and inside xylem vessels. No β-glucuronidase activity was observed in non-inoculated plants. High nitrogen fertilization of fields might be a threat to maintaining naturally occurring endophytic associations.