Gluconacetobacter diazotrophicus General Description

Gluconacetobacter diazotrophicus (formerly Acetobacter diazotrophicus) is a bacilli, aerobic, obligate endophytic (an endosymbiont), diazotrophic (bacteria that fix atmospheric N) bacterium discovered by Joana Dobereiner (1924 to 2000).  It has been undergoing lab and field tests in research institutions around the globe for the past 50 years, ever since it was first isolated from the phyllosphere as well as the rhizophere of inter-cellular spaces of sugarcane. It was discovered in the high yielding Brazilian sugar cane varieties (e.g. SP 70‐1143, SP 79‐2312, CB 45‐3, Krakatau). It is however found in other crops such as pineapple in Mexico and other South American countries. It may actually fix up to 70% of their N requirements.  Researchers feel G  diazotrophicusso is so important that recently a complete genome sequence of the sugarcane nitrogen-fixing endophyte Gluconacetobacter diazotrophicus has been completed. It’s map is Pal5. You can catch up on the 50 year investigative history starting in Brazil on this pdf file entitled History on the biological nitrogen fixation research in graminaceous plants- special emphasis on the Brazilian experience. Or read the synopses in the info below. There are a lot more diazotrophic bacterium than I had at first realized, the rhizospheric (Beijerinckia fluminensis and Azotobacter paspali), associative, (Azospirillum lipoferum, A. brasilense, A. amazonense) and the endophytic (Herbaspirillum seropedicae, H. rubrisubalbicans, Gluconacetobacter diazotrophicus, Burkholderia brasilensis and B. tropica). It’s a “must Read” for us natural-horticulturists.

History on the nitrogen fixation research in graminaceous plants in Brazil

This review covers the history on Biological Nitrogen Fixation (BNF) in Graminaceous plants grown in Brazil, and describes research progress made over the last 40 years, most of whichwas coordinated by Johanna Döbereiner. One notable accomplishment during this period was the discovery of several nitrogen-fixing bacteria such as the rhizospheric (Beijerinckia fluminensis and Azotobacter paspali), associative (Azospirillum lipoferum, A. brasilense, A. amazonense) and the endophytic (Herbaspirillum seropedicae, H. rubrisubalbicans, Gluconacetobacter diazotrophicus, Burkholderia brasilensis and B. tropica). The role of these diazotrophs in association with grasses, mainly with cereal plants, has been studied and a lot of progress has been achieved in the ecological, physiological, biochemical, and genetic aspects. The mechanisms of colonization and infection of the plant tissues are better understood, and the BNF contribution to the soil/plant system has been determined. Inoculation studies with diazotrophs showed that endophytic bacteria have a much higher BNF contribution potential than associative diazotrophs. In addition, it was found that the plant genotype influences the plant/bacteria association. Recent data suggest that more studies should be conducted on the endophytic association to strengthen the BNF potential. The ongoing genome sequencing programs: RIOGENE (Gluconacetobacter diazotrophicus) and GENOPAR (Herbaspirillum seropedicae) reflect the commitment to the BNF study in Brazil and should allow the country to continue in the forefront of research related to the BNF process in Graminaceous plants.

Gluconacetobacter diazotrophicus Taxonomy

  • Kingdom: Bacteria
  • Phylum: Proteobacteria
  • Class: Alphaproteobacteria
  • Order: Rhodospirillales
  • Family: Acetobacteraceae
  • Genus: Gluconacetobacter
  • Species: diazotrophicus

Gluconacetobacter diazotrophicus | Diazotrophic

gluconacetobacter-diazotrophicus-featuredUsing seedlings grown aseptically in sucrose-containing culture media, it has been shown that inoculation with very low numbers of G. diazotrophicus results in extensive intracellular colonization of roots and progressive systemic intracellular root colonization, enabling non-nodular endosymbiotic nitrogen fixation using naturally-occurring nitrogen directly from the atmosphere.  The amazing thing is the bacterium is capable of effecting a very wide range of plants. One of the studies on this topic by The University of Nottingham’s Prof. Edward Cocking, showed results in Arabidopsis thaliana and the crop plants maize (Zea mays), rice (Oryza sativa), wheat (Triticum aestivum), oilseed rape, Brassica napus), tomato Lycopersicon esculentum), and white clover (Trifolium repens).

Gluconacetobacter diazotrophicus Multi Characteristics

The nitrogen-fixation systems of the bacterium provide the plant with essential nitrogenous compounds from the atmosphere while the plant provides a protected environment for the bacterium to grow in. In addition to being able to fix nitrogen it has been shown to possess many other characteristics potentially valuable in the area of agriculture. These characteristics include, plant growth promotion (above and beyond Nitrogen-fixation), sugar metabolism pathways, secretion of organic acids, promotes an increase in the solubility of phosphate as well as zinc[1], synthesis of auxin, antifungal-antibacterial properties and the occurrence of bacteriocins (proteinaceous toxins inhibiting the growth of closely related bacterial strains).  Gluconacetobacter diazotrophicus produces a lysozyme-like bacteriocin that inhibits the growth of the sugarcane pathogen Xanthomonas albilineans [2] It has antifungal activity against Fusarium sp. and Helminthosporium carbonum. [3]

Gluconacetobacter diazotrophicus Mode of Inoculation

Gluconacetobacter diazotrophicus is not found in the soil. It so far has only been collected from plant cuttings. One study states their Gluconacetobacter diazotrophicus isolates were obtained from inner tissues of roots and leaves of different sugarcane varieties maintained in the Germoplasm Bank in Brazil. The largest and most important Germoplsim Bank in Brazil being the University of São Paulo Gracilariaceae Germplasm Bank. This bank has been used as a source of material for research developed locally and abroad. It harbors over 200 species, some of which have high economic value.

Even though most cultures are obtained from naturally inoculated plant tissues, Gluconacetobacter diazotrophicus applied together with arbuscular mycorrhizal fungi in a dual inoculation (pdf), has shown very positive results. Gluconacetobacter diazotrophicus has not been isolated in soils. The bacterium is passed on to another plant by vegetative propagation, stem pieces (Cavalacante VA, Dobereiner J. A new acid tolerant nitrogen fixing bacterium associated with sugarcane, 1988). Apparently, dual inoculation with AM is key to applying the new N-fix bacteria in the field, other than plant propagation cuttings.

Technical approaches to inoculate micropropagated sugar cane plants with Gluconacetobacter diazotrophicus

The below is a short description of the Abstract that may be purchased at Springer Link.

Micropropagated plantlets of sugar cane were inoculated with the N2-fixing bacterium Gluconacetobacter diazotrophicus. Various modifications on the basic plant culture medium MS were made for the plant/bacteria association. The protocol required the inoculation of the bacteria at the end of the rooting period in a medium without hormones or vitamins, and with the concentration of sugar and mineral nutrients reduced by a factor of 10. Individual plants were inoculated with A. diazotrophicus and maintained under the appropriate light and temperature condition used for micropropagation up to 7 days. The system favored the infection and the establishment of the bacteria within the plant tissue. Bacteria colonized the plant tissue and accumulated in inter-cellular cavities and the region of lateral root emergence and also colonizes the xylem vessels. The inoculated plantlets were subsequently transferred to the acclimatization phase and after 30 days it was possible to isolate the bacteria from plant tissue. This protocol permitted studies of infection and comparison among strains.

Important Gluconacetobacter diazotrophicus Links, laboritories & .pdfs

  1. Intracellular colonization of roots of Arabidopsis and crop plants by Gluconacetobacter diazotrophicus (2006) Edward C. Cocking
  2. Nitrogen fixation associated with grasses and cereals: Recent progress and perspectives for the future, Robert M. Boddey, Johanna Dobereiner
  3. Further Observations of Gluconacetobacter diazotrophicus by the Department of Biologgical Sciences, University of Dundee.pdf
  4. The effect of inoculating endophytic N2-fixing bacteria on micropropagated sugarcane plants (7 different combinations of inoculum , using 5 endophytic diazotrophic species, Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae, Herbaspirillum rubrisubalbicans, Azospirillum amazonense and Burkholderia sp.)pdf
  • National Center for Vegetable Crops Research (CNPH), Embrapa Hortaliças, CP 218, 70359-970 Brasília, DF, Brazil
  • Departamento de Biologia Celular, Universidade de Brasília, Campus Universitário, Asa Norte, 70910-900 Brasília, DF, Brazil
  • Embrapa Recursos Genéticos e Biotecnologia, Parque Estação Biológica, Final Av. W3 Norte, 70770-900 Brasília, DF, Brazil

References

[1]-Saravanan VS, Kalaiarasan P, Madhaiyan M, Thangaraju M: Solubilization of insoluble zinc compounds by Gluconacetobacter diazotrophicus and the detrimental action of zinc ion (Zn2+) and zinc chelates on root knot nematode Meloidogyne incognita.

[2]- Blanco Y, Blanch M, Pin D, Legaz ME, Vicente C: Antagonism of Gluconacetobacter diazotrophicus (a sugarcane endosymbiont) against Xanthomonas albilineans (pathogen) studied in alginate-immobilized sugarcane stalk tissues.

[3]- Mehnaz S, Lazarovits G: Inoculation effects of Pseudomonas putida, Gluconacetobacter azotocaptans, and Azospirillum lipoferum on corn plant growth under greenhouse conditions.

Reis V M, Olivares F L, Oliveira A L M, Reis F B Jr, Baldani J Iand Döbereiner J 1999 Technical approaches to inoculate micropropagated sugarcane plants with Acetobacter diazotrophicus. Plant Soil 206, 205–211.