Gluconacetobacter diazotrophicus

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Classification

Bacteria; Proteobacteria; Alphaproteobacteria; Rhodospirillales; Acetobacteraceae; Gluconacetobacter

Species

NCBI: [1]

Gluconacetobacter diazotrophicus

Description

Figure 1 : Electron micrograph of a G. diazotrophicus cell. Peritrichous flagella are visible. The dimensions of the cell are 0.7-0.9 μm x 2 μm. Photo taken by M. Gillis, K. Kersters, B. Hoste et al. (1989)[2]

Gluconacetobacter diazotrophicus is a symbiotic, plant-growth promoting bacteria. It was isolated from the roots and stems of Brazilian sugarcane plants in 1988 [1]. Upon discovery, the bacterium was named Saccharobacter nitrocaptans. Due to its acetic acid production and similarity to previously classified bacteria, however, it was later renamed to Aacetobacter diazotrophicus. Completion of 16S ribosomal RNA analysis led to a reclassification to its current designation and taxonomy [1,2,3].

G. diazotrophicus is a Gram-negative, nonspore forming and nitrogen fixing obligate aerobe [2]. The bacterium’s cells are shaped like straight rods with rounded ends and motility is provided by 1-3 lateral or peritrichous flagella. Cellular dimensions are approximately 0.7-0.9 μm x 2 μm [2]. When viewed under a microscope, cells are single, paired, or chainlike in structure. The temperature and pH growth optimums are 30°C and 5.5 respectively. The bacterium is acid-tolerant and can also both grow and fix nitrogen at pH of 3.0 and below [1,2]. Additionally, G. diazotrophicus grows optimally at a sucrose concentration of 10%, as found in its natural host, but is capable of growth at up to 30% sucrose under laboratory conditions. The bacteria has been shown to grow abundantly on other carbon substrates like D-galactose, D-fructose, and D-mannose [1].

Unlike many other bacteria that engage in symbiosis with plants, G. diazotrophicus is an endophyte and does not stimulate the production of nodules [1]. Without a host plant, the bacteria will not survive in the soil for more than two days [4]. Most host plants of G. diazotrophicus contain relatively high levels of sucrose, similar to the sugarcane on which it was discovered [5].

Significance

Figure 2. Corn and wheat, two monocot crops of agricultural significance, pictured side by side. Photo retrieved from: [9]

The ability of G. diazotrophicus to fix nitrogen and effectively promote the growth of its host plant opens the possibility for agricultural applications. Additionally, G. diazotrophicus has many other attractive characteristics. The bacteria is of monocot origin, less plant specific than other symbiotic nitrogen fixing bacteria, and does not require nodule structures for growth and nitrogen fixation [6]. Given these factors, G. diazotrophicus could be a less costly and more environmentally friendly alternative to nitrogen fertilizers that the agricultural industry currently relies on heavily [6,7]. The bacteria could be adapted to colonize other monocot plants if sucrose levels were not a limiting factor. Monocot staples in agriculture include corn, wheat, and rice. These crops account for approximately 70% of the total world crop production [8]. If nitrogen fertilizers could be supplemented or replaced by G. diazotrophicus colonization in these crops, that could lead to more sustainable and less environmentally damaging agricultural practices on a large scale [6].

Genome Structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence?

Cell Structure, Metabolism and Life Cycle

Interesting features of cell structure; how it gains energy; what important molecules it produces.

Figure 3. Molybdenum-dependent nitrogenase. G. diazotrophicus uses a Mo-dependent nitrogenase for nitrogen fixation. The Fe protein binds and hydrolyzes ATP, and the MoFe protein binds the substrate [23]

Ecology and Pathogenesis

Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Figure 4. Damage to X. albilineans structure. Transmission electron micrograph of X. albilineans when treated with gluconacin [22].

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

[1] V. A. Cavalcante and J. Dobereiner. “A new acid-tolerant nitrogen-fixing bacterium associated with sugarcane.” Plant and Soil. 1988. Volume 108. No. 1. p. 23–31.

[2] M. Gillis, K. Kersters, B. Hoste et al. “Acetobacter diazotrophicus sp. nov., a nitrogen-fixing acetic acid bacterium associated with sugarcane.” International Journal of Systematic Bacteriology. 1989. Volume 39. No. 3. p. 361–364.

[3] Y. Yamada, K.-I. Hoshino, and T. Ishikawa. “The phylogeny of acetic acid bacteria based on the partial sequences of 16S ribosomal RNA: the elevation of the subgenus gluconoacetobacter to the generic level.” Bioscience, Biotechnology and Biochemistry. 1997. Volume 61. No. 8. p. 1244–1251.

[4] M. A. Paula, V. M. Reis, and J. Döbereiner. “Interactions of Glomus clarum with Acetobacter diazotrophicus in infection of sweet potato (Ipomoea batatas), sugarcane (Saccharum spp.), and sweet sorghum (Sorghum vulgare).” Biology and Fertility of Soils. 1991. Volume 11. No. 2, p. 111–115.

[5] P. J. Riggs, M. K. Chelius, A. L. Iniguez, S. M. Kaeppler, and E. W. Triplett. “Enhanced maize productivity by inoculation with diazotrophic bacteria.” Australian Journal of Plant Physiology. 2001. Volume 28. No. 9. p. 829–836.

[6] N. Eskin, K. Vessey, L. Tian. "Research Progress and Perspectives of Nitrogen Fixing Bacterium, Gluconacetobacter diazotrophicus, in Monocot Plants." International Journal of Agronomy. 2014. Volume 2014. Article ID 208383. 13 pages.

[7] M. B. Peoples, D. F. Herridge, and J. K. Ladha. “Biological nitrogen fixation: an efficient source of nitrogen for sustainable agricultural production?” Plant and Soil. 1995. Volume 174. No. 1-2. p. 3–28.

[8] Van Vu, T., Sung, Y.W., Kim, J. et al. Challenges and Perspectives in Homology-Directed Gene Targeting in Monocot Plants. Rice. 2019. Volume 12. Article number 95.

[9] Lakeviewgrains2323243243. (2017, December 6). Wheat Technology Races to Catch Soybean and Corn. Lakeview Grains.

Authors

Page authored by Isaac Coker, Kyra Colston, and Danielle DeCesaris, students of Prof. Jay Lennon at Indiana University.