Azospirillum brasilense

Azospirillum brasilense is a well studied, nitrogen-fixing (diazotroph), genetically tractable, Gram-negative, alpha-proteobacterium bacterium.[1] A. brasilense is able to fix nitrogen in the presence of low oxygen levels, making it a microaerobic diazotroph. Originally isolated from nitrogen poor soils in the Netherlands in 1925, it is widely found in the rhizospheres of grasses around the world where it confers plant growth promotion.[2][3] Whether growth promotion occurs through direct nitrogen flux from the bacteria to the plant or through hormone regulation is debated.[4] The two most commonly studied strains are Sp7 (ATCC 29145) and Sp245.

Azospirillum brasilense
Scientific classification
Kingdom:
Bacteria
Phylum:
Proteobacteria
Class:
Alpha Proteobacteria
Order:
Rhodospirillales
Family:
Rhodospirillaceae
Genus:
Azospirillum
Species:
A. brasilense

Tarrand, Krieg & Döbereiner, 1978
A. brasilense promoting the growth of Setaria viridis, a model plant for Zea mays (corn).

The genome of A. brasilense Sp245 has been sequenced and is 7Mbp in size and spread across 7 chromosomes. The high GC content (70%) makes it challenging to engineer.[5] Sp245 can be transformed with OriV origin of replication plasmids through conjugation and electroporation. The strain is natively resistant to both spectinomycin and ampicillin antibiotics. Kanamycin resistance is used as a selectable marker.[6] A. brasilense has a high evolutionary adaptation rate driven by codon mutation and transposon hopping.

Annotated 42kbp genetic context of the nitrogenase genes in A. brasilense Sp245 compiled from raw sequencing data.[7] There are a total of 45 genes, 26 of them annotated by homology, 8 putative functions, 11 completely unknown and no homologs.

A strain originally classified as Roseomonas fauriae was reclassified as A. brasilense. It was first isolated from a hand wound of a woman in Hawaii in 1971, and was named for Yvonne Faur "for her contributions to public health bacteriology and, specifically, for her contribution to the recognition of pink-pigmented bacteria."[8][9]

References
  1. Tarrand, Jeffrey J.; Krieg, Noel R.; Döbereiner, Johanna (1978). "A taxonomic study of theSpirillum lipoferumgroup, with descriptions of a new genus,Azospirillumgen. nov. and two species,Azospirillum lipoferum(Beijerinck) comb. nov. andAzospirillum brasilensesp. nov". Canadian Journal of Microbiology. 24 (8): 967–980. doi:10.1139/m78-160. ISSN 0008-4166. PMID 356945.
  2. Holguin, G.; Patten, C. L.; Glick, B. R. (1999-04-07). "Genetics and molecular biology of Azospirillum". Biology and Fertility of Soils. 29 (1): 10–23. doi:10.1007/s003740050519. ISSN 0178-2762.
  3. Tien TM, Gaskins MH, Hubbell DH (May 1979). "Plant Growth Substances Produced by Azospirillum brasilense and Their Effect on the Growth of Pearl Millet (Pennisetum americanum L.)". Applied and Environmental Microbiology. 37 (5): 1016–24. PMC 243341. PMID 16345372. Retrieved 2013-07-18.
  4. Boddey, Robert M.; Urquiaga, Segundo; Alves, Bruno J.R.; Reis, Veronica (May 2003). "Endophytic nitrogen fixation in sugarcane: present knowledge and future applications". Plant and Soil. 252 (1): 139–149. doi:10.1023/a:1024152126541. ISSN 0032-079X.
  5. Mammedov, TG.; Pienaar, E.; Whitney, SE.; TerMaat, JR.; Carvill, G.; Goliath, R.; Subramanian, A.; Viljoen, HJ. (December 2008). "A Fundamental Study of the PCR Amplification of GC-Rich DNA Templates". Computational Biology and Chemistry. 32 (6): 452–457. doi:10.1016/j.compbiolchem.2008.07.021. ISSN 1476-9271. PMC 2727727. PMID 18760969.
  6. PhD qualifying exam talk, Department of Bioengineering at Stanford University, Tim Schnabel, 12/12/2017
  7. "KEGG GENOME: Azospirillum brasilense Sp245". www.genome.jp. Retrieved 2018-11-05.
  8. Helsel, L. O.; Hollis, D. G.; Steigerwalt, A. G.; Levett, P. N. (2006). "Reclassification of Roseomonas fauriae Rihs et al. 1998 as a later heterotypic synonym of Azospirillum brasilense Tarrand et al. 1979". International Journal of Systematic and Evolutionary Microbiology. 56 (12): 2753–2755. doi:10.1099/ijs.0.64549-0. PMID 17158972.
  9. Rihs JD, Brenner DJ, Weaver RE, Steigerwalt AG, Hollis DG, Yu VL. Roseomonas, a new genus associated with bacteremia and other human infections. Journal of clinical microbiology. 1993 Dec 1;31(12):3275-83.
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