Mesorhizobium sp. BNC1
   
   
 

PLEASE NOTE: Mesorhizobium sp. BNC1 was formerly known as Agrobacterium sp. BNC1

Proposal to Sequence the Genome of the EDTA-Degrading Bacterium Agrobacterium sp. Strain BNC1

Harvey Bolton, Jr., Environmental Microbiology Group, Pacific Northwest National Laboratory, Richland, WA99352. Phone: (509) 376-3950, Fax: (509) 3761321, email: [email protected]; and Luying Xun, School of Molecular Biosciences, Washington State University, Pullman, WA 99164-4234.

DOE Relevance. Synthetic chelating agents such as ethylenediaminetetraacetate (EDTA), diethylenetriaminepentaacetate (DTPA), and nitrilotriacetate (NTA) form stable water-soluble complexes with a wide range of metals and radionuclides. The co-disposal of synthetic chelating agents with radionuclides at several DOE sites has lead to the enhanced transport of radionuclides in groundwater, because the chelate substantially alters the adsorptive properties of the radionuclides (see review in (2)). EDTA is very recalcitrant in the environment, presumably because it can complex cations present in bacterial cell walls (e.g., CaEDTA2-, MgEDTA2-) (2).

Agrobacterium sp. Strain BNC1. Agrobacterium sp. strain BNC1 was isolated from an enrichment of industrial sewage receiving EDTA-containing wastewater effluents added to surface soil (7). This strain is able to use EDTA as a sole source of C and N. Two other EDTA-degrading bacteria have been isolated including Agrobacterium strain (ATCC 55002) (5) and DSM 9103 (8)). All of the EDTA-degrading strains are phylogenetically closely related and belong to the alpha Proteobacterial subdivision (6). We have cloned and sequenced a gene cluster involved in EDTA degradation and the elongation factor Tu (EF-Tu) gene from strain BNC1 (1). The EF-Tu is 91% identical to the EF-Tu from Agrobacterium tumefaciens. For this reason we have identified BNC1 as an Agrobacterium sp. The genus Agrobacterium is generally present in soil, belongs to the alpha Proteobacterial subdivision, and are characterized as gram-negative, non-spore forming rods that have a few peritrichous flagella when they are motile. Strain BNC1 grows very well on standard A. tumefaciens media, and genetic systems applicable to A. tumefaciens have worked in BNC1 (3). For example, plasmids can be introduced into BNC1 by conjugation. Strain BNC1 can serve as a model system because it degrades EDTA, NTA, and DTPA and it is the most well characterized EDTA-degrading bacterium. The genome size of BNC1 should be about 5 Mb, similar to that of Agrobacterium tumefaciens (5.3 Mb). A 16 kb DNA fragment containing an EDTA-degrading gene cluster has been sequenced and the GC content is 61.5%; therefore, the GC content of BNC1 should be similar to A. tumefaciens at 57-63 mol% (4). Agrobacterium spp. are known to degrade nitrogen-containing organic compounds, sequencing strain BNC1 will facilitate the studies on the degradation of these compounds, including chelating agents.

References

  1. Bohuslavek, J., J. W. Payne, Y. Liu, H. Bolton, Jr., and L. Xun. 2001. Cloning, sequencing, and characterization of a gene cluster involved in EDTA degradation from the bacterium BNC1. Appl. Environ. Microbiol. 67:688-695.
  2. Bolton, H., Jr., L. Xun, and D. C. Girvin. 2000. Biodegradation of synthetic chelating agents, p. 363-383. In D. R. Lovley (ed.), Environmental microbe-metal interactions. American Society for Microbiology, Washington, D.C.
  3. Cangelosi, G. A., E. A. Best, G. Martinetti, and E. W. Nester. 1991. Genetic analysis of Agrobacterium. Meth. Enzymol. 204:384-397.
  4. Kerr, A. 1992. The genus Agrobacterium., p. 2214-2235. In H. G. T. A. Balows, M. Dworkin, W. Harder, K-H. Schleifer (ed.), The Prokaryotes, vol. 3. Springer-Verlag, New York.
  5. Lauff, J. J., D. B. Steele, L. A. Coogan, and J. M. Breitfeller. 1990. Degradation of the ferric chelate of EDTA by a pure culture of an Agrobacterium sp. Appl. Environ. Microbiol. 56:3346-3353.
  6. Nörtemann, B. 1999. Biodegradation of EDTA. Appl. Microbiol. Biotechnol. 51:751-759.
  7. Nörtemann, B. 1992. Total degradation of EDTA by mixed cultures and a bacterial isolate. Appl. Environ. Microbiol. 58:671-676.
  8. Witschel, M., S. Nagel, and T. Egli. 1997. Identification and characterization of the two-enzyme system catalyzing oxidation of EDTA in the EDTA-degrading bacterial strain DSM 9103. J. Bacteriol. 179:6937-6943.