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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
- 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.
- 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.
- Cangelosi, G.
A., E. A. Best, G. Martinetti, and E. W. Nester. 1991. Genetic analysis
of Agrobacterium. Meth. Enzymol. 204:384-397.
- 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.
- 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.
- Nörtemann,
B. 1999. Biodegradation of EDTA. Appl. Microbiol. Biotechnol. 51:751-759.
- Nörtemann,
B. 1992. Total degradation of EDTA by mixed cultures and a bacterial
isolate. Appl. Environ. Microbiol. 58:671-676.
- 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.
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