Burkholderia xenovorans LB400
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The Burkholderia xenovorans strain LB400 (formerly known as B. fungorum) is the best aerobic PCB degrader yet discovered. It oxidizes more than 20 PCB congeners including some with 4,5 and 6 chlorine substitutions on the biphenyl rings (Bedard et. al., 1986). It was isolated from a PCB-containing landfill near in upper New York State by a research team at General Electric Research. The strain is also of interest because it has a large number of oxygenases and comes from a phylogenetic group that is commonly isolated from grass rhizospheres and soils with a variety of complex naturally-occurring aromatic compounds. This strain was also sequenced because it has among the largest prokaryotic genomes, 9.7 Mb, which may contribute to its versatile appetite for more difficult to degrade compounds in soil. The genome sequence has allowed us to begin to understand the pathways it uses for PCB degradation and by using genome arrays, we found not one but three pathways for degradation or the benzoate intermediates from biphenyl oxidation (Denef et.al., 2004). Besides degradation of one of the most difficult to degrade and widespread pollutants, the Burkholderia group to which this strain belongs is also important to the soil’s carbon economy and, since it fixes N2 gas, aids plant CO2 fixation.

This strain is known by many names. Originally is was described as Pseudomonas cepacia and later, in succession, Burkholderia cepacia, Burkholderia spp., Burkholderia fungorum and now, the first time that its validly described, as Burkholderia xenovorans (Goris et.al., 2004). The original strain is deposited in the USDA ARS Culture Collection in Peoria, Ill, under its patent collection, Accession no. NRRL B-18064. This clone was the one sequenced. We do know the genome does exhibit transpositions readily in culture.

Bedard, D.L., R Unterman, L H Bopp, M J Brennan, M L Haberl, and C Johnson. 1986. Rapid assay for screening and characterizing microorganisms for the ability to degrade polychlorinated biphenyls. Appl. Environ. Microbiol. 51:761–768.

Denef, V.J., J. Park, T.V. Tsoi, J.-M. Rouillard, H. Zhang, J.A. Wibbenmeyer, W. Verstraete, E. Gulari, S.A. Hashsham, and J.M. Tiedje. 2004. Biphenyl and benzoate metabolism in a genomic context: Outlining genome-wide metabolic networks in Burkholderia xenovorans LB400. Appl. Environ. Microbiol. 70:4961-4970.

Goris, Johan, Paul De Vos, Jesús Caballero-Mellado, Joon-Hong Park, Enevold Falsen, James M. Tiedje, and Peter Vandamme. Classification of the PCB- and biphenyl degrading strain LB400 and relatives as Burkholderia xenovorans sp. nov. Intl J. Syst Evol Microbiol. 54:1677-1681. (2004).