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Title: The oxalic acid biosynthetic activity of Burkholderia mallei is encoded by a single locus

item Nakata, Paul

Submitted to: Microbiological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2010
Publication Date: 10/1/2011
Citation: Nakata, P.A. 2011. The oxalic acid biosynthetic activity of Burkholderia mallei is encoded by a single locus. Microbiological Research. 166(7):531-538.

Interpretive Summary: Some microbes make oxalic acid, which is required to infect their host. Although oxalic acid has been shown to play such an important role in the infection process we still do not understand how this acid is made. Once we understand how this acid is made we can develop strategies to inhibit its production. Such a strategy may find use in inhibiting the infection of both plants (including many crop plants) and animals by oxalate-secreting microbial pathogens. To try and figure out how oxalic acid is made we identified, isolated, and partial characterized the enzyme responsible for making the acid from the animal pathogen, Burkholderia mallei. Enzyme assays revealed that B. mallei used the same enzyme as plant pathogenic bacteria, B. glumae for making the acid, but a different number of genes encoded this enzyme. Such a finding is important in our efforts to understand how oxalic acid is made and in our efforts to identify possible gene targets to inhibit its production.

Technical Abstract: Although it is known that oxalic acid provides a selective advantage to the secreting microbe, our understanding of how this acid is biosynthesized remains incomplete. This study reports the identification, cloning, and partial characterization of the oxalic acid biosynthetic enzyme from the animal bacterial pathogen, Burkholderia mallei. The discovered gene was named oxalate biosynthetic component (obc) 1. Complementation of Burkholderia oxalate defective (Bod) 1, a B. glumae mutant that lacks expression of a functional oxalic acid biosynthetic operon, revealed that the obc1 was able to fully rescue the no oxalate mutant phenotype. This single gene rescue is in contrast to the situation found in B. glumae, which required the expression of two genes, obcA, and obcB, to achieve full complementation. Enzyme assays showed that even though the two Burkholderia species differed in the number of genes required to encode a fully functional enzyme, both catalyzed the same acyl-CoA dependent biosynthetic reaction. Furthermore, mutagenesis studies revealed that the single obc1 gene could be split into two gene fragments, which upon co-expression also resulted in full oxalate production. This finding suggests the possibility of a similar domain structure of the assembled oxalate biosynthetic enzymes whether encoded by one or two genes.