Isolation and Characterization ofAlicycliphilus denitrificansStrain BC, Which Grows on Benzene with Chlorate as the Electron Acceptor

Abstract

A bacterium, strain BC, was isolated from a benzene-degrading chlorate-reducing enrichment culture. Strain BC degrades benzene in conjunction with chlorate reduction. Cells of strain BC are short rods that are 0.6 m wide and 1 to 2 m long, are motile, and stain gram negative. Strain BC grows on benzene and some other aromatic compounds with oxygen or in the absence of oxygen with chlorate as the electron acceptor. Strain BC is a denitrifying bacterium, but it is not able to grow on benzene with nitrate. The closest cultured relative is Alicycliphilus denitrificans type strain K601, a cyclohexanol-degrading nitrate-reducing betaproteobacterium. Chlorate reductase (0.4 U/mg protein) and chlorite dismutase (5.7 U/mg protein) activities in cell extracts of strain BC were determined. Gene sequences encoding a known chlorite dismutase (cld) were not detected in strain BC by using the PCR primers described in previous studies. As physiological and biochemical data indicated that there was oxygenation of benzene during growth with chlorate, a strategy was developed to detect genes encoding monooxygenase and dioxygenase enzymes potentially involved in benzene degradation in strain BC. Using primer sets designed to amplify members of distinct evolutionary branches in the catabolic families involved in benzene biodegradation, two oxygenase genes putatively encoding the enzymes performing the initial successive monooxygenations (BC-BMOa) and the cleavage of catechol (BC-C23O) were detected. Our findings suggest that oxygen formed by dismutation of chlorite can be used to attack organic molecules by means of oxygenases, as exemplified with benzene. Thus, aerobic pathways can be employed under conditions in which no external oxygen is supplied.

Genome Sequences of Alicycliphilus denitrificans Strains BC and K601 T

“…These values are close to those of 66% and 67.7%, respectively, previously determined by conventional techniques (6,8). Both genomes are comprised of a circular chromosome, which has a size of 4,637,013 bp in strain BC and 4,995,263 bp in strain K601 T , and both contain plasmids.…”

“…This finding explains the predicted horizontal gene transfer of genes involved in chlorate respiration (1). Furthermore, genes coding for a benzene/phenol monooxygenase (BC-BMOa) and a catechol 2,3-dioxygenase (BC-C23O), both postulated to be involved in benzene degradation (8), are localized in one gene cluster in the chromosomes of strain BC and strain K601…”

“…T are able to grow with benzene aerobically (6,8). Furthermore, only strain BC can degrade benzene using chlorate as an electron acceptor (8).…”

“…Furthermore, only strain BC can degrade benzene using chlorate as an electron acceptor (8). During chlorate reduction, molecular oxygen is formed, which might be used by oxygenases to attack benzene (7,8).…”

Comparative genomics of two ‘Candidatus Accumulibacter’ clades performing biological phosphorus removal

“…The fusion protein is proposed to allow for oxidation of reduced quinone from succinate dehydrogenase in the absence of oxygen by transferring electrons to NAD þ and FAD (Garcia Martin et al, 2006). Since then, the genomes of two strains of Alicycliphilus denitrificans (BC and K601), which were isolated from a wastewater treatment plant, were found to have an protein with homologous structure (Mechichi et al, 2003;Weelink et al, 2008;Oosterkamp et al, 2011). We determined that the wrong gene id (JGI-IMG/M gene OID: 2 001 028 710 or 645 009 129 in finished genome) was provided for the novel cytochrome in that report rather than the actual protein with these domains (JGI-IMG/M gene OID: 2 001 028 680 or 645 009 126 on finished genome), so recent studies exploring its expression targeted the wrong gene (Burow et al, 2008;He et al, 2010b).…”