Beijerinckia sp strain B1: a strain by any other name ...

Beijerinckia sp strain B1 grows with biphenyl as its sole source of carbon and energy. A mutant, strain 88/36, oxidized biphenyl to cis-(2S,3R)-dihydr oxy-1-phenylcyclohexa-4,6-diene (cis-biphenyl dihydrodiol). Strain 88/36 ox idized anthracene, phenanthrene, benz[a]anthracene and benzo[a]pyrene to ci s dihydrodiols. Other substrates oxidized to cis-dihydrodiols were dibenzof uran, dibenzothiophene and dibenzo-p-dioxin, Biphenyl dioxygenase activity was observed in cells of Beijerinckia B1 and 88/36 after growth in the pres ence of biphenyl, m-, p-xylene and salicylate. Recent studies have led to t he reclassification of Beijerinckia B1 as Sphingomonas yanoikuyae strain B1 . Subsequent biotransformation studies showed that S. yanoikuyae 88/36 oxid ized chrysene to a bis-cis-diol with hydroxyl substituents at the 3,4- and 9,10-positions. Dihydronaphthalene was oxidized to cis-1,2-dihydroxy-1,2,3, 4-tetrahydronaphthalene, naphthalene, cis-1,2-dihydroxy-1,2-dihydronaphthal ene and 2-hydroxy-1,2-dihydronaphthalene. Anisole and phenetole were oxidiz ed to phenol. Thus the S. yanoikuyae biphenyl dioxygenase catalyzes cis-dih ydroxylation, benzylic monohydroxylation, desaturation and dealkylation rea ctions. To date, the genes encoding biphenyl dioxygenase have not been clon ed. However, the nucleotide sequence of a S. yanoikuyae B1 DNA fragment con tains five different alpha subunits as determined by conserved amino acids coordinating iron in a Rieske [2Fe-2S] center and mononuclear iron at the c atalytic site. The specific role of the different putative oxygenases in bi otransformation reactions catalyzed by S. yanoikuyae is not known and prese nts an exciting challenge for future studies.