Abstract
Pseudomonas pseudoalcaligenes KF707 is a soil bacterium which is known for its capacity to aerobically degrade harmful organic compounds such as polychlorinated biphenyls (PCBs) using biphenyl as co-metabolite. Here we provide the first genetic and functional analysis of the KF707 respiratory terminal oxidases in cells grown with two different carbon sources: glucose and biphenyl. We identified five terminal oxidases in KF707: two c(c)aa3 type oxidases (Caa3 and Ccaa3), two cbb3 type oxidases (Cbb31 and Cbb32), and one bd type cyanide-insensitive quinol oxidase (CIO). While the activity and expression of both Cbb31 and Cbb32 oxidases was prevalent in glucose grown cells as compared to the other oxidases, the activity and expression of the Caa3 oxidase increased considerably only when biphenyl was used as carbon source in contrast to the Cbb32 oxidase which was repressed. Further, the respiratory activity and expression of CIO was up-regulated in a Cbb31 deletion strain as compared to W.T. whereas the CIO up-regulation was not present in Cbb32 and C(c)aa3 deletion mutants. These results, together, reveal that both function and expression of cbb3 and caa3 type oxidases in KF707 are modulated by biphenyl which is the co-metabolite needed for the activation of the PCBs-degradation pathway.
Highlights
The bacterium Pseudomonas pseudoalcaligenes KF707, isolated in the 1980s near a biphenyl (BP) manufacturing plant in Japan (Furukawa and Miyazaki, 1986), is known as one of the most effective aerobic degraders of polychlorinated biphenyls (PCBs) (Fedi et al, 2001)
A single colony of KF707 was first inoculated in 10 mL of Luria Bertani medium (LB) medium and grown overnight, cells were centrifuged and washed twice with 0.1 M phosphate buffer inoculated (1.0% v/v) on mineral salt medium (MSM) medium supplemented with a single carbon source
The aa3 Type Cytochrome Oxidases of KF707 The analysis of the P. pseudoalcaligenes KF707 complete genome shows the presence of two gene clusters for two different cox oxidases of aa3 type whose subunits are predicted to contain ctype hemes: caa3 and ccaa3 type oxidases
Summary
The bacterium Pseudomonas pseudoalcaligenes KF707, isolated in the 1980s near a biphenyl (BP) manufacturing plant in Japan (Furukawa and Miyazaki, 1986), is known as one of the most effective aerobic degraders of polychlorinated biphenyls (PCBs) (Fedi et al, 2001). These harmful and highly hydrophobic organic compounds are not primary substrates for cell growth so that a substrate such as biphenyl is required to support growth and induction of the PCBs degradation pathway. Mutation of the cco genes coding for the Cbb oxidase causes up-regulation of the CIO promoter in P. aeruginosa (Kawakami et al, 2010) indicating that the interactive regulation of the genes for Cbb and CIO is mediated by the redox-sensitive transcriptional regulator RoxSR (Bueno et al, 2012)
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