Complex Effects of Cytochrome P450 Monooxygenase on Purple Membrane and Bacterioruberin Production in an Extremely Halophilic Archaeon: Genetic, Phenotypic, and Transcriptomic Analyses

Abstract

Halophilic archaea are known to produce a diverse array of pigments for phototrophy and photoprotection. The aim of this paper was to determine the role of a Halobacterium gene encoding the predicted cytochrome P450 monooxygenase (CYP174A1) in pigment synthesis through a combined genetic, phenotypic, and transcriptomic approach. We report on the observed phenotype changes [increased bacterioruberin levels and the loss of purple membrane (PM)] between the Halobacterium salinarum R1 and its CYP174A1-deletion mutant. In addition, we report on the whole-genome DNA microarray analysis, which supports the phenotype of PM loss. This work expands our understanding of the bop-gene regulon, and its relation to carotenoid biosynthesis, and sheds light on our broader understanding of the role (s) of CYP174A1 in archaeal pigment synthesis. To date, this is the first study in which the physiological role of any cytochrome P450 monooxygenase (CYP450) in extremely halophilic archaea has been reported.

Deciphering Pathways for Carotenogenesis in Haloarchaea

“…The pathway deciphered in this work (Figure 2) sheds light on the knowledge of carotenogenesis in archaea and will contribute to the production of mutants over pigmented in order to upscale carotenoids production using archaea as biofactories [80,90]. Other issues like regulation of carotenogenesis [91] in haloarchaea and connections between carotenogenesis, synthesis of bacteriorhodopsin, and monooxygenases [69] should be explored into detail in the near future in order to understand the whole process making possible cellular pigmentation in this kind of microorganisms.…”

“…mediterranei possess potential zinc recognition sites [85]. Another potential connection between this zinc transporter and carotenogenesis could be the "bop-gene regulon [69,[86][87][88]. bop gene is part of a cluster of genes, which is tightly regulated by a sensor regulator called bat and potentially also by a small zinc-finger containing a protein called Brz [69].…”

“…Another potential connection between this zinc transporter and carotenogenesis could be the "bop-gene regulon [69,[86][87][88]. bop gene is part of a cluster of genes, which is tightly regulated by a sensor regulator called bat and potentially also by a small zinc-finger containing a protein called Brz [69]. bop gene codes for bacterio-opsin protein: part of the light-driven proton pump called bacteriorhodopsin [60,88].…”

“…Nevertheless, the genes and enzymes involved in the synthesis of canthaxanthin were not clearly identified in neither of these species during this bioinformatic analysis. Another possible explanation would be the existence of undescribed pathways for the synthesis of other carotenoids, which would justify the allusion to them in some bibliography [68,69]. However, to this day, no other pigments have been clearly identified in haloarchaea.…”

Extremophilic models for astrobiology: haloarchaeal survival strategies and pigments for remote sensing

“…The two genes, brp and blh, are also likely differentially regulated, with the brp gene located directly upstream of the bop gene and the blh gene located in a gene cluster with β-carotene cyclase and subunits of ATP synthase Peck, et al 2001). Finally, the cytochrome P450 monooxygenase was also implicated in carotenoid biosynthesis, deletion of which increased bacterioruberin while decreasing purple membrane content (Müller, et al 2019).…”