title: Aerobic kinetoplastid flagellate Phytomonas does not require heme for viability.
abstract: Heme is an iron-coordinated porphyrin that is universally essential as a protein cofactor for fundamental cellular processes, such as electron transport in the respiratory chain, oxidative stress response, or redox reactions in various metabolic pathways. Parasitic kinetoplastid flagellates represent a rare example of organisms that depend on oxidative metabolism but are heme auxotrophs. Here, we show that heme is fully dispensable for the survival of Phytomonas serpens, a plant parasite. Seeking to understand the metabolism of this heme-free eukaryote, we searched for heme-containing proteins in its de novo sequenced genome and examined several cellular processes for which heme has so far been considered indispensable. We found that P. serpens lacks most of the known hemoproteins and does not require heme for electron transport in the respiratory chain, protection against oxidative stress, or desaturation of fatty acids. Although heme is still required for the synthesis of ergosterol, its precursor, lanosterol, is instead incorporated into the membranes of P. serpens grown in the absence of heme. In conclusion, P. serpens is a flagellate with unique metabolic adaptations that allow it to bypass all requirements for heme.
authors.affiliation: Biology Centre, Institute of Parasitology, Czech Academy of Sciences and Faculty of Science, University of South Bohemia, 370 05 České Budějovice, Czech Republic.
authors.forename: Luděk
authors.initials: L
authors.lastname: Kořený
authors.forename: Roman
authors.initials: R
authors.lastname: Sobotka
authors.forename: Julie
authors.initials: J
authors.lastname: Kovářová
authors.forename: Anna
authors.initials: A
authors.lastname: Gnipová
authors.forename: Pavel
authors.initials: P
authors.lastname: Flegontov
authors.forename: Anton
authors.initials: A
authors.lastname: Horváth
authors.forename: Miroslav
authors.initials: M
authors.lastname: Oborník
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Ayala
authors.forename: Julius
authors.initials: J
authors.lastname: Lukeš
mesh_terms: D016831:Crithidia fasciculata / Q000378:metabolism; D004579:Electron Transport; D004875:Ergosterol / Q000737:chemistry; D005227:Fatty Acids / Q000737:chemistry; D006418:Heme / Q000737:chemistry*; D016830:Kinetoplastida / Q000378:metabolism*; D007810:Lanosterol / Q000737:chemistry; D008954:Models, Biological; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry; D010802:Phylogeny; D011166:Porphyrins / Q000737:chemistry; D013261:Sterols / Q000737:chemistry; D014351:Trypanosomatina / Q000378:metabolism*
chemical_list: D005227:Fatty Acids; D011166:Porphyrins; D013261:Sterols; D007810:Lanosterol; D006418:Heme; D010100:Oxygen; D004875:Ergosterol