Browsing by Author "Harhangi, Harry R."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Anaerobic Oxidation f Dimethylsul¢De AndmethanethiolIn Mangrove Sediments s Dominated By Sulfate-Reducing Bacteria
    (2009-08) Lyimo, Thomas J.; Pol, Arjan; Harhangi, Harry R.; Jetten, Mike S. M.; Op den Camp, Huub J. M.
    The oxidation of dimethylsulfide and methanethiol by sulfate-reducing bacteria (SRB) was investigated in Tanzanian mangrove sediments. The rate of dimethylsulfide and methanethiol accumulation in nonamended sediment slurry (control) incubations was very low while in the presence of the inhibitors tungstate and bromoethanesulfonic acid (BES), the accumulation rates ranged from 0.02-0.34 to 0.2-0.4 nmol g FW sediment(-1) h(-1), respectively. Degradation rates of methanethiol and dimethylsulfide added were 2-10-fold higher. These results point to a balance of production and degradation. Degradation was inhibited much stronger by tungstate than by BES, which implied that SRB were more important. In addition, a new species of SRB, designated strain SD1, was isolated. The isolate was a short rod able to utilize a narrow range of substrates including dimethylsulfide, methanethiol, pyruvate and butyrate. Strain SD1 oxidized dimethylsulfide and methanethiol to carbon dioxide and hydrogen sulfide with sulfate as the electron acceptor and exhibited a low specific growth rate of 0.010 +/- 0.002 h(-1), but a high affinity for its substrates. The isolated microorganism could be placed in the genus Desulfosarcina (the most closely related cultured species was Desulfosarcina variabilis, 97% identity). Strain SD1 represents a member of the dimethylsulfide/methanethiol-consuming SRB population in mangrove sediments.
  • Thumbnail Image
    Item
    Cytosolic Enzymes with a Mitochondrial Ancestry from the Anaerobic Chytrid Piromyces Sp. E2. Mol Microbiol 30:1017-1027
    (1998) Akhmanova, Anna; Voncken, Frank; Harhangi, Harry R.; Hosea, Ken M.; Vogels, Godfried D.; Hackstein, Johannes H. P.
    The anaerobic chytrid Piromyces sp. E2 lacks mitochondria, but contains hydrogen-producing organelles, the hydrogenosomes. We are interested in how the adaptation to anaerobiosis influenced enzyme compartmentalization in this organism. Random sequencing of a cDNA library from Piromyces sp. E2 resulted in the isolation of cDNAs encoding malate dehydrogenase, aconitase and acetohydroxyacid reductoisomerase. Phylogenetic analysis of the deduced amino acid sequences revealed that they are closely related to their mitochondrial homologues from aerobic eukaryotes. However, the deduced sequences lack N-terminal extensions, which function as mitochondrial leader sequences in the corresponding mitochondrial enzymes from aerobic eukaryotes. Subcellular fractionation and enzyme assays confirmed that the corresponding enzymes are located in the cytosol. As anaerobic chytrids evolved from aerobic, mitochondria-bearing ancestors, we suggest that, in the course of the adaptation from an aerobic to an anaerobic lifestyle, mitochondrial enzymes were retargeted to the cytosol with the concomitant loss of their N-terminal leader sequences.