title: INT (2-(4-Iodophenyl)-3-(4-Nitrophenyl)-5-(Phenyl) Tetrazolium Chloride) Is Toxic to Prokaryote Cells Precluding Its Use with Whole Cells as a Proxy for In Vivo Respiration.
abstract: Prokaryote respiration is expected to be responsible for more than half of the community respiration in the ocean, but the lack of a practical method to measure the rate of prokaryote respiration in the open ocean resulted in very few published data leaving the role of organotrophic prokaryotes open to debate. Oxygen consumption rates of oceanic prokaryotes measured with current methods may be biased due to pre-incubation size filtration and long incubation times both of which can change the physiological and taxonomic profile of the sample during the incubation period. In vivo INT reduction has been used in terrestrial samples to estimate respiration rates, and recently, the method was introduced and applied in aquatic ecology. We measured oxygen consumption rates and in vivo INT reduction to formazan in cultures of marine bacterioplankton communities, Vibrio harveyi and the eukaryote Isochrysis galbana. For prokaryotes, we observed a decrease in oxygen consumption rates with increasing INT concentrations between 0.05 and 1 mM. Time series after 0.5 mM INT addition to prokaryote samples showed a burst of in vivo INT reduction to formazan and a rapid decline of oxygen consumption rates to zero within less than an hour. Our data for non-axenic eukaryote cultures suggest poisoning of the eukaryote. Prokaryotes are clearly poisoned by INT on time scales of less than 1 h, invalidating the interpretation of in vivo INT reduction to formazan as a proxy for oxygen consumption rates.
authors.affiliation: Facultad de Ciencias Marinas, UABC, Carretera Tijuana-Ensenada km 106, Ensenada, Baja California, México, CP 22860. villegas.josue@uabc.edu.mx.
authors.forename: Josué
authors.initials: J
authors.lastname: Villegas-Mendoza
authors.affiliation: UABC, Carretera Tijuana-Ensenada km 106, Ensenada, Baja California, México, CP 22860.
authors.forename: Ramón
authors.initials: R
authors.lastname: Cajal-Medrano
authors.affiliation: CICESE, Carretera Tijuana-Ensenada No. 3918, Ensenada, Baja California, México, CP 22860.
authors.forename: Helmut
authors.initials: H
authors.lastname: Maske
mesh_terms: D001420:Bacteria, Aerobic / Q000187:drug effects / Q000378:metabolism; D019069:Cell Respiration / Q000187:drug effects*; D017753:Ecosystem; D056890:Eukaryota / Q000187:drug effects; D005562:Formazans / Q000032:analysis / Q000378:metabolism; D058087:Haptophyta / Q000187:drug effects / Q000378:metabolism; D008386:Marine Biology / Q000379:methods; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects*; D010933:Plankton / Q000187:drug effects / Q000378:metabolism; D011387:Prokaryotic Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D013778:Tetrazolium Salts / Q000633:toxicity*; D014733:Vibrio / Q000187:drug effects / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D005562:Formazans; D013778:Tetrazolium Salts; C013574:iodonitrotetrazolium
keywords: INT reduction; Prokaryotes; Respiration