title: A single-cell view on the ecophysiology of anaerobic phototrophic bacteria.
abstract: Quantitative information on the ecophysiology of individual microorganisms is generally limited because it is difficult to assign specific metabolic activities to identified single cells. Here, we develop and apply a method, Halogen In Situ Hybridization-Secondary Ion Mass Spectroscopy (HISH-SIMS), and show that it allows simultaneous phylogenetic identification and quantitation of metabolic activities of single microbial cells in the environment. Using HISH-SIMS, individual cells of the anaerobic, phototropic bacteria Chromatium okenii, Lamprocystis purpurea, and Chlorobium clathratiforme inhabiting the oligotrophic, meromictic Lake Cadagno were analyzed with respect to H(13)CO(3)(-) and (15)NH(4)(+) assimilation. Metabolic rates were found to vary greatly between individual cells of the same species, showing that microbial populations in the environment are heterogeneous, being comprised of physiologically distinct individuals. Furthermore, C. okenii, the least abundant species representing approximately 0.3% of the total cell number, contributed more than 40% of the total uptake of ammonium and 70% of the total uptake of carbon in the system, thereby emphasizing that numerically inconspicuous microbes can play a significant role in the nitrogen and carbon cycles in the environment. By introducing this quantification method for the ecophysiological roles of individual cells, our study opens a variety of possibilities of research in environmental microbiology, especially by increasing the ability to examine the ecophysiological roles of individual cells, including those of less abundant and less active microbes, and by the capacity to track not only nitrogen and carbon but also phosphorus, sulfur, and other biological element flows within microbial communities.
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany. nmusat@mpi-bremen.de
authors.forename: Niculina
authors.initials: N
authors.lastname: Musat
authors.forename: Hannah
authors.initials: H
authors.lastname: Halm
authors.forename: Bärbel
authors.initials: B
authors.lastname: Winterholler
authors.forename: Peter
authors.initials: P
authors.lastname: Hoppe
authors.forename: Sandro
authors.initials: S
authors.lastname: Peduzzi
authors.forename: Francois
authors.initials: F
authors.lastname: Hillion
authors.forename: Francois
authors.initials: F
authors.lastname: Horreard
authors.forename: Rudolf
authors.initials: R
authors.lastname: Amann
authors.forename: Bo B
authors.initials: BB
authors.lastname: Jørgensen
authors.forename: Marcel M M
authors.initials: MM
authors.lastname: Kuypers
mesh_terms: D001421:Bacteria, Anaerobic / Q000166:cytology* / Q000502:physiology*; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D019414:Chlorobi / Q000166:cytology; D002841:Chromatiaceae / Q000166:cytology; D017753:Ecosystem; D005618:Fresh Water; D008856:Microscopy, Fluorescence; D009584:Nitrogen / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D052817:Phototrophic Processes; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D013557:Switzerland; D013997:Time Factors
chemical_list: D000644:Quaternary Ammonium Compounds; D002244:Carbon; D009584:Nitrogen; D010100:Oxygen