Photosynthetic activity and population dynamics of Amoebobacter purpureus in a meromictic saline lake

• From linkinghub.elsevier.com/retrieve/pii/016864969490104X
• XJörg Overmann^{, a, ∗∗},
• J. Thomas Beatty^a,
• Ken J. Hall^b

• ^a Department of Microbiology and Immunology, University of British Columbia, # 300-6174 University Boulevard, Vancouver BC, Canada V6T 1Z3
• ^b Westwater Research Centre, University of British Columbia, Vancouver BC, Canada

• Received 4 April 1994. Revised 18 July 1994. Accepted 18 July 1994. Available online 14 November 2002.

• Abstract

• Image from Flickr site of Daniel Innouye

• A dense population of the purple sulfur bacterium Amoebobacter purpureus in the chemocline of meromictic Mahoney Lake (British Columbia, Canada) underwent consistent changes in biomass over a two year study period. The integrated amount of bacteriochlorophyll reached maxima in August and declined markedly during early fall. Bacteriochlorophyll was only weakly correlated with the light intensity and water temperature in the chemocline. In the summer, bacterial photosynthesis was limited by sulfide availability. During this period the intracellular sulfur concentration of A. purpureus cells decreased. A minimum concentration was measured at the top of the bacterial layer in August, when specific photosynthetic rates of A. purpureus indicated that only 14% of the cells were photosynthetically active. With the exception of a time period between August and September, the specific growth rates calculated from CO₂ fixation rates of A. purpureus were similar to growth rates calculated from actual biomass changes in the bacterial layer. Between August and September 86% of the A. purpureus biomass disappeared from the chemocline and were deposited on the littoral sediment of Mahoney Lake or degraded within the mixolimnion. This rise of cells to the lake surface was not mediated by an increase in the specific gas vesicle content which remained constant between April and November. The upwelling phenomenon was related to the low sulfur content of A. purpureus cells and a low resistance of surface water layers against vertical mixing by wind.

  Keywords

  • Anoxygenic photosynthesis;
  • Low-light-adaptation;
  • Sulfur cycle;
  • Sulfate reduction;
  • Aggregation;
  • Gas vesicle

  

  Corresponding author.

  ∗∗

  Present address: ICBM, Universität Oldenburg, Postfach 2503, D-26111 Oldenburg, FRG.

  Copyright © 1994 Published by Elsevier B.V.