Patterns in Abundance, Cell Size and Pigment Content of Aerobic Anoxygenic Phototrophic Bacteria along Environmental Gradients in Northern Lakes
Date
2015-04-30
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PLOS (Public Library of Science)
Abstract
There is now evidence that aerobic anoxygenic phototrophic (AAP) bacteria are widespread
across aquatic systems, yet the factors that determine their abundance and activity are still not
well understood, particularly in freshwaters. Here we describe the patterns in AAP abundance,
cell size and pigment content across wide environmental gradients in 43 temperate and boreal
lakes of Québec. AAP bacterial abundance varied from 1.51 to 5.49 x 105 cellsmL-1, representing
<1 to 37%of total bacterial abundance. AAP bacteria were present year-round, including
the ice-cover period, but their abundance relative to total bacterial abundance was
significantly lower in winter than in summer (2.6%and 7.7%, respectively). AAP bacterial cells
were on average two-fold larger than the average bacterial cell size, thus AAP cells made a
greater relative contribution to biomass than to abundance. Bacteriochlorophyll a (BChla) concentration
varied widely across lakes, and was not related to AAP bacterial abundance, suggesting
a large intrinsic variability in the cellular pigment content. Absolute and relative AAP
bacterial abundance increased with dissolved organic carbon (DOC), whereas cell-specific
BChla content was negatively related to chlorophyll a (Chla). As a result, both the contribution
of AAP bacteria to total prokaryotic abundance, and the cell-specific BChla pigment content
were positively correlated with the DOC:Chla ratio, both peaking in highly colored, low-chlorophyll
lakes.Our results suggest that photoheterotrophymight represent a significant ecological
advantage in highly colored, low-chlorophyll lakes, where DOC pool is chemically and structurally
more complex.
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Citation
Fauteux L, Cottrell MT, Kirchman DL, Borrego CM, Garcia-Chaves MC, del Giorgio PA (2015) Patterns in Abundance, Cell Size and Pigment Content of Aerobic Anoxygenic Phototrophic Bacteria along Environmental Gradients in Northern Lakes. PLoS ONE 10(4): e0124035. doi:10.1371/journal. pone.0124035