Long-Term Population Dynamics of Phototrophic Sulfur Bacteria in the Chemocline of Lake Cadagno, Switzerland

Abstract

Population analyses in water samples obtained from the chemocline of crenogenic, meromictic Lake Cadagno, Switzerland, in October for the years 1994 to 2003 were studied using in situ hybridization with specific probes. During this 10-year period, large shifts in abundance between purple and green sulfur bacteria and among different populations were obtained. Purple sulfur bacteria were the numerically most prominent phototrophic sulfur bacteria in samples obtained from 1994 to 2001, when they represented between 70 and 95% of the phototrophic sulfur bacteria. All populations of purple sulfur bacteria showed large fluctuations in time with populations belonging to the genus Lamprocystis being numerically much more important than those of the genera Chromatium and Thiocystis. Green sulfur bacteria were initially represented by Chlorobium phaeobacteroides but were replaced by Chlorobium clathratiforme by the end of the study. C. clathratiforme was the only green sulfur bacterium detected during the last 2 years of the analysis, when a shift in dominance from purple sulfur bacteria to green sulfur bacteria was observed in the chemocline. At this time, numbers of purple sulfur bacteria had decreased and those of green sulfur bacteria increased by about 1 order of magnitude and C. clathratiforme represented about 95% of the phototrophic sulfur bacteria. This major change in community structure in the chemocline was accompanied by changes in profiles of turbidity and photosynthetically available radiation, as well as for sulfide concentrations and light intensity. Overall, these findings suggest that a disruption of the chemocline in 2000 may have altered environmental niches and populations in subsequent years.Lake Cadagno is a crenogenic meromictic lake located in the catchment area of a dolomite vein rich in gypsum in the Piora valley in the southern Alps of Switzerland (46°33ЈN, 8°43ЈE). This lake is characterized by a compact chemocline with high concentrations of sulfate; steep gradients of oxygen, sulfide, and light; and a turbidity maximum that correlates to large numbers of bacteria (up to 10 7 cells ml Ϫ1 ) (5, 21, 31). Molecular methods such as 16S rRNA gene clone library analysis and subsequent in situ hybridization with specific fluorescent probes identified the most abundant bacteria in the chemocline as large-and small-celled purple sulfur bacteria. These accounted for up to 35% of all bacteria (34) and consisted of Chromatium okenii as the only representative of the largecelled purple sulfur bacteria and of four populations related to the genus Lamprocystis that represented the small-celled purple sulfur bacteria (31). Small-celled purple sulfur bacteria were most abundant with two populations accounting for 40 to 80% of the purple sulfur bacteria depending on the season (31). These populations, designated D and F, were not represented by a cultured relative, whereas the remaining populations were identified as Lamprocystis purpurea and Lamprocystis roseopersicina. L. purpurea and L. roseopersicina wer...

A single-cell view on the ecophysiology of anaerobic phototrophic bacteria

“…Other anaerobic phototrophs present were Lamprocystis roseopersicina and Chlorobium phaeobacteroides, amounting to 2.7 ϫ 10 5 cells mL Ϫ1 and 5.1 ϫ 10 4 cells mL Ϫ1 , respectively (Table S1). These results confirmed previous studies (17,22) describing a numerically stable phototrophic community strongly dominated by C. chlatratiforme.…”

“…Temperature, conductivity, dissolved oxygen, turbidity, and redox potential were measured at depth intervals of 1 m by a pumpcast conductivity-temperature-depth system equipped with an oxygen sensor (17). Nutrients were analyzed at the same depth intervals using standard methods (SI Text).…”

“…The seasonal variations of this assemblage have been studied intensively in the past 10 years (15)(16)(17) and make this lake an attractive test system for investigating the activities of single cells. These anaerobic phototrophs, which use light energy to oxidize sulfide and other reduced sulfur compounds, are commonly found in seasonally or permanently stratified lakes, anoxic ponds or sediments.…”

Micron-scale mapping of sulfur cycling across the oxycline of a cyanobacterial mat: a paired nanoSIMS and CARD-FISH approach

“…Whole-cell FISH surveys of microbial assemblages within the mat, focusing on sulfate reducers and other known monophyletic sulfur-metabolizing guilds, allow for micron-scale mapping of the spatial distribution of these organisms (for example, Minz et al, 1999a;Wieland et al, 2003;Tonolla et al, 2005;Baumgartner et al, 2006). The spatial relationships of mat-associated SRB populations ( Figure 5) have not been previously reported within these highly structured microbial communities at this resolution and continuous physical extent (412 mm 2 ).…”

Fine scale analysis of shifts in bacterial community structure in the chemocline of meromictic Lake Cadagno, Switzerland

“…While GSB were entirely represented by Chlorobium phaeobacteroides (Tonolla et al 2003) and Chromatium okenii was the only representative of the large-celled PSB, small-celled PSB consisted of at least six populations related to the genera Lamprocystis and Thiocystis (Tonolla et al 2003;Tonolla et al 2005). While two populations related to the genus Thiocystis were found in small numbers in two years only of a monitoring study that covered a decade (Tonolla et al 2005), the remaining four populations of small-celled PSB affiliated with the genus Lamprocystis were continuously present as prominent component of the bacterial community in the chemo-cline with two populations accounting for 40-80% of these PSB depending on the season (Tonolla et al 1999;Tonolla et al 2003).…”