Ecology and microbial structures of archaeal/bacterial strings-of-pearls communities and archaeal relatives thriving in cold sulfidic springs

Abstract

Recently, a unique microbial community, growing in a whitish, macroscopically visible strings-of-pearls-like structure was discovered in the cold, sulfidic marsh water of the Sippenauer Moor near Regensburg, Bavaria, Germany. The pearls interior is predominated by microcolonies of the non-methanogenic SM1 euryarchaeon; the outer part of the pearls is mainly composed of Thiothrix. To screen sulfidic ecosystems for the distribution of such unique microbial communities, comparative microbial and geochemical analyses of cold, sulfidic springs of three geographically distinct locations in Bavaria, Germany, and Dalyan, Turkey, were performed. Here, we report on the discovery and study of another type of strings-of-pearls revealing a new microbial community structure. While the SM1 euryarchaeon is again the predominant archaeal constituent, the bacterial partner is the so-called IMB1 eta-proteobacterium. Due to the predominance of the IMB1 eta-proteobacterium, the strings-of-pearls reveal a fluffy and greyish macroscopical appearance. The phylogenetic survey revealed SM1 euryarchaeal relatives, designated as SM1 group, in all sites studied, indicating a widespread distribution of these archaea in terrestrial ecosystems.

Tackling the minority: sulfate-reducing bacteria in an archaea-dominated subsurface biofilm

“…No oxygen could be measured in the subsurface water before mixing with the atmosphere in the streamlet, indicating a complete oxygen-free environment in the subsurface. These on-site measurements are in contrast to previous investigations that reported low amounts of oxygen in the spring water (Rudolph et al, 2004;Henneberger et al, 2006). Dominance of the SM1 Euryarchaeon in the subsurface biofilm FISH with Archaea-directed and SM1 Euryarchaeonspecific probes confirmed previous results showing the archaeal dominance within the biofilm.…”

“…Its physical characteristics (pH and water composition) have already been described previously (Rudolph et al, 2004;Henneberger et al, 2006), and are found to be very constant over several years of measurement (including sulfate 16 mg l À 1 , thiosulfate 14 mg l À 1 , ammonia 0.33 mg l À 1 ). Oxygen concentrations at different locations of the spring and the stream were re-measured using a highly sensitive oxygen dipping probe (PSt6) coupled with temperature measurement (Fibox 3, LCD trace; PreSens, Regensburg, Germany).…”

“…The dominant clone sequence (88% of all clones, IM-A1, JN861739) and two others (2%, IM-C8, JN861741; 2% IM-4-1, JN861742) showed high similarity to publicly available 16S rRNA gene sequences of the SM1 Euryarchaeon and among each other (499%). One clone sequence (8%, IM-C4, JN861740) was closely related to the environmental clone sequence SMK5 (Rudolph et al, 2004), which was retrieved from Sippenauer Moor string-of-pearls community in 2005 (99% similarity) but shows a genetic distance of 20% to the SM1 Euryarchaeon sequence.…”

“…The SM1 Euryarchaeon is found in sulfidecontaining fresh and marine waters all over Europe (Rudolph et al, 2004), but only two sites (close to Regensburg, Bavaria, Germany) were studied extensively during the past 10 years: The Sippenauer Moor and the Muehlbacher Schwefelquelle (''Islinger Muehlbach''; Henneberger et al, 2006). Both of these sites are characterized by a main, sulfidic spring, emanating into a streamlet where whitish mats of sulfide-oxidizing bacteria cover the submerged surfaces.…”

“…Although, sulfidic springs represent o10% of terrestrial fresh water springs (Palmer, 1991), they are believed to have an important role in global sulfur-cycling (Engel et al, 2003), as they can spawn huge amounts of microbial biomass mainly consisting of sulfur-oxidizing bacteria such as Thiothrix, Beggiatoa and Sulfuricuvum. These filamentous bacteria live as microbial mats or streamers in fluctuating gradients of sulfide and oxygen, and may also be responsible for the environmental success of the SM1 Euryarchaeon under oxygen-rich conditions (Moissl et al, 2002;Rudolph et al, 2004). Surrounding the archaeal colony, Thiothrix (Sippenauer Moor) and Sulfuricurvum (Muehlbacher Schwefelquelle) form the string-of-pearls community and possibly interact with the archaeon through an inter-species sulfur cycle (Moissl et al, 2002).…”