Partaking of Archaea to biogeochemical cycling in oxygen‐deficient zones of meromictic saline Lake Faro (Messina, Italy)

Abstract

We used a combination of molecular and microbiological approaches to determine the activity, abundance and diversity of archaeal populations inhabiting meromictic saline Lake Faro (Messina, Italy). Analysis of archaeal 16S rRNA, amoA, accA and hbd genes and transcripts revealed that sub- and anoxic layers of Lake Faro are primarily inhabited by the organisms related to the clusters of Marine Group I.1a of Thaumarchaeota frequently recovered from oxygen-depleted marine ecosystems. These organisms dominated the metabolically active archaea down to the bottom of the lake, indicating their adaptation to recurrent changes in the levels of water column hypoxia. The upper microaerobic layer of Lake Faro redoxcline has the maximal rates of dark primary production much lower than those of other previously studied pelagic redoxclines, but comparable to the values of meso- and bathypelagic areas of Mediterranean Sea. Application of bacterial inhibitors, especially azide, significantly declined the CO2 fixation rates in the low interface and monimolimnion, whereas archaea-specific inhibitor had effect only in upper part of the redoxcline. Based on these findings, we hypothesize that dark bicarbonate fixation in suboxic zone of Lake Faro results mainly from archaeal activity which is affected by the predicted lack in oxygen in lower layers.

Contrasting taxonomic stratification of microbial communities in two hypersaline meromictic lakes

“…Ammonium reached the highest concentrations in the deep anoxic layers of the lakes, indicating a higher rate of mineralization than assimilation, coupled with a higher stability in the acidic pH range. The depth profiles of ammonium concentration were comparable for both Ursu and Fara Fund lakes, and similar to the ones described in other stratified lakes (Auguet et al, 2012;La Cono et al, 2013;Yau et al, 2013). The vertical profiles of nutrients (sulfate, sulfide, nitrite, nitrate and phosphate) were found to be a result of sedimentation, biogeochemical cycling or conservative mixing (Pasche et al, 2009), and were also comparable with those found in other studied lakes (Lepère et al, 2010;La Cono et al, 2013;Marteinsson et al, 2013).…”

“…As a consequence, they commonly comprise an upper stratum where mixing occurs (mixolimnion), a stagnant lower one (monimolimnion) and an interposing boundary layer (chemocline) (Boehrer and Schultze, 2009). These lakes are important model systems for aquatic biology research, because their constant vertical stratification, steep chemical gradients and the presence of oxygen-deprived zones favor niche partitioning among prokaryotic populations, enabling the study of vertical zonations in microbially-mediated biogeochemical cycling (Lauro et al, 2011;Lopes et al, 2011;La Cono et al, 2013).…”

Heterotrophic bicarbonate assimilation is the main process of de novo organic carbon synthesis in hadal zone of the Hellenic Trench, the deepest part of Mediterranean Sea

“…3.1 (Copyright 1992–1995; Jandel Corporation). Differences were considered significant at P < 0.05, as described elsewhere (La Cono et al ., ).…”

“…The PCR products were further purified and sequenced at Macrogen (Amsterdam, Netherlands). Phylogenetic affiliation was performed as reported elsewhere (La Cono et al ., ).…”

Snow Surface Microbiome on the High Antarctic Plateau (DOME C)

“…For archaeal 16S rRNA gene amplification two different protocols were tested: a) primers 340f (5′-CCCTAYGGGGYGCASCAG-3′) and 1000r (5′-GAGARGWRGTGCATGGCC-3′) [32] with GoTaq Green Master Mix (Promega); b) primers Arc20f (5′-GTTTCCGGTTGATCCYGCCRG-3′) and Arc958r (5′-GTTTYCCGGCGTTGAMTCCAATT-3′) [33] with Takara's Ex Taq DNA Polymerase. No amplification of archaeal 16S rRNA genes was detected.…”