Biology subjects

Eiler, A.

Publications and source records attributed to Eiler, A..

4 recordsLinked to original sources

bioRxiv2018

Novel autotrophic organisms contribute significantly to the internal carbon cycling potential of a boreal lake

The authors declare no conflict of interest\n\nFunding sources: the Academy of Finland, Science for Life Laboratories, Tryggers Foundation, the Swedish Research Council VR and the Swedish Foundation for strategic research\n\nAbstractOxygen stratified lakes are typical for the boreal zone, and also a major source of greenhouse gas emissions in the region. Due to shallow light penetration, restricting the growth of phototrophic organisms, and large allochthonous organic carbon inputs from the catchment area, the lake metabolism is expected to be dominated by heterotrophic organisms. In this study we test this assumption and show that the potential for autotrophic carbon fixation and internal carbon cycling is high throughout the water column. Further, we show that during the summer stratification carbon fixation can exceed respiration in a boreal lake even below the euphotic zone. Metagenome assembled genomes and 16S profiling of a vertical transect of the lake revealed multiple organisms in oxygen depleted compartment belonging to novel or poorly characterized phyla. Many of these organisms were chemolithotrophic, deriving their energy from reactions related to sulfur, iron and nitrogen transformations. The community as well as the functions were stratified following the redox potentials. The autotrophic potential in the lake metagenome below the oxygenic zone was high, pointing towards a need for revising our concepts of internal carbon cycling in boreal lakes. Further, the importance of chemolithoautotrophy for the internal carbon cycling suggests that many predicted climate change associated changes in the physical properties of the lake, such as altered mixing patterns, likely have consequences for the whole lake metabolism even beyond the impact to the phototrophic community.\n\nImportanceAutotrophic organisms at the base of the food web are the only life form capable of turning inorganic carbon into organic form, facilitating the survival of all other organisms. In certain environments the autotrophic production is limited by environmental conditions and the food web is supported by carbon coming from outside the ecosystem. One such environment is stratified boreal lakes, which are one of the biggest sources of greenhouse gas emissions in the boreal region. Thus, carbon cycling in these habitats is of outmost importance for the future climate. Here we demonstrate a high potential for internal carbon cycling via phototrophic and novel chemolithotrophic organisms in the dark and anoxic layers of a boreal lake. Our results significantly increase our knowledge on the microbial communities and their metabolic potential in oxygen depleted freshwaters and help to understand and predict how climate change induced alterations could impact the lake carbon dynamics.

ecology↗

bioRxiv2017

Novel Chemolithotrophic And Anoxygenic Phototrophic Genomes Extracted From Ice-Covered Boreal Lakes

Although an important fraction of the worlds lakes remains ice-covered during a large proportion of the year, little is known about the microorganisms that govern the biogeochemical processes occurring under-ice along the stratigraphic redox gradients. Reconstructed genomes provide evidence for anoxygenic photosynthesis involving fixation of carbon using reduced sulphur and iron as an electron donor in the anoxic zone of the sampled lake systems. In addition to anoxygenic photosynthesis, our molecular data reveals novel chemolithoautotrophic organisms and supports the existence of methanotrophs in bottom anoxic waters. Reconstructed genomes matched methanotrophs related to Methylobacter tundripaludum, phototrophic Chloroflexi and Chlorobia, as well as lithoautotrophic genomes affiliated to the Betaproteobacteria class and Planctomycetes phylum. Based on our in-depth characterization, complex metabolic interactomes emerge unique to each lakes redox tower and with sulfur, iron and carbon cycling tightly intertwined through chemolithotrophy and anoxygenic photosynthesis.

ecology↗

bioRxiv2017

Vitamin and amino acid auxotrophy in anaerobic consortia operating under methanogenic condition

Syntrophy among Archaea and Bacteria facilitates the anaerobic degradation of organic compounds to CH4 and CO2. Particularly during aliphatic and aromatic hydrocarbon mineralization, as in crude oil reservoirs and petroleum-contaminated sediments, metabolic interactions between obligate mutualistic microbial partners are of central importance1. Using micro-manipulation combined with shotgun metagenomic approaches, we disentangled the genomes of complex consortia inside a short chain alkane-degrading cultures operating under methanogenic conditions. Metabolic reconstruction revealed that only a small fraction of genes in the metagenome-assembled genomes of this study, encode the capacity for fermentation of alkanes facilitated by energy conservation linked to H2 metabolism. Instead, inferred lifestyles based on scavenging anabolic products and intermediate fermentation products derived from detrital biomass was a common feature in the consortia. Additionally, inferred auxotrophy for vitamins and amino acids suggests that the hydrocarbon-degrading microbial assemblages are structured and maintained by multiple interactions beyond the canonical H2-producing and syntrophic alkane degrader-methanogen partnership2. Our study uncovers the complexity of interactomes within microbial consortia mediating hydrocarbon transformation under anaerobic conditions.

microbiology↗

bioRxiv2017

Model communities hint to promiscuous metabolic linkages between ubiquitous free-living freshwater bacteria

Free-living microorganisms with streamlined genomes are very abundant in the environment. Genome streamlining results in losses in the cells biosynthetic potential generating physiological dependencies between microorganisms. However, there exists no consensus on the specificity of these microbial associations. To verify specificity and extent of these associations, mixed cultures were established from three different freshwater environments. These cultures contained free-living streamlined organisms lacking multiple biosynthetic pathways. Among the co-occurring members of the mixed cultures, there was no clear recurring pattern of metabolic complementarity and dependencies. This, together with weak temporal co-occurrence patterns observed using time-series metagenomics, suggests that free-living freshwater bacteria form loose and unspecific cooperative loops. Comparative genomics suggests that the proportion of accessory genes in populations of streamlined bacteria allows for flexibility in interaction partners. Altogether this renders these free-living bacterial lineages functionally versatile despite their streamlining tendencies.

microbiology↗