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PhD project 1:

The candidate will isolate cold-active and xerotolerant bacteria, archaea and fungi from soil samples collected in extremely dry and/or cold environments, e.g. McMurdo Dry Valleys, North Greenland, and hyper-arid Atacama and Namib deserts. Along with selected microbial strains from commercial strain collections, these isolates will form the basis for the PhD project. Focus will be on chemolithotrophic and phototrophic prokaryotes.

The candidate will investigate the survival and activity of the microorganisms under conditions simulating Mars. Selected microorganisms will be genome sequenced to characterize their genetic potential and transcriptomic studies will be used to characterize their responses to Martian challenges. The candidate will work closely together with Postdoc 1 to modify the genome of selected bacteria for enhanced survival under Martian conditions; and will initiate atmospheric manipulation studies. The latter involves close collaboration with PhDs 2 and 3, where microbial strains and soil samples containing complex microbial communities will be employed to infer and quantify the microbial production of organic and inorganic volatile compounds and how these compounds are involved in photochemical reactions. In addition, the candidate will engage in the work of PhD 4 where selected cold-active and xerotolerant bacteria will be used as cloud condensation nuclei to study cloud formation processes as well as the activity and survival of bacteria in atmospheres simulating Earth, Mars or exoplanets.

Timeline & Milestones. First 18 months: culture microorganisms from samples collected in selected environments and establish collection of cultured microorganisms. Screening the microorganisms for activity at low temperature, low water availability, use of perchlorate as electron acceptor and use of electron donors relevant to Mars and exoplanets. Selecting bacteria for different experiments, i.e. for testing their ability to cope with combinations of Mars-like environmental conditions, for quantification of their production and consumption of volatile organic compounds, and for description of their potential as cloud condensation nuclei. Sequence the genome of selected microorganisms to unravel the genomic adaptations to life under extreme conditions. Second 18 months: engaging in experiments where selected microorganisms are subjected to poly-extreme conditions simulating life on non-Earth planets. The candidate will identify and quantify the production and consumption of volatile organic compounds by selected microorganisms, soil samples and other environmental samples with a focus on organic compounds affecting atmospheric properties.

Qualifications: We advertise for a candidate with a MSc in biology, biochemistry, biotechnology or similar with knowledge on isolating and characterizing (poly)extremophile bacteria, archaea or fungi, and with experience in transcriptomic studies involving bacteria, archaea or fungi, including basic bioinformatics skills.

Supervisor: Anders Priemé; main co-supervisors: Henrik Grum Kjærsgaard and Jan Härter.

PhD project 2: “Spectral signature of gasses from metabolism of extremophiles”.

The candidate will measure vibrational and electronic spectra of collected compounds produced by the bacteria and archaea in the test chamber and other relevant biosignature molecules. In addition, spectra will be calculated based on methods we have developed and continue to develop for molecules we suspect are plausible in exoplanetary atmospheres. This will include molecules like dimethyl sulphide, terpenoids and alcohols. Theoretical chemistry will be used to investigate photolysis and chemical reactions.

Timeline: During the first year the student will become proficient in use of the vibrational and electronic codes that we have available. The student will initially apply these codes to sulphur oxides relevant the sulphur cycle which is initiated with the dimethyl sulphide, known to be emitted in large quantities on earth. During the second year, the student will continue the simulation of molecular spectra in close collaboration with PhD student project 3, to ensure spectra that are applicable to the models. The student will also acquire expertise in operating our spectrometers. In the third year, aside from writing a thesis, the student will start with recording spectra of collected samples, using our spectrometers. In addition, calculations on perchlorate formation mechanism will be accomplished. Goals: To measure and/or simulate vibrational and electronic spectra of molecules relevant to model planetary atmospheres. To identify molecules produced by the extremophile bacteria and archaea. To investigate new and relevant photochemical reactions in extreme environments.

Qualifications: We will advertise for a student with knowledge in experimental spectroscopy (FT-IR, UV-vis, Matrix isolation) and with expertise in theoretical/computational chemistry with a focus on spectroscopy and reaction dynamics.

Supervisor: Henrik Grum Kjærgaard; main co-supervisor: Uffe Gråe Jørgensen.

PhD project 3: “Cloud formation and cloud properties on Earth and in exoplanets”.

In most exoplanets a major fraction of the energy balance is governed by clouds, as it is on Earth, Venus and the gas giants in our solar system. In our present exoplanet models, cloud formation and destruction is a self-consistent but static circulation phenomenon, governed by the temperature and convection structure of the model. The main goal of the project will be to develop the cloud description in the numerical models. The student is foreseen to begin with spending some time on becoming familiar with the MARCS model atmosphere code (e.g. Gustafsson et al 2008, Juncher et al 2017) and with the cloud formation codes, in order to be able to combine them and perform numerical simulations of various cloud formation scenarios and study the effect on the atmospheric structure and the emergent spectrum. Questions that could be addressed include whether there is an observable difference between clouds formed by nucleation on mineral seeds (such as small sand grains, sulfur-aerosols, salt from ocean water etc) and clouds formed on microbiological nucleation seeds (e.g. bacteria), and whether this can be used to identify the existence of life from observed exoplanet spectra. The PhD is expected to benefit in particular from a strong collaboration with PhD 4, and with postdoc 2.

Qualifications: We advertise for a candidate with a MSc in astrophysics, geophysics, biocomplexity or related fields, with knowledge preferable in one or more of the fields of exoplanet atmospheres, spectroscopy, cloud formation, optical properties of clouds, and/or other relevant areas for the project. Experience in coding in Fortran and/or related computer languages is an advantage.

Supervisor: Uffe Gråe Jørgensen; main co-supervisor: Jan Härter

PhD project 4: “Micro-biological influence on atmospheric dynamics”.

The role of aerosols, which often are organic particles, such as bacteria, in the climate system is currently still insufficiently understood. Yet, aerosols play a key role in influencing planetary albedo through changes to cloud properties. Bacteria can form the cloud condensation nuclei, which both allow cloud droplets to form, and grow to yield precipitation. One needs to distinguish effects that lead to longer cloud lifetimes and higher precipitation efficiency. It is even possible that microbial aerosol particles could influence the formation of clouds in ways to improve local conditions – hence an evolutionary life-climate feedback. The possibility of this will be explored with simulations and theoretical models.

The project aims to untangle the effect of climate on allowing microbes to spread in space, interact with one another, and thus evolve under changing environmental boundary conditions. It will be explored, under which biogeographic circumstances evolution might be fostered or hampered - thus opening for new knowledge on which planetary atmospheres promote the emergence of life.

Qualifications: Knowledge about climate systems and basic knowledge about the spread of bacteria and diseases.

Supervisor: Jan Härter, main co-supervisor: Anders Priemé.

Postdoc 1

The postdoc will in collaboration with PhD 1 manipulate the genomes of selected bacterial and archaeal isolates to give them new abilities (e.g. genes encoding perchlorate reduction, carbon monoxide oxidation, rhodopsin-mediated phototrophic activity, or mechanisms to reduce UV radiation damage) and/or enhance their tolerance to even more extreme conditions than the already extreme (for Earth) environments where they were collected. This work will include microbial taxa where stable genomic constructs often prove challenging to establish, e.g. cyanobacteria.

Postdoc 1 will lead the genetic and physiological characterization of our main bacterial, archaeal and fungal isolates in order to identify the genetic and physiological background for adaptations to the main environmental challenges relating to life on other planets. Postdoc 1 will collaborate closely with PhD 1 and 4 on estimating the activity of bacteria and their roles in cloud formation under different atmospheric conditions.

Main mentor: Anders Priemé, main co-mentor: Jan Härter.

Postdoc 2: “Synthetic spectra of exoplanet atmospheres with and without biological activity”.

On both Mars and Venus, the visual-infrared spectrum is dominated by strong CO2 features. On Earth the spectrum is dominated by a combination of water, oxygen (in the form of O3), methane, and CO2. Water in the spectrum comes from equilibrium with liquid water on the surface, oxygen from photosynthesis, methane from methane producing bacteria (including those in our guts), and CO2 is in a broader context the remnants of the primordial CO2 (as on Mars and Venus) processed via lifeforms and human technology. The Earth’s atmosphere is out of chemical equilibrium due to the large-scale existence of life. Such out-of-equilibrium would be visible on many light years distance, but lifeforms on other planets could of course be based on metabolisms that involve other exhaust gasses than oxygen and methane. It is a main aim of postdoc 2 to contribute to understanding how various kinds of biological activity could contribute to non-equilibrium in the atmosphere of exoplanets, traceable in the atmospheric spectra. Our existing atmospheric models are based on the 1D self-consistent and very well tested stellar atmospheric code MARCS (Gustafsson et al 2008) now being developed into the planetary regime (e.g. Juncher et al 2017). The candidate will spend some time becoming familiar with the MARCS code and non-equilibrium chemistry codes, and thereafter participate in including the non-equilibrium into the atmospheric code. With the inclusion of non-equilibrium, we would be able to not only identify, but also quantify, the existence of life on exoplanets through the strength of non-equilibrium spectral features. Such features would include gasses we measure from our bacteria experiments in our Mars-simulation chamber. The postdoc will develop the non-equilibrium routines to be coupled with the atmospheric code in close collaboration with PhD3. Collaboration with PhD1 and PhD2 is also expected on the identification of the exhaust gasses from bacteria in our lab experiments, and in calculation of the line absorption coefficient of such gasses and other biomarker gasses of interest.

Qualifications: We advertise for a candidate with a PhD in astrophysics or atmospheric chemistry, with knowledge preferable in one or more of the fields atmospheric non-equilibrium processes, exoplanet atmospheres, calculations of molecular spectra, experimental spectroscopy, and/or similar areas. Experience in coding in Fortran and/or related computer languages is an advantage.

Main mentor: Uffe Gråe Jørgensen, main co-mentor: Henrik Grum Kjærgaard.