Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022

EXOA15

Habitability and biosignatures for the search for life in our Solar system

Our search for life on our neighboring planets and moons is guided by increasing our knowledge on terrestrial life’s survivability and adaptability and on our capacity to detect its traces. On one hand, extremophilic organisms of all domains of life have shown us extraordinary adaptations strategies in colonizing Earth’s most inhospitable environments and their study has far reaching implications not only for astrobiology research but also in different fields such as ecology, molecular and cellular biology, physiology, and biotechnology. On the other hand, each planetary target presents unique environments and conditions that could enhance or decrease biosignatures’ preservation and therefore their detectability by in situ, sample return, or remote measurements. Studies from field analogs, laboratory, simulation and space experiments or theoretical investigations can greatly support and guide current and future missions dedicated to search for life and its traces. Experiments on space platforms and missions, for instance, allow the exposure of biological and chemical samples to unique outer space conditions but require special hardware developments of high interest for astrobiology and related fields.

Conveners: Mickael Baqué, Frédéric Foucher, Ruth-Sophie Taubner, Rosa de la Torre Noetzel, Alex Price, Silvana Pinna, Hector-Andreas Stavrakakis | Co-conveners: Kensei Kobayashi, Petra Rettberg, Jean-Pierre Paul de Vera, Daniela Billi, Lena Noack, Barbara Cavalazzi, Séverine Robert
Orals
| Fri, 23 Sep, 15:30–18:30 (CEST)|Room Manuel de Falla
Posters
| Attendance Thu, 22 Sep, 18:45–20:15 (CEST)|Poster area Level 2

Orals: Fri, 23 Sep | Room Manuel de Falla

Chairpersons: Silvana Pinna, Ruth-Sophie Taubner
15:30–15:50
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EPSC2022-187
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solicited
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MI
Frances Westall, Laura Clodore, Frédéric Foucher, Tetyana Milojevic, Denise Kölbl, Pamela Guérillot, Keyron Hickman-Lewis, Barbara Cavalazzi, and Jorge Vago

Two missions are on Mars looking for traces of life (MSL and Mars 2020) while the ExoMars mission, slated for launch later this year, is postponed. All missions are equipped with a powerful array of instrumentation for in situ analyses. In addition, the ExoMars rover, Rosalind Franklin, has the advantage of a 2 m drill to penetrate beneath the oxidised and UV-irradiated surface [1]. However, unless phototrophic life forms were able to develop on a planet that was never permanently habitable and that was characterised by punctuated and likely unconnected habitable niches [2, 3], martian life likely remained in a very primitive state of evolution, potentially similar to terrestrial chemotrophs, i.e. discrete, very small cells and colonies that leave even more subtle fossil remains. Indeed, only in the vicinity of nutrient-rich hydrothermal environments can chemotrophic biomass develop to create potentially visible morphological signatures in the form of a clotted texture in the associated sediments – a texture that is not immediately identifiable as a biosignature but that would warrant further analysis of such rocks by other instruments, such as SAM on Curiosity, SHERLOC on Perseverance, or MOMA on Rosalind Franklin.

Taking the early terrestrial environment and early life as analogues for habitable environments and primitive life forms on early Mars, it is becoming clearer that the most primitive of life forms known on Earth, chemolithotrophs that obtain energy from oxidation of inorganic substrates (e.g. ferrous iron, hydrogen sulfide, elemental sulfur, thiosulfate, or ammonia), were widely distributed but, because of their very small size (< 1 µm diameter) and very small, heterogeneously distributed colonies (5 µm to some tens of microns), are typically undetectable through bulk analyses (bulk carbon contents are generally 0.01-0.05 %.) (Fig. 1). To compound the challenge, morphologically-recognisable cells are rarely observed, while degraded cells mixed with generic extracellular polymeric substances (EPS) are more frequent. Chemolithotrophs can inhabit sediment particle surfaces and pore space close to the surface or at depth, as long as they have access to nutrients and water. But how to identify them in situ on Mars? Even on Earth with well-equipped, state of the art laboratories, detection and identification of fossil chemolithotrophs is difficult and, often, controversial. The solution requires seeking to simultaneously detect structural information of the organisms’ presence and analyse well-preserved organogeochemical signature with spatial precisions on the order of a micron and detection limits as low as possible. This would be a challenge for Mars Sample Return in the near future.

Figure 1. (A-C) distribution of tiny colonies and EPS clumps (red circles) in a silicified, volcanic sediment [3] at increasing magnifications. Individual dividing cells visible only at maximum resolution in (C).

References: [1] Vago, J.L., et al. (2017) Astrobiology, 17: 471–510. [2] Cockell et al., 2012. Icarus, 217:184–193. [3] Westall et al., (2015) Astrobiology, 17: 998-1029. [4] Author J. et al. (2002) LPS XXXIII, Abstract #2110.

How to cite: Westall, F., Clodore, L., Foucher, F., Milojevic, T., Kölbl, D., Guérillot, P., Hickman-Lewis, K., Cavalazzi, B., and Vago, J.: The search for extraterrestrial life and the problem of primitive life forms, now you see them, now you don’t, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-187, 2022.

15:50–16:00
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EPSC2022-1195
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ECP
Lorenzo Biasiotti, Paolo Simonetti, Giovanni Vladilo, Laura Silva, Giuseppe Murante, Stavro Ivanovski, Michele Maris, Sergio Monai, Erica Bisesi, and Jost von Hardenberg

INTRODUCTION

Over the past two decades, ground- and space-based observations have unveiled thousands exoplanets and planetary systems around other stars in our Galaxy. About 5000 exoplanets are currently confirmed, in large part detected as transits by the Kepler and TESS missions. Launched in 2019, PLATO mission represents the first-step characterisation towards the understanding of the structural properties of these planets. Nevertheless, a significant boost for the detection of transiting Earth-analogues around bright stars is expected from the PLATO mission. 
However, it's only through remote atmospheric spectroscopy of potentially habitable rocky planets, that one of the main goals of exoplanetary science, the quest for life outside the Solar System, can be tackled. This observational challenge should be partly within reach of the recently launched JWST and the next ground-based astronomical observatory, E-ELT.

To accomplish the demanding task of searching for and  deciphering spectral signatures, a thorough and holistic observational and theoretical characterization of carefully selected rocky exoplanets is required.
The selection, among the observationally reachable targets for high-resolution spectroscopy of thin atmospheres, requires habitability studies with climate models. 
These simulations will enable the identification of those exoplanets with the largest chance of potentially hosting a surface diffuse life, i.e. with the largest habitability, that must be evaluated over a wide range of mostly unknown conditions. 
A considerable effort of modelization that exploits all available observations will be needed in order to assess the global physical characterization of the selected exoplanets, and in particular precisely of their potential surface climate and habitability.

 

THE MODEL

Here we present EOS-ESTM, a flexible climate model aimed at simulating the surface and atmospheric conditions that characterize habitable planets. The model allows one to perform a fast exploration of the parameter space representative of planetary quantities, including those currently not measurable in rocky exoplanets. EOS-ESTM has been built up starting from ESTM (Vladilo et al. 2013, 2015), a seasonal-latitudinal EBM featuring an advanced treatment of surface and cloud components and a 2D (vertical and latitudinal) treatment of the energy transport.

The main features of the model that we have implemented can be summarised as follows.

Firstly, we have calculated the atmospheric radiative transfer using EOS (Simonetti et al. 2022), a procedure tailored for atmospheres of terrestrial-type planets, based on the opacity calculator HELIOS-K (Grimm & Heng 2015; Grimm et al. 2021) and the radiative transfer code HELIOS (Malik et al. 2017, 2019). Thanks to EOS, the ESTM radiative transfer can be now calculated for a variety of atmospheres with different bulk and greenhouse compositions, illuminated by stars with different SEDs.

Then, we have upgraded the parameterizations that describe the clouds properties. New equations have been introduced for the albedo of the clouds and its dependence on the albedo of the underlying surface. The clouds coverage over ice is now a function of the global planetary ice coverage. A specific treatment for the transmittance and OLR forcing of clouds at very low temperature has been introduced.

Lastly, we have introduced a generalized logistic function to estimate the ice coverage as a function of mean zonal surface temperature. Based on a detailed study of the ice distribution on Earth, the adopted algorithm discriminates between ice over lands and oceans. The albedo and thermal capacity of transitional ice is now estimated using the fractional ice coverage. 


RESULTS

With the aim of providing a reference model for studies of habitable planets, we calibrated EOS-ESTM using a large set of Earth satellite and reanalysis data.  
The reference Earth model satisfies a variety of diagnostic tests, including mean latitudinal profiles of surface temperature (Figure 1), TOA albedo, OLR and ice coverage.

Fig. 1. Mean annual latitude profile of surface temperature predicted by the reference Earth model The temperature profile is compared with ERA5 temperatures averaged in the period 2005-2015 (blue dots).

To test the consistency of EOS-ESTM with previous studies of non-terrestrial climate conditions we performed a series of comparisons with a hierarchy of climate models, varying the levels of insolation (Figure 2), the stellar spectrum and planetary parameters (radius and rotation rate).

Fig. 2. Comparison of global and annual  mean surface temperature obtained from different climate Earth's models by increasing the solar constant. Red, solid line: EOS-ESTM (this work). Black, solid line: 3D model CAM4 (Wolf & Toon, 2015). Cyan, solid line: 3D model CAM3 (Wolf & Toon, 2014). Green, solid line: 3D model by Leconte et al. (2013).

The application of EOS-ESTM to the case of a CO2-dominated atmosphere in maximum greenhouse conditions (Kasting et al. 1993) yields a detailed description of the transition to a snowball state that takes place when the insolation decreases in the proximity of the outer edge of the HZ. Thanks to the flexibility of our model we can explore how this transition develops in different planetary conditions (e.g. rotation rate, Figure 3).

Fig. 3. Dependence on planetary rotation period rotation period, Prot, of the fractional ice coverage calculated at the outer edge of the HZ. The results were obtained for an Earth-like planet with a CO2-dominated, maximum greenhouse atmosphere, the remaining parameters being fixed to Earth values.

 

REFERENCES

Grimm S. L., Heng K., 2015, HELIOS-K: Opacity Calculator for Radiative Transfer (ascl:1503.004)

Grimm S. L., et al., 2021, ApJS, 253, 30

Kasting J. F., Whitmire D. P., Reynolds R. T., 1993, Icarus, 101, 108

Leconte J., Forget F., Charnay B., Wordsworth R., Pottier A., 2013, Nature, 504, 268

Malik M., et al., 2017, AJ, 153, 56

Malik M., Kitzmann D., Mendonça J. M., Grimm S. L., Marleau G.-D., Linder E. F., Tsai S.-M., Heng K., 2019, AJ, 157, 170

Simonetti P., Vladilo G., Silva L., Maris M., Ivanovski S. L., Biasiotti L., Malik M., von Hardenberg J., 2022, ApJ, 925, 105

Vladilo G., Murante G., Silva L., Provenzale A., Ferri G., Ragazzini G., 2013, ApJ, 767, 65

Vladilo G., Silva L., Murante G., Filippi L., Provenzale A., 2015, ApJ, 804,50

Wolf E. T., Toon O. B., 2014, Geophys. Res. Lett., 41, 167

Wolf E. T., Toon O. B., 2015, Journal of Geophysical Research (Atmospheres), 120, 5775

How to cite: Biasiotti, L., Simonetti, P., Vladilo, G., Silva, L., Murante, G., Ivanovski, S., Maris, M., Monai, S., Bisesi, E., and von Hardenberg, J.: EOS-ESTM: a flexible climate model for habitable exoplanets, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1195, 2022.

16:00–16:10
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EPSC2022-378
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ECP
Jaume Puig, Nastassia Knödlseder, Jaume Quera, Manuel Algara, and Marc Güell

Some organisms have shown to be able to naturally survive environments which we consider extreme, including the Low Earth Orbit, or even Outer Space. These microorganisms have natural mechanisms to repair severe DNA damage, such as the caused by ionizing and non-ionizing radiation or extreme temperatures and pressures. Some examples are Deinococcus radiodurans, which proved to be capable of surviving in the Exposure Facility of the International Space Station (ISS) for up to three years, and tardigrade species, such as Ramazzottius varieornatus, which are some of the most resilient known organisms. In this study, performed at the Barcelona Biomedical Research Park in collaboration with Hospital del Mar, survival under simulated Low Earth Orbit environmental conditions was tested in engineered and wild-type Escherichia coli strains. Ionizing radiation resistance was enhanced by transforming the Dsup gene from R. varieornatus and two genes from D. radiodurans involved in DNA damage repair, RecA and uvrD. This enhancement, together with a directed evolution process, resulted in a significant increase in the surviving fraction of the E. coli strain protected with the Dsup gene after a high dose, up to 3000 Gy, of ionizing radiation exposure in the form of a continuous spectrum of X-ray photons. Additionally, the survival to wide ranges of temperatures and low pressures was tested for the same strains, revealing a lack of relevance of cell aggregation for survival under the mentioned conditions in contrast with the case of D. radiodurans. However, survival rates showed no enhancement for any of the new E. coli strains. In a new collaboration with the Subterranean Laboratory of Canfranc, both the absence of radiation and extreme levels of radiation will be further studied. Additionally, an extreme environments analogue for several environmental conditions will be built, allowing for more specific testing on a controlled environment. This research represents a first step in the creation of new bacterial strains engineered to survive severe conditions and adapting existing species for their survival in remote environments, like extra-terrestrial habitats. These species could pave the road for future human expeditions, helping develop environments hospitable to life. In addition, studying the efficacy and the functioning of the genetic mechanisms used in this study could be beneficial for fields such as ecological restoration and medical and life sciences engineering, addressing treatments and/or diseases caused or related to radiation and DNA damage. Space is believed to be the last frontier, but the truth is, we are still a frontier to ourselves.

How to cite: Puig, J., Knödlseder, N., Quera, J., Algara, M., and Güell, M.: DNA Damage Protection for Enhanced Bacterial Survival Under Simulated Low Earth Orbit Environmental Conditions in Escherichia coli, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-378, 2022.

16:10–16:20
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EPSC2022-962
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MI
fabien stalport, hervé cottin, noel grand, anais feron, cecile gaimoz, mathieu Gourichon, kristian harge, xavier landsheere, ines louison, florent mignon, sylvain triquet, lisa viallon, pascal zapf, isabelle savin de larclause, didier chaput, and christian mustin

The study of the evolution of organic matter subjected to space conditions, and more specifically to solar photons in the vacuum ultraviolet range (120-200 nm) has been undertaken in low Earth Orbit since the 90’s and implemented on various space platforms.

 

On the European side the most recent exposure facilities are BIOPAN outside the Russian automatic capsules FOTON, and EXPOSE-E & -R (1&2) on the International Space Station. They allowed the photolysis of many different samples simultaneously and provided us with valuable data about the formation and evolution of organic matter in the Solar System (meteorites, comets, Titan’s atmosphere, Martian surface…) and in the Interstellar Medium. They have been used by European teams in the recent past (ORGANIC on BIOPAN V-FOTON M2 and UVolution on BIOPAN VI-FOTON M3, PROCESS on EXPOSE-E, AMINO and ORGANICS on EXPOSE-R, and PSS on EXPOSE-R2 returned from the ISS in 2016). These existing tools are very valuable; however, they have significant limitations that limit their capabilities and scientific return. One of the most critical issues for current studies is the lack of any in-situ analysis of the evolution of the samples as a function of time. Only two measurements are available for the experiment: one before and one after the exposure. However, critical science return from the studies relies on assumptions about how the samples behave between the two time points (linear, exponential…). A significant step forward has been achieved with the O/OREOS NASA cubesat with onboard UV-visible measurements. However, for organic samples, following the evolution of the samples would be more informative and provide greater insight with infrared measurements, which display specific patterns characteristic of major organic functionalities in the mid-infrared range (4000-1000 cm-1).

 

The goal of the IR-COASTER (InfraRed-Cubic Orbital Astrobiology Exposure Research) experiment is to conceive, develop, and implement a compact exposure device which could enable exposure of astrobiology-related samples to solar radiation, with an embedded compact infrared spectrometer for regular analysis of the samples during the exposure. A compact design inspired by cubesat technology would enable the use of this tool either outside the International Space Station or within cubesats or as a “hitchhiker” on planetary missions. A first version of IR-COASTER is planned to be installed on the Bartolomeo platform of the ISS end of 2023/early 2024 for 18 months and will bring important lessons learned for a future CubeSat development. ESA has a similar project with the EXOcube experiment which is also planned for installation outside ISS. 

How to cite: stalport, F., cottin, H., grand, N., feron, A., gaimoz, C., Gourichon, M., harge, K., landsheere, X., louison, I., mignon, F., triquet, S., viallon, L., zapf, P., savin de larclause, I., chaput, D., and mustin, C.: The IR-COASTER project for Astrobiology experiments outside the International Space Station or as a payload for 6U Cubesats, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-962, 2022.

16:20–16:40
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EPSC2022-1055
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solicited
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MI
Rosa de la Torre Noetzel

The search for extraterrestrial life and finding habitable environments on other planets and satellites like Mars, Europa, Enceladus and Titan are a priority of NASA and ESA, since the last decade. To contribute to these highly significant challenges, research has been done with established exposure platforms like those on the Foton satellite and EXPOSE on the ISS expanding now to ESA’s platform Bartolomeo. These were used to expose samples to space vacuum and space radiation, but also to provide gas supply and selected planetary radiation environments. Results obtained by these experiments have allowed to get supplemental knowledge necessary for supporting future investigations to search for life in the universe.

Several extremophile lichen species, have been exposed to extraterrestrial environments, i.e. space- and Mars like parameters, during short and long periods on board of ESA’s space missions (Foton M2 and M3, EXPOSE E and R2) to investigate the limits of terrestrial life. To maximize the scientific outcome of these experiments, LICHENS [1], LITHOPANSPERMIA [2], LIFE [3], and BIOMEX [4], a common elaboration and analysis of the results obtained on analogue field studies with results obtained in planetary simulation facilities was necessary to check the survival potential and vitality of the samples before flight. Tests and experiments at different simulation facilities at DLR, and at INTA, included the exposure to space vacuum, space UV radiation and space cosmic radiation, and to Mars-like environment, i.e. Mars atmospheric composition and pressure, as well as Mars UV radiation. Not microgravity or reduced gravity, which is present in space and on Mars, was tried.

Here we show the results of the resistance of two extremophile vagrant lichen species, Xanthoparmelia hueana and Circinaria gyrosa, to simulated microgravity (rotation speed of clinostate: 1 rpm) using the UNZIP clinostate at CIB-CSIC (Centro Investigaciones Biológicas Margarita Salas). This is the first time that lichens will be exposed to weightlessness environment in an attempt to isolate the potential contribution of microgravity from other extraterrestrial factors (radiation, vacuum). Combinations of simulated spaceflight conditions, including microgravity, will be necessary to check how this parameter affects the biomolecular level of lichens and their microbiome.

 

References

[1] Sancho, L.G., de la Torre, R., Horneck, G., Ascaso, C., de los Rios, A., Pintado, A., and Schuster, M. (2007) Lichens survive in space: results from the 2005 LICHENS experiment. Astrobiology 7:443–454. https://doi.org/10.1089/ast.2006.0046

[2] de la Torre, R., Sancho, L.G., Horneck, G., de los Ríos, A., Wierzchos, J., Olsson-Francis, K., and Ott, S. (2010) Survival of lichens and bacteria exposed to outer space conditions—results of the Lithopanspermia experiments. Icarus 208:735–748. https://doi.org/10.1016/j.icarus.2010.03.010

[3] Onofri, S., de la Torre, R., de Vera, J.P., Ott, S., Zucconi, L., Selbmann, L., Scalzi, G., Venkateswaran, K.J., Rabbow, E., Sánchez, F.J., and Horneck, G. (2012) Survival of rock-colonizing organisms after 1.5 year in outer space. Astrobiology 12: 508-516. https://doi.org/10.1089/ast.2011.0736

[4] de Vera, J.P., , and the BIOMEX-Team and associatesTeam (Ute Boettger, Rosa de la Torre Noetzel et al.) (2019) Limits of Life and the Habitability of Mars: The ESA Space Experiment BIOMEX on the ISS. Astrobiology, 19-2. https://doi.org/10.1089/ast.2018.1897.

How to cite: de la Torre Noetzel, R.: Limits of life at spaceflight conditions: survival of lichens to simulated microgravity , Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1055, 2022.

16:40–16:50
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EPSC2022-1227
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ECP
Alvaro del Moral, Dominic Siggs, Mark G. Fox-Powell, Victoria K. Pearson, and Karen Olsson-Francis

Introduction

Icy moons of the giant planets contain liquid water oceans where habitability is feasible. A prime example is Jupiter’s moon, Europa, which could contain multiple regions where life might be sustained under its thick ice layer [1]. However, whether the physical and chemical conditions in Europa’s ocean are conducive to life is currently unknown. Terrestrial analogue environments provide one opportunity to study microbial dynamics under chemical conditions relevant to Europa. Knowledge of Europa’s ocean chemistry comes from models based on Earth-based observations and spacecraft flybys [2,3], which suggest that the ocean might be favourable to support life, specifically, chemolithotrophs that obtain energy by oxidising inorganic compounds [1,4]. Developments in machine learning (ML) algorithms offer the possibility of selecting terrestrial analogues with a high degree of similarity to the physicochemical environment proposed for Europa [5].

However, there are limitations to terrestrial analogues; conditions in these environments do not perfectly match the physicochemical conditions in Europa, especially when the moon’s ocean pressure ranges from a few hundred bar to over 1200 bar [1,2]. Thus, controlled lab experiments must also be used to fully simulate the desired extraterrestrial environment. The aim of this study was to integrate analogue and experimental approaches to cultivate a microbial community capable of growth under the specific physical and chemical conditions of Europa’s sub-surface ocean that can serve as a proxy to study the habitability of Europa.

Methods

The selection of a suitable analogue sample through ML[5] and the design of a growth media was based on a model for Europa’s ocean composition[6]. The environmental sample came from Basque Lake, Canada and the media was dominated by a carbonate-chloride rich chemistry at a salinity of 12.6 g/L and under 2 bar of 80%-20% H2/CO2 gas headspace [4,6]. Sub-culturing was performed to eliminate contaminants from the initial sample, with final cultures reaching cell densities of 105-107 cells per millilitre. This community was then transferred to a bespoke environmental simulation chamber (Figure 1) where it could be gradually conditioned to the physical conditions within Europa’s ocean. Specifically, the pressure was initially set at 20 bar (10-fold increase from the benchtop control) and then increased to 100, 200 and 300 bar to selectively cultivate communities adapted for growth under Europa ocean conditions. At the same time, samples were taken to monitor pressure-induced changes in the microbial community composition and their physiology. The chemical composition of the media was monitored using Ion Chromatography (IC) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The growth of the microbial community was monitored using fluorescence cell microscopy and its composition using 16s rRNA sequencing. Changes in microbial morphology due to pressure were investigated using Transmission Electron Microscopy (TEM).