Biology subjects

PILLOT, G.

Publications and source records attributed to PILLOT, G..

3 recordsLinked to original sources

bioRxiv2021

Optimization of growth and electrosynthesis of PolyHydroxyAlcanoates by the thermophilic bacterium Kyrpidia spormannii

The electrosynthesis of valuable compounds by biofilms on electrodes is being intensively studied since few years. However, so far, the actual biofilms growing on cathodes produce mainly small and relatively inexpensive compounds such as acetate or ethanol. Recently, a novel Knallgas bacterium, Kyrpidia spormannii EA-1 has been described to grow on cathodes under thermophilic and microaerophilic conditions, producing significant amounts of PolyHydroxyAlkanoates (PHAs). These PHA are promising sustainable bioplastic polymers with the potential to replace petroleum-derived plastics in a variety of applications. However, the effect of culture conditions and electrode properties on the growth of K. spormannii EA-1 biofilms and PHA production is still unclear. In this study, we report on the optimization of growth and PHA production in liquid culture and on the cathode of a Microbial Electrosynthesis System. Optimization of the preculture allows to obtain high cell density of up to 8.5 Log10 cells{middle dot}ml-1 in 48h, decreasing the time necessary by a factor of 2.5. With respect to cathodic biofilm formation, this study was focused on the optimization of three main operating parameters, which are the applied cathode potential, buffer pH, and the oxygen concentration in the feed gas. Maximum biofilm formation and PHA production was observed at an applied potential of -844mV vs. SCE, pH 6.5, O2 saturation of 2.5%. The PHA concentration in the biofilm reached a maximum of {approx}26.8 g{middle dot}cm-2 after optimization, but at 2.9% the coulombic efficiency remains relatively low. We expect that further nutrient limitation will allow the accumulation of more PHA, based on a dense biofilm growth. In conclusion, these findings take microbial electrosynthesis of PHA a step forward towards practical implementation.

bioengineering↗

bioRxiv2021

Thriving of hyperthermophilic microbial communities from a deep-sea sulfidic hydrothermal chimney under electrolithoautotrophic conditions with nitrate as electron acceptor.

Recent studies have shown the presence of an abiotic electrical current across the walls of deep-sea hydrothermal chimneys, allowing the growth of electroautotrophic microbial communities. To understand the role of the different phylogenetic groups and metabolisms involved, this study focused on an electrotrophic enrichment, with nitrate as electron acceptor. The biofilm density, the community composition, the organic products released, and the electrical consumption were monitored by FISH confocal microscopy, qPCR, Metabarcoding, MNR and potentiostat measurements. A statistic analysis by PCA showed the correlation between the different parameters in 3 distinct temporal phases. The Archaeoglobales have been shown to play a key role in the development of the community, as first colonizers and producing pyruvate, therefor used as organic source for heterotrophs. Some Thermococcales showed the ability to perform electrofermentation of this pyruvate into acetate and H2. Finally, through subcultures of the community, we showed the development of a larger biodiversity over time. This observed phenomenon could explain the biodiversity development in hydrothermal context where energy sources are transient and unstable.

microbiology↗

bioRxiv2020

Electrotrophy as potential primary metabolism for colonization of conductive surfaces in deep-sea hydrothermal chimneys

Deep-sea hydrothermal vents are extreme and complex ecosystems based on a trophic chain. We are still unsure of the identities of the first colonizers of these environments and their metabolism, but they are thought to be (hyper)thermophilic autotrophs. Here we investigate whether the electric potential observed across hydrothermal chimneys could serve as an energy source for these first colonizers. Experiments were performed in a two-chamber microbial electrochemical system inoculated with deep-sea hydrothermal chimney samples, with a cathode as sole electron donor, CO2 as sole carbon source, and nitrate, sulfate, or oxygen as electron acceptors. After a few days of culture, all three experiments showed growth of electrotrophic biofilms consuming the electrons (directly or indirectly) and producing organic compounds including acetate, glycerol, and pyruvate. Within the biofilms, the only known autotroph species retrieved were members of Archaeoglobales. Various heterotrophic phyla also grew through trophic interactions, with Thermococcales growing in all three experiments as well as other bacterial groups specific to each electron acceptor. This electrotrophic metabolism as energy source driving initial microbial colonization of conductive hydrothermal chimneys is discussed.

microbiology↗