Study of the stress response and its connection with PHA metabolism in bacterium Rhodospirillum rubrum

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In recent years, there have been major advances in overall technology. This shift has caused an increase in the standard of living for humanity, but also caused a significant increase and accumulation of human waste, especially plastic waste. This phenomenon could be reduced by materials that are degradable, such as polyhydroxyalkanoates (PHAs). These bioplastics are the products of the metabolism of various microorganisms that can later broken down into water and carbon dioxide. One of the promising producers of PHAs is the G- mesophilic bacterium Rhodospirillum rubrum, mainly it is interesting for its versatile metabolic apparatus that allows it to produce various metabolites using waste gases (for example CO2), or other waste substrates (for example waste from food industry) This work is focused on the production of PHAs and its connection with the stress response, particularly in the bacterium Rhodospirillum rubrum (DSM 467). In the first part of this work, PHA-producing the wild-type (R. rubrum) and its PHA-non-producing mutant in terms of cell morphology. These strains were also exposed to various stresses and the effect of PHA on the stress response was determined by advanced analytical techniques. The viability of these samples after exposure to selected stresses was found using a fluorescent probe (propidium iodide) by flow cytometry, while cell disruption was also examined by electron microscopy. Last an additional experiment was carried out under microaerobic conditions in the light for 120 h for both wild-type and the mutant strain. Both strains were exposed to the same selected stresses and the collected samples were also analyzed by the same analytical methods as in the previous experiments. We were able to repeatedly confirm the ability of the wild-type strain to produce copolymer P(3HB-co-3HV) on acetate as a sole carbon source. Also, the hypothesis of the cryo-protective effect of PHA granules during exposure to multiple freezing cycles was confirmed. In contrast, the protective properties of PHA granules against osmotic stress were not proven.

Rhodospirillum rubrum, polyhydroxyalkanoates, stress factors, pigments, gas chromatography, flow cytometry, electron microscopy.

PACASOVÁ, V.; MRÁZOVÁ, K.; SLANINOVÁ, E.; OBRUČA, S.

30. 11. 2023

978-80-214-6204-5

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