PHA Metabolism and Stress Response in Bacterium Rhodospirillum rubrum

abstract

English

Technological changes caused by the industrial revolution have led to environmental pollution in the recent decades. This phenomenon could also be reduced by using materials that are easily degradable in nature, including polyhydroxyalkanoates (PHAs). One of the promising producers of PHAs is the G- mesophilic bacterium Rhodospirillum rubrum, which is interesting mainly for its versatile metabolic apparatus, which includes the synthesis of PHAs from different carbon sources. This work was focused on polyhydroxyalkanoate (PHA) production in Rhodospirillum rubrum, comparing wild-type PHA-producing (R. rubrum) and mutant PHA-non-producing strains in terms of cell morphology. These bacterial strains were also subjected to selected stresses and the effect of PHA on the stress response was determined using advanced analytical techniques. Viability of these samples after exposure to selected stresses was determined using a fluorescent probe (propidium iodide) by flow cytometry, while cell disruption was examined by electron microscopy. As an additional experiment, the production of pigments was carried out under microaerobic conditions in the light. UV-VIS spectroscopy was used to determine the extracted pigments. Furthermore, both strains were exposed to the same selected stresses as in previous experiments. Samples were also examined by flow cytometry and electron microscopy. We were able to confirm the ability of wild-type stain of R. rubrum to produce the copolymer P(3HB-co-3HV). The hypothesis of the cryo-protective property of PHA granule during exposure to multiple freezing cycles was also confirmed. In the contrast, the protective function of PHA was not proven when exposed to osmotic stress.

Rhodospirillum rubrum, polyhydroxyalkanoates, flow cytometry, electron microscopy

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

13. 9. 2023

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