LIFE UNDER PRESSURE: THE OSMOTIC CHALLENGE FOR RHODOSPIRILLUM RUBRUM

LIFE UNDER PRESSURE: THE OSMOTIC CHALLENGE FOR RHODOSPIRILLUM RUBRUM

Abstrakt

In recent years, significant industrial advancements have not only enhanced the quality of daily life but they have also led to severe environmental pollution, such as plastic waste. One potential solution to this issue is replacing petroleum-based plastics with biodegradable materials, for example polyhydroxyalkanoates (PHAs). These materials can be produced various microorganisms such as the purple non-sulfur bacterium Rhodospirillum rubrum. A key advantage of R. rubrum as a PHAs producer is its metabolic flexibility, allowing it to thrive under diverse conditions, including light, dark, anaerobic, and aerobic environments. This study was focused on the adaptation of R. rubrum to osmotic stress through evolutionary engineering to enhance PHAs production. Initially, the bacterial strain was exposed to various salt concentrations to identify the optimal concentration for subsequent adaptation experiments. During these evolutionary trials, PHA content in the adapted strains was measured using GC-FID, and total dry biomass was also quantified. After the evolutionary experiments, the cultures were subjected to selected stressors, including high temperatures, osmotic shock, and freezing-thawing cycles, followed by viability assessment using flow cytometry. In addition, a series of experiments were performed to verify the effect of increased NaCl content on PHA production in a wild-type R. rubrum strain, a knock-out PHA synthase (phaC1 and phaC2) mutant strain and a knock-out PHA depolymerase (phaZ2) mutant strain." Our results confirmed that continuous exposure to 40 g/l NaCl osmotic stress positively impacted PHA production in R. rubrum, with concentrations ranging from 15–30% throughout the experiments. The evolutionary engineering approach proved effective for boosting PHA production in R. rubrum. The phaZ2 mutant strain did not show significantly increased PHA production when compared to the wild-type strain, however, follow-up experiments will need to be performed to confirm or refute this

In recent years, significant industrial advancements have not only enhanced the quality of daily life but they have also led to severe environmental pollution, such as plastic waste. One potential solution to this issue is replacing petroleum-based plastics with biodegradable materials, for example polyhydroxyalkanoates (PHAs). These materials can be produced various microorganisms such as the purple non-sulfur bacterium Rhodospirillum rubrum. A key advantage of R. rubrum as a PHAs producer is its metabolic flexibility, allowing it to thrive under diverse conditions, including light, dark, anaerobic, and aerobic environments. This study was focused on the adaptation of R. rubrum to osmotic stress through evolutionary engineering to enhance PHAs production. Initially, the bacterial strain was exposed to various salt concentrations to identify the optimal concentration for subsequent adaptation experiments. During these evolutionary trials, PHA content in the adapted strains was measured using GC-FID, and total dry biomass was also quantified. After the evolutionary experiments, the cultures were subjected to selected stressors, including high temperatures, osmotic shock, and freezing-thawing cycles, followed by viability assessment using flow cytometry. In addition, a series of experiments were performed to verify the effect of increased NaCl content on PHA production in a wild-type R. rubrum strain, a knock-out PHA synthase (phaC1 and phaC2) mutant strain and a knock-out PHA depolymerase (phaZ2) mutant strain." Our results confirmed that continuous exposure to 40 g/l NaCl osmotic stress positively impacted PHA production in R. rubrum, with concentrations ranging from 15–30% throughout the experiments. The evolutionary engineering approach proved effective for boosting PHA production in R. rubrum. The phaZ2 mutant strain did not show significantly increased PHA production when compared to the wild-type strain, however, follow-up experiments will need to be performed to confirm or refute this

Rhodospirillum rubrum, osmotic stress, evolutionary engineering, polyhydroxyalkanoates

Rhodospirillum rubrum, osmotic stress, evolutionary engineering, polyhydroxyalkanoates

PACASOVÁ, V.; FIALA, T.; CENTNEROVÁ, R.; MRÁZOVÁ, K.; FLEURIOT-BLITMAN, H.; ZINN, M.; OBRUČA, S.

03.10.2025

NOVA School of Science and Technology

Lisabon

26

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https://media.sci-meet.com/www.esbp2025.org/5668be5d-0ba1-4400-9612-ad0388fbe354/BookofAbstractsESBP2025.pdf