@conference{
author = "Vojvodić, Snežana and Stanić, Marina and Zechmann, Bernd and Dimitrijević, Milena and Opačić, Miloš and Danilović Luković, Jelena and Morina, Arian and Pittman, Jon K. and Spasojević, Ivan",
year = "2021",
abstract = "Many neutrophilic and acidophilic microalgal species tolerate high metal concentrations
and can survive or colonize metal-polluted waters. They show significant biotechnological
potential for the remediation and wastewaters processing. On the other hand, negative effects
of metal pollution on microalgae may affect the function of aquatic ecosystems because these
photosynthetic microorganisms represent the primary producers of O2 and biomass. However,
adaptive mechanisms that microalgae employ to detoxify metal excess are largely unknown.
Herein we analyzed the response of the freshwater microalga Chlorella sorokiniana to high
but non-toxic levels of Mn2+. Manganese is a key metal pollutant, with five possible oxidation
forms that can bind to a variety of different ligands. At pH below 7, it is predominantly present in
Mn2+ form. Scanning electron microscopy showed that in response to 1 mM Mn2+, C. sorokiniana
released mucilage polymers within 1 h. Electron paramagnetic resonance spectroscopy (EPR)
showed that the early response involved loose Mn2+ binding to mucilage and/or the cell wall.
The amount of loosely bound Mn2+ was significantly decreased after 24 h, whereas biomass
showed significant accumulation of Mn, O and P, as determined by energy dispersive X-ray
spectrometry, indicating the production of polyphosphates, which may sequester Mn. Further,
it was found that the exposure to Mn2+ resulted in rapid and transient decrease of total free
glutathione concentration; the drop was observed after 1 h, and the concentration returned to
initial values after 24 h. EPR measurements showed a similar trend in the level of reduced thiols.
The observed changes can be explained either by the synthesis of phytochelatins – sulfurrich
short-chain peptides that sequester metals, or by glutathionylation of proteins. Reduced
thiols could not be detected in the extracellular space, indicating that C. sorokiniana did not
release thiols in response to high Mn. These results demonstrate that the adaptive response
of C. sorokiniana to high Mn levels involves multiple components and time phases. The early
phase involves mucilage release, phytochelatins and/or protection of protein thiols, whereas
the successive phase involves Mn coordination by polyphosphates and other mechanisms that
remain to be resolved.",
publisher = "Elsevier, Society for Free Radical Research Europe (SFRR-E), Ministry of Education, Science and Technological Development (Republic of Serbia), Oxygen Club of California",
journal = "Redox Biology in the 21st Century: A New Scientific Discipline, Meeting Abstracts",
title = "Mechanisms of detoxification of high manganese concentrations by the microalga Chlorella sorokiniana",
pages = "145-145",
doi = "10.1016/j.freeradbiomed.2021.08.148"
}
