Specific toxicity of azithromycin to the freshwater microalga Raphidocelis subcapitata

Abstract

Pharmaceuticals are produced to inflict a specific physiological response in organisms. However, as only partially metabolized after administration, these types of compounds can also originate harmful side effects to non-target organisms. Additionally, there is still a lack of knowledge on the toxicological effects of legacy pharmaceuticals such as the antibiotic azithromycin. This macrolide occurs at high concentrations in the aquatic environment and can constitute a threat to aquatic organisms that are at the basis of the aquatic food chain, namely microalgae. This study established a high-throughput methodology to study the toxicity of azithromycin to the freshwater microalga Raphidocelis subcapitata. Flow cytometry and pulse amplitude modulated (PAM) fluorometry were used as screening tools. General toxicity was shown by effects in growth rate, cell size, cell complexity, cell viability and cell cycle. More specific outcomes were indicated by the analysis of mitochondrial and cytoplasmatic membrane potentials, DNA content, formation of ROS and LPO, natural pigments content and photosystem II performance. The specific mode of action (MoA) of azithromycin to crucial components of microalgae cells was revealed. Azithromycin had a negative impact on the regulation of energy dissipation at the PSII centers, along with an insufficient protection by the regulatory mechanisms leading to photodamage. The blockage of photosynthetic electrons led to ROS formation and consequent oxidative damage, affecting membranes and DNA. Overall, the used methodology exhibited its high potential for detecting the toxic MoA of compounds in microalgae and should be considered for future risk assessment of pharmaceuticals.

Photosynthetic response of Chlamydomonas reinhardtii and Chlamydomonas sp. 1710 to zinc toxicity

“…Therefore, the discussion focused on the variations in qN. As a regulatory function, non-photochemical quenching was found to either increase ( Nama et al, 2019 ; Rocha et al, 2021 ) or decrease ( Almeida et al, 2021 ; Aparicio et al, 2022 ) with increased concentration of toxic substances. This divergence may be due to the fact that most previous studies have only focused on a single time point without temporal trends.…”

“…Despite the wide utilization of NPQ, OJIP, and RLC parameters, previous studies have largely focused on only one of the aforementioned approaches ( Marečková et al, 2019 ; Almeida et al, 2021 ; Gebara et al, 2023 ). Additionally, the temporal variations of these parameters are rarely accounted for, and few studies have compared the chlorophyll fluorescence characteristics across different algal species.…”

The effect of nanoparticle surface charge on freshwater algae growth, reproduction, and lipid production

“…33 Environmental Science: Nano Paper nucleation state or DNA content of algal cells dividing by multiple fission. 15,40 R. subcapitata divides by multiple fission, with cells typically undergoing an increase in size, followed by a series of nuclear divisions. Commonly, this results in the formation of four autospores, but up to eight and as few as two autospores have also been observed to result from these divisions.…”

Interactive effects of selected pharmaceutical products (metronidazole, diclofenac, ibuprofen) and differently functionalized nanoplastics on marine algae Chlorella sp.

“…The maximum quantum yield of PS II (Fv/Fm) functions as an indicator of PS II's ability to harness photon energy and utilize it for photochemical reactions during both dark and light adaptation phases (X. L. Yang et al, 2018). The electron transport rate (ETR) re ects the rate at which electrons traverse the photosynthetic chain, consequently in uencing electron transport between PSII-PSI and the associated biochemical processes (Almeida et al, 2021). When compared to the control group, all three pristine PPs showed a substantial decrease (p < 0.001) in the Fv/Fm values (Supplementary Fig.…”