Describing the Cell Biology of Saprolegnia parasitica: Role of Metals and Respiration

Saprolegnia parasitica is a pathogenic oomycete that causes saprolegniasis, a serious disease affecting freshwater fish and aquaculture systems. Despite the increasing use of copper-based treatments to control this infection, little is known about how S. parasitica responds to fluctuations in metal availability at the physiological and mitochondrial levels. This study investigates the impact of copper and iron availability on Saprolegnia parasitica growth, metal uptake, and respiratory function. We cultured S. parasitica in chemically defined media supplemented with or depleted of essential metals using specific chelators— Bathocuproinedisulfonic acid (BCS) (a high-affinity Cu(I) chelator), Ferrozine (Fe(II)), and BPS (Fe(II)). Growth responses were assessed via biomass measurements, while intracellular metal content was quantified using inductively coupled plasma mass spectrometry (ICP-MS). Interestingly, BCS treatment did not significantly inhibit growth or reduce copper content compared to control growth conditions, suggesting that S. parasitica may bypass extracellular copper chelation through alternative uptake pathways or internal copper reservoirs. To assess mitochondrial function, we measured Saprolegnia parasitica oxygen consumption using a Clark-type oxygen electrode under varying growth conditions. BCS-treated S. parasitica maintained respiration rates similar to the untreated controls, with a sustained contribution from the alternative oxidase (AOX) pathway, even under copper-limited conditions. These results indicate a possible shift in electron transport chain dynamics, allowing S. parasitica to maintain mitochondrial function when cytochrome c oxidase (CcO) is compromised by metal limitation. Overall, this study provides novel insights into the adaptive mechanisms employed by S. parasitica to overcome metal deprivation. The ability to maintain respiration through AOX and resist copper chelation suggests that targeting metal homeostasis may require more nuanced strategies in the management of saprolegniasis. Results revealed that S. parasitica modulates growth and respiration in relation to environmental metal concentrations, with specific uptake mechanisms contributing to metal homeostasis. These findings highlight the importance of metal bioavailability in regulating the pathogen’s physiology and may inform approaches to limit its spread in aquaculture systems by manipulating environmental conditions or targeting metal acquisition pathways.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Biochemistry

Grantor

Texas State University

Year dc:date.issued

2025

Author dc:creator

• Akter, Rahima

Advisor dc:contributor.advisor

• Peterson, Ryan

Committee members dc:contributor.committeemember

• Lewis, Lysle Kevin
• Du, Liqin

• Saprolegnia parasitica
• freshwater fish
• aquaculture systems

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10877/22931

OAI identifier oai:identifier

oai:digital.library.txst.edu:10877/22931