Fluctuation analysis to select for Samarium bio-uptaking microalgae clones the repurposing of a classical evolution...

Area of Science:

• Biotechnology
• Environmental Science
• Microbiology

Background:

• Increasing demand for Rare Earth Elements (REEs) necessitates exploring secondary resources.
• Biotechnological approaches are being investigated for REE extraction and management.
• Microalgae offer potential for metal sequestration and recovery.

Purpose of the Study:

• To adapt Chlamydomonas reinhardtii strains for resistance to Samarium (Sm), a representative REE.
• To investigate the relationship between Sm adaptation, cellular fitness, and Sm uptake in microalgae.
• To evaluate the potential of adapted microalgae for REE recovery and biotechnology applications.

Main Methods:

• Utilized an adapted Fluctuation analysis experiment to select for Sm-resistant Chlamydomonas reinhardtii ChlA strains.
• Exposed microalgae populations to Sm-containing media at low pH (~3) to induce adaptation.
• Quantified Sm uptake in selected resistant strains and compared cellular features to control populations.

Main Results:

• Successfully adapted Chlamydomonas reinhardtii to 1.33·10^-4 M Sm, with 13 of 99 populations showing evolutionary rescue.
• Resistant strains exhibited a mutation rate of 8.65·10^-7 and unexpectedly showed increased growth and larger cell size, contradicting expected fitness costs.
• One of three isolated resistant strains demonstrated enhanced Sm uptake (46.64 μg Sm g^-1 wet biomass), primarily through bioaccumulation.

Conclusions:

• Adapted microalgae strains show promise for REE sequestration and biotechnological recovery from secondary resources.
• Increased tolerance to REEs does not always correlate with enhanced uptake; cellular features are not directly linked to metal uptake performance.
• This evolutionary rescue methodology provides a viable strategy for selecting microalgae with improved REE tolerance for environmental and industrial applications.