Microbial helpers allow cyanobacteria to thrive in ferruginous waters

Area of Science:

• * Origin of Life
• * Paleobiology
• * Biogeochemistry

Background:

• * The Great Oxidation Event (GOE) marked a significant rise in atmospheric oxygen, driven by cyanobacteria.
• * Early cyanobacteria faced cellular damage from hydroxyl radicals produced in iron-rich Archean oceans.
• * Protection mechanisms were likely essential for cyanobacteria's ecological success and atmospheric oxygenation.

Purpose of the Study:

• * To identify protective factors for early cyanobacteria against hydroxyl radical damage.
• * To investigate the role of microbial cooperation in mitigating iron toxicity.
• * To understand the conditions enabling cyanobacteria colonization before the GOE.

Main Methods:

• * Co-culturing experiments with cyanobacteria (Synechococcus) and heterotrophic bacteria (Shewanella).
• * Assessing the fitness and survival of cyanobacteria in ferruginous (iron-rich) conditions.
• * Evaluating the impact of Shewanella strains with specific defense mechanisms, including manganese transporters.

Main Results:

• * Facultative anaerobic heterotrophic bacteria (Shewanella) enhanced cyanobacteria fitness in iron-rich waters.
• * Shewanella strains possessing manganese transporters offered the greatest protection.
• * These findings indicate a protective role for microbial interactions against iron toxicity.

Conclusions:

• * Microbial cooperation was likely vital for early cyanobacteria survival in harsh, iron-rich Archean seas.
• * Manganese-rich environments may have facilitated cyanobacteria's ability to tolerate higher iron concentrations.
• * These symbiotic relationships could have been a prerequisite for the Great Oxidation Event.