Chameleon-Like Anammox Bacteria: Color Change Under Starvation

Researchers have discovered that anammox bacteria undergo surface color changes when subjected to prolonged starvation. This phenomenon is not driven by cytochrome c levels, as previously suspected, but rather by metabolic shifts that lead to iron-sulfur compound formation.

Key Findings

• Cysteine Degradation – Under starvation, anammox bacteria activate cysteine degradation pathways, leading to hydrogen sulfide (H₂S) production.

• Iron-Sulfur Cluster Formation – The bacteria contain iron-rich nanoparticles and cytochrome c, which release free iron during starvation. H₂S reacts with free iron to form Fe-S compounds, resulting in a blackened appearance.

• Reversible Color Change – When exposed to aeration, Fe-S compounds oxidize, restoring the bacteria's red coloration.

• Self-Protection Mechanism – The blackened state helps bacteria avoid inhibition by high H₂S concentrations while simultaneously storing iron.

Why This Matters

This study expands our understanding of bacterial survival mechanisms under nutrient deprivation. The ability to reversibly alter surface color highlights anammox bacteria's adaptive strategies, which could have implications for environmental biotechnology and microbial resilience research.