Phosphorus Influences the Interaction Between Toxigenic Microcystis and Chloramphenicol

Area of Science:

• Environmental Microbiology
• Aquatic Ecotoxicology
• Bioremediation

Background:

• Microcystis blooms are a significant environmental concern.
• Chloramphenicol (CAP) is a common antibiotic pollutant in aquatic ecosystems.
• The interaction between nutrient levels, algal physiology, and antibiotic stress is not fully understood.

Purpose of the Study:

• To investigate the effects of varying phosphorus (P) concentrations on Microcystis responses to chloramphenicol (CAP) stress.
• To elucidate the mechanisms underlying Microcystis' tolerance and degradation of CAP under different P availabilities.
• To assess the ecological risks associated with co-occurring Microcystis blooms and CAP pollution.

Main Methods:

• Microcystis cultures were exposed to CAP at different phosphorus concentrations (0.05-0.5 mg/L and 5 mg/L) for 20 days.
• Physiological responses including protein synthesis and antioxidant defenses were monitored.
• CAP removal via biodegradation and microcystin production/release were quantified.

Main Results:

• At 5 mg/L P, Microcystis showed enhanced protein synthesis and antioxidant defenses, and greater CAP biodegradation, alleviating CAP toxicity.
• Lower P concentrations (0.05-0.5 mg/L) resulted in more inhibited Microcystis growth but higher microcystin release and residual CAP.
• Microcystin production and release were significantly dependent on phosphorus availability under CAP stress.

Conclusions:

• Phosphorus availability critically influences Microcystis' tolerance to CAP and its degradation capacity.
• While higher P mitigates direct CAP toxicity to Microcystis, lower P conditions pose greater eco-risks due to increased microcystin release and persistent CAP.
• Findings have crucial implications for risk assessment in aquatic environments with concurrent algal blooms and antibiotic pollution.