Dose-dependent transcriptional responses of marine prokaryotes to Fe-rich colloids of glacial and non-glacial origin in the Kerguelen region (Southern Ocean)

Non-glacial Fe-rich colloids (20–200 nm) stimulated dose-dependent growth of Kerguelen-region marine prokaryotes, while glacial colloids produced the opposite growth pattern.

• Why it matters: Iron inputs from glacier melt may alter microbial carbon cycling, but how different Fe species in colloids affect prokaryotic nutrition and metabolism is unclear.
• What they did: Marine prokaryotes were incubated with dose additions of Fe-rich colloids from Cook Ice Cap meltwater versus a non-glacial source, measuring growth and gene transcriptional profiles.
• The result: Transcripts indicating increasing Fe-limitation rose with either colloid type, but only non-glacial colloids showed dose-dependent increases in aromatic compound degradation transcripts, linking nutritional stress to Fe and C co-limitation.

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