High diversity but limited expression of biosynthetic gene clusters in a peatland microbial community.

The in situ relevance of biosynthetic gene clusters (BGCs) remains poorly understood. We apply meta-omics to characterize BGC diversity and activity along a peatland redox gradient. From seven metagenomes, we recover 9,694 BGCs, spanning diverse taxa, most lacking close relatives in reference databases, indicating extensive novelty. Only 9-27% of this potential is expressed in situ, with Acidobacteriota, despite moderate repertoires, accounting for over half of all BGC transcription. Talented producers with up to 24 clusters are largely silent, and expression is inversely related to BGCs per genome. Acidobacteriota, specialized in complex carbon processing potential express a larger proportion of their BGC repertoires than BGC-rich Pseudomonadota, which had shorter doubling times and lower potential for complex carbon processing. At the genome level, the degree of BGC expression is most strongly coupled to carbohydrate-active enzyme expression, particularly glycoside hydrolases, linking secondary metabolism to active carbon processing in peatland microbes. Thus, although BGCs are widespread, BGC expression in situ is integrated into the carbon-cycling activity of individual taxa rather than a shared physiological state.