Regulation of plasmid‐encoded isoprene metabolism in R hodococcus , a representative of an important link in the global isoprene cycle

Abstract

Summary Emissions of biogenic volatile organic compounds ( VOCs ) form an important part of the global carbon cycle, comprising a significant proportion of net ecosystem productivity. They impact atmospheric chemistry and contribute directly and indirectly to greenhouse gases. Isoprene, emitted largely from plants, comprises one third of total VOCs , yet in contrast to methane, which is released in similar quantities, we know little of its biodegradation. Here, we report the genome of an isoprene degrading isolate, R hodococcus sp. AD 45, and, using mutagenesis shows that a plasmid‐encoded soluble di‐iron centre isoprene monooxygenase ( IsoMO ) is essential for isoprene metabolism. Using RNA sequencing ( RNAseq ) to analyse cells exposed to isoprene or epoxyisoprene in a substrate‐switch time‐course experiment, we show that transcripts from 22 contiguous genes, including those encoding IsoMO , were highly upregulated, becoming among the most abundant in the cell and comprising over 25% of the entire transcriptome. Analysis of gene transcription in the wild type and an IsoMO ‐disrupted mutant strain showed that epoxyisoprene, or a subsequent product of isoprene metabolism, rather than isoprene itself, was the inducing molecule. We provide a foundation of molecular data for future research on the environmental biological consumption of this important, climate‐active compound.

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