Abstract
Isoprene is the most abundant biogenic volatile organic compound (BVOC) in the Earth’s atmosphere and plays important roles in atmospheric chemistry. Despite this, little is known about microbiological processes serving as a terrestrial sink for isoprene. While aerobic isoprene degrading bacteria have been identified, there are no known anaerobic, isoprene-metabolizing organisms. In this study an H2-consuming homoacetogenic enrichment was shown to utilize 1.6 μmoles isoprene h−1 as an electron acceptor in addition to HCO3−. The isoprene-reducing community was dominated by Acetobacterium spp. and isoprene was shown to be stoichiometrically reduced to three methylbutene isomers (2-methyl-1-butene (>97%), 3-methyl-1-butene (≤2%), 2-methyl-2-butene (≤1%). In the presence of isoprene, 40% less acetate was formed suggesting that isoprene reduction is coupled to energy conservation in Acetobacterium spp. This study improves our understanding of linkages and feedbacks between biogeochemistry and terrestrial microbial activity.
Highlights
Ecosystems emit numerous biogenic volatile organic compounds (BVOCs), which affect atmospheric chemistry and the Earth’s climate [1,2,3,4]
The evolution of isoprene reduction products 2-methyl-1-butene (>97%), 3-methyl-1-butene (≤2%), and 2-methyl-2-butene (≤1%) was observed in activated sludge microcosms, suggesting the compound is reduced by the inocula [Mass spectra: Supplementary Fig. S1])
Depletion of electron acceptors creates a niche for acetogens and methanogens due to their ability to obtain energy from CO2 reduction via H2 oxidation [70, 71]
Summary
Ecosystems emit numerous biogenic volatile organic compounds (BVOCs), which affect atmospheric chemistry and the Earth’s climate [1,2,3,4]. Between 30 and 50% of the estimated total global BVOC flux is isoprene (2-methyl-1,3-butadiene (CH2 = C(CH3)-CH = CH2)), a highly volatile, unsaturated hydrocarbon [5, 6]. The physiological role of isoprene in natural environments remains enigmatic [11]. It is mainly emitted by woody plants [12,13,14,15], though it is released in the breath of. These authors contributed : Miriam Kronen, Matthew Lee
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