Microbial metabolism of isoprene: a much-neglected climate-active gas

Abstract

The climate-active gas isoprene is the major volatile produced by a variety of trees and is released into the atmosphere in enormous quantities, on a par with global emissions of methane. While isoprene production in plants and its effect on atmospheric chemistry have received considerable attention, research into the biological isoprene sink has been neglected until recently. Here, we review current knowledge on the sources and sinks of isoprene and outline its environmental effects. Focusing on degradation by microbes, many of which are able to use isoprene as the sole source of carbon and energy, we review recent studies characterizing novel isoprene degraders isolated from soils, marine sediments and in association with plants. We describe the development and use of molecular methods to identify, quantify and genetically characterize isoprene-degrading strains in environmental samples. Finally, this review identifies research imperatives for the further study of the environmental impact, ecology, regulation and biochemistry of this interesting group of microbes.

Isoprene-Degrading Bacteria from Soils Associated with Tropical Economic Crops and Framework Forest Trees

“…There is no obvious reason for the differential capacity for potential isoprene degradation with the the rubber plantation soil, as rubber is a polymer of isoprene, and some bacteria, e.g., Gordonia spp., can degrade both [ 23 ]. From previous studies, there is no evidence of a relationship between plant isoprene production and isoprene consumption in associated soils, probably because soil microbiota primarily consume isoprene produced in the soil, e.g., by bacteria and fungi rather than from the atmosphere [ 15 , 16 ]. Isoprene production from the studied plants has only been documented for oil palm and rubber trees [ 10 , 11 , 12 ].…”

“…Soil is a sink for some of this isoprene [ 13 , 14 ]. There is also the potential for internal cycling (both production and consumption) of isoprene within soils [ 15 ], with a range of microbes being responsible for isoprene consumption, such as members of the genera Arthrobacter , Nocardia, Nocardiodes, Rhodococcus, Bacillus, Alcaligenes, Ramlibacter, Variovorax, Klebsiella, Pantoea and Pseudomonas [ 16 ]. Knowing the potential and the capacity of soil bacteria and bacterial communities to consume isoprene will lead to a better understanding of isoprene degradation mechanisms in soil and the global atmospheric isoprene budget.…”

Molecular Ecology of Isoprene-Degrading Bacteria

“…AD45 from freshwater sediments, which has become a key bacterial strain for the study of isoprene metabolism [43,[58][59][60][61]. Details about the isoprene-degrading strains belonging to these genera are provided in [62]. Finally, to our knowledge, no anaerobic bacteria, archaea, or fungi have been reported to use isoprene as a sole carbon and energy source, although Kronen et al [63] have recently shown that strict anaerobes can use isoprene as an electron acceptor to support homoacetogenesis, and thus anaerobic degradation of isoprene also warrants further attention.…”

Microbial Musings – July 2020

“…This is a molecule that I really had very little awareness of, but it is a major volatile hydrocarbon emitted in vast quantities by trees and other vegetation. The authors of the review, Colin Murrell and Andrew Crombie from the University of East Anglia, UK, and Terry McGenity (@TMcgenity), from the University of Essex, UK, point out that this chemical, more formally known as 2-methyl-1,3 butadiene, is produced in the biosphere in quantities of around 500 teragrams (Tg) of carbon per year [2], which is of a similar magnitude to that of methane! The chemical has complex interactions in the atmosphere, being implicated in both warming and cooling events.…”