Houseplants as human health monitors

Plants provide humans with many products and services that are not only important but essential to our existence. We don’t have space to catalogue all of those bountiful botanical benefits here (although we have done our best in this column over the years!). But we can showcase a new one, which may be a glimpse of the future in which houseplants are not only a treat for the eyes – and a boost to our wellbeing – but also act as “functional sirens of home health”.

Old man and a plant
Image: Canva.

Although the built environment – of which homes are a significant part – only accounts for 0.5% of the livable surface of the Earth, it is the habitat in which most humans live and is recognised as an “evolving microbiome incubator”. Although humans share their homes with a myriad of microbes, some are harmful and implicated in sick house (or building) syndrome, an illness of the built environment.

Fungi that are particularly relevant to this malaise – and which are frequent house-dwellers – include species in such genera as Aspergillus, Cladosporium, Penicillium, and Fusarium. Although they may largely be invisible to the casual observer, they produce volatile organic compounds (VOCs) that can reduce indoor air quality, and have associated human-health implications. As envisaged by C Neal Stewart Jr et al. houseplants – which are already commonplace companions of humans in their homes – would be engineered (yes, genetically via GM [genetic modification]) to detect the presence of such microbes by reacting to the VOCs that they produce.*

The simplest ‘phytosensor platform’ – the bio-engineered houseplant – could report the presence of the harmful fungi by producing a visible signal from green fluorescent protein (GFP) in the plant tissues. The GFP would be synthesised in response to detection of the microbes’ VOCs. Once alerted to the fungal threat it would need to be treated appropriately, but at least the home-dweller would know it was present and have the choice to do something about it or not.

As co-author of the paper Rana Abudayyeh states, “Our work should result in an interior environment that is more responsive to overall health and well-being of its occupants while continuing to provide the benefits plants bring to people every day”. However, as Stewart et al. also recognise, we currently lack the tools to engineer many popular types of houseplants. Until such time as that is possible we either wait for this built environment transformative technology to come of age, or fill our homes in the meantime with easily-grown and engineered model plants such as tobacco and Arabidopsis.

Cynically, one might envisage the situation where the technology will only be developed for annual plants, so that healthy-home-concerned humans would have to buy a new set of sensing-plants each growing season. Rumours that Monsanto (“a global modern agriculture company”) – famously associated with forbidding the saving and re-use of its GM seed to sow the following year’s crop thereby avoiding the need to repurchase from Monsanto – are investigating this potential new income stream are just that.

* This work builds upon successful field trials of phytosensing plants that respond to bacteria by glowing orange.

Further reading

Martin, L. J., Adams, R. I., Bateman, A., Bik, H. M., Hawks, J., Hird, S. M., … Dunn, R. R. (2015). Evolution of the indoor biome. Trends in Ecology & Evolution, 30(4), 223–232. https://doi.org/10.1016/j.tree.2015.02.001

Hodgson, M. (2005). Sick Building Syndrome. Encyclopedia of Toxicology, 8–13. https://doi.org/10.1016/b0-12-369400-0/00876-0

Norbäck, D. (2009). An update on sick building syndrome. Current Opinion in Allergy and Clinical Immunology, 9(1), 55–59. https://doi.org/10.1097/ACI.0b013e32831f8f08

Schwab, C. J., & Straus, D. C. (2004). The Roles of Penicillium and Aspergillus in Sick Building Syndrome. Advances in Applied Microbiology, 215–238. https://doi.org/10.1016/S0065-2164(04)55008-6

Morath, S. U., Hung, R., & Bennett, J. W. (2012). Fungal volatile organic compounds: A review with emphasis on their biotechnological potential. Fungal Biology Reviews, 26(2-3), 73–83. https://doi.org/10.1016/j.fbr.2012.07.001

Hung, R., Lee, S., & Bennett, J. W. (2015). Fungal volatile organic compounds and their role in ecosystems. Applied Microbiology and Biotechnology, 99(8), 3395–3405. https://doi.org/10.1007/s00253-015-6494-4

Bennett, J., & Inamdar, A. (2015). Are Some Fungal Volatile Organic Compounds (VOCs) Mycotoxins? Toxins, 7(9), 3785–3804. https://doi.org/10.3390/toxins7093785

Stewart, C. N., Abudayyeh, R. K., & Stewart, S. G. (2018). Houseplants as home health monitors. Science, 361(6399), 229–230. https://doi.org/10.1126/science.aau2560

Fethe, M. H., Liu, W., Burris, J. N., Millwood, R. J., Mazarei, M., Rudis, M. R., … Stewart, C. N. (2014). The performance of pathogenic bacterial phytosensing transgenic tobacco in the field. Plant Biotechnology Journal, 12(6), 755–764. https://doi.org/10.1111/pbi.12180