This review article (2015) summarizes the available knowledge about the role and potential of plant-microbe interactions in improving indoor and outdoor air quality. Phytoremediation means the use of living plants in removal, degradation, or containment of contaminants. The power of plants to collect and metabolize pollutants has been known for some time, and they are able to do this by the symbiosis with bacteria and fungi. These plant-microbe interactions are known to be important in phytoremediation processes, as the stems, leaves, and roots of plants are covered in bacteria.

Air pollution has a significant and complex effect on ecosystems and human health. Plants with their microorganisms play a leading role in maintaining biodiversity and ecological sustainability of urban green infrastructures. Outdoors, leaf fall leads to transfer of the absorbed pollutants to the soil rhizosphere in the ground, where microorganisms degrade, detoxify or sequestrate the pollutants and promote plant growth.

Plants and microbes in removing PM:

• Plants absorb PM on the foliage or stabilize them in waxes
• Plant-associated microorganisms promote plant growth and improve their PM absorbance capacity and help plants to cope with pollutant caused stress
• Microorganisms also degrade PM by themselves

Plants and microbes in removing VOCs:

• Plants remove VOCs via phytoremediation by uptake via leaf stomata and plant surface, degrading then inside the plant
• Microorganisms on the leaves and roots metabolise VOCs and enhance VOCs' bioavailability for the plant via the production of biosurfactants

Indoor plants increase humidity, but unlike using industrially produced devices, they are not accompanied by an increase of microbes that are potentially harmful for humans. This is likely due to allelochemicals that are released by the plants microbiome, and inhibit the growth of airborne microorganisms.

Researchers conclude, that in plants and their microbes lies a huge unexploited potential for purifying both indoor and outdoor air. They are very promising as a tool to improve air quality and in these plant-microbe systems, both partners are of high importance.