Phytoremediation, Bioaugmentation, and the Plant Microbiome

Abstract

Understanding plant biology and related microbial ecology as a means to phytoremediate soil and groundwater contamination has broadened and advanced the field of environmental engineering and science over the past 30 years. Using plants to transform and degrade xenobiotic organic pollutants delivers new methods for environmental restoration. Manipulations of the plant microbiome through bioaugmentation, endophytes, adding various growth factors, genetic modification, and/or selecting the microbial community via insertion of probiotics or phages for gene transfer are future areas of research to further expand this green, cost-effective, aesthetically pleasing technology─phytoremediation.

Keywords: Phytoremediation; bioaugmentation; bioremediation; groundwater; microbiome; rhizosphere.

Figure 1

Hybrid poplar plantation and riparian zone buffer strip from the Ph.D. research of Louis Licht at Amana, Iowa. Photo was taken in 1997, approximately 7 years after planting.⁻

Figure 2

Inextricable mutualism between plants and attendant microbes. (A) Axenic poplar shoot culture growing in minimal agar with the leakage of the endophyte, Methylobacterium populi, emanating from inside the plant shoot onto the agar, revealing itself. (B) (Right) Agar plate shows the slow growth of M. populi on minimum agar. (Left) Plate shows how a small piece of living plant tissue (callus cell culture of Populus deltoides x nigra, DN34) provides carbon substrate (fructose) for vigorous growth of the endophyte bacteria, M. populi. In turn, the callus cells receive growth hormones (indole-3-acetic acid and cis-zeatin) from the bacteria.

Figure 3

Concept of bioaugmented phytoremediation showing the synergy between the two technologies deployed together for the biodegradation of 1,4-dioxane and co-occurring chlorinated solvents, including trichloroethylene (TCE), cis-dichloroethylene (cDCE), 1,1,1-trichloroethane (TCA), and dichloroethane (DCA).