Bacterium · All six BTEX, even without air
Variovorax paradoxus
It degrades all six BTEX compounds, including benzene, and it keeps doing it at a fraction of normal oxygen. It also produces the enzyme that keeps plants growing on contaminated ground.
| Contaminant | What the research documents |
|---|---|
| Petroleum hydrocarbons | Degrades benzene, toluene, ethylbenzene and all three xylenes, aerobically and at 0.5 mg/L dissolved oxygen (strain BFB1_13) |
| Heavy metals | ACC deaminase lowers plant stress ethylene, increasing biomass and cadmium phytoextraction (strain 5C-2) |
| Pesticides & herbicides | Hydrolysis of the herbicide linuron (genus-level isolates) |
From published research on the species, not tests of an Elm Dirt product. Studies often work with one strain, and sequencing identifies species, so results on a site are measured on that site.
On this page (5 sections)
What it is
Variovorax paradoxus is a root-zone bacterium found in soils worldwide. It shows up in this library for two separate reasons: it eats the benzene family, and it keeps plants growing on ground that would otherwise stunt them.
Peer-reviewed research shows Variovorax paradoxus can degrade all six BTEX compounds and increase plant growth and cadmium uptake on contaminated soil. It is one of the 291 microbial species identified in Plant Juice by independent lab analysis (Biome Makers).
What the research shows
Strain BFB1_13 degraded benzene, toluene, ethylbenzene and all three xylenes, at normal dissolved oxygen and at 0.5 mg/L, with no statistically significant difference between the two [5], and benzene went fastest. Whole-genome sequencing annotated the pathways, and the authors propose the strain for reactive biobarriers at contaminated sites. A two-strain consortium built on it cleared a 20 mg/L BTEX mixture in six hours, then worked in real contaminated groundwater alongside the native community [6].
The low-oxygen result is the useful one. Fuel-soaked ground is usually short of air, and that is where most hydrocarbon degraders stall.
Strain 5C-2, isolated from polluted soil, was introduced in the paper that characterized ACC deaminase in plant-growth-promoting bacteria from contaminated ground [1].
In soil at 15 milligrams of cadmium per kilogram, a consortium of this organism, rhizobia and mycorrhizal fungi more than doubled pea biomass and brought a cadmium-sensitive mutant up to the tolerance of Indian mustard [2].
Separate Variovorax isolates degrade the herbicide linuron, though that evidence is at genus level [3,4].
How it works
A stressed plant makes ethylene, a hormone that tells it to stop growing. On contaminated soil the signal never switches off, and the plant stays small. ACC deaminase breaks down ethylene’s chemical precursor before the plant can convert it, so the plant keeps growing.
The organism leaves the cadmium itself untouched, and its value is as support biology: a plant with twice the root mass simply pulls far more metal out of the ground, which can decide whether a phytoextraction project ever finishes.
Where it fits
On fuel and solvent ground, it degrades the benzene family and keeps going when oxygen runs low; see petroleum hydrocarbons. On metal ground, it keeps plants growing so phytoextraction can finish, and the metal leaves in the harvested plants; see heavy metals. Either way, an independent lab tracks progress over months to a year or more.
Studies
- Belimov AA, et al. (2001). Characterization of plant growth promoting rhizobacteria isolated from polluted soils and containing 1-aminocyclopropane-1-carboxylate deaminase. Canadian Journal of Microbiology 47(7):642–652. doi:10.1139/w01-062
- Belimov AA, et al. (2020). Microbial consortium of PGPR, rhizobia and arbuscular mycorrhizal fungus makes pea mutant SGECd(t) comparable with Indian mustard in cadmium tolerance and accumulation. Plants 9(8):975. doi:10.3390/plants9080975
- Dejonghe W, et al. (2003). Synergistic degradation of linuron by a bacterial consortium and isolation of a single linuron-degrading Variovorax strain. Applied and Environmental Microbiology 69(3):1532–1541. doi:10.1128/AEM.69.3.1532-1541.2003
- Breugelmans P, et al. (2010). Proteomic study of linuron and 3,4-dichloroaniline degradation by Variovorax sp. WDL1. Research in Microbiology 161(4):291–298. doi:10.1016/j.resmic.2010.01.010
- Benedek T, et al. (2021). Potential of Variovorax paradoxus isolate BFB1_13 for bioremediation of BTEX contaminated sites. AMB Express 11(1):126. doi:10.1186/s13568-021-01289-3
- Szentgyörgyi F, et al. (2022). Development of a bacterial consortium from Variovorax paradoxus and Pseudomonas veronii isolates applicable in the removal of BTEX. AMB Express 12(1):4. doi:10.1186/s13568-022-01349-2
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