Amazonian soil fungi are efficient degraders of glyphosate herbicide; novel isolates of Penicillium, Aspergillus, and Trichoderma

Abstract

Pesticide residues that contaminate the environment circulate within the hydrological cycle can accumulate within the food chain and cause problems to both environmental and human health. Microbes, however, are well known for their metabolic versatility and the ability to degrade chemically stable substances, including recalcitrant xenobiotics. The current study focused on bio-prospecting within Amazonian rainforest soils to find novel strains fungi capable of efficiently degrading the agriculturally and environmentally ubiquitous herbicide, glyphosate. Of 50 fungal strains isolated (using culture media supplemented with glyphosate as the sole carbon-substrate), the majority were Penicillium strains (60%) and the others were Aspergillus and Trichoderma strains (26 and 8%, respectively). All 50 fungal isolates could use glyphosate as a phosphorous source. Eight of these isolates grew better on glyphosate-supplemented media than on regular Czapek Dox medium. LC-MS revealed that glyphosate degradation by Penicillium 4A21 resulted in sarcosine and aminomethylphosphonic acid.

Glyphosate-Eating Fungi: Study on Fungal Saprotrophic Strains’ Ability to Tolerate and Utilise Glyphosate as a Nutritional Source and on the Ability of Purpureocillium lilacinum to Degrade It

“…The findings of this study are consistent with the results obtained on other fungal species by Adelowo et al [46] (Trichoderma viridae, Aspergillus niger, and Fusarium oxysporum) and Correa et al [45] (Penicillium sp., Aspergillus sp., and Trichoderma sp.). However, Adelowo and Correa also detected AMPA, the first metabolite reported in another known glyphosate degradation pathway in fungi, in their samples [44][45][46].…”

“…The findings of this study are consistent with the results obtained on other fungal species by Adelowo et al [46] (Trichoderma viridae, Aspergillus niger, and Fusarium oxysporum) and Correa et al [45] (Penicillium sp., Aspergillus sp., and Trichoderma sp.). However, Adelowo and Correa also detected AMPA, the first metabolite reported in another known glyphosate degradation pathway in fungi, in their samples [44][45][46]. The AMPA pathway involves the cleavage of the C-N bond of glyphosate releasing AMPA as first step of degradation, which can either be degraded to methylamine and phosphate or to phosphoformaldehyde and, later, to formaldehyde [10,44,73].…”

“…In fact, in CDB, degradation occurred to the same extent as that in CDB P−, where RU represents the only P source. This finding also suggests that the enzymes probably responsible for the glyphosate degradation in P. lilacinum are not induced by P starvation as for other microorganisms [10,45,55].…”

“…Unfortunately, due to the impossibility to detect methylamine with the applied analytical technique, it is not possible to confidently affirm if glyphosate was not degraded to AMPA at all or, if otherwise, it has been completely degraded. Since AMPA has been reported for its toxicity [45], the absence of its residues in P. lilacinum glyphosate degradation products makes it a particularly suitable candidate for bioremediation applications.…”

“…For instance, in Aspergillus oryzae A-F02, AMPA is further metabolised to methylamine, which is then metabolized into other products, suggesting that glyphosate could be used also as N or C sources [44]. In addition, Correa et al [45] observed that the Penicillium 4A21 strain produced both AMPA and sarcosine as glyphosate degradation metabolites. Similarly, Adelowo et al [46] detected AMPA and sarcosine working on Trichoderma viridae, Aspergillus niger, and Fusarium oxysporum.…”