Intimate communication between Comamonas aquatica and Fusarium solani in remediation of heavy metal-polluted environments

Worldwide, humanity is facing a major environmental crisis with the disposal of heavy metal contaminated waste. The current study describes, for the first time, the interactions between gram-negative Comamonas aquatica and filamentous fungus Fusarium solani in removing heavy metal toxicity as an eco-friendly system. When combined, C. aquatica and F. solani grew well in a co-culture setup without showing any antagonistic indications. Monoculture versus co-culture setups were used to determine the metal tolerance concentration (MTC). Based on the metal tolerance concentration (MTC) values, cells of C. aquatica were able to tolerate 4, 5, 6, and 7 mM of Cr, Zn, Cu, and Ni, respectively. Moreover, C. aquatica withstood up to 6 mM of Pb. Although F. solani exhibited sensitivity to high concentrations of heavy metals in monoculture, the MTC of F. solani increased considerably in a co-culture setup. The results presented here revealed that F. solani facilitated the dispersion of C. aquatica and heightened bioavailability, whereas C. aquatica reduced the toxicity of heavy metals and promoted the growth of F. solani. Transmission electron microscopy (TEM) displayed different mechanisms for heavy metal removal by C. aquatica. Biosorption was evident for Cr and Pb, while transformation was recorded for Ni and Zn. Also, C. aquatica was able to reduce and accumulate Cu in cells.