Biofilm-Mediated Heavy Metals Bioremediation in PGPR Pseudomonas

Abstract

It is often reported that biofilm-grown cells exhibit enhanced tolerance toward adverse environmental stress conditions, and thus there has been a growing interest in recent years to use biofilms for biotechnological applications such as the uptake of heavy metal. We present in this study the promising application of Pseudomonas biofilms in heavy metal uptake. The main objective of this study is to investigate if these isolates can withstand metal toxicity, and concomitantly to evaluate the interaction between heavy metals and biofilm formation. Compared to control experiments, all Strains were found to produce a greasy-looking biofilm which varied in thickness from an ‘almost invisible film’ to a paper-thick structure depending on the presence of zinc and lead, they exhibited an important biofilm mass. These findings underline the robustness of biofilms under stress conditions and its potential to maintain a favorable niche in stressful environments with increased heavy metal concentrations. Statistically, the biofilms formation seems to be more correlated to the antibiotics resistance (r=0.73; P<0.05) than the heavy metals resistance (r=0.31; P<0.05). Surprisingly, stationary-phase growing was found to be more resistant than logarithmically growing. There is no direct evidence that links metal resistance in biofilms according to the statistical analysis.