APLICATION OF A SYNTHETIC WHOLE-CELL BIOSENSOR TO EVALUATE THE MERCURY DETOXIFICATION CAPACITY OF BIOFILM-FORMING ENVIRONMENTAL ISOLATES.

MARTELLI E; PARRA L; TESSORE A; OTTADO J; GOTTIG N; CHECA SK

Chapadmalal

Congreso; XVIII Congreso de la Sociedad Argentina de Microbiología General; 2023

Sociedad Argentina de Microbiología General

Water contamination by mercury (Hg), one of the ten chemicals of major worldwide concern, is directly linked to human activities such as mining, industrialization and improper deposition of electric and electronic waste. Prolonged exposure to this intoxicant, particularly to its bioavailable fraction, results in severe illness and teratogenic effects. So, water monitoring and remediation is important to preserve health and protect the biota. Previously, we generated GOLS-HG, a synthetic whole-cell biosensor that coupled Hg detection to emission of green fluorescence, and design a single test to efficiently quantify specifically bioavailable Hg in water or just perceive the signal with the naked eyes using a blue light. Also, we isolated from groundwater and characterized a biofilm-forming Pseudomonas sagittaria strain named MOB-181 strain, that efficiently removes manganese present in these water samples. In this work, we evaluated the ability of MOB-181 to remove Hg(II) ions, using the GOLS-HG biosensor. We found that biofilms of this environmental isolate almost completely remove the toxic metal from the medium after one day of incubation at room temperature in static cultures. The colonies of MOB-181 also exhibited at least 6-fold more tolerance to HgCl2 than other biofilm-forming Pseudomonas strains used as control. To understand the mechanism involved in Hg removal, we explored the genome of this strain looking for genes encoding putative Hg resistance determinants. One of the identified locus codes for a set of transporters, its linked periplasmic chaperon and cytoplasmic reductase, and two regulatory determinants, while the other locus lacks some of these factors. An in silico analysis of these genes products revealed high levels of sequence and structural similarity to factors that effectively undergo Hg detoxification in other bacteria. Our results, not only validate the use of the GOLS-HG biosensor as a cost-effective, easy to apply and powerful tool to evaluate Hg contamination, but also establish the bases for the application of the Hg-resistant MOB-181 strain in biofilters from treatment plants to remediate water contaminated with one of the most harmful metals.