Phenotyping characterization of methylmercury marine bacteria detoxifiers

Abstract

Mercury (Hg) is a toxic heavy metal with an even more toxic form, methylmercury (MeHg). MeHg is a neurotoxic compound that can reach human population through consumption of big fish. Itis mainly formed in the sediments by anaerobic bacteria in aquatic depths. However, bacteria have developed resistance mechanisms against this toxic, by harbouring the mer operon, which gives them the capacity to volatilize this MeHg. Some marine bacteria, like Alteromonas and Marinobacter spp., include the mer operon and therefore have the potential to remove this pollutant from the environment. In this study, the growth characteristics from marine isolates belonging to Alteromonas and Marinobacter were stablished at different MeHg concentrations (0, 1, 2.5 and 5 μM) measuring optical density (OD600). Alteromonas was able to grow at 5 μM, displaying a higher resistance to MeHg than Marino bacter that was only capable of growing at 1 μM of MeHg. Additionally, epifluorescence microscopy for cell counting and inclusion bodies (IBs) quantification was performed. Also scanning transmission electron microscopy (STEM)-Energy Dispersive X-Ray Microscopy (EDX)was used to examine the nature of those IBsat the highest resolution. The results confirmed that Alteromonas produced higher number of IBs inside their cells associated with Polyphosphate (poly-P). In summary, due to its tolerance for growing in MeHg, Alteromonas is a clear candidate to be used in bioremediation of MeHgin marine environments