Mercury methylation and hydrogen sulfide production among unexpected strains isolated from periphyton of two macrophytes of the Amazon

Abstract

The periphyton of macrophytes had previously been identified as important spots for mercury methylation in the Amazon basin, but the microorganisms that facilitate methylation in such compartment are still to be identified. Here, bacteria were isolated from periphyton associated with Eichhornia crassipes and Polygonum densiflorum in Widdel and Pfennig medium and tested for mercury methylation with a stable isotope tracer technique using 198 HgCl, hydrogen sulfide production and molybdate inhibition. Three Pleomorphomona spp., one unidentified Deltaproteobacteria, two Klebsiella spp., and one Tolumonas sp. were isolated. All except Tolumonas sp. were able to methylate mercury (up to 5% of the 198 HgCl added) and produce up to 4 mM of H 2 S, while the Deltaproteobacteria was also able to demethylate methylmercury. Although these bacteria may not be as strong mercury methylators as sulfate-reducing bacteria, they have the potential to contribute to methylmercury accumulation in the system.

Diurnal variability and biogeochemical reactivity of mercury species in an extreme high-altitude lake ecosystem of the Bolivian Altiplano

“…This may suggests that more reductive conditions in the water column likely associated to organic matter mineralization can promote Hg methylation as previously observed (Bouchet et al 2013;Monperrus et al 2007). The occurrence of anaerobic bacteria communities in the water column located into anoxic microenvironments (e.g., particles) playing a role in Hg methylation, such as SRB, has been shown in this study and also previously established in other aquatic systems (Acha et al 2012). During daytime, water in Lake Uru Uru exhibited oxygen supersaturation, demonstrating intense primary productivity when MMHg levels are decreasing.…”

Distinct Network Interactions in Particle-Associated and Free-Living Bacterial Communities during a Microcystis aeruginosa Bloom in a Plateau Lake

“…Alphaproteobacteria was the most important group in the PAB network and occupied the three module centers: Meganema, Pleomorphomonas and Brevundimonas sp.. For the Meganema genus, M. perideroedes is the sole described species, which was found to be a versatile facultative anaerobe in activated sludge with ability to utilize various organic substrates in aerobic conditions and use nitrate and nitrite as electron acceptors (Kragelund et al, 2005), and McIlroy et al (2015) thought it is a potentially facultative methylotrophy based on the genome of stain Gr1; for Pleomorphomonas , almost all the species of this genus are N-fixing bacteria, i.e., P. diazotrophica, P. diazotrophica , and P. oryzae (Xie and Yokota, 2005; Im et al, 2006; Madhaiyan et al, 2013), and Pleomorphomonas sp. were found can methylate Hg (II) (Achá et al, 2012); Brevundimonas sp. have been found the abilities of algicidal effect on M. aeruginosa , growth promotion on Chlorella ellipsoide , cadmium biosorption, lactofen-hydrolyzing, quinoline-degrading and antimicrobial silver nanoparticles producing (Park et al, 2008; Masoudzadeh et al, 2011; Rajamanickam et al, 2013; Wang C. et al, 2015).…”

Mercury Remediation Technology Development for Lower East Fort Poplar Creek - FY2018 Update

“…However, recent research has highlighted freshwater streams as sites of Hg methylation, with favorable conditions for methylation including increased temperatures, the presence of certain filamentous algae, and the presence or absence of certain organic nutrients (Tsui et al 2010). The methylation of Hg from periphyton-and macrophyte-associated bacteria also has highlighted additional opportunities for Hg methylation within freshwater streams (Acha et al 2012).…”