New sensitive tools to characterize meta-metabolome response to short- and long-term cobalt exposure in dynamic river biofilm communities

Cobalt effects on prokaryotic communities living in growing river biofilms: impact on their colonization kinetics, structure and functions

“…It was in line with a recent study undertaken on mature biofilms where intracellular fraction of bioaccumulated Co increased over time, and represented the majority of bioaccumulated Co (71 ± 14%) 22 . After 28 days of exposure to 1 µM Co, comparable levels of intracellular Co were measure between studies (7.68 ± 1.10 and 8.81 ± 0.45 µmol.g DW -1 22 ) even if the Co bioaccumulation profile was more rapid and significant for mature biofilms. The higher bioaccumulation when exposed to higher Co was concomitant with higher prokaryotic abundances from D21 and a distinct microbial composition of biofilms, probably driven by selection of tolerant organisms.…”

“…Cobalt concentrations within growing biofilms were well correlated with ambient free Co 2+ concentrations, as recently observed in experiments with mature biofilms 21,22 . Similar correlations were also found for metals such as Ni, Cd, Zn and Cu with biofilms, highlighting the potential for metal bioaccumulation in biofilms to be a good proxy for metal bioavailability 28,36–38 .…”

“…However, structural changes were observed in growing biofilms exposed to 0.5 µM and 1 µM Co. While the impact of metals on mature biofilms microbial communities has been widely described 22,[38][39][40][41] , our study highlighted Co effects on early stages of biofilm colonization. Dissimilarities in the composition of the communities were already visible at D7, with this increasing with exposure time.…”

“…Total and intracellularly bioaccumulated Co were measured in freeze-dried biofilms mineralized with a mixture of nitric acid 70% (metalgrade) and hydrogen peroxide (H 2 O 2 ; ultratrace) 30 % (v/v; 2:1) in a UltraWAVE oven (Milestone, Italy). For intracellular analysis, fresh biofilms were firstly rinsed with 10 mM of ethylenediaminetetraacetic acid (EDTA >= 99%, Sigma-Aldrich, Germany) for 10 min and rinsed with filtered (0.45 µM) water from the control stream of pilot rivers 22,28 . Cobalt concentrations in the mineralized biofilms were measured using ICP-MS (Agilent ICP-MS 7500, CA, USA).…”

“…A study demonstrated that Co bioaccumulation was associated with a disruption of chlorophyll a synthesis while EPS production was enhanced 21 . Also, it was demonstrated that prokaryotic and microeukaryotic communities’ compositions and meta-metabolome from mature biofilms translocated in Co contaminated waters were rapidly impacted in comparison with natural biofilms 22 . These studies, led mature biofilms have not dealt with Co impact on biofilm colonization and setup yet.…”