Microbial Community in Hyperalkaline Steel Slag-Fill Emulates Serpentinizing Springs

Abstract

To date, a majority of studies of microbial life in hyperalkaline settings focus on environments that are also highly saline (haloalkaline). Haloalkaline conditions offer microbes abundant workarounds to maintain pH homeostasis, as salt ions can be exchanged for protons by dedicated antiporter proteins. Yet hyperalkaline freshwater systems also occur both naturally and anthropogenically, such as the slag fill aquifers around former Lake Calumet (Chicago, IL, USA). In this study, 16S rRNA gene sequences and metagenomic sequence libraries were collected to assess the taxonomic composition and functional potential of microbes present in these slag-polluted waterways. Relative 16S rRNA gene abundances in Calumet sediment and water samples describe community compositions not significantly divergent from those in nearby circumneutral conditions. Major differences in composition are mainly driven by Proteobacteria, primarily one sequence cluster closely related to Hydrogenophaga, which comprises up to 85% of 16S rRNA gene abundance in hyperalkaline surface sediments. Sequence identity indicates this novel species belongs to the recently established genus Serpentinomonas, a bacterial lineage associated with natural freshwater hyperalkaline serpentinizing springs.

Contrasted microbial community colonization of a bauxite residue deposit marked by a complex geochemical context

“…The bacterial community composition of the recently deposited bauxite residues (Bo1 and Bo2) was similar to that observed in soda lakes, alkaline residues, and other unamended BRDAs (Bondici et al, 2013;Chakraborty et al, 2021;Kalwasińska et al, 2017;Ohlsson et al, 2019), characterized by the dominance of Actinobacteria (Actinobacteria, Nitriliruptoria, Acidimicrobiia) and Proteobacteria (especially Gammaproteobacteria) and relatively high proportions (1 to 16 %) of Bacteroidetes (Cytophagia, Rhodothermi, Flavobacteriia), Firmicutes (Bacilli, Clostridia), and other alkalophilic classes (Opitutae, Deinococci) (Fig. 5-6).…”

Theoretical Predictions Versus Environmental Observations on Serpentinization Fluids: Lessons From the Samail Ophiolite in Oman

“…However, it is of note that pH values higher than those predicted by Ctl–Brc–Di equilibrium are rare, implying that upper limits on the pH of serpentinization‐generated fluids are constrained by diopside dissolution. Extremely high‐pH values (12.5 to >13) were observed in a few continental sites such as in Maqarin, Jordan (Alexander et al., 1992; Khoury et al., 1992; Pedersen et al., 2004) and Lake Calumet, Chicago (Ohlsson et al., 2019; Roadcap et al., 2005). These localities, however, are not hosted by ultramafic lithologies and the extremely alkaline pH values are likely results of reactions akin to that of groundwater–concrete interactions (Gaucher & Blanc, 2006).…”

Metabolic challenges and key players in serpentinite-hosted microbial ecosystems

“…Based on varying Na + concentrations, it is likely that these mechanisms differ between terrestrial and marine serpentinization-influenced site microorganisms. In low salt environments, alkaliphiles might excrete Na + via V 1 V 0 -ATPases to maintain a sodium motive force ( Suzuki et al, 2014 ; Ohlsson et al, 2019 ). Other alkaliphiles such as Serpentinimonas spp.…”