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.
Highlights
The Earth offers many natural habitats that appear very strange and inhospitable, at least to human observers
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
Actinobacteria and Bacteroidetes are present at significant abundance in most samples, though Actinobacteria abundance is much lower in neutral soil samples (S5S, S7S), while these samples have a higher relative abundance of Acidobacteria
Summary
The Earth offers many natural habitats that appear very strange and inhospitable, at least to human observers. Anthropogenic environments, on the other hand, are established over mere years or decades, which allows us to observe how microbes and microbial communities rapidly adapt to persistent changes in their environment. The former Calumet Wetlands abut the southwestern shore of Lake Michigan in the central US, encompassing parts of southern Chicago, IL and western Gary, IN [7]. Surviving parts of the wetlands include the Calumet River, Calumet Lake, Wolf Lake and Lake George, though very little of the area can be described as marsh. As steel mills and other heavy industry expanded operations in the area, slag from steel production and other solid debris was used to fill in the marshes, simultaneously providing more land for development and disposing of industrial wastes “safely” by the standards of Diversity 2019, 11, 103; doi:10.3390/d11070103 www.mdpi.com/journal/diversity
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