Astrobiology Science Conference 2017 (LPI Contrib. No. 1965)
3341.pdf
CHARACTERIZATION OF DARK MATTER BACTERIA FROM THE CALUMET WETLANDS, AN
EXTREME ALKALINE SITE AND ANALOGUE FOR SERPENTINIZING SYSTEMS. J. T. Osvatic1, J. I.
Ohlsson2, W.D. Swingley3 1Biological Sciences, Northern Illinois University, DeKalb, IL, USA, [email protected],
2
Biological Sciences, Northern Illinois University, DeKalb, IL, USA, [email protected] 3Biological Sciences,
Northern Illinois University, DeKalb, IL, USA, [email protected]
Introduction: Serpentinizing sites are a strong
candidate to be associated with the origin of life on
early-Earth as well as a potential environment for the
orgins of extraterrestrial life [1]. These sites are of
great interest as they sustain a variety of microbes,
despite being on the extreme limits of life on Earth.
Serpentinization relies on the presence of certain olivine rocks. However, anthropogenic analogues to serpenetinizing sites have been produced through industrial steel and lime production.
The Calumet Wetlands, located in southern Chicago, Illinois, USA, is a historical steel waste dumping
area that has produced one of the highest pH microbial
habitats in the world and an analogue to naturally occurring serpentinizing systems. During the rapid industrial expansion and production surrounding Chicago in
the early 1900’s, industrial byproducts created the
challenge of how to process the wastes from these industries. Slag from Chicago’s steel industry, containing high concentrations of heavy metals, was used as
inexpensive fill material to create buildable land out of
the surrounding marsh areas, without consideration to
the environmental effects of the waste. Decades of
weathering have led to a very highly alkaline pH (up to
>13.2), non-saline environment, as weathering of the
slag releases large amounts of Ca(OH)2 into the
groundwater. The exposure of hyperalkaline groundwater to the atmosphere results in massive precipitation of insoluble calcium carbonate in the waterways
[2]. These features, high pH and calcium carbonate
production, are also characteristic of serpentinizing
systems.
Previous 16S rRNA gene surveys of these sites revealed the microbial community was low in microbial
diversity and a notable portion of the community, particularly at the most alkaline sites, contained divergent
sequences possibly representing a novel class. The
alkalinity of this site makes cultivation of these novel
bacteria difficult and current ex situ culturing attempts
have seen limited success. As an alternative to the cultivation of these divergent taxa, metagenomic sampling
and assembly was used to examine the genomes of
these novel bacteria without cultivation.
Results: Three samples from a single sediment
core were sequenced and used in this project. In order
to assemble accurate genomes from the metagenomic
sample sequences, de novo metagenomic sequence
assemblies (SPAdes [3]) ware binned using tetramer
frequency and coverage values to separate contigs in
Anvi’o [4]. To analyze the genome products and understand how the bacteria are coping with the stress of
the Calumet environment, KEGG [5] and RAST [6]
were used for annotation.
A total of nine putative genomes have been extracted from the metagenome. Of those, two are potentially representative of a novel class of Firmicutes indicated in 16S rRNA gene surveys allowing for further
research into new alkaline survival methods and proteins.
Outlook: This project has revealed the existence of
a new class of Firmicutes that could be exclusively
associated with non-saline high-pH systems. These
orgamisms’ exclusivity to alkaline systems could be
confirmed by investigations into other high-pH systems. Understaning the microbial diversity of extremely alkaline environments, particulariy Calumet, could
provide knowledge on the origination of life and its
possibility in extraterrestrial environments.
References:
[1] Russell M. J. et al (2010) Geobiology, 8, 355371. [2] Roadcap G. S. et al (2006) Ground Water,
44(4), 511-517. [3] Bankevich A. et al (2012) Journal
of Computer Biology, 19(5). [4] Eren A. M. et al
(2015) PeerJ 3. [5] Moriya Y. et al (2007) Nucleic
Acid Research, 35, W182-W185. [6] Aziz R. K. et al
(2008) BMC Genomics, 9:75.