@article {2879,
	title = {Biosignatures Associated with Freshwater Microbialites},
	journal = {Life},
	volume = {10},
	year = {2020},
	month = {Jan-05-2020},
	pages = {66},
	abstract = {Freshwater microbialites (i.e., lithifying microbial mats) are quite rare in northern latitudes of the North American continent, with two lakes (Pavilion and Kelly Lakes) of southeastern BC containing a morphological variety of such structures. We investigated Kelly Lake microbialites using carbon isotope systematics, phospholipid fatty acids (PLFAs) and quantitative PCR to obtain biosignatures associated with microbial metabolism. δ13CDIC values (mean δ13CDIC -4.9 {\textpm} 1.1‱, n = 8) were not in isotopic equilibrium with the atmosphere; however, they do indicate 13C-depleted inorganic carbon into Kelly Lake. The values of carbonates on microbialite surfaces (δ13C) fell within the range predicted for equilibrium precipitation from ambient lake water δ13CDIC (-2.2 to -5.3‱). Deep microbialites (26 m) had an enriched δ13Ccarb value of -0.3 {\textpm} 0.5‱, which is a signature of photoautotrophy. The deeper microbialites (>20 m) had higher biomass estimates (via PLFAs), and a greater relative abundance of cyanobacteria (measured by 16S copies via qPCR). The majority of PLFAs constituted monounsaturated and saturated PLFAs, which is consistent with gram-negative bacteria, including cyanobacteria. The central PLFA δ13C values were highly depleted (-9.3 to -15.7‱) relative to δ13C values of bulk organic matter, suggesting a predominance of photoautotrophy. A heterotrophic signature was also detected via the depleted iso- and anteiso-15:0 lipids (-3.2 to -5.2‱). Based on our carbonate isotopic biosignatures, PLFA, and qPCR measurements, photoautotrophy is enriched in the microbialites of Kelly Lake. This photoautotrophy enrichment is consistent with the microbialites of neighboring Pavilion Lake. This indication of photoautotrophy within Kelly Lake at its deepest depths raises new insights into the limits of measurable carbonate isotopic biosignatures under light and nutrient limitations. },
	keywords = {Biosignatures, Kelly Lake, microbialites, Pavilion Lake},
	doi = {10.3390/life10050066},
	url = {https://pubmed.ncbi.nlm.nih.gov/32429118/},
	author = {White, Richard Allen and Soles, Sarah A. and Brady, Allyson L. and Southam, Gordon and Lim, Darlene S.S. and Slater, Greg F.}
}
@article {2820,
	title = {Life and its traces in Antarctica{\textquoteright}s McMurdo Dry Valley paleolakes: a survey of preservation},
	journal = {Micron},
	volume = {131},
	year = {2020},
	month = {Jan-04-2020},
	pages = {102818},
	abstract = {The extremely cold and arid conditions of Antarctica make it uniquely positioned to investigate fundamental questions regarding the persistence of life in extreme environments. Within the McMurdo Dry Valleys and surrounding mountain ranges are multiple ancient relict lakes, paleolakes, with lacustrine deposits spanning from thousands to millions of years in age. Here we present data from light microscopy, scanning electron microscopy, electron dispersive x-ray spectroscopy, and radiocarbon dating to catalog the remarkable range of life preserved within these deposits. This includes intact microbes and nanobacteria-sized cocci, CaCO3 precipitations consistent with biogenic calcium, previously undescribed net-like structures, possible dormant spores, and long-extinct yet exquisitely preserved non-vascular plants. These images provide an important reference for further microbiome investigations of Antarctic paleolake samples. In addition, these findings may provide a visual reference for the use of subsurface groundwater microbial communities as an analog for paleolake subsurface water on planets such as Mars.},
	keywords = {Antarctica, Biosignatures, Microbes, Paleolakes, SEM},
	issn = {09684328},
	doi = {10.1016/j.micron.2019.102818},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0968432819304160},
	author = {Greenfield, Samuel R. and Tighe, Scott W. and Bai, Yu and Goerlitz, David S. and Von Turkovich, Michele and Taatjes, Douglas J. and Dragon, Julie A. and Johnson, Sarah Stewart}
}
