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Siderophilic Cyanobacteria: Implications for Early Earth.Of all extant environs, iron-depositing hot springs (IDHS) may exhibit the greatest similarity to late Precambrian shallow warm oceans in regards to temperature, O2 gradients and dissolved iron and H2S concentrations. Despite the insights into the ecology, evolutionary biology, paleogeobiochemistry, and astrobiology examination of IDHS could potentially provide, very few studies dedicated to the physiology and diversity of cyanobacteria (CB) inhabiting IDHS have been conducted. Results. Here we describe the phylogeny, physiology, ultrastructure and biogeochemical activity of several recent CB isolates from two different greater Yellowstone area IDHS, LaDuke and Chocolate Pots. Phylogenetic analysis of 16S rRNA genes indicated that 6 of 12 new isolates examined couldn't be placed within established CB genera. Some of the isolates exhibited pronounced requirements for elevated iron concentrations, with maximum growth rates observed when 0.4-1 mM Fe(3+) was present in the media. In light of "typical" CB iron requirements, our results indicate that elevated iron likely represents a salient factor selecting for "siderophilicM CB species in IDHS. A universal feature of our new isolates is their ability to produce thick EPS layers in which iron accumulates resulting in the generation of well preserved signatures. In parallel, siderophilic CB show enhanced ability to etch the analogs of iron-rich lunar regolith minerals and impact glasses. Despite that iron deposition by CB is not well understood mechanistically, we recently obtained evidence that the PS I:PS II ratio is higher in one of our isolates than for other CB. Although still preliminary, this finding is in direct support of the Y. Cohen hypothesis that PSI can directly oxidize Fe(2+). Conclusion. Our results may have implications for factors driving CB evolutionary relationships and biogeochemical processes on early Earth and probably Mars.
Document ID
20060013506
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Brown, I. I.
(NASA Johnson Space Center Houston, TX, United States)
Mummey, D.
(Montana Univ. Missoula, MT, United States)
Sarkisova, S.
(NASA Johnson Space Center Houston, TX, United States)
Shen, G.
(Pennsylvania State Univ. University Park, PA, United States)
Bryant, D. A.
(Pennsylvania State Univ. University Park, PA, United States)
Lindsay, J.
(Lunar and Planetary Inst. Houston, TX, United States)
Garrison, D.
(NASA Johnson Space Center Houston, TX, United States)
McKay, D. S.
(NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2006
Subject Category
Exobiology
Meeting Information
Meeting: 12th International Symposium on Phototrophic Prokaryotes
Location: Pau
Country: France
Start Date: August 27, 2006
End Date: September 1, 2006
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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