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Proceedings Paper

Multi-fractal property of perchlorate reductase gene sequences and DNA photonics application to UV fluorescence detection on Mars-like surfaces
Author(s): George Tremberger; Eric Cheung; N. Gadura; Todd Holden; Raji Subramaniam; Regina Sullivan; Pat Schneider; Alex Flamholz; David H. Lieberman; Tak D. Cheung
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Paper Abstract

The discovery of perchlorate on Mars raises the possibility of the existence of perchlorate reduction microbes on that planet. The perchlorate reductase gene sequence fractal dimensions of two Dechloromonas species were compared with five other sequences in the microbial dimethyl sulfoxide (DMSO) reductase family. A nucleotide sequence can be expressed as a numerical sequence where each nucleotide is assigned its proton number. The resulting numerical sequence can be investigated for its fractal dimension in terms of evolution and chemical properties for comparative studies. Analysis of the fractal dimensions for the DMSO reductase family supports phylogenetic analyses that show that the perchlorate reductase gene sequences are members of the same family. A sub-family with roughly the same nucleotide length emerges having the property that the gene fractal dimension is negatively correlated with the Shannon di-nucleotide entropy (R2 ~ 0.95, N =5). The gene sequence fractal dimension is found to be positively correlated with the neighbor joining distances reported in a published protein phylogeny tree (R2~ 0.92, N = 5). The multi-fractal property associated with these genes shows that perchlorate reductase has lower dimensionality as compared to the relatively higher dimensionality DNA-break repair genes Rec-A and Rad-A observed in the Dechloromonas aromatica and Deinococcus radiodurans genomes. The studied perchlorate gene sequences show a higher Shannon di-nucleotide entropy (~3.97 bits) relative to Dechloromonas aromatica DNA repair sequences (~3.87 bits Rec-A, ~3.92 bits Rad-A), suggesting that there are fewer constraints on nucleotide variety in the perchorlate sequences . These observations thus allow for the existence of perchlorate reducing microbes on Mars now or in the past. Timeresolved UV fluorescence study near the emission bands of nucleotide sequences could be used for bio-detection on Mars-like surfaces and the results may further constrain the proposed conjectures.

Paper Details

Date Published: 3 September 2009
PDF: 13 pages
Proc. SPIE 7441, Instruments and Methods for Astrobiology and Planetary Missions XII, 74410G (3 September 2009); doi: 10.1117/12.825819
Show Author Affiliations
George Tremberger, Queensborough Community College, CUNY (United States)
Eric Cheung, Queensborough Community College, CUNY (United States)
N. Gadura, Queensborough Community College, CUNY (United States)
Todd Holden, Queensborough Community College, CUNY (United States)
Raji Subramaniam, Queensborough Community College, CUNY (United States)
Regina Sullivan, Queensborough Community College, CUNY (United States)
Pat Schneider, Queensborough Community College, CUNY (United States)
Alex Flamholz, Queensborough Community College, CUNY (United States)
David H. Lieberman, Queensborough Community College, CUNY (United States)
Tak D. Cheung, Queensborough Community College, CUNY (United States)


Published in SPIE Proceedings Vol. 7441:
Instruments and Methods for Astrobiology and Planetary Missions XII
Kurt D. Retherford; Richard B. Hoover; Gilbert V. Levin; Alexei Yu. Rozanov, Editor(s)

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