HR: 1330h
AN: B52B-1036    [PDF]
TI: Development and Test of a Probe to Remotely Sense Microbial Life
AU: * Bramall, N
EM: bramall@socrates.berkeley.edu
AF: U.C. Berkeley Department of Physics, 366 LeConte Hall, Berkeley, CA 94720 United States
AU: Bay, R
AF: U.C. Berkeley Department of Physics, 366 LeConte Hall, Berkeley, CA 94720 United States
AU: Price, B
AF: U.C. Berkeley Department of Physics, 366 LeConte Hall, Berkeley, CA 94720 United States
AB: Fluorescence spectroscopy is a powerful and highly sensitive tool useful for remotely searching for sub-surface microbial life. Ubiquitous biomolecules in microorganisms (e.g. tryptophan and NADH) have unique autofluorescence spectra that allow them to be optically detected at low levels even in the presence of a fluorescence background from minerals. Based on this technique, we have developed and tested a first-generation Biospectral Logger (BSL); an instrument suitable for logging boreholes and aquatic environments which uses a 370 nm excitation source and a bank of seven notch-filtered phototubes to record the spectrum of microbial NADH fluorescence. The first generation BSL was constructed and tested in Lake Tahoe, where it recorded chlorophyll fluorescence that peaked at a depth of about 57 m and then decreased with depth. NADH fluorescence was found to peak and fall off with chlorophyll for shallow depths, but then began increasing again at deeper depths, which agrees with the results of independently performed cell counts. In order to optimize the discrimination between microbial life and its environment, we used a laboratory fluorimeter to map out the emission spectra of a diverse collection of microbes and minerals as a function of excitation wavelength, which we varied between 224 nm and 460 nm. Based on these data, we have planned future developments of the BSL technology that make it more selective and able to be used in more extreme environments such as deep mine boreholes, permafrost, deep-ocean settings, and ultimately Martian permafrost, where its greatly-increased sensitivity will be sufficient to detect microbial concentrations down to ~1 cell/cm3 in media with relatively low background
DE: 0400 Biogeosciences
DE: 4803 Bacteria
DE: 4840 Microbiology
DE: 4847 Optics
DE: 4894 Instruments and techniques
SC: Biogeosciences [B]
MN: 2003 Fall Meeting