Fluorescence Microscopy as a Tool forIn SituLife Detection

Abstract

The identification of extant and, in some cases, extinct bacterial life is most convincingly and efficiently performed with modern high-resolution microscopy. Epifluorescence microscopy of microbial autofluorescence or in conjunction with fluorescent dyes is among the most useful of these techniques. We explored fluorescent labeling and imaging of bacteria in rock and soil in the context of in situ life detection for planetary exploration. The goals were two-fold: to target non-Earth-centric biosignatures with the greatest possible sensitivity and to develop labeling procedures amenable to robotic implementation with technologies that are currently space qualified. A wide panel of commercially available dyes that target specific biosignature molecules was screened, and those with desirable properties (i.e., minimal binding to minerals, strong autofluorescence contrast, no need for wash steps) were identified. We also explored the potential of semiconductor quantum dots (QDs) as bacterial and space probes. A specific instrument for space implementation is suggested and discussed.

The Role of Terrestrial Analogs in the Exploration of the Habitability of Martian Evaporitic Environments

“…Even in the latter case, however, some information on cell density can still be recovered by fl uid inclusions preserved in evaporite crystals, especially in halite (Adamski et al, 2006 ) , or, in the case of species adapted to long-lasting extreme desiccation, such as the cyanobacterium Chroococcidiopsis , by endospore accumulation (Billi and Potts, 2002 ) . The sudden density changes and their measurements, including the means of detecting extremely rare fi ed densities of different categories of biomolecules (Nadeau et al, 2008 ) , can provide useful information in an astrobiological perspective and in consideration of the type of payload on board the forthcoming new generation of Mars rovers (e.g., NASA's Curiosity of the MSL mission).…”

Overview of analogue science activities at the McGill Arctic Research Station, Axel Heiberg Island, Canadian High Arctic

“…These particles have many desirable properties for in situ instrumentation, such as broad absorption spectra allowing them to be excited by nearly any visible or near UV light source; narrow emission spectra, allowing for multicolour labelling; and resistance to radiation, aging, and freeze-thaw (Bruchez et al, 1998;Nadeau et al, 2008). We have developed QD probes that are specific for Gram positive and Gram negative bacteria, and which can be used directly on unprocessed, living environmental samples for both fluorescence and electron microscopy (Fig.…”

Degradation of microbial fluorescence biosignatures by solar ultraviolet radiation on Mars

“…These include the assessment of pollution (JiJi et al 1999;Ko et al 2003;Alberts & Takács 2004;Cory and McKnight 2005) and identification of potentially pathogenic or toxic microorganisms in environmental water or food preparation (Patra & Mishra 2001;Hua et al 2007;Sohn et al 2009;Ziegmann et al 2010). Of most direct relevance here, fluorescence systems have successfully detected trace biomolecules or microbial life in the Atacama desert (Weinstein et al 2008), Antarctic sandstone (Nadeau et al 2008), and glacial (Rohde & Price 2007) and Antarctic ice (Storrie-Lombardi & Sattler 2009).…”