ASTID

High Throughput Screening, Concentration, and Characterization of Biological Particles Entrained in Martian Water-Ice Matrices (2)

PI: James Lambert

Periodic changes in tilt angle of the polar axis of Mars (obliquity) occur approximately every 124,000 years and cause significant climatic change. Temperatures in the polar regions may increase from the current maximum of -67 degrees C to temperatures potentially above 0 degrees C during periods of high obliquity. Water is known to exist as thin films surrounding particulates entrained in ice at temperatures as low as -20 degrees C. Hence, putative microbial communities trapped in the dust laden Martian polar ice may have opportunities to perform DNA repair and growth during periods of high obliquity, potentially allowing them to survive millions of years. The polar regions may represent one of the few habitable zones accessible for robotic exploration since water trapped in groundwater may be deep and/or so heavily laden with regolith that drilling operations at lower latitudes would be impractical. We propose to develop a fluid-based particle analyzer based on a flow cytometer architecture that uses deep UV fluorescence to analyze, isolate, and concentrate particles with intrinsic fluorescence signature known to be associated with microbial life. Such an instrument could be integrated with current cryobot probe development efforts to provide a reagentless triage method comprised of high throughput screening, concentration, and extraction of microbes and bioremnants from Martian polar melt-ice matrices. Once particles with biogenic intrinsic signatures are isolated using this method, we propose to incubate the sample with spectrally tagged antibodies and cytometrically process the sample again. Here the instrument will be used
to identify biomarkers present on the surface of the isolates. We will use
fluorescent quantum dots with unique emission wavelengths as tags. The advantage of using quantum dots is that a single wavelength of UV light can be used to cause all of them to fluoresce in a variety of narrowband colors, thereby reducing the complexity of the instrument. We will explore the use of quantum beads consisting of two or more quantum dots mixed in fixed ratios and embedded in nanospheres. The Qbeads will be evaluated for their potential to serve as spectral barcodes for a great number of possible binding agents including antibodies, peptides, aptamers, lectins, chelators, and other ligands which when used with the cytometer can effectively be used to implement a liquid biochip. We will also validate these techniques using Martian water-ice analogs developed using JSC Mars- 1 soil simulant and Greenland dusty and silty ice. In the third year, a miniaturized prototype will be developed and tested using a commercially available 280nm UV light emitting diode source. The advantage of this two-phased approach (triage followed by immunoassay) is that reagents would only be required in step two, after putative biota has been concentrated. Additionally, the triaged concentrate could be processed by other instruments such as LC/MS or GS/MS for analysis.