Microbial Contamination Detection at Very Low Levels by [125] I Radiolabeling

Grant #: NNX09AV32A
Senior Scientist: David Summers

This work develops a new method for the determination of bioburdens (and the detection of microorganisms and life) for planetary protection purposes. It works by detecting the organism’s proteins and labeling them with a radioactive label, [125]I. This provides greater sensitivity while preserving a fast  turn-around time for analysis. This method utilizes the current NASA sampling techniques and thus could be directly compared against existing methods. Radiolabeling techniques are inherently sensitive and [125]I benefits from a 60 day halflife, providing greater activity and signal per unit number of labels. Additional sensitivity can be obtained by use of a Multiphoton Detection (MPD). By taking advantage of selected isotopes that decay by the emission of multiple photons, MPD can screen out many background events and detect radioisotopes, such as [125]I, at below

background levels. This enables detection to lower levels than previously possible, down to the level of single cells. By utilizing a universal biosignature (cell proteins), this method provides broad generality with regard to the range of organisms that can be detected. This method isn’t restricted to any type(s) of organism, or the ability of the organisms to be cultured, etc. In this work we develop a quick and simple method for detecting the proteins from cells.   

This detection involves:

1) Separation of cells/spores.

2) Lysis of cells.

3) Labeling of released proteins & separation from unreacted label.

4) Detection by standard or multiphoton detection.

This more sensitive detection of microbial contamination directly addresses the solicitations call for “modern molecular analytical methods to rapidly detect, classify, and/or enumerate the widest possible spectrum of Earth microbes carried by spacecraft”. The method also has applicability for testing returned samples hardware and for testing sterilization methods. Future work could extend to species such as viruses and prions.