(109a) Transcriptional Biosensors That Discriminate between Radiation Sources

Detection of nuclear fuel cycle, enrichment, and weapon development activities is critical for supporting warfighter preparation in chemical, biological, radiological, nuclear, and explosives (CBRNE) operations, nuclear compliance, and clandestine activities. Disadvantages of conventional radiation monitoring and detection systems of being easily identifiable, mandatory placement near a radioactive source for detection, and capacity to report radioactivity at a specific moment in time diminish their applications in the field.In the event of source relocation and contamination, the ability to detect trace amounts of ionizing radiation is a paramount concern for CBRNE operations and prevention of clandestine activities.Microbes in the environment experience behavioral and morphological changes in response to environmental stress, including low-dose ionizing radiation. These responses are known to sometimes persist even after the stress is removed. We hypothesized that these responses can be monitored through transcriptional changes and could be harnessed for biosensors capable of discerning radionuclide type have the potential to monitor and report on nuclear fuel cycle, enrichment, and weapon development activities in diverse environmental conditions.

Transcriptomic profiling through mRNA sequencing analysis revealed unique responses of microorganisms after exposure to acute and chronic radionuclides representative of the nuclear fuel cycle. After quantitative PCR verification, genes with high abundance and overexpression were selected as candidates for biosensor development. Key differences in gene expression were seen in Pseudomonas putida, Escherichia coli, and Saccharomyces cerevisiaeafter acute and chronic exposure to plutonium-239, tritium, and iron-55 at a dose rate of 8.7 mGy/d. Substantial differences in differentially expressed genes were noted between acute and chronic exposures datasets indicating the potential presence of a radiation-induced time signature. Unique genes that were overexpressed only by a single radionuclide source were selected for toehold switch biosensor development, where selected transcripts trigger fluorescent protein translation from an otherwise repressed state. Future sensor development will include engineering circuits of switch sensors permitting detection of time dependent signals for individual radionuclide sources. In addition to developing passive and autonomous monitoring or clandestine activities, the results of this work will expand upon the limited knowledge of low dose radiation effects in microorganisms.