S1623
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
Digital Poster 124 Human gut microbiome functional resilience to radiation Michaela Walsh 1,2 , Brendan McClean 2 , Luis Leon- Vintro 1 , Nicholas Brereton 3 1 School of Physics, University College Dublin, Dublin, Ireland. 2 Physics, St. Luke's Radiation Oncology Network, Dublin, Ireland. 3 School of Biology and Environmental Science, University College Dublin, Dublin, Ireland Purpose/Objective: The gut microbiome is involved in functions important for human health and is implicated in cancer therapy effectiveness[1] and side-effects[2][3]. It is also implicated in astronaut health, with mice displaying gut microbiome dysfunction during spaceflight[4] potentially underlying spaceflight pathology. Radiotherapy patients and astronauts are exposed to high levels of radiation, and the effect this has on the gut microbiome is poorly understood. This study aims to develop a tractable system for accurate microbial irradiation, and to characterise the radiation response of specific gut microbiome strains important for human health. Material/Methods: This study investigated the resilience of the gut microbiome to radiation by characterising the radiosensitivity of exemplar gut bacterial species important for bile acid metabolism. A system to expose bacteria to 6 MV radiation was developed. Dosimetry was verified using Gafchromic film with a Farmer chamber as reference. The system was used to irradiate bacterial samples, with growth subsequently characterised. Results: The growth of Lactobacillus acidophilus was resilient to doses of 50 Gy. Growth rate was unaffected, and no statistically significant decreases (t-test, p ≥ 0.05) in population were observed in irradiated vs control samples (Figure 1). Lacticaseibacillus paracasei was also exposed to the same dose. Significant growth compromise was not observed (t-test, p ≥ 0.05) (Figure 2), however the irradiated population was consistently
reduced compared to the control.
Figure 1: L. acidophilus growth curve (top) and bacterial population at different time points (bottom) after 0Gy or 50 Gy irradiation. Error bars denote standard error (n = 8).
Figure 2: L. paracasei growth curve (top) and bacterial population at different time points (bottom) after 0Gy or 50 Gy irradiation. Error bars denote standard error (n = 8). Conclusion: A tractable culture and irradiation system was developed to assess bacterial responses to radiation. The similar growth response between closely related species highlights that assessment of radiosensitivity of different taxa is needed. However, growth is only one component of radiosensitivity, with other functions potentially affected. The system developed here provides a platform to characterise gut microbial radiosensitivity and understand potential functional
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