Identification of Gut Microbiota Biomarkers for Radiation Exposure

Introduction: High doses of radiation can cause Acute Radiation Syndrome, with one fatal complication being bacteremia and septicemia due to intestinal bacteria entering the bloodstream after epithelial damage. Over the 130 years since radiation’s discovery, survival has been observed at exposures below 3–4 Gy; patients exposed to over 4–5 Gy with severe gastrointestinal damage have a 0% survival rate, making gastrointestinal health key for survival. This study investigated short-term changes in gut microbiota following radiation exposure to aid in developing diagnostic and therapeutic methods for radiation accidents. Methods: Eight-week-old male C57BL mice were divided into three groups (0, 4, and 8 Gy; n = 4) and exposed to whole-body X-rays. Cecal contents and rectal feces were collected 72 h post-exposure. Gut microbiota was analyzed by sequencing the V3-V4 region of the 16S rRNA gene (2 × 300 bp, MiSeq) and comparing sequences with the EzBioCloud 16S database. Alpha and beta diversity and bacterial composition were analyzed using Qiime2, with regression analysis performed using the R package MaAsLin2. Alpha diversity was calculated with the Shannon Index, and beta diversity with the Weighted Unifrac distance. Statistical analysis was performed using one-way ANOVA. Results: Significant differences in alpha diversity were observed in cecal flora (CF) between the 4 Gy and non-irradiated groups, with irradiated groups showing higher median values, even when no significant differences were found. Beta diversity differed significantly in both CF and rectal flora between the 4 Gy and 8 Gy groups compared with the non-irradiated group. Genera in the families Muribaculaceae and Lachnospiraceae correlated positively with radiation dose, whereas the genus Kineothrix showed a negative correlation. Ruminococcus and Turicibacter increased only at the high exposure levels. These bacterial genera could serve as dose markers. Conclusion: Further research will investigate the reproducibility of these findings and whether restoring disrupted microbiota could aid in treatment.