Population dynamics and universal statistics of tumor-inhabiting bacteria

Bacteria inhabit different areas of the human body and perform essential functions. Increasing evidence of bacterial effects on cancer progression has brought interest to tumor-inhabiting bacteria. However, it is not understood how bacteria affect the tumor, nor how the tumor environment affects bacterial dynamics. Recent experiments, done with barcoded bacterial colonies, show that clone sizes of bacteria inhabiting tumors in mice exhibit universal statistical patterns. The patterns are robust across experiments and collection times, and unique to bacteria grown in the tumor environment rather than in liquid culture. In this work, we develop a mechanistic understanding of the microecological dynamics of tumor-inhabiting bacteria. We present a theory that incorporates a consumer-resource model, a bottlenecking effect, and environmental stochasticity. Our results explain the population dynamics and statistics in experimental data.