RT Journal Article SR Electronic T1 Ecological Dynamics Imposes Fundamental Challenges in Microbial Source Tracking JF bioRxiv FD Cold Spring Harbor Laboratory SP 2022.05.21.492809 DO 10.1101/2022.05.21.492809 A1 Xu-Wen Wang A1 Lu Wu A1 Lei Dai A1 Xiaole Yin A1 Tong Zhang A1 Scott T. Weiss A1 Yang-Yu Liu YR 2022 UL http://biorxiv.org/content/early/2022/05/21/2022.05.21.492809.abstract AB Quantifying the contributions of possible environmental sources (“sources”) to a specific microbial community (“sink”) is a classical problem in microbiology known as microbial source tracking (MST). Solving the MST problem will not only help us understand how microbial communities were formed, but also have far-reaching applications in pollution control, public health, and forensics. Numerous computational methods, referred to as MST solvers hereafter, have been developed in the past and applied to various real datasets to demonstrate their utility across different contexts. Yet, those MST solvers do not consider microbial interactions and priority effects in microbial communities. Here, we revisit the performance of several representative MST solvers. We show compelling evidence that solving the MST problem using existing MST solvers is impractical when ecological dynamics plays a role in community assembly. In particular, we clearly demonstrate that the presence of either microbial interactions or priority effects will render the MST problem mathematically unsolvable for any MST solver. We further analyze data from fecal microbiota transplantation studies, finding that the state-of-the-art MST solvers fail to identify donors for most of the recipients. Finally, we perform community coalescence experiments to demonstrate that the state-of-the-art MST solvers fail to identify the sources for most of the sinks. Our findings suggest that ecological dynamics imposes fundamental challenges in solving the MST problem using computational approaches.Competing Interest StatementThe authors have declared no competing interest.