Chaotic signatures in host-microbe interactions

Abstract

AbstractHost-microbe interactions constitute dynamical systems that can be represented by mathematical formulations that determine their dynamic nature. Dynamical interactions can be categorized as deterministic, stochastic, or chaotic. Knowing the type of dynamical interaction is essential for understanding the system under study. Very little experimental work has been done to determine the dynamical characteristics of host-microbe interactions and its study poses significant challenges. The most straightforward experimental outcome involves an observation of time to death upon infection. However, in measuring this outcome, the internal parameters and dynamics of each host-microbe interaction are hidden from the experimentalist. To investigate whether a time-to-death (time to event) dataset provides adequate information for searching for chaotic signatures, we first determined our ability to detect chaos in simulated data sets of time-to-event measurements and successfully distinguished the time-to-event distribution of a chaotic process from a comparable stochastic one. To do so, we introduced aninversion measureto test for a chaotic signature in time-to-event distributions. Next, we searched for chaos in time-to-death ofCaenorhabditis elegansandDrosophila melanogasterinfected withPseudomonas aeruginosaorPseudomonas entomophila, respectively. We found suggestions of chaotic signatures in both systems, but caution that our results are still preliminary and highlight the need for more fine-grained and larger data sets in determining dynamical characteristics. If validated, the occurrence of chaos in host-microbe interactions would have important implications for the occurrence and outcome of infectious diseases, the reproducibility of experiments in the field of microbial pathogenesis and the prediction of future microbial threats.ImportanceIs microbial pathogenesis a predictable scientific field? At a time when we are dealing with Coronavirus Disease 2019 (COVID-19) there is intense interest in knowing about the epidemic potential of other microbial threats and new emerging infectious diseases. To know whether microbial pathogenesis will ever be a predictable scientific field requires knowing whether a host-microbe interaction follows deterministic, stochastic, or chaotic dynamics. If randomness and chaos are absent from virulence, there is the hope for prediction in the future regarding the outcome of microbe-host interactions. Chaotic systems are inherently unpredictable although it is possible to generate short-term probabilistic models, as is done in applications of stochastic processes and machine learning to weather forecasting. Information on the dynamics of a system is also essential for understanding the reproducibility of experiments, a topic of great concern in biological sciences. Our study finds preliminary evidence for chaotic dynamics in infectious diseases.