Microbial and chemical mechanisms of rapid fear signaling

Many species, including humans, use odors to communicate. These odors are typically complex, and describing them is challenging. Furthermore, we do not know much about how they are produced. However, in some species, such as hyenas and some primates, individuals may share similar skin bacteria that produce distinctive chemical compounds as part of their metabolism; these compounds have become co-opted for communication and are how the animals infer species, sex, and social group membership. We aim to understand the mechanisms by which human odors are produced. We focus on emotional odors, especially fear, for two main reasons. First, we know that humans do produce a distinct 'fear odor,' even though we do not know the precise chemical compounds involved nor whether the skin bacteria are responsible for them. Second, a signal of fear requires a very rapid response—in a matter of seconds or minutes—a change that is much faster than any microbially mediated signal studied to date, in any species. Indeed, we do not know whether bacterially produced odors are even possible on this time scale; addressing this possibility is bold and innovative but could lead to a discovery of enormous significance. Our interdisciplinary team has expertise in the psychology of odor communication, dynamic changes in skin bacteria, and analysis of airborne (volatile) chemical compounds. We will study the odor of fear by showing people scenes that arouse emotional responses (including fear) at the same time as measuring changes in bacterial metabolic activity and the release of chemical compounds from the skin. We thus aim to provide the first description and identification of rapid changes in bacterial activity and odor chemistry as people experience fear. Next, we will attempt to confirm the odor production pathway by analyzing the chemicals produced by our candidate bacteria in the lab, as they are cultured on an artificial blend of human skin secretions. Finally, we will test how people respond to the identified chemical compounds. We will compare people's emotional responses when they are exposed to the isolated compounds with how they respond to the complete (natural) odor of scared people; if the responses are comparable, it will suggest that we have correctly identified the compounds responsible for the smell of fear.

 

Project Partner:

ROBERTS S. Craig (United Kingdom) - University of Stirling - Stirling - United Kingdom

KALAN Lindsay (CANADA) - McMaster University, Faculty of Health Sciences - Hamilton - CANADA

WILLIAMS Jonathan (GERMANY) - Max Planck Institute for Chemistry - Mainz - GERMANY