title: A bacterial filter protects and structures the gut microbiome of an insect.
abstract: Associations with symbionts within the gut lumen of hosts are particularly prone to disruption due to the constant influx of ingested food and non-symbiotic microbes, yet we know little about how partner fidelity is maintained. Here we describe for the first time the existence of a gut morphological filter capable of protecting an animal gut microbiome from disruption. The proventriculus, a valve located between the crop and midgut of insects, functions as a micro-pore filter in the Sonoran Desert turtle ant (Cephalotes rohweri), blocking the entry of bacteria and particles ⩾0.2 μm into the midgut and hindgut while allowing passage of dissolved nutrients. Initial establishment of symbiotic gut bacteria occurs within the first few hours after pupation via oral-rectal trophallaxis, before the proventricular filter develops. Cephalotes ants are remarkable for having maintained a consistent core gut microbiome over evolutionary time and this partner fidelity is likely enabled by the proventricular filtering mechanism. In addition, the structure and function of the cephalotine proventriculus offers a new perspective on organismal resistance to pathogenic microbes, structuring of gut microbial communities, and development and maintenance of host-microbe fidelity both during the animal life cycle and over evolutionary time.
authors.affiliation: Chair of the Natural Sciences, Deep Springs College, Big Pine, CA, USA.
authors.forename: Michele Caroline
authors.initials: MC
authors.lastname: Lanan
authors.affiliation: Graduate Interdisciplinary Program in Entomology and Insect Science, University of Arizona, Tucson, AZ, USA.
authors.forename: Pedro Augusto Pos
authors.initials: PA
authors.lastname: Rodrigues
authors.affiliation: School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ, USA.
authors.forename: Al
authors.initials: A
authors.lastname: Agellon
authors.affiliation: Department of Neuroscience, University of Arizona, Tucson, AZ, USA.
authors.forename: Patricia
authors.initials: P
authors.lastname: Jansma
authors.affiliation: Department of Entomology, University of Arizona, Tucson, AZ, USA.
authors.forename: Diana Esther
authors.initials: DE
authors.lastname: Wheeler
mesh_terms: D000818:Animals; D001000:Ants / Q000166:cytology / Q000382:microbiology*; D001419:Bacteria / Q000235:genetics*; D005075:Biological Evolution; D000069196:Gastrointestinal Microbiome; D011531:Proventriculus / Q000166:cytology / Q000382:microbiology*