The effect of bacterial sepsis on animal behavior and physiology is complex due to direct and indirect actions. The most common form of bacterial sepsis in humans is from gram-negative bacterial strains. The endotoxin (lipopolysaccharide, LPS) and/or associated peptidoglycans from the bacteria are the key agents to induce an immune response, which then produces a cascade of immunological consequences. However, there are direct actions of LPS and associated peptidoglycans on cells which are commonly overlooked. This study showed behavioral and neural changes in larval Drosophila fed commercially obtained LPS from Serratia marcescens. Locomotor behavior was not altered, but feeding behavior increased and responses to sensory tactile stimuli were decreased. In driving a sensory-central nervous system (CNS)-motor neural circuit in in-situ preparations, direct application of commercially obtained LPS initially increased evoked activity and then decreased and even stopped evoked responses in a dose-dependent manner. With acute LPS and associated peptidoglycans exposure (10 min), the depressed neural responses recovered within a few minutes after removal of LPS. Commercially obtained LPS induces a transitory hyperpolarization of the body wall muscles within seconds of exposure and alters activity within the CNS circuit. Thus, LPS and/or associated peptidoglycans have direct effects on body wall muscle without a secondary immune response.

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Published in Insects, v. 10, issue 4, 115, p. 1-12.

© 2019 by the authors. Licensee MDPI, Basel, Switzerland.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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Sustaining Excellence-2014 Howard Hughes Medical Institute (Grant #52008116) awarded to the Univ. of KY (VM Cassone, PI). The authors confirm that the funder had no influence over the study design, content of the article, or selection of this journal; Dept. of Biology, Univ. of KY student laboratory funds Bio199 and Bio446 bought the reagents for this study.

Related Content

The following are available online at https://www.mdpi.com/2075-4450/10/4/115/s1, Video S1: mouth hook movements 3rd instar larva. (A supplementary file as a video is provided illustrating mouth hook movements This is also on a YouTube link (https://youtu.be/0VJx6bYpruc)), Table S1: Raw data from the behavioral touch assay, File S1: behaviors defined-INSECT 2019.pptx (An ethogram with behavioral positions observed when applying light touch to the side of the crawling larvae, a power point file of the various positions observed in this study of larvae places on a 1% agar apple juice plate.)

Cooper, R. (13 December 2018). LPS- Fly sensory-CNS-motor data. Retrieved from osf.io/qvp5n.

insects-10-00115-s001.zip (10960 kB)
Supplementary Material