The unique Phospholipidome of the enteric pathogen Campylobacter jejuni: Lysophosholipids are required for motility at low oxygen availability

Authors: CAO, XUEFENG - Utrecht University; BROUWERS, JOS - Utrecht University; HEIJMEN VAN DIJK, LINDA - Utrecht University; VAN DE LEST, CHRIS H.A. - Utrecht University; Parker, Craig; Huynh, Steven; VAN PUTTEN, JOS - Utrecht University; KELLY, DAVID - University Of Sheffield; WOSTEN, MARC M - Utrecht University

Submitted to: Journal of Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2020
Publication Date: 7/22/2020
Citation: Cao, X., Brouwers, J., Heijmen Van Dijk, L., Van De Lest, C., Parker, C., Huynh, S., Van Putten, J., Kelly, D.J., Wosten, M. 2020. The unique Phospholipidome of the enteric pathogen Campylobacter jejuni: Lysophosholipids are required for motility at low oxygen availability. Journal of Molecular Biology. 432(19):5244-5258. https://doi.org/10.1016/j.jmb.2020.07.012.
DOI: https://doi.org/10.1016/j.jmb.2020.07.012

Interpretive Summary: The Gram-negative bacterium Campylobacter jejuni is one of the leading causes of bacterial foodborne illness causing approximately 400 million cases of intestinal infection each year. C. jejuni grows best at low O2 and high CO2 levels and an ambient temperature of 42ºC. These conditions are present in the intestinal tract of poultry, which is often colonized by C. jejuni in very high numbers. The cell membranes of C. jejuni are composed primarily of phospholipids and proteins. The activity of the membrane proteins is affected by the structure of the surrounding phospholipids. In response to changes in their environment bacteria need to change not only their protein repertoire, but also their lipid composition in the membrane. Therefore, bacteria need to modify or replace existing phospholipids to adjust their membrane viscosity to match environmental requirements. Most bacterial phospholipids are composed of two fatty acids, a glycerol moiety, a phosphate group and a variable head group. Phospholipids were long neglected because of lack of adequate methods to analyze them and therefore most studies focused on lipid classes and not on phospholipid species. In this study, we identified 203 phospholipid species in the human pathogen C. jejuni. RNA-seq showed that the phospholipid-associated genes producing these species are differentially expressed in the logarithmic versus stationary growth phase. Thus, we followed the changes that took place among all of the phospholipids (the phospholipidome) during aging of the culture under different oxygen and carbon conditions by using high-throughput method for lipid analysis. The phospholipidome appeared to be highly dynamic. The ratio of the main phospholipid head groups PE and PG changed rapidly by age of culture, as well as, the number of cyclopropane bond containing fatty acids. When more cyclopropane fatty acids are present than unsaturated lipids, the bacteria are coccoid instead of spiral shaped. Large amounts of the phospholipids of C. jejuni are lysophospholipids (30-45%), which are almost absent in a phospholipase PldA mutant. The pldA mutant is nonmotile at low oxygen conditions indicating that lysophospholipids are necessary for C. jejuni motility and therefore are crucial to cause campylobacteriosis.

Technical Abstract: Cell membranes are composed primarily of phospholipids and proteins. The activity of the membrane proteins is affected by the structure of the surrounding phospholipids. In response to changes in their environment bacteria need to change not only their protein repertoire, but also their lipid composition in the membrane. Therefore, bacteria need to modify or replace existing phospholipids to adjust their membrane viscosity to match environmental requirements. Most bacterial phospholipids are composed of two fatty acids, a glycerol moiety, a phosphate group and a variable head group. Phospholipids were long neglected because of lack of adequate methods to analyze them and therefore most studies focused on lipid classes and not on phospholipid species. By using high performance liquid chromatography (LC-MS/MS), we identified 203 phospholipid species in the human pathogen Campylobacter jejuni. RNA-seq showed that the phospholipids genes producing these species are differentially expressed in the logarithmic versus stationary growth phase. Thus, we followed the changes that took place in the phospholipidome during aging of the culture under different oxygen and carbon conditions by using high-throughput method for lipid analysis. The phospholipidome appeared to be highly dynamic. The ratio of the main phospholipid head groups PE and PG changed rapidly by age of culture, as well as, the number of cyclopropane bond containing fatty acids. When more cyclopropane fatty acids are present than unsaturated lipids, the bacteria are coccoid instead of spiral shaped. Large amounts of the phospholipids of C. jejuni are lysophospholipids (30-45%), which are almost absent in a phospholipase PldA mutant. The pldA mutant is nonmotile at low oxygen conditions indicating that lysophospholipids are necessary for C. jejuni motility and therefore are crucial to cause campylobacteriosis.