Dataset Information

GNPS - The Campylobacter jejuni cell membrane protects against the bactericidal activity of human breastmilk

ABSTRACT: Campylobacter jejuni is a common foodborne pathogen worldwide that is associated with high rates of morbidity and mortality among infants in low-to-middle income countries (LMICs). Human milk provides infants with an important source of nutrients and also contains antimicrobial components for protection against infection. However, recent studies, including our own, have found significantly higher levels of Campylobacter in diarrheal stool samples collected from breastfed infants from LMICs compared to non-breastfed infants. We hypothesized that C. jejuni may have unique strategies to resist the antimicrobial properties of human milk. In this study, RNAseq comparisons indicated that exposure of C. jejuni strains 81-176 and 11168 to human milk results in increased expression of ribosomal proteins, iron receptors and transporters, and proteins for amino acid utilization. However, unidentified proteinaceous components of human milk prevent bacterial growth. After evolving both C. jejuni isolates in increasing concentrations of human milk, followed by genomic sequence comparisons, we identified mutations in genes encoding the acyl carrier protein, AcpP, and major outer membrane porin, PorA, in addition to strain specific changes. Introduction of the observed PorA and AcpP amino acid changes back into the parental backgrounds followed by transmission electron microscopy indicated that changes in both proteins lead to distinctly altered cell membrane architectures. However, only the C. jejuni AcpP changes significantly improved growth in human milk presumably through the formation of a continuous layer of outer membrane vesicles. Analyses of the phospholipid and lipooligosaccharide lipid A composition demonstrated that these vesicles likely form due to an imbalance in acyl chain distribution. In the case of strain 11168, this added layer of vesicles protected both evolved and acpP mutated strains from bacteriophage infection and polymyxin killing. Taken together, this study provides insights into how C. jejuni strains may evolve to resist the bactericidal activity of human milk and flourish in the hostile environment of the gastrointestinal tract.

INSTRUMENT(S): ACQUITY UPLC I-Class, Synapt XS

ORGANISM(S): Campylobacter Jejuni (ncbitaxon:197)

SUBMITTER: Christine Szymanski Kelly M. Hines