Morphology heterogeneity within a Campylobacter jejuni helical population

Authors: FRIRDICH, EMILISA - University Of British Columbia; BIBOY, JACOB - Newcastle University; Huynh, Steven; Parker, Craig; VOLLMER, WALDEMAR - Newcastle University; GAYNOR, ERIN - University Of British Columbia

Submitted to: Molecular Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2017
Publication Date: 3/18/2017
Citation: Frirdich, E., Biboy, J., Huynh, S., Parker, C., Vollmer, W., Gaynor, E. 2017. Morphology heterogeneity within a Campylobacter jejuni helical population. Molecular Microbiology. 104(6):948-971. https://doi.org/10.1111/mmi.13672.
DOI: https://doi.org/10.1111/mmi.13672

Interpretive Summary: The helical shape of Campylobacter jejuni is an important factor in colonization and host interactions with straight mutants having altered biological properties. Passage on calcofluor white (CFW) led to the selection of C. jejuni 81-176 isolates with altered colony fluorescence and changes in morphology resulting in either a straight morphology arising from frameshift mutations and single nucleotide polymorphisms in peptidoglycan hydrolase genes pgp1 or pgp2 or a reduction in curvature due a frameshift mutation in cjj81176_1105 a putative peptidoglycan endopeptidase. Shape defects were restored by complementation. Whole genome sequencing of CFW passaged strains showed that no changes that could be directly attributed to CFW exposure. The cjj81176_1279 (recR; recombinational DNA repair) and cjj81176_1449 (unknown function) genes were highly variable in all 81-176 strains sequenced. A frameshift mutation was identified in the pgp1 gene of our laboratory isolate of the straight genome sequenced variant of 11168 (11168-GS). The PG muropeptide profile of 11168-GS was identical to that of a pgp1 mutant in the original minimally passaged 11168 strain (11168-O). However, introduction of pgp1 into 11168-GS did not restore helical morphology. The recR gene was also highly variable in 11168 strains. Cell to cell heterogeneity in microbial populations is a common phenomenon proposed as a mechanism of ensuring bacterial survival in sub-optimal conditions. Therefore, in certain environments, changes in C. jejuni morphology due to genetic heterogeneity may promote C. jejuni survival and the recR gene appears to be involved in this process.

Technical Abstract: Campylobacter jejuni helical shape is an important factor in colonization and host interactions with straight mutants having altered biological properties. Passage on calcofluor white (CFW) led to the selection of C. jejuni 81-176 isolates with changes in morphology resulting in either a straight morphology arising from frameshift mutations and single nucleotide polymorphisms in peptidoglycan hydrolase genes pgp1 or pgp2 or a reduction in curvature due a frameshift mutation in cjj81176_1105 a putative peptidoglycan endopeptidase. Shape defects were restored by complementation. Whole genome sequencing of CFW passaged strains showed no changes that could be directly attributed to CFW exposure. The cjj81176_1279 (recR; recombinational DNA repair) and cjj81176_1449 (unknown function) genes were highly variable in all 81-176 strains sequenced. A frameshift mutation was identified in the pgp1 gene of our laboratory isolate of the straight genome sequenced variant of 11168 (11168-GS). The PG muropeptide profile of 11168-GS was identical to that of a pgp1 mutant in the original minimally passaged 11168 strain (11168-O). However, introduction of pgp1 into 11168-GS did not restore helical morphology. The recR gene was also highly variable in 11168 strains. Cell to cell heterogeneity in microbial populations is a common phenomenon proposed as a mechanism of ensuring bacterial survival in sub-optimal conditions. Therefore, in certain environments, changes in C. jejuni morphology due to genetic heterogeneity may promote C. jejuni survival.