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Deletion of the zinc transporter lipoprotein adcaii causes hyperencapsulation of streptococcus pneumoniae associated with distinct alleles of the type i restriction-modification system

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posted on 19.05.2020, 13:28 by C Durmort, G Ercoli, E Ramos-Sevillano, S Chimalapati, RD Haigh, M De Ste Croix, K Gould, J Hinds, Y Guerardel, T Vernet, M Oggioni, JS Brown
The capsule is the dominant Streptococcus pneumoniae virulence factor, yet how variation in capsule thickness is regulated is poorly understood. Here, we describe an unexpected relationship between mutation of adcAII, which encodes a zinc uptake lipoprotein, and capsule thickness. Partial deletion of adcAII in three of five capsular serotypes frequently resulted in a mucoid phenotype that biochemical analysis and electron microscopy of the D39 adcAII mutants confirmed was caused by markedly increased capsule thickness. Compared to D39, the hyperencapsulated ΔadcAII mutant strain was more resistant to complement-mediated neutrophil killing and was hypervirulent in mouse models of invasive infection. Transcriptome analysis of D39 and the ΔadcAII mutant identified major differences in transcription of the Sp_0505-0508 locus, which encodes an SpnD39III (ST5556II) type I restriction-modification system and allelic variation of which correlates with capsule thickness. A PCR assay demonstrated close linkage of the SpnD39IIIC and F alleles with the hy-perencapsulated ΔadcAII strains. However, transformation of ΔadcAII with fixed SpnD39III alleles associated with normal capsule thickness did not revert the hyper-encapsulated phenotype. Half of hyperencapsulated ΔadcAII strains contained the same single nucleotide polymorphism in the capsule locus gene cps2E, which is required for the initiation of capsule synthesis. These results provide further evidence for the importance of the SpnD39III (ST5556II) type I restriction-modification system for modulating capsule thickness and identified an unexpected linkage between capsule thickness and mutation of ΔadcAII. Further investigation will be needed to characterize how mutation of adcAII affects SpnD39III (ST5556II) allele dominance and results in the hyperencapsulated phenotype. IMPORTANCE The Streptococcus pneumoniae capsule affects multiple interactions with the host including contributing to colonization and immune evasion. During in-fection, the capsule thickness varies, but the mechanisms regulating this are poorly understood. We have identified an unsuspected relationship between mutation of adcAII, a gene that encodes a zinc uptake lipoprotein, and capsule thickness. Mutation of adcAII resulted in a striking hyperencapsulated phenotype, increased resistance to complement-mediated neutrophil killing, and increased S. pneumoniae virulence in mouse models of infection. Transcriptome and PCR analysis linked the hyperencapsulated phenotype of the ΔadcAII strain to specific alleles of the SpnD39III (ST5556II) type I restriction-modification system, a system which has previously been shown to affect capsule thickness. Our data provide further evidence for the importance of the SpnD39III (ST5556II) type I restriction-modification system for modulating capsule thickness and identify an unexpected link between capsule thickness and ΔadcAII, further investigation of which could further characterize mechanisms of capsule regulation.

Funding

This work was undertaken at UCLH/UCL, which received a proportion of funding from the Department of Health’s NIHR Biomedical Research Centre’s funding scheme. G.E. was supported by MRC (grant MR/R001871/1), M.O. was supported by grants from the MRC and BBSRC (MR/M003078/1 and BB/N002903/1), and S.C. was supported by the Wellcome Trust (grant WT076442).

History

Citation

Deletion of the Zinc Transporter Lipoprotein AdcAII Causes Hyperencapsulation of Streptococcus pneumoniae Associated with Distinct Alleles of the Type I Restriction-Modification System Claire Durmort, Giuseppe Ercoli, Elisa Ramos-Sevillano, Suneeta Chimalapati, Richard D. Haigh, Megan De Ste Croix, Katherine Gould, Jason Hinds, Yann Guerardel, Thierry Vernet, Marco Oggioni, Jeremy S. Brown mBio Mar 2020, 11 (2) e00445-20; DOI: 10.1128/mBio.00445-20

Published in

mBio

Volume

11

Issue

2

Pagination

e00445-20

Publisher

American Society for Microbiology

issn

2161-2129

eissn

2150-7511

Acceptance date

03/03/2020

Copyright date

2020

Available date

31/03/2020

Publisher version

https://mbio.asm.org/content/11/2/e00445-20.full

Language

eng