In:
Journal of Bacteriology, American Society for Microbiology, Vol. 201, No. 21 ( 2019-11)
Abstract:
Streptococcus pneumoniae rapidly kills Staphylococcus aureus by producing membrane-permeable hydrogen peroxide (H 2 O 2 ). The mechanism by which S. pneumoniae -produced H 2 O 2 mediates S. aureus killing was investigated. An in vitro model that mimicked S. pneumoniae - S. aureus contact during colonization of the nasopharynx demonstrated that S. aureus killing required outcompeting densities of S. pneumoniae . Compared to the wild-type strain, isogenic S. pneumoniae Δ lctO and S. pneumoniae Δ spxB , both deficient in production of H 2 O 2 , required increased density to kill S. aureus . While residual H 2 O 2 activity produced by single mutants was sufficient to eradicate S. aureus , an S. pneumoniae Δ spxB Δ lctO double mutant was unable to kill S. aureus . A collection of 20 diverse methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) strains showed linear sensitivity ( R 2 = 0.95) for S. pneumoniae killing, but the same strains had different susceptibilities when challenged with pure H 2 O 2 (5 mM). There was no association between the S. aureus clonal complex and sensitivity to either S. pneumoniae or H 2 O 2 . To kill S. aureus , S. pneumoniae produced ∼180 μM H 2 O 2 within 4 h of incubation, while the killing-defective S. pneumoniae Δ spxB and S. pneumoniae Δ spxB Δ lctO mutants produced undetectable levels. Remarkably, a sublethal dose (1 mM) of pure H 2 O 2 incubated with S. pneumoniae Δ spxB eradicated diverse S. aureus strains, suggesting that S. pneumoniae bacteria may facilitate conversion of H 2 O 2 to a hydroxyl radical ( · OH). Accordingly, S. aureus killing was completely blocked by incubation with scavengers of · OH radicals, dimethyl sulfoxide (Me 2 SO), thiourea, or sodium salicylate. The · OH was detected in S. pneumoniae cells by spin trapping and electron paramagnetic resonance. Therefore, S. pneumoniae produces H 2 O 2 , which is rapidly converted to a more potent oxidant, hydroxyl radicals, to rapidly intoxicate S. aureus strains. IMPORTANCE Streptococcus pneumoniae strains produce hydrogen peroxide (H 2 O 2 ) to kill bacteria in the upper airways, including pathogenic Staphylococcus aureus strains. The targets of S. pneumoniae -produced H 2 O 2 have not been discovered, in part because of a lack of knowledge about the underlying molecular mechanism. We demonstrated that an increased density of S. pneumoniae kills S. aureus by means of H 2 O 2 produced by two enzymes, SpxB and LctO. We discovered that SpxB/LctO-produced H 2 O 2 is converted into a hydroxyl radical ( · OH) that rapidly intoxicates and kills S. aureus . We successfully inhibited the toxicity of · OH with three different scavengers and detected · OH in the supernatant. The target(s) of the hydroxyl radicals represents a new alternative for the development of antimicrobials against S. aureus infections.
Type of Medium:
Online Resource
ISSN:
0021-9193
,
1098-5530
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2019
detail.hit.zdb_id:
1481988-0
SSG:
12
