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Formation of Streptococcus pneumoniae non-phase-variable colony variants is due to increased mutation frequency present under biofilm growth conditions.

Abstract：

:In this report, we show that biofilm formation by Streptococcus pneumoniae serotype 19 gives rise to variants (the small mucoid variant [SMV] and the acapsular small-colony variant [SCV]) differing in capsule production, attachment, and biofilm formation compared to wild-type strains. All biofilm-derived variants harbored SNPs in cps19F. SCVs reverted to SMV, but no reversion to the wild-type phenotype was noted, indicating that these variants were distinct from opaque- and transparent-phase variants. The SCV-SMV reversion frequency was dependent on growth conditions and treatment with tetracycline. Increased reversion rates were coincident with antibiotic treatment, implicating oxidative stress as a trigger for the SCV-SMV switch. We, therefore, evaluated the role played by hydrogen peroxide, the oxidizing chemical, in the reversion and emergence of variants. Biofilms of S. pneumoniae TIGR4-DeltaspxB, defective in hydrogen peroxide production, showed a significant reduction in variant formation. Similarly, supplementing the medium with catalase or sodium thiosulfate yielded a significant reduction in variants formed by wild-type biofilms. Resistance to rifampin, an indicator for mutation frequency, was found to increase approximately 55-fold in biofilms compared to planktonic cells for each of the three wild-type strains examined. In contrast, TIGR4-DeltaspxB grown as a biofilm showed no increase in rifampin resistance compared to the same cells grown planktonically. Furthermore, addition of 2.5 and 10 mM hydrogen peroxide to planktonic cells resulted in a 12- and 160-fold increase in mutation frequency, respectively, and gave rise to variants similar in appearance, biofilm-related phenotypes, and distribution of biofilm-derived variants. The results suggest that hydrogen peroxide and environmental conditions specific to biofilms are responsible for the development of non-phase-variable colony variants.

journal_name

J Bacteriol

journal_title

Journal of bacteriology

authors

Allegrucci M,Sauer K

doi

10.1128/JB.00707-08

subject

Has Abstract

pub_date

2008-10-01 00:00:00

pages

6330-9

issue

eissn

0021-9193

issn

1098-5530

pii

JB.00707-08

journal_volume

190

pub_type

杂志文章

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Formation of Streptococcus pneumoniae non-phase-variable colony variants is due to increased mutation frequency present under biofilm growth conditions.