Formation of Streptococcus pneumoniae non-phase-variable colony variants is due to increased mutation frequency present under biofilm growth conditions
Formation of Streptococcus pneumoniae non-phase-variable colony variants is due to increased mutation frequency present under biofilm growth conditions
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DOI：
10.1128/jb.00707-08
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发表时间：
2008-10-01
影响因子：
3.2
通讯作者：
Sauer, Karin
中科院分区：
文献类型：
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作者：
Allegrucci, Magee;Sauer, Karin
在这份报告中，我们表明，肺炎链球菌血清型19的生物膜形成引起的变种（小粘液变体[SMV]和无囊小菌落变体[SCV]）不同的胶囊生产，附着和生物膜形成相比，野生型菌株。所有生物膜衍生的变体在cps 19 F中具有SNP。SCV回复为SMV，但未观察到回复为野生型表型，表明这些变异体与不透明相和半透明相变异体不同。SCV-SMV回复频率取决于生长条件和四环素处理。增加的回复率与抗生素治疗一致，暗示氧化应激是SCV-SMV转换的触发因素。因此，我们评估了过氧化氢（氧化化学品）在变异体的逆转和出现中所起的作用。S.肺炎链球菌TIGR 4-Δ spxB（过氧化氢产生缺陷）显示变体形成的显著减少。类似地，用过氧化氢酶或硫代硫酸钠补充培养基产生由野生型生物膜形成的变体的显著减少。利福平，突变频率的指标，耐药性增加约55倍，生物膜相比，每三个野生型菌株的细胞检查。相比之下，作为生物膜生长的TIGR 4-Delta spxB与非渗透性生长的相同细胞相比未显示利福平抗性的增加。此外，添加2.5和10 mM的过氧化氢的细胞导致突变频率分别增加12倍和160倍，并产生了类似的外观，生物膜相关的表型和分布的生物膜衍生的变体的变体。结果表明，过氧化氢和特定的生物膜的环境条件是负责非相变量的菌落变体的发展。
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-Delta spxB, 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-Delta spxB 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.