Carrolo Margarida, Pinto Francisco Rodrigues, Melo-Cristino José, Ramirez Mário
Instituto de Microbiologia, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal; Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal.
Centro de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal.
PLoS One. 2014 Mar 19;9(3):e92138. doi: 10.1371/journal.pone.0092138. eCollection 2014.
In Streptococcus pneumoniae the competence-stimulating peptide (CSP), encoded by the comC gene, controls competence development and influences biofilm growth. We explored the influence of pherotype, defined by the two major comC allelic variants (comC1 and comC2), on biofilm development and recombination efficiency. Among isolates recovered from human infections those presenting comC1 show a higher capacity to form in vitro biofilms. The influence of pherotype on biofilm growth was confirmed by experiments with isogenic strains differing in their comC alleles. Biofilm architecture evaluated by confocal laser scanning microscopy showed that strains carrying comC1 form biofilms that are denser and thicker than those carrying the comC2 allele. Isogenic strains carrying the comC1 allele yielded more transformants than those carrying the comC2 allele in both planktonic and biofilm growth. Transformation assays with comC knockout strains show that ComD1 needs lower doses of the signaling peptide to reach the same biological outcomes. In contrast to mixed planktonic growth, within mixed biofilms inter-pherotype genetic exchange is less frequent than that occurring between bacteria of the same pherotype. Since biofilms are a major bacterial lifestyle, these observations may explain the genetic differentiation between populations with different pherotypes reported previously. Considering that biofilms have been associated with colonization our results suggest that strains carrying the comC1 allele may be more transmissible and more efficient at persisting in carriage. Both effects may help explain the higher prevalence of the comC1 allele in the pneumococcal population.
在肺炎链球菌中，由comC基因编码的感受态刺激肽（CSP）控制感受态发育并影响生物膜生长。我们探究了由两个主要的comC等位基因变体（comC1和comC2）定义的菌型对生物膜发育和重组效率的影响。在从人类感染中分离出的菌株中，呈现comC1的菌株在体外形成生物膜的能力更强。通过使用comC等位基因不同的同基因菌株进行实验，证实了菌型对生物膜生长的影响。通过共聚焦激光扫描显微镜评估生物膜结构表明，携带comC1的菌株形成的生物膜比携带comC2等位基因的菌株更致密、更厚。在浮游生长和生物膜生长中，携带comC1等位基因的同基因菌株产生的转化子都比携带comC2等位基因的菌株多。对comC基因敲除菌株进行的转化试验表明，ComD1达到相同生物学结果所需的信号肽剂量更低。与混合浮游生长不同，在混合生物膜中，不同菌型之间的基因交换比同一菌型细菌之间的基因交换频率更低。由于生物膜是细菌的一种主要生存方式，这些观察结果可能解释了先前报道的不同菌型群体之间的遗传分化。考虑到生物膜与定植有关，我们的结果表明，携带comC1等位基因的菌株可能更具传播性，并且在持续携带方面更有效。这两种效应可能有助于解释comC1等位基因在肺炎球菌群体中更高的流行率。
