Ricomini Filho Antonio Pedro, Khan Rabia, Åmdal Heidi Aarø, Petersen Fernanda C
Department of Physiological Science, Piracicaba Dental School, University of Campinas, Piracicaba, Brazil.
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Oslo, Norway.
Front Microbiol. 2019 Sep 13;10:2140. doi: 10.3389/fmicb.2019.02140. eCollection 2019.
, a bacterium with high cariogenic potential, coordinates competence for natural transformation and bacteriocin production via the XIP and CSP pheromones. CSP is effective in inducing bacteriocin responses but not competence in chemically defined media (CDM). This is in contrast to XIP, which is a strong inducer of competence in CDM but can also stimulate bacteriocin genes as a late response. Interconnections between the pathways activated by the two pheromones have been characterized in certain detail in UA159, but it is mostly unknown whether such findings are representative for the species. In this study, we used bioassays based on luciferase reporters for the bacteriocin gene and the alternative sigma factor to investigate various isolates for production and response to CSP and XIP pheromones in CDM. Similar to UA159, endogenous CSP was undetectable in the culture supernatants of all tested strains. During optimization of the bioassay using the reporter, we discovered that the activity of exogenous CSP used as a standard was reduced over time during growth. Using a FRET-CSP reporter peptide, we found that UA159 was able to degrade CSP, and that such activity was not significantly different in isogenic mutants with deletion of the protease gene or the competence genes , , and . CSP cleavage was also detected in all the wild type strains, indicating that this is a conserved feature in . For the XIP pheromone, endogenous production was observed in the supernatants of all 34 tested strains at peak concentrations in culture supernatants that varied between 200 and 26000 nM. Transformation in the presence of exogenous XIP was detected in all but one of the isolates. The efficiency of transformation varied, however, among the different strains, and for those with the highest transformation rates, endogenous XIP peak concentrations in the supernatants were above 2000 nM XIP. We conclude that XIP production and inducing effect on transformation, as well as the ability to degrade CSP, are conserved functions among different isolates. Understanding the functionality and conservation of pheromone systems in may lead to novel strategies to prevent or treat unbalances in oral microbiomes that may favor diseases.
一种具有高致龋潜力的细菌，通过XIP和CSP信息素协调自然转化能力和细菌素的产生。CSP在化学限定培养基（CDM）中可有效诱导细菌素反应，但不能诱导自然转化能力。这与XIP形成对比，XIP是CDM中自然转化能力的强诱导剂，但也能作为晚期反应刺激细菌素基因。在UA159中，已对由两种信息素激活的途径之间的相互联系进行了一定程度的详细表征，但这些发现是否代表该物种大多仍不清楚。在本研究中，我们使用基于荧光素酶报告基因的生物测定法来检测细菌素基因和替代sigma因子，以研究各种分离株在CDM中对CSP和XIP信息素的产生和反应。与UA159类似，在所有测试菌株的培养上清液中均未检测到内源性CSP。在使用报告基因优化生物测定法的过程中，我们发现用作标准的外源性CSP的活性在生长过程中随时间降低。使用FRET-CSP报告肽，我们发现UA159能够降解CSP，并且在缺失蛋白酶基因或自然转化能力基因、、和的同基因突变体中，这种活性没有显著差异。在所有野生型菌株中也检测到了CSP裂解，表明这是该菌的一个保守特征。对于XIP信息素，在所有34个测试菌株的培养上清液中均观察到内源性产生，其峰值浓度在200至26000 nM之间变化。除一个分离株外，在所有分离株中均检测到在外源性XIP存在下的转化。然而，不同菌株之间的转化效率有所不同，对于那些转化率最高的菌株，上清液中的内源性XIP峰值浓度高于2000 nM XIP。我们得出结论，XIP的产生及其对转化的诱导作用，以及降解CSP的能力，是不同分离株中的保守功能。了解该菌中信息素系统的功能和保守性可能会带来预防或治疗可能有利于疾病发生的口腔微生物群失衡的新策略。
