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首页> 外文期刊>Infection and immunity >luxS and arcB Control Aerobic Growth of Actinobacillus actinomycetemcomitans under Iron Limitation
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luxS and arcB Control Aerobic Growth of Actinobacillus actinomycetemcomitans under Iron Limitation

机译：铁限制下luxS和arcB控制放线放线放线杆菌的有氧生长

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LuxS is responsible for the production of autoinducer 2 (AI-2), which functions in Vibrio harveyi as a quorum-sensing signal that controls the cell density-dependent expression of the lux operon. In nonluminescent organisms, the physiologic role of AI-2 is not clear. We report that inactivation of luxS in Actinobacillus actinomycetemcomitans JP2 results in reduced growth of the mutant, but not the wild-type organism, under aerobic, iron-limited conditions. Stunted cultures of the luxS mutant A. actinomycetemcomitans JP2-12 grew to high cell density when subcultured under iron-replete conditions. In addition, the mutant strain grew to high cell density under iron limitation after transformation with a plasmid containing a functional copy of luxS. Results of real-time PCR showed that A. actinomycetemcomitans JP2-12 exhibited significantly reduced expression of afuA (eightfold), fecBCDE (10-fold), and ftnAB (>50-fold), which encode a periplasmic ferric transport protein, a putative ferric citrate transporter, and ferritin, respectively. The expressions of putative receptors for transferrin, hemoglobin, and hemophore binding protein were also reduced at more modest levels (two- to threefold). In contrast, expressions of sidD and frpB (encoding putative siderophore receptors) were increased 10- and 3-fold, respectively, in the luxS mutant. To better understand the mechanism of the AI-2 response, the A. actinomycetemcomitans genome was searched for homologs of the V. harveyi signal transduction proteins, LuxP, LuxQ, LuxU, and LuxO. Interestingly, ArcB was found to be most similar to LuxQ sensor/kinase. To determine whether arcB plays a role in the response of A. actinomycetemcomitans to AI-2, an arcB-deficient mutant was constructed. The isogenic arcB mutant grew poorly under anaerobic conditions but grew normally under aerobic iron-replete conditions. However, the arcB mutant failed to grow aerobically under iron limitation, and reverse transcriptase PCR showed that inactivation of arcB resulted in decreased expression of afuA and ftnAB. Thus, isogenic luxS and arcB mutants of A. actinomycetemcomitans exhibit similar phenotypes when cultured aerobically under iron limitation, and both mutants exhibit reduced expression of a common set of genes involved in the transport and storage of iron. These results suggest that LuxS and ArcB may act in concert to control the adaptation of A. actinomycetemcomitans to iron-limiting conditions and its growth under such conditions.
机译：LuxS负责自动诱导子2（AI-2）的产生，该自动诱导子在哈姆氏弧菌（embrio harveyi）中发挥作用，是一种群体感应信号，可控制依赖于细胞密度的lux（em）表达。 >操纵子。在不发光的生物中，AI-2的生理作用尚不清楚。我们报告说，在有氧，铁限制条件下，放线放线杆菌 JP2中的 luxS 失活导致突变体（而非野生型生物）生长减少。 luxS 突变体 A的发育不良。在铁充足的条件下继代培养时，放线放线菌 JP2-12生长到高细胞密度。此外，该突变株用含有功能拷贝的 luxS 的质粒转化后，在铁限制下生长至高细胞密度。实时PCR结果显示 A。放线菌纲 JP2-12显着降低了 afuA （八倍）， fecBCDE （十倍）和 ftnAB （> 50倍），分别编码周质铁转运蛋白，推定的柠檬酸铁转运蛋白和铁蛋白。转铁蛋白，血红蛋白和血红蛋白结合蛋白的推定受体的表达也以较适度的水平降低（2至3倍）。相反，在 luxS 突变体中， sidD 和 frpB （编码假定的铁载体受体）的表达分别增加了10倍和3倍。 。为了更好地理解AI-2响应的机制， A。搜索放线放线菌基因组中 V的同源物。 harveyi 信号转导蛋白LuxP，LuxQ，LuxU和LuxO。有趣的是，发现ArcB与LuxQ传感器/激酶最相似。确定 arcB 是否在 A的响应中起作用。用放线菌对COM-2进行诱变，构建了一个 arcB 缺陷型突变体。同基因的 arcB 突变体在厌氧条件下生长较差，而在需氧充足的铁条件下生长正常。然而， arcB 突变体在缺铁条件下不能有氧生长，逆转录酶PCR显示， arcB 的失活导致 afuA 和 ftnAB 。因此， A的同基因 luxS 和 arcB 突变体。在缺铁条件下有氧培养时放线放线菌表现出相似的表型，并且两个突变体均显示出与铁的运输和储存有关的一组共同基因的表达降低。这些结果表明，LuxS和ArcB可能协同作用以控制 A的适应。放线菌对铁的限制条件及其在这种条件下的生长。

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