Growth phase mediated regulation of the Actinobacillus pleuropneumoniae ApxI and ApxII toxins
Growth phase mediated regulation of the Actinobacillus pleuropneumoniae ApxI and ApxII toxins
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DOI：
10.1016/j.micpath.2003.11.005
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发表时间：
2004-04-01
影响因子：
3.8
通讯作者：
Regassa, LB
中科院分区：
文献类型：
--
作者：
Jarma, E;Regassa, LB
胸膜肺炎放线杆菌是猪胸膜肺炎的病原体，猪胸膜肺炎是猪的一种高度传染性且常常致命的呼吸道疾病。 Apx 毒素是该病原体的主要毒力因子，北美所有高毒力菌株均产生 ApxI 和 ApxII。需要进一步表征这些溶血毒素，以充分了解它们在疾病中的作用，并阐明在感染过程中影响其产生的环境信号和基因。许多细菌根据生长阶段调节基因，在本报告中，我们研究了生长阶段对 ApxI 和 ApxII 基因表达的影响。生产 ApxI 和 ApxII 菌株的分批培养物在补充有 β-NAD 的心脏浸液肉汤中生长，并在整个生长曲线中制备样品。最大基因表达发生在指数晚期或稳定期早期，如 Northern 印迹分析中 apx mRNA 浓度的峰值所示。累积的 Apx 蛋白量和 Apx 溶血活性证实了基因表达的这种增加。这些发现表明一种新的转录调控机制，可以在高细胞密度和/或缓慢生长速率的体外条件下增强 Apx 基因表达。 (C) 2004 Elsevier Ltd. 保留所有权利。
Actinobacillus pleuropneumoniae is the causative agent of porcine pleuropneumonia, a highly contagious and often fatal respiratory tract disease of pigs. The Apx toxins are primary virulence factors of this pathogen, with ApxI and ApxII being produced by all highly virulent strains in North America. Further characterization of these hemolytic toxins is needed to fully understand their role in disease and elucidate the environmental signals and genes that affect their production during infection. Many bacteria regulate genes in response to growth phase, and in this report we examined the effect of growth phase on ApxI and ApxII gene expression. Batch cultures of ApxI- and ApxII-producing strains were grown in heart infusion broth supplemented with beta-NAD, and samples were prepared throughout the growth curve. Maximal gene expression occurred in late exponential or early stationary phase, as indicated by a peak in apx mRNA concentration in Northern blot analysis. The amount of accumulated Apx protein and Apx hemolytic activity confirmed this increase in gene expression. These findings suggest a novel transcriptional regulatory mechanism that enhances Apx gene expression under in vitro conditions of high cell density and/or slow growth rate. (C) 2004 Elsevier Ltd. All rights reserved.