Aggregatibacter actinomycetemcomitans is a facultative anaerobic Gram‐negative bacterium associated with periodontal diseases, especially aggressive periodontitis. The virulence factors of this pathogen, including adhesins, exotoxins, and endotoxin, have been extensively studied. However, little is known about their gene expression mode in the host. Herein, we investigated whether culture conditions reflecting in vivo environments, including serum and saliva, alter expression levels of virulence genes in the strain HK1651, a JP2 clone. Under aerobic conditions, addition of calf serum (CS) into a general medium induced high expression of two outer membrane proteins (omp100 and omp64). The high expression of omp100 and omp64 was also induced by an iron‐limited medium. RNA‐seq analysis showed that the gene expressions of several factors involved in iron acquisition were increased in the CS‐containing medium. When HK1651 was grown on agar plates, genes encoding many virulence factors, including the Omps, cytolethal distending toxin, and leukotoxin, were differentially expressed. Then, we investigated their expression in five other A. actinomycetemcomitans strains grown in general and CS‐containing media. The expression pattern of virulence factors varied among strains. Compared with the other five strains, HK1561 showed high expression of omp29 regardless of the CS addition, while the gene expression of leukotoxin in HK1651 was higher only in the medium without CS. HK1651 showed reduced biofilm in both CS‐ and saliva‐containing media. Coaggregation with Fusobacterium nucleatum was remarkably enhanced using HK1651 grown in the CS‐containing medium. Our results indicate that the expression of virulence factors is altered by adaptation to different conditions during infection.

中文翻译：

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不同环境条件下毒力因子在伴放线聚合杆菌中的表达

Aggregatibacter actinomycetemcomitans是一种兼性厌氧革兰氏阴性菌，与牙周病，尤其是侵袭性牙周炎有关。这种病原体的毒力因子，包括粘附素、外毒素和内毒素，已被广泛研究。然而，对它们在宿主中的基因表达模式知之甚少。在此，我们研究了反映体内环境（包括血清和唾液）的培养条件是否会改变 JP2 克隆 HK1651 毒力基因的表达水平。在有氧条件下，将小牛血清 (CS) 添加到一般培养基中会诱导两种外膜蛋白（omp100和omp64）的高表达。omp100和omp64的高表达也由铁限制介质诱导。RNA-seq 分析表明，在含有 CS 的培养基中，参与铁获取的几个因素的基因表达增加。当 HK1651 在琼脂平板上生长时，编码许多毒力因子的基因，包括 Omps、细胞致死膨胀毒素和白细胞毒素，差异表达。然后，我们研究了它们在其他五种在普通和含 CS 培养基中生长的伴放线放线菌菌株中的表达。毒力因子的表达模式因菌株而异。与其它五种菌株相比，显示出HK1561高表达omp29无论是否添加 CS，HK1651 中白细胞毒素的基因表达仅在不含 CS 的培养基中较高。HK1651 在含 CS 和含唾液的培养基中显示生物膜减少。使用在含 CS 培养基中生长的HK1651显着增强了与具核梭杆菌的共聚集。我们的结果表明，毒力因子的表达会因感染期间对不同条件的适应而改变。