The Riemerella anatipestifer AS87_01735 Gene Encodes Nicotinamidase PncA, an Important Virulence Factor
The Riemerella anatipestifer AS87_01735 Gene Encodes Nicotinamidase PncA, an Important Virulence Factor
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鸭瘟里默氏菌 AS87_01735 基因编码烟酰胺酶 PncA，一种重要的毒力因子
DOI：
10.1128/aem.01829-16
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发表时间：
2016-10-01
影响因子：
4.4
通讯作者：
Yu, Shengqing
中科院分区：
文献类型：
--
作者：
Wang, Xiaolan;Liu, Beibei;Yu, Shengqing
摘要鸭疫里默氏杆菌是引起鸭败血症和渗出性疾病的主要病原菌。在我们先前的研究中，我们发现AS87_01735基因的缺失显著降低了鸭疫杆菌突变株Yb2(RA625)的细菌毒力。AS87_01735基因编码烟酰胺酶(NcA)，这是烟酰胺转化为烟酸的关键酶，是NAD+挽救途径中的一个重要反应。在本研究中，我们表达了AS87_01735基因，并用酶法鉴定为编码pncA的基因。Western印迹分析表明，鸭疫杆菌pncA定位于细胞质。突变菌株RA625(在本研究中命名为Yb2ΔpncA)在胰酶酱油肉汤培养中表现出与野生型菌株Yb2相似的生长速度，但在对数和稳定期都降低了NAD+的含量。此外，感染Yb2ΔpncA的鸭血液中的细菌负荷要低得多，心、肝和脾没有观察到明显的组织学变化。此外，Yb2ΔpncA免疫鸭对Yb2强毒株的攻击具有有效的保护作用。我们的结果表明，鸭疫杆菌AS87_01735基因编码pncA，pncA是一个重要的毒力因子，Yb2ΔpncA突变体可以作为一种新的活疫苗候选。重要性鸭疫里默氏杆菌在世界范围内被报道为引起家鸭败血症和渗出性疾病的原因。PncA基因编码烟酰胺酶(PncA)，这是催化烟酰胺转化为烟酸的关键酶，是NAD+挽救途径中的一个重要反应。在本研究中，我们鉴定并鉴定了鸭疫杆菌Yb2株的pncA同源基因AS87_01735。鸭疫杆菌PncA是一种细胞质蛋白，与其他生物相比具有相似的PncA活性。PncA突变体Yb2ΔpncA的产生导致NAD+含量下降，这与鸭的入侵能力降低和毒力减弱有关。此外，Yb2ΔpncA免疫鸭对Yb2强毒株的攻击具有有效的保护作用。综上所述，这些结果表明pncA参与了鸭疫杆菌的毒力，Yb2ΔpncA突变体可以作为一种新的活疫苗候选。
ABSTRACT Riemerella anatipestifer is a major bacterial pathogen that causes septicemic and exudative diseases in domestic ducks. In our previous study, we found that deletion of the AS87_01735 gene significantly decreased the bacterial virulence of R. anatipestifer strain Yb2 (mutant RA625). The AS87_01735 gene was predicted to encode a nicotinamidase (PncA), a key enzyme that catalyzes the conversion of nicotinamide to nicotinic acid, which is an important reaction in the NAD+ salvage pathway. In this study, the AS87_01735 gene was expressed and identified as the PncA-encoding gene, using an enzymatic assay. Western blot analysis demonstrated that R. anatipestifer PncA was localized to the cytoplasm. The mutant strain RA625 (named Yb2ΔpncA in this study) showed a similar growth rate but decreased NAD+ quantities in both the exponential and stationary phases in tryptic soy broth culture, compared with the wild-type strain Yb2. In addition, Yb2ΔpncA-infected ducks showed much lower bacterial loads in their blood, and no visible histological changes were observed in the heart, liver, and spleen. Furthermore, Yb2ΔpncA immunization of ducks conferred effective protection against challenge with the virulent wild-type strain Yb2. Our results suggest that the R. anatipestifer AS87_01735 gene encodes PncA, which is an important virulence factor, and that the Yb2ΔpncA mutant can be used as a novel live vaccine candidate. IMPORTANCE Riemerella anatipestifer is reported worldwide as a cause of septicemic and exudative diseases of domestic ducks. The pncA gene encodes a nicotinamidase (PncA), a key enzyme that catalyzes the conversion of nicotinamide to nicotinic acid, which is an important reaction in the NAD+ salvage pathway. In this study, we identified and characterized the pncA-homologous gene AS87_01735 in R. anatipestifer strain Yb2. R. anatipestifer PncA is a cytoplasmic protein that possesses similar PncA activity, compared with other organisms. Generation of the pncA mutant Yb2ΔpncA led to a decrease in the NAD+ content, which was associated with decreased capacity for invasion and attenuated virulence in ducks. Furthermore, Yb2ΔpncA immunization of ducks conferred effective protection against challenge with the virulent wild-type strain Yb2. Altogether, these results suggest that PncA contributes to the virulence of R. anatipestifer and that the Yb2ΔpncA mutant can be used as a novel live vaccine candidate.