Role of aspartate ammonia-lyase in Pasteurella multocida
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RESEARCH ARTICLE
Open Access
Role of aspartate ammonia-lyase in Pasteurella multocida Zui Wang1, Li Li1, Peng Liu1,2, Chen Wang1,2, Qin Lu1, Lina Liu1, Xiaozhong Wang2, Qingping Luo1,3* and Huabin Shao1,3*
Abstract Background: Pasteurella multocida is responsible for a highly infectious and contagious disease in birds, leading to heavy economic losses in the chicken industry. However, the pathogenesis of this disease is poorly understood. We recently identified an aspartate ammonia-lyase (aspA) in P. multocida that was significantly upregulated under ironrestricted conditions, the protein of which could effectively protect chicken flocks against P. multocida. However, the functions of this gene remain unclear. In the present study, we constructed aspA mutant strain △aspA::kan and complementary strain C△aspA::kan to investigate the function of aspA in detail. Result: Deletion of the aspA gene in P. multocida resulted in a significant reduction in bacterial growth in LB (LuriaBertani) and MH (Mueller-Hinton) media, which was rescued by supplementation with 20 mM fumarate. The mutant strain △aspA::kan showed significantly growth defects in anaerobic conditions and acid medium, compared with the wild-type strain. Moreover, growth of △aspA::kan was more seriously impaired than that of the wild-type strain under iron-restricted conditions, and this growth recovered after supplementation with iron ions. AspA transcription was negatively regulated by iron conditions, as demonstrated by quantitative reverse transcription-polymerase chain reaction. Although competitive index assay showed the wild-type strain outcompetes the aspA mutant strain and △aspA::kan was significantly more efficient at producing biofilms than the wild-type strain, there was no significant difference in virulence between the mutant and the wild-type strains. Conclusion: These results demonstrate that aspA is required for bacterial growth in complex medium, and under anaerobic, acid, and iron-limited conditions. Keywords: Pasteurella multocida, Aspartate ammonia-lyase, Iron acquisition, Virulence
Background Pasteurella multocida is a capsulated, Gram-negative facultative anaerobic bacterium responsible for fowl cholera in poultry, leading to great economic losses in commercial layer flocks and local chicken breeds [1]. P. multocida is currently classified into five serogroups (A, B, D, E, and F) based on its capsular antigens, and fowl cholera is mainly caused by strains of serovars A, F, and very rarely D [2]. Once a * Correspondence: [email protected]; [email protected] 1 Institute of Animal Husbandry and Veterinary Sciences, Hubei Academy of Agricultural Sciences, Special one, Nanhuyaoyuan, Hongshan District, Wuhan 430064, China Full list of author information is available at the end of the article
chicken flock becomes infected with the bacterium, it may become endemic and difficult to remove, resulting in repeated infectious episodes [3]. However, the molecular basis of P. multocida pathogenesis is still poorly understood. Aspartate ammonia-
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