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Effects of two-component system NarQ/P deletion on gene expression of Actinobacillus pleuropneumoniae in nitrate-rich anaerobic growth

ABSTRACT: Nitrate metabolism is an adaptation mechanism used by many bacteria for survival under anaerobic environments. As a by-product of inflammation, nitrate is used by the intestinal bacterial pathogens to enable gut infection. However, the responses of bacterial respiratory pathogens to nitrate are less well understood. Actinobacillus pleuropneumoniae is an important bacterial respiratory pathogen of swine. Previous studies have suggested that adaptation of A. pleuropneumoniae to anaerobiosis is important for infection. In this work, A. pleuropneumoniae growth and pathogenesis in response to the nitrate were investigated. Nitrate significantly promoted A. pleuropneumoniae growth under anaerobic condition in vitro and lethality in mice. By using narQ and narP deletion mutants, and single-residue mutation complementary strains of ΔnarQ, the two-component system NarQ/P were confirmed to be critical for nitrate induced growth, with Arg50 in NarQ as an essential functional residue. Transcriptome analysis showed that nitrate up-regulated multiple energy-generating pathways, including nitrate metabolism, mannose and pentose metabolism and glycerolipid metabolism via the regulation of NarQ/P. Furthermore, narQ, narP and its target gene encoding the nitrate reductase Nap contributed to the pathogenicity of A. pleuropneumoniae. The Nap inhibitor tungstate significantly reduced the survival of A. pleuropneumoniae in vivo, suggesting that Nap is a potential drug target. These results give new insights into how the respiratory pathogen A. pleuropneumoniae utilizes alternative electron acceptor nitrate to overcome the hypoxia microenvironment, which can occur in the inflammatory or necrotic infected tissues.

ORGANISM(S): Actinobacillus pleuropneumoniae serovar 1 str. 4074

PROVIDER: GSE207497 | GEO | 2022/07/29

REPOSITORIES: GEO

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Project description:Actinobacillus pleuropneumoniae is an important porcine respiratory pathogen causing great economic losses in the pig industry worldwide. Oxygen deprivation is a stress that A. pleuropneumoniae will encounter during both early infection and the later, persistent stage. To understand modulation of A. pleuropneumoniae gene expression in response to the stress caused by anaerobic conditions, gene expression profiles under anaerobic and aerobic conditions were compared in this study. The microarray results showed that 631 genes (27.7% of the total ORFs) were differentially expressed in anaerobic conditions. Many genes encoding proteins involved in glycolysis, carbon source uptake systems, pyruvate metabolism, fermentation and the electron respiration transport chain were up-regulated. These changes led to an increased amount of pyruvate, lactate, ethanol and acetate in the bacterial cells as confirmed by metabolite detection. Genes encoding proteins involved in cell surface structures, especially biofilm formation, peptidoglycan biosynthesis and lipopolysaccharide biosynthesis were up-regulated as well. Biofilm formation was significantly enhanced under anaerobic conditions. These results indicate that induction of central metabolism is important for basic survival of A. pleuropneumoniae after a shift to an anaerobic environment. Enhanced biofilm formation may contribute to the persistence of this pathogen in the damaged anaerobic host tissue and also in the early colonization stage. These discoveries give new insights into adaptation mechanisms of A. pleuropneumoniae in response to environmental stress. Transcriptional profiles were analyzed using microarray to compare the gene expressions of A. pleuropneumoniae cultured under aerobic and anaerobic condition. The bacteria was cultured under aerobic condition to mid-log phase (3 hours) and then divided into two separate groups, one group was continually cultured under aerobic condition for 1 hour (OD600nm = 0.417 M-BM-1 0.008) and the other group was cultured under anaerobic condition for 1 hour (OD600nm = 0.333 M-BM-1 0.015). Three independent biological replicates were performed. The total RNA were extracted and hybridized with the whole genome microarray of A. pleuropneumoniae. The signal intensities were normalized and transformed into log2 values. The genes with P-value < 0.05 were selected as differentially expressed genes.

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Effects of two-component system NarQ/P deletion on gene expression of Actinobacillus pleuropneumoniae in nitrate-rich anaerobic growth

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