Effect of cAMP Receptor Protein Gene on Growth Characteristics and Stress Resistance of Haemophilus parasuis Serovar 5.

Hua Cao,Chang Li,Ling Zhu,Jing Li,Zhonghua Li,Bingzhou Zhang,Yufang Cheng,Wei Zeng,Changsheng Jiang,Qigai He

doi:10.3389/fcimb.2020.00019

Abstract

Haemophilus parasuis (HPS), a member of the family Pasteurellaceae, is a common bacteria in the upper respiratory tract of pigs but under certain circumstances can cause serious systemic disease (Glasser's disease) characterized by severe infection of the upper respiratory tract, fibrinous polyserositis, polyarthritis, and meningitis. cAMP receptor protein (CRP) is among the most important global regulators, playing a vital role in adapting to environmental changes during the process of bacterial infection. In order to investigate the function of the crp gene in the growth characteristics of H. parasuis serovar 5 (HPS5) and its ability to overcome adverse environmental stresses, a crp mutant strain (Δcrp) was constructed and verified. In this study, we found that the crp gene was involved in growth rate, biofilm formation, stress tolerance, serum resistance, and iron utilization. Compared with the wild type, both the growth rate of the crp mutant and its resistance to osmotic pressure decreased significantly. Similar phenomena were also found in biofilm formation and iron utilization. However, the resistance to heat shock and serum complement of the crp mutant were enhanced. This study aimed to reveal the function in growth characteristics and stress resistance of the crp gene in HPS5. Whether it relates to virulence requires additional in-depth research.

Highlights

Haemophilus parasuis is a member of the family Pasteurellaceae, the growth of which is strictly dependent on V factor but not X factor (Biberstein and White, 1969; Jin et al, 2006)
These results indicated that the crp gene was able to increase the tolerance of osmotic stress, but it decreased the tolerance of heat shock and did not affect the tolerance of H. parasuis serovar 5 (HPS5) to oxidative stress
In order to explore the function of the crp gene in H. parasuis, a crp mutant strain of HPS5 was constructed, and the polarity effect assay (Supplementary Table 1 and Figure S1) verified the change in function of the crp strain was caused by crp gene rather than any other upstream or downstream genes

Summary

Introduction

Haemophilus parasuis is a member of the family Pasteurellaceae, the growth of which is strictly dependent on V factor (nicotinamide adenine dinucleotide, NAD) but not X factor (hemin) (Biberstein and White, 1969; Jin et al, 2006). H. parasuis is a common bacteria that existed in the upper respiratory tract of pigs, but under specific circumstances, such as hypoimmunity, stress, poor feeding, and management practices, etc., it can cause serious systemic disease (Glasser’s disease). Glasser’s disease is characterized by severe infection of the upper respiratory tract, fibrinous polyserositis, polyarthritis, and meningitis in pigs, which leads to the huge economic losses in the global pig industry (Liu et al, 2016). H. parasuis could be classified into at least 15 serotypes. Serotypes 1, 5, 10, The Crp Gene in HPS5

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