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Front Cell Infect Microbiol. 2018 Feb 8;8:32. doi: 10.3389/fcimb.2018.00032. eCollection 2018.

Basic Characterization of Natural Transformation in a Highly Transformable Haemophilus parasuis Strain SC1401.

Dai K1,2, He L1,2, Chang YF3, Cao S1,2,4, Zhao Q1,2, Huang X1,2, Wu R1,2, Huang Y2, Yan Q2, Han X2, Ma X2, Wen X1,2, Wen Y1,2.

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Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.
College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China.
Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States.
Sichuan Science-Observation Experimental Station of Veterinary Drugs and Veterinary Diagnostic Technology, Ministry of Agriculture, Chengdu, China.


Haemophilus parasuis causes Glässer's disease and pneumonia, incurring serious economic losses in the porcine industry. In this study, natural competence was investigated in H. parasuis. We found competence genes in H. parasuis homologous to ones in Haemophilus influenzae and a high consensus battery of Sxy-dependent cyclic AMP (cAMP) receptor protein (CRP-S) regulons using bioinformatics. High rates of natural competence were found from the onset of stationary-phase growth condition to mid-stationary phase (OD600 from 0.29 to 1.735); this rapidly dropped off as cells reached mid-stationary phase (OD600 from 1.735 to 1.625). As a whole, bacteria cultured in liquid media were observed to have lower competence levels than those grown on solid media plates. We also revealed that natural transformation in this species is stable after 200 passages and is largely dependent on DNA concentration. Transformation competition experiments showed that heterogeneous DNA cannot outcompete intraspecific natural transformation, suggesting an endogenous uptake sequence or other molecular markers may be important in differentiating heterogeneous DNA. We performed qRT-PCR targeting multiple putative competence genes in an effort to compare bacteria pre-cultured in TSB++ vs. TSA++ and SC1401 vs. SH0165 to determine expression profiles of the homologs of competence-genes in H. influenzae. Taken together, this study is the first to investigate natural transformation in H. parasuis based on a highly naturally transformable strain SC1401.


CRP; Haemophilus parasuis; natural competence; transformation; uptake signal sequence

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