Woo Sung Ho, Park Soo Il
Institute of Fisheries Sciences, Pukyong National University, 474, Ilgwang-Ro, Ilgwang-myeon, Gijang-gun, Busan 619-911, South Korea; Department of Aquatic Life Medicine, Pukyong National University, 45, Yongso-ro, Namgu, Busan 608-737, South Korea.
Department of Aquatic Life Medicine, Pukyong National University, 45, Yongso-ro, Namgu, Busan 608-737, South Korea.
Fish Shellfish Immunol. 2014 Dec;41(2):317-25. doi: 10.1016/j.fsi.2014.09.012. Epub 2014 Sep 18.
In recent years, Streptococcus parauberis infection has been an emerging problem in aquaculture in South Korea because of its more frequent isolation than other streptococcal bacteria including Streptococcus iniae. To develop effective treatment and prophylaxis methods against this emerging disease by S. parauberis, it is necessary to understand the underlying pathogenic mechanisms. To uncover the pathogenicity, the mutant strain of S. parauberis with a deleted phosphoglucomutase (PGM) gene which has been known to be an important virulence factor in bacterial pathogens was generated to investigate the relationship between virulence and gene function using an allelic exchange mutagenesis method. Allelic exchange mutagenesis of the phosphoglucomutase gene resulted in phenotype changes including decreased extracellular capsules, reduced buoyancy, increased hydrophobicity and reduced growth. Moreover, the S. parauberis mutant was more sensitive to innate immune clearance mechanisms including serum, mucus and phagocyte killing and could not induce mortality in olive flounder. These phenotype changes and the attenuated virulence of the pathogen to fish could be due to the reduction in capsule production by mutation of the PGM gene. The results provide evidences that phosphoglucomutase expression contributes to S. parauberis virulence in fish by affecting bacterial survival against the host's humoral and cellular defense mechanisms.
近年来，副乳房链球菌感染在韩国水产养殖中已成为一个新出现的问题，因为与包括海豚链球菌在内的其他链球菌相比，它的分离频率更高。为了开发针对副乳房链球菌这种新出现疾病的有效治疗和预防方法，有必要了解其潜在的致病机制。为了揭示致病性，利用等位基因交换诱变方法构建了副乳房链球菌磷酸葡萄糖变位酶（PGM）基因缺失的突变株，以研究毒力与基因功能之间的关系。磷酸葡萄糖变位酶基因的等位基因交换诱变导致了表型变化，包括细胞外荚膜减少、浮力降低、疏水性增加和生长减少。此外，副乳房链球菌突变株对包括血清、黏液和吞噬细胞杀伤在内的先天免疫清除机制更敏感，并且不能在牙鲆中诱导死亡。这些表型变化和病原体对鱼类毒力的减弱可能是由于PGM基因突变导致荚膜产生减少。结果表明，磷酸葡萄糖变位酶的表达通过影响细菌抵抗宿主体液和细胞防御机制的生存能力，对副乳房链球菌在鱼类中的毒力有贡献。
