Vasi J, Lindberg M, Guss B
Department of Microbiology, Swedish University of Agricultural Sciences, Uppsala, S-750 07, Sweden.
Plasmid. 2000 Nov;44(3):220-30. doi: 10.1006/plas.2000.1481.
Streptococcus dysgalactiae, a Lancefield group C streptococcus, is commonly isolated from bovine mastitis. We recently identified a putative regulon in two S. dysgalactiae strains, 8215 and Epi9, consisting of two consecutive genes, dmg and dem, coding for a possible regulatory protein and an M-like protein with fibrinogen- and IgG-binding-properties, respectively. During these studies a short sequence homologous to an IS element was found to be inserted in the dmg gene of strain 8215. The present investigation describes the complete sequence of this IS-like element, named ISSdy1, which consists of 1218 bp and contains two ORFs, flanked by imperfect repeats. The nucleotide sequence of the IS-like element shows 82% identity to the previously reported sequence of IS199 from Streptococcus mutans V403. The deduced amino acid sequences of the ORFs also revealed high homology to transposases from IS elements in Enterococcus faecium, Escherichia coli, and Shigella dysenteriae, all belonging to the IS3 family. We studied the distribution of ISSdy1 in 57 S. dysgalactiae isolates using PCR analysis with specific primers derived from the IS element. Ninety-eight percent of the isolates contained the ISSdy1 element. Surprisingly, in the majority of studied strains a copy of the IS-like element was found to be inserted in the dmg gene, a putative virulence regulator.
停乳链球菌，一种兰斯菲尔德C群链球菌，通常从牛乳腺炎中分离得到。我们最近在两株停乳链球菌8215和Epi9中鉴定出一个假定的调控子，它由两个连续的基因dmg和dem组成，分别编码一种可能的调控蛋白和一种具有纤维蛋白原结合及IgG结合特性的M样蛋白。在这些研究过程中，发现与一个插入序列元件同源的短序列插入到了菌株8215的dmg基因中。本研究描述了这个类插入序列元件的完整序列，命名为ISSdy1，它由1218个碱基对组成，包含两个开放阅读框，两侧为不完全重复序列。该类插入序列元件的核苷酸序列与先前报道的变形链球菌V403的IS199序列具有82%的同一性。开放阅读框推导的氨基酸序列也显示与粪肠球菌、大肠杆菌和痢疾志贺菌中插入序列元件的转座酶具有高度同源性，这些转座酶均属于IS3家族。我们使用从该插入序列元件衍生的特异性引物通过PCR分析研究了ISSdy1在57株停乳链球菌分离株中的分布。98%的分离株含有ISSdy1元件。令人惊讶的是，在大多数研究菌株中，发现一个类插入序列元件的拷贝插入到了dmg基因中，dmg基因是一个假定的毒力调节因子。
