Woo Patrick C Y, Teng Jade L L, Ma Shirley S L, Lau Susanna K P, Yuen Kwok-Yung
Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
New Microbiol. 2007 Apr;30(2):139-47.
We report the complete nucleotide sequence and characterization of a cryptic plasmid, pHLHK26, recovered from a strain of Laribacter hongkongensis isolated from a patient with community acquired gastroenteritis. pHLHK26 consists of 8700 bp, with G + C content 51.3%. The copy number (mean +/- SD) is 0.57 +/- 0.07 and it is stable after four passages (about 240 generations) in the absence of selection. There is a predicted origin of replication that consists of a DnaA box and five 22-bp direct repeats. pHLHK26 has four ORFs with two genes encoded in the sense direction and the other two in antisense direction. These four ORFs encode a putative plasmid partitioning protein of the ParA family, a putative protein that contains putative ADP-ribose 1"-phosphatase activity belonging to the Appr-1-p processing enzyme family, a putative recombinase (TniR) of the resolvase/invertase family, and a putative replication protein, respectively. We speculate that pHLHK26 is a theta, possibly Class A, replicative plasmid, as it contains an origin of replication with AT-rich region, a number of iterons and a DnaA box and a gene that encodes a replicative protein most homologous to those of other theta replicative plasmids and it shares eight of the nine positions of the consensus sequence TTAT(C/A)CA(C/A)A (TTTTCCACA in pHLHK26) in the DnaA boxes observed in other classical examples of Class A plasmids of this group.
我们报告了从一名社区获得性肠胃炎患者分离出的香港拉氏杆菌菌株中回收的隐秘质粒pHLHK26的完整核苷酸序列及特征。pHLHK26由8700个碱基对组成，G + C含量为51.3%。拷贝数（平均值±标准差）为0.57±0.07，在无选择条件下传代四次（约240代）后仍保持稳定。存在一个预测的复制起点，由一个DnaA框和五个22碱基对的直接重复序列组成。pHLHK26有四个开放阅读框，其中两个基因按正义方向编码，另外两个按反义方向编码。这四个开放阅读框分别编码一个假定的ParA家族质粒分配蛋白、一个假定的含有属于Appr-1-p加工酶家族的假定ADP-核糖1"-磷酸酶活性的蛋白、一个假定的解离酶/转化酶家族的重组酶（TniR）和一个假定的复制蛋白。我们推测pHLHK26是一个θ型复制质粒，可能属于A类，因为它包含一个富含AT区域的复制起点、多个迭代子和一个DnaA框，以及一个编码与其他θ型复制质粒最同源的复制蛋白的基因，并且它在该组A类质粒的其他经典例子中观察到的DnaA框中共享共有序列TTAT(C/A)CA(C/A)A（pHLHK26中为TTTTCCACA）九个位置中的八个。
