Spotorno O Angel E, Córdova Luis, Solari I Aldo
Programas de Genética Humana, ICBM, Facultad de Medicina, Universidad de Chile, Independencia 1027, Clasificador No. 7, Casilla 70005, Santiago 7, Chile.
Infect Genet Evol. 2008 Dec;8(6):898-900. doi: 10.1016/j.meegid.2008.08.006. Epub 2008 Aug 26.
To identify and characterize chilean samples of Trypanosoma cruzi and their association with hosts, the first 516 bp of the mitochondrial cytochrome b gene were sequenced from eight biological samples, and phylogenetically compared with other known 20 American sequences. The molecular characterization of these 28 sequences in a maximum likelihood phylogram (-lnL = 1255.12, tree length = 180, consistency index = 0.79) allowed the robust identification (bootstrap % > 99) of three previously known discrete typing units (DTU): DTU IIb, IIa, and I. An apparently undescribed new sequence found in four new chilean samples was detected and designated as DTU Ib; they were separated by 24.7 differences, but robustly related (bootstrap % = 97 in 500 replicates) to those of DTU I by sharing 12 substitutions, among which four were nonsynonymous ones. Such new DTU Ib was also robust (bootstrap % = 100), and characterized by 10 unambiguous substitutions, with a single nonsynonymous G to T change at site 409. The fact that two of such new sequences were found in parasites from a chilean endemic caviomorph rodent, Octodon degus, and that they were closely related to the ancient DTU I suggested old origins and a long association to caviomorph hosts.
为了鉴定和表征克氏锥虫的智利样本及其与宿主的关联，从八个生物样本中对线粒体细胞色素b基因的前516个碱基对进行了测序，并与其他20个已知的美洲序列进行了系统发育比较。在最大似然系统发育树（-lnL = 1255.12，树长 = 180，一致性指数 = 0.79）中对这28个序列进行分子表征，从而能够可靠地鉴定（自展支持率> 99）出三个先前已知的离散分型单元（DTU）：DTU IIb、IIa和I。在四个新的智利样本中发现了一个明显未描述的新序列，并将其指定为DTU Ib；它们之间有24.7个差异，但通过共享12个替换与DTU I的序列紧密相关（在500次重复中自展支持率 = 97），其中四个是非同义替换。这种新的DTU Ib也很可靠（自展支持率 = 100），其特征是有10个明确的替换，在409位点有一个从G到T的单非同义变化。在智利特有的豚鼠型啮齿动物八齿鼠的寄生虫中发现了两个这样的新序列，并且它们与古老的DTU I密切相关，这一事实表明其起源古老且与豚鼠型宿主有长期关联。
