Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), Onogawa 16-1, Tsukuba, Ibaraki 305-8569, Japan.
Syst Appl Microbiol. 2011 Feb;34(1):76-80. doi: 10.1016/j.syapm.2010.07.003. Epub 2010 Sep 15.
The taxonomic positions of the subspecies of Bifidobacterium longum (B. longum subsp. longum, subsp. infantis, and subsp. suis) have been controversial. A current proposal is that the former two species "B. infantis" and "B. suis" be unified with B. longum and all three reclassified as three subspecies. To test this proposal, ribosomal protein profiling as observed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was applied to the classification of 17 strains of B. longum, including three subspecies. Among 41 different kinds of ribosomal proteins selected as biomarkers whose masses were calculated from their amino acid sequences, 31-41 ribosomal proteins were observed in sample strains with the same masses as the references. The high matching rate indicates high conservation of ribosomal proteins within the sample strains, and therefore strongly supports the unification of the former species. However, the masses of some ribosomal proteins varied within species. The phylogenetic tree constructed from the profiles of ribosomal proteins matched the references, showing a clear cluster of the subsp. longum and the subsp. infantis strains. This result supports the proposal to reclassify B. longum into subsp. longum and subsp. infantis. The subsp. suis strains formed an individual sub-cluster within the infantis cluster. However, their ribosomal proteins have both characters of longum and infantis types. This result suggests that the taxonomic position of the subsp. suis should be reconsidered.
长双歧杆菌亚种（B. longum subsp. longum、subsp. infantis 和 subsp. suis）的分类地位一直存在争议。目前的建议是将前两个物种“B. infantis”和“B. suis”与 B. longum 统一起来，将这三个物种重新分类为三个亚种。为了验证这一建议，应用基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）的核糖体蛋白分析对包括三个亚种在内的 17 株长双歧杆菌进行了分类。在从氨基酸序列计算质量的 41 种不同核糖体蛋白中，有 31-41 种核糖体蛋白在与参考品质量相同的样本菌株中观察到。高匹配率表明核糖体蛋白在样本菌株中具有高度保守性，因此强烈支持物种的统一。然而，一些核糖体蛋白的质量在种内有所不同。从核糖体蛋白图谱构建的系统发育树与参考文献一致，清楚地显示了 subsp. longum 和 subsp. infantis 菌株的聚类。这一结果支持将 B. longum 重新分类为 subsp. longum 和 subsp. infantis 的建议。subsp. suis 菌株在 infantis 聚类中形成了一个单独的亚群。然而，它们的核糖体蛋白既有 longum 型又有 infantis 型的特征。这一结果表明，subsp. suis 的分类地位需要重新考虑。
