Gao Beile, Paramanathan Ragi, Gupta Radhey S
Department of Biochemistry and Biomedical Science, McMaster University, L8N3Z5, Hamilton, Canada.
Antonie Van Leeuwenhoek. 2006 Jul;90(1):69-91. doi: 10.1007/s10482-006-9061-2. Epub 2006 May 3.
The Actinobacteria constitute one of the main phyla of Bacteria. Presently, no morphological and very few molecular characteristics are known which can distinguish species of this highly diverse group. In this work, we have analyzed the genomes of four actinobacteria (viz. Mycobacterium leprae TN, Leifsonia xyli subsp. xyli str. CTCB07, Bifidobacterium longum NCC2705 and Thermobifida fusca YX) to search for proteins that are unique to Actinobacteria. Our analyses have identified 233 actinobacteria-specific proteins, homologues of which are generally not present in any other bacteria. These proteins can be grouped as follows: (i) 29 proteins uniquely present in most sequenced actinobacterial genomes; (ii) 6 proteins present in almost all actinobacteria except Bifidobacterium longum and another 37 proteins absent in B. longum and few other species; (iii) 11 proteins which are mainly present in Corynebacterium, Mycobacterium and Nocardia (CMN) subgroup as well as Streptomyces, T. fusca and Frankia sp., but they are not found in Bifidobacterium and Micrococcineae; (iv) 8 proteins that are specific for T. fusca and Streptomyces species, plus 2 proteins also present in the Frankia species; (v) 13 proteins that are specific for the Corynebacterineae or the CMN group; (vi) 14 proteins only found in Mycobacterium and Nocardia; (vii) 24 proteins unique to different Mycobacterium species; (viii) 8 proteins specific to the Micrococcineae; (ix) 85 proteins which are distributed sporadically in actinobacterial species. Additionally, many examples of lateral gene transfer from Actinobacteria to Magnetospirillum magnetotacticum have also been identified. The identified proteins provide novel molecular means for defining and circumscribing the Actinobacteria phylum and a number of subgroups within it. The distribution of these proteins also provides useful information regarding interrelationships among the actinobacterial subgroups. Most of these proteins are of unknown function and studies aimed at understanding their cellular functions should reveal common biochemical and physiological characteristics unique to either all actinobacteria or particular subgroups of them. The identified proteins also provide potential targets for development of drugs that are specific for actinobacteria.
放线菌是细菌的主要门类之一。目前，对于这个高度多样化的类群，已知的可区分物种的形态学特征极少，分子特征也非常有限。在这项研究中，我们分析了四种放线菌（即麻风分枝杆菌TN、木糖利夫森氏菌木糖亚种CTCB07、长双歧杆菌NCC2705和栖热栖热放线菌YX）的基因组，以寻找放线菌特有的蛋白质。我们的分析鉴定出了233种放线菌特异性蛋白质，其同源物通常不存在于任何其他细菌中。这些蛋白质可分为以下几类：（i）在大多数已测序的放线菌基因组中独特存在的29种蛋白质；（ii）除长双歧杆菌外几乎存在于所有放线菌中的6种蛋白质，以及在长双歧杆菌和其他少数物种中不存在的另外37种蛋白质；（iii）主要存在于棒杆菌属、分枝杆菌属和诺卡氏菌属（CMN）亚群以及链霉菌属、栖热放线菌和弗兰克氏菌属中的11种蛋白质，但在双歧杆菌属和微球菌科中未发现；（iv）栖热放线菌和链霉菌属物种特有的8种蛋白质，另外还有2种蛋白质也存在于弗兰克氏菌属中；（v）棒杆菌科或CMN组特有的13种蛋白质；（vi）仅在分枝杆菌属和诺卡氏菌属中发现的14种蛋白质；（vii）不同分枝杆菌物种特有的24种蛋白质；（viii）微球菌科特有的8种蛋白质；（ix）在放线菌物种中零星分布的85种蛋白质。此外，还鉴定出了许多从放线菌横向基因转移到趋磁螺菌的例子。所鉴定的蛋白质为界定和划分放线菌门及其内部的一些亚群提供了新的分子手段。这些蛋白质的分布也为放线菌亚群之间的相互关系提供了有用信息。这些蛋白质大多功能未知，旨在了解其细胞功能的研究应揭示所有放线菌或其特定亚群特有的共同生化和生理特征。所鉴定的蛋白质也为开发针对放线菌的特异性药物提供了潜在靶点。
