漫谈宏基因组学

Metagenomics

基因组学随着人类基因组计划的实施而诞生,现已成为后基因组时代一门重要的生命科学学科.研究者已经逐渐习惯于在对生物体的个别基因或蛋白质研究之前,先测定或分析该物种的基因组序列.目前已经知道全基因组序列的真核生物有40多种,而原核生物则多达200多种.这些工作表明,研究人员在基因组序列分析方面已经取得了巨大的进展.但是,对于自然界现存的物种而言,人类所测定的物种依然是少之又少.在原核生物世界中,仅仅是被命名的就达到5700种,而那些未知微生物的种类则可能多达上百万种.

The classification and evolutionary relationships are important issues in the study of the groupers. Cytochrome b gene fragment of twenty-eight grouper species within six genera of subfamily Epinephelinae was amplified using PCR techniques and the sequences were analyzed to derive the phylogenetic relationships of the groupers from the China Seas. Genetic information indexes, including Kimura-2 parameter genetic distance and Ts/Tv ratios, were generated by using a variety of biology softwares. With Niphon spinosus, Pagrus major and Pagrus auriga as the designated outgroups, phylogenetic trees, which invoke additional homologous sequences of other Epinephelus fishes from GenBank, were constructed based on the neighbor-joining (NJ), maximum-parsimony (MP), maximum-likelihood (ML) and minimum-evolution (ME) methods. Several conclusions were drawn from the DNA sequences analysis: (1) genus Plectropomus, which was early diverged, is the most primitive group in the subfamily Epinephelinae; (2) genus Variola is more closely related to genus Cephalopolis than the other four genera; (3) genus Cephalopolis is a monophyletic group and more primitive than genus Epinephelus; (4) Promicrops lanceolatus and Cromileptes altivelis should be included in genus Epinephelus; (5) there exist two sister groups in genus Epinephelus.