We have determined the complete 1,694,969 nucleotide sequence of the GC-rich genome of
Methanopyrus kandleri
using a novel approach. It is based on unlinking genomic DNA with the ThermoFidelase version of
M. kandleri
topoisomerase V and cycle sequencing directed by 2′-modified oligonucleotides (Fimers). 3.3× sequencing redundancy was sufficient to assemble the genome with <1 error per 40 kb. Using a combination of sequence database searches and coding potential prediction, 1692 protein-coding genes and 39 genes for structural RNAs were identified.
M. kandleri
proteins show an unusually high content of negatively charged amino acids, which might be an adaptation to its high intracellular salinity. Previous phylogenetic analysis of 16S RNA suggested that
M. kandleri
belonged to a very deep branch, close to the root of the archaeal tree. However, genome comparisons, using both trees constructed from concatenated alignments of ribosomal proteins and trees based on gene content, indicate that
M. kandleri
consistently groups with other archaeal methanogens.
M. kandleri
shares the set of genes implicated in methanogenesis and, in part, its operon organization with
Methanococcus jannaschii
and
Methanothermobacter thermoautotrophicus
. These findings indicate that archaeal methanogens are monophyletic. A distinctive feature of
M. kandleri
is the paucity of proteins involved in signaling and regulation of gene expression: Also,
M. kandleri
appears to have fewer genes acquired via lateral transfer than other archaea. These features might reflect the extreme habitat of this organism.
我们测定了富含 GC 的甲壳虫
基因组 1 694 969 个核苷酸的完整序列。
Methanopyrus kandleri
采用了一种新方法。该方法基于用 ThermoFidelase 版本的
的 ThermoFidelase 版本解开
基因组 DNA
拓扑异构酶 V 和 2′修饰寡核苷酸(Fimers)引导的循环测序。3.3 倍的测序冗余足以组装
基因组,每 40 kb 的误差小于 1。通过序列数据库搜索和编码潜能预测相结合的方法,确定了 1692 个蛋白质编码
基因和 39 个结构 RNA
基因。
M. kandleri
蛋白质显示出异常高的带负电荷
氨基酸含量,这可能是为了适应其细胞内的高盐度。先前的 16S RNA 系统进化分析表明,M.
属于一个非常深的分支
属于一个很深的分支,靠近古菌树的根部。然而,利用
核糖体蛋白质的连接排列构建的树和基于
基因含量的树进行的
基因组比较表明,M.
kandleri
与其他古
甲烷菌一致。
M. kandleri
与其他古
甲烷菌有相同的
甲烷发生
基因集,其操作体组织也部分与
和
和
热自养
甲烷杆菌
.这些发现表明,古
甲烷菌是单系的。坎德勒氏
甲烷菌的一个显著特点是
Kandleri
的一个显著特点是缺乏参与信号传导和
基因表达调控的蛋白质:另外、
此外,M.
通过横向转移获得的
基因似乎少于其他古细菌。这些特征可能反映了这种
生物的极端生境。