William B. Whitman博士，微生物学教授，同时兼任International Journal of Systematic Bacteriology副主编，Journal of Bacteriology编委，Bergey’s Manual责任主编，美国NIH，DOE，NSF等项目评审专家，并曾担任多个重要微生物国际会议的主席，在国际微生物学领域具有很高的学术地位和声誉。Whitman教授长期专注于微生物学研究，尤其在产甲烷菌的研究方面取得了杰出的研究成果，发表于Nature, PNAS, JBC等国际顶级期刊。由于在微生物研究领域的突出贡献，Whitman博士被遴选为美国微生物科学院(American Academy of Microbiology, AAM)院士，美国科学促进会会士(The American Association for the Advancement of Science Fellow)，并荣获美国青年科学家总统奖，伯杰氏奖章等多个杰出奖项。

报告内容：

1. Assembly and activation of the methyl-coenzyme M reductase from methanogenic Archaea（7月31日 09:30-10:30）

Methanogens and anaerobic methane-oxidizing archaea (ANME) are important players in the global carbon cycle. Methyl-coenzyme M reductase (MCR) is a key enzyme in methane metabolism, catalyzing the last step in methanogenesis and the first step in anaerobic methane oxidation. Assembly and activation of this complex enzyme requires a large number of other proteins, the functions of which are poorly defined. These include the enzymes required for posttranslational modification, biosynthesis and insertion of a unique nickel tetrapyrrole coenzyme F430, and reductive activation of the coenzyme. In most methanogens, the operon encoding MCR is mcrBDCGA, where mcrBGA are the genes encoding the enzyme subunits and the functions of mcrDC are unknown. To better understand its assembly, the recombinant MCR from the thermophile Methanothermococcus okinawensis (rMCRok) was expressed in the mesophile Methanococcus maripaludis. The rMCRok was posttranslationally modified correctly and contained coenzyme F430 and small amounts of McrD. Subunits of the native M. maripaludis (MCRmar) were largely absent, suggesting that the recombinant enzyme was formed by an assembly of cotranscribed subunits. Support for this hypothesis was obtained by expressing a chimeric operon comprising the His-tagged mcrA from M. maripaludis and the mcrBDCG from M. okinawensis in M. maripaludis. The His-tagged purified rMCR then contained the M. maripaludis McrA and the M. okinawensis McrBDG. Deletion of mcrD or mcrC from the recombinant operon also reduced the amount of rMCR by about two third, indicating that the genomic copies of mcrD and mcrC were sufficient to allow some MCR assembly. Pull down experiments with McrC bait identified interactions between McrC and MCR as well as a number of methanogen marker proteins (MMPs). These proteins are highly conserved in methanogens, but the functions of many are not known. Reciprocal pull down experiments with the MMPs supported the presence of a complex comprising MMPs 3, 5, 6, 7, 15, and 17 with MCR. Pull-down and isotope labelling experiments also provided evidence for significant amounts of free McrG. While the role of the MMP clear is not clear, it might play a role in activation. In conclusion, the assembly and activation of MCR appears to require a large number of accessory proteins whose functions are not well described.

2. Methanogenesis: an ancient respiration （7月31日 14:00-15:00 ）

Methanogens are a group of anaerobic Archaea that grow by production of methane. Methanogenesis is one of the earliest lifestyles to evolve on earth and a major contributor to the production of the atmospheric methane, a greenhouse gas. They are also closely related to the anaerobic methane- and alkane-oxidizing Archaea. In spite of their phylogenetic diversity, the methanogens share a number of general features. Their metabolism is restricted and most are obligate methane producers. While only a few compounds are substrates for methanogenesis, methanogens can form syntrophic associations with bacteria and eukaryotes that allow them to colonize a wide variety of habitats. The biochemistry of methanogenesis is complex and utilizes at least six coenzymes rarely found in other organisms. An anaerobic respiration, it is reversible depending upon the environment. In the methanogenic direction, it couples oxidation of H2 or a few other compounds to the reduction of CO2 or other C-1 compounds to methane. At least five different mechanisms of energy conservation are utilized. Because methanogenesis predates the evolution of aerobic respiration and cytochrome-dependent electron transport chains, it provides insight into metabolisms of ancient organisms that may now be extinct or exist outside of earth.

3. Phylogeny of the Archaea（8月1日 09:00-10:00）

The taxonomy of prokaryotes is based upon the formal rules of the International Code of Nomenclature of Prokaryotes or ICNP. These rules enable creation of stable names for prokaryotes. The evolutionary history or phylogeny of microorganisms serves as the basis for their taxonomy and provides insights into their lifestyle and ecology. The phylogeny of Archaea has been particularly difficult to discover because of the relative paucity of species and sequencing data. Initial studies based on 16S rRNA gene sequences included representatives of only seven linages and classified them into two phyla, Euryarchaeota and Crenarchaeota. Subsequent analyses with many more lineages represented and genome sequences identified many more phylum-level groups. As an example, the Genome Taxonomy DataBase recognizes 21 phyla within the Archaea, many of which are from uncultivated microorganisms. As more is learned about the Archaea, this classification is likely to change.