Process Used By Microbes To Make Greenhouse Gases Uncovered

Tag : acid acetic

The findings relate to organisms called methanogens and areexplained in the latest issue of the journal Proceedings of theNational Academy of Sciences.
The publication capped a 12-year effort and can offer some insightsinto how industrial processes might be improved, explained MichaelChan, professor of biochemistry, and Joseph Krzycki, professor ofmicrobiology, both of Ohio State University.
“This enzyme is the key to the whole process ofmethanogenesis from acetic acid,” Krzycki said. “Without it, this form of methanogenesis wouldn’thappen. Since it is so environmentally important worldwide, theimpact of understanding this would be enormous.”
Methanogenesis is the process by which the gas methane is made, andit takes place everywhere across the globe, from swamps tolandfills, releasing the gas that ultimately seeps into theatmosphere.
One central player in this process is the microbe calledMethanosarcina barkeri, a member of an unusual group of organismscalled the Archaea that is similar to both bacterial and animalcells. This organism possesses large amounts of the enzyme soimportant for making methane.
“We often think only of humans putting carbon dioxide andmethane into the atmosphere but natural biology itself actuallyprovides its own sizeable share,” said Chan. “Thisenzyme plays an important role in the process that converts acetateinto these two gases.”
The research can be traced to work that Krzycki did as a graduatestudent in the mid-1980s studying the protein known as acetyl-CoAdecarbonylase/synthase (ACDS). He was focusing on whether carbonmonoxide oxidation was part of the process of methanogenesis fromacetate, which had not been suspected before.
In 1995, Chan approached Krzycki about working with this protein asone of the first projects Chan took on after coming to Ohio State. The goal was to use protein crystallography to get a picture of itand figure out how it works.
An important initial step in this kind of research is to“grow” crystals of the protein molecules, and fromthese crystals, scientists can actually map out the protein’sstructure.
“We tried for six months when I first arrived at Ohio Statebut at the end of that period, we couldn’t get any crystalsto grow,” Chan said.
Two years later, Chan and a former graduate student, Bing Hao, wentback to look at those previous crystallization experiments anddiscovered that crystals had eventually grown.
“The identification of these crystals allowed us to solve thestructure of the protein making up the crystals, although it took10 more years to do that,” he said. “From thestructure, we got a beautiful picture of the protein that we coulduse to understand how it works. Viewing a structure is somewhatlike looking at the schematics of an engine.”
Krzycki said that processes similar to those performed by thisprotein are currently being used in industry, although in thosecases, high temperatures are required.
“From studying this process in these microbes, hopefullyscientists can understand how their natural catalysts make thisreaction work at lower temperatures,” he said.
Along with Chan, Krzycki and Hao, Weimin Gong, Zhiyi Wei, DonaldFerguson Jr. and Thomas Tallant also worked on the project. Theresearch was supported by grants from both the National Institutesof Health and the Department of Energy.