The United States Department of Energy (DOE) is providing $1.6 million for the sequencing the DNA of six related strains of Cyanothece photosynthetic bacteria that biologists at Washington University in St. Louis will examine for their potential as sources of biofuel—especially ethanol.
One additional Cyanothece strain, 54112, has already been sequenced (earlier post) by the Joint Genome Institute (JGI) in Walnut Creek, California—DOE’s sequencing facility, the largest in the world. JGI will also sequence the additional six.
All six strains—two isolated from rice paddies in Taiwan, one from a rice paddy in India, and three others from the deep ocean—are related, but each one comes from different environmental backgrounds and might metabolize differently. Cyanobacteria produce hydrogen, ethanol, lactate, formate and acetate as a result of their fermentative processes. Thus, one or more strains might have features that the others do not. Combining traits of the different strains could provide the most efficient bioenergy producer.
The Department of Energy is very interested in the production of ethanol or hydrogen and other kinds of chemicals through biological processes. Cyanobacteria have a distinct advantage over biomass, such as corn or other grasses, in producing ethanol, because they use carbon dioxide as their primary cellular carbon source and emit no carbons and they naturally do fermentation. In biomass, yeast needs to be added for fermentation, which leads to the production of ethanol. Cyanobacteria can offer a simpler, cleaner approach to ethanol production.
The diversity in those sequences will give us the breadth of what these organisms do, and then we can pick and choose and make a designer microbe that will do what we want it to do. We want to tap into the life history of these organisms to find the golden nuggets.—Prof. Himadri Pakrasi, Washington University, research leader
One possible way to produce ethanol using Cyanothece strains is a hybrid combination of the microbe and plant matter where the cyanobacteria coexist with plants and enable fermentation. The model exists in nature where cyanobacteria form associations with plants and convert nitrogen into a useful form so that plants can use the nitrogen product.
Pakrasi and his collaborators have designed a photobioreactor to watch Cyanothece convert available sunlight into thick mats of green biomass, from which liquid ethanol can be extracted.
Pakrasi led the sequencing of Cyanothece 54112 as the focus of a Department of Energy grand challenge project that resulted in the sequencing and annotation of a cyanobacterium gene that could yield clues to how environmental conditions influence key carbon fixation processes at the gene-mRNA-protein levels in an organism.
Pakrasi is leading a Grand Challenge Project in membrane biology that is using a systems approach to understand the network of genes and proteins that governs the structure and function of membranes and their components responsible for photosynthesis and nitrogen fixation in two species of unicellular cyanobacteria, specifically Cyanothece and Synechocystis. A systems approach integrates all temporal information into a predictive, dynamic model to understand the function of a cell and the cellular membranes.
The Cyanothece sequencing is the second Joint Genome Institute project involving Washington University. In 2004, the university was directly involved in sequencing the entire genome of the moss Physcomitrella patens at the Joint Genome Institute.