IMPORTANT UPDATE

Since the original publication of this work, an important advance has been made.  Our laboratory has stably integrated cellulose synthase genes into the cyanobacteria chromosome through recombination. Compared to cellulose synthesis by other bacteria such as Acetobacter, the use of cyanobacteria eliminates the need for a fixed carbon source and, in some cases, also eliminates the need for a fixed nitrogen source. Although cyanobacteria have been shown to synthesize cellulose, to date, no cyanobacterium has demonstrated the ability to make cellulose at levels useful for commercial production. For further information about this invention see The University of Texas, Office of Technology Commercialization.

Cellulose Biosynthesis by Cyanobacteria

David R. Nobles, Dwight K. Romanovicz, and R. M. Brown, Jr.

The first conclusive evidence has been presented that cyanobacteria synthesize cellulose. The significance of this finding is:

• Cellulose synthesized by cyanobacteria may offer a new industrial resource for this biomaterial
   
• Cellulose genes from cyanobacteria shown to be a likely source of genetic material for present day cellulose crops such as trees and cotton
   
• Cellulose genes from cyanobacteria provide clues to the early evolution of eukaryotic cells

Cellulose is a biopolymer that plants use as the primary building block for their cell walls and has economic significance because it is the major constituent of  such familiar products as cotton, wood, and flax.  

The cyanobacteria are among the most ancient groups of organisms having existed for more than 3.5 billion years.  Discovery of cellulose in cyanobacteria led to the use of sophisticated data mining from sequenced genomes of other organisms.  This work has shown that the cyanobacterial genes for cellulose production are closely related to those genes in land plants. This strongly suggests that the genetic code for the major building blocks for cellulose production of land plants came directly from the cyanobacteria. 

The research furthermore supports the endosymbiotic hypothesis which states that at least 2.2 billion years ago, a singular event took place in which chloroplasts, the site of photosynthesis in land plants, originated from a cellular ingestion or uptake of a cyanobacterium. Cyanobacteria do not have chloroplasts, but they do have photosynthesizing membranes. The primitive cellular recipient of this endosymbiosis, also received the genes for cellulose assembly which eventually were transferred to the nucleus, the present day site for the genes of cellulose biosynthesis in land plants. Since cellulose is essential as a structural component to support plants on land, this event probably was key in leading to the initiation of plant life on land. The appearance of terrestrial plants from the oceans was a necessary event in the evolution of life as we presently know it. 

This research takes on added significance since it is now known that the earth's oxygen atmosphere originated from eons of photosynthesis by cyanobacteria.  If cellulose synthesis were a primitive form of metabolism among the first life on earth, it may have played a major role in the survival of organisms in the harsh, early conditions of primordial earth. Cyanobacteria inhabit vast, incredibly diverse environments ranging from hyper-saline waters to deserts which have never recorded rainfall.  

Discovery of cyanobacterial cellulose is significant because unlike plants, many cyanobacteria are able to use or "fix" nitrogen from the atmosphere and thus do not require nitrate-based fertilizers.  Additionally, some nitrogen fixing cyanobacteria are able to grow in salt water, which would eliminate the need for fresh water.  Thus, cyanobacteria are an attractive potential new crop source for the industrial production of cellulose and would not require arable land. In large scale production, this new cellulose resource could reduce the depletion of conventional resources for timber and textiles.
 
The research was presented in full in Plant Physiology, October 2001, Vol. 127, pp. 529-542, "Cellulose in Cyanobacteria. Origin of Vascular Plant Cellulose Synthase?"  The abstract of this article is reproduced below:

Although cellulose biosynthesis among the cyanobacteria has been suggested previously, we present the first conclusive evidence, to our knowledge, of the presence of cellulose in these organisms. Based on the results of x-ray diffraction, electron microscopy of microfibrils, and cellobiohydrolase I-gold labeling, we report the occurrence of cellulose biosynthesis in nine species representing three of the five sections of cyanobacteria. Sequence analysis of the genomes of four cyanobacteria revealed the presence of multiple amino acid sequences bearing the DDD35QXXRW motif conserved in all cellulose synthases. Pairwise alignments demonstrated that CesAs from plants were more similar to putative cellulose synthases from Anabaena sp. Pasteur Culture Collection 7120 and Nostoc punctiforme American Type Culture Collection 29133 than any other cellulose synthases in the database. Multiple alignments of putative cellulose synthases from Anabaena sp. Pasteur Culture Collection 7120 and N. punctiforme American Type Culture Collection 29133 with the cellulose synthases of other prokaryotes, Arabidopsis, Gossypium hirsutum, Populus alba × Populus tremula, corn (Zea mays), and Dictyostelium discoideum showed that cyanobacteria share an insertion between conserved regions U1 and U2 found previously only in eukaryotic sequences. Furthermore, phylogenetic analysis indicates that the cyanobacterial cellulose synthases share a common branch with CesAs of vascular plants in a manner similar to the relationship observed with cyanobacterial and chloroplast 16s rRNAs, implying endosymbiotic transfer of CesA from cyanobacteria to plants and an ancient origin for cellulose synthase in eukaryotes.

 

Bonus Movie: Gliding motility in the cyanobacterium Oscillatoria
(click play to start)

Further Information

• University of California Museum of Paleotology has "An Introduction to the Cyanobacteria"
• Purdue University hosts "Cyanosite" -- A webserver for Cyanobacterial Research
• Kazusa DNA Research Institute hosts "CyanoBase" -- The Genome Database of Cyanobacteria
• "Microbial Genomics" at the U.S. Department of Energy Joint Genome Institute

Acknowledgements

This work was supported by a grant from the Energy Biosciences Division, Department of Energy DE-FG03-94ER20145, a Welch Foundation Grant F-1217 to RMB, and the Johnson & Johnson Centennial Chair Fund at The University of Texas at Austin

Created Oct. 15, 2001/ revised Dec 2006
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