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-producing crops such as trees and cotton
Cellulose genes from cyanobacteria provide clues to the early evolution of eukaryotic cells
The first conclusive evidence has been presented
that cyanobacteria synthesize cellulose. 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.
Nobles is a second year graduate student with Dr. Brown in the Section of Molecular Genetics and Microbiology in the School of Biological Sciences at the University of Texas at Austin. Romanovicz is a research associate in the Brown laboratory.
For further information, contact Dr. Brown at email@example.com or (512) 471-3364.
The manuscript can be downloaded at the following
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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
Plant Physiol 2001 Oct;127(2):529-42
Cellulose in cyanobacteria. origin of vascular plant cellulose synthase?
Nobles DR, Romanovicz DK, Brown RM Jr
Section of Molecular Genetics and Microbiology, The University of Texas, Austin, Texas 78712.
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 x 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.
sample cover page
Electron microsopy-negative staining of cellulose from 6 species of cyanophyceae. Negative staining. Note the dark spots which are colloidal gold bound to cellobiohydrolase I which is specific for cellulose.
x-ray diffraction analysis of 4 cyanobacterial celluloses
Multiple alignment of amino acid sequences from 17 prokaryotic cellulose synthase homologues with CesA sequences from A. thaliana, G. hirsutum, Z. mays, P. tremulus x alba, and D. discoideum. The alignment demonstrates the presence of a CR-P region between the U1 and U2 domains present only in eukaryotic and cyanobacterial sequences.
Comparison of NJ and MP trees. The tree shown is a NJ tree subjected to 5000 bootstrap trials. Bootstrap values are shown as percentages with MP bootstrap values shown in parenthesis. Differences in the MP tree are denoted by bold lines (multifurcations), dashed arrow (variable position), and * indicates rooting at the base of the tree. Note the distribution of cyanobacterial sequences in the tree: 2 Sequences from Anabaena sp. PCC 7120 and N. punctiforme branch with vascular plants; 2 sequences from N. punctiforme and Synechococcus branch distantly with Thermotogales and Proteobacteria; and 3 sequences from Synechocystis, N. punctiforme, and Anabaena, which are most likely CSL proteins, group with Bacillus subtilus. The high bootstrap values support the validity of the tree.
The maximum likelihood phylogeny for the cellulose synthase sequences showing confidence values and the log likelihood. With the exception of D. discoideum (which groups with the Euryarchea in this tree), the relationships in this tree are nearly identical to those shown in Figure 6.
David is examining his cultures of cyanobacteria. Most cultures are maintained on agar.
David is holding a Petri dish with Oscillatoria sp. The gliding trichomes aggregate to produce
macroscopically visible bundles