Cell walls, evolution

This essay was written in an attempt to explain our overview of primary cell walls and to reach consensus on the nomenclature of primary cell wall polysaccharides. We present evidence supporting the hypothesis that cellulose, xyloglucan, arabinoxylan, homogalacturonan, RG-I, and RG-II are the six polysaccharides common to all primary cell walls of higher plants. In many cells, these six polysaccharides account for all or nearly all of the primary wall polysaccharides. Like the physically interacting proteins that constitute the electron transport machinery of mitochondria, the structures of the six patently ubiquitous polysaccharides of primary cell walls have been conserved during evolution. Indeed, we hypothesize that the common set of six structural polysaccharides of primary cell walls have been structurally... 

Low density PE foam sheets having a thickness of 10 mm were cut from a block produced by compression moulding and their thermal conductivities over the temperature range from 24 to 50C determined. The evolution of the properties along the block was analysed and the cell structure, apparent mean cell diameter, anisotropy, mean cell wall thickness and relative fraction of polymer determined using quantitative image analysis and a previously reported model utilised to predict the thermal conductivity of the foams. 30 refs. 

Williams, D. H. and Maplestone, R. A., Why are secondary metabolites synthesized Sophistication in the inhibition of cell wall biosynthesis by vancomycin group antibiotics, in Secondary Metabolites Their Function and Evolution, Chadwick, D. J. and Whelan, J., Eds., Ciba Foundation Symposium 171, John Wiley Sons, New York, 1992, 45. 

At this point, however, we cannot ignore the fact that the evolution of protein synthesis started before the origin of the first cells, in systems which could not have cell walls, cytoskeleton filaments or sodium pumps, for the very good reason that all these structures require well-developed proteins. How could precellular systems have high potassium concentrations, and low sodium levels, without any of the molecular mechanisms that cells employ to this end The most plausible answer is that those concentrations did not have to be produced in prebiotic systems because they already existed in the environment of the primitive seas. The ribotype world, in short, was also a potassium world. 

Prillinger H, Schweigkofler W, Lopandic K, Bauer R, Mueller UG Evolution of Asco- and Basidiomycota based on cell wall sugars, 18S ribosomal DNA sequences and coevolution with animals and plants. Yeast Newslett 1999 48 12. 

The participation of a nucleotide-activated disaccharide and UDP-activated peptide intermediates are unique features of pseudomurein biosynthesis. Usually, oligosaccharide precursors of bacterial cell-wall polymers are formed at the lipid stage [38,44] and amino acids carrying a nucleotide residue at the. /V -amino group have not been found in nature so far. The distinct differences between the two biosynthetic routes support the hypothesis that murein and pseudomurein represent independent inventions made after the domains bacteria and archaea had been separated from each other during evolution [40,46]. 

Deep water systems with hot VMits (400 C). Accidental signals from pigments on cell walls leads to evolution of infrared sensitivity in motile bacteria. This confers advantage as they can detect proximal heat sources—both food and danger. 

Another group of archaebacteria is methanogens, which produce methane from carbon dioxide emd hydrogen. These bacteria are killed by oxygen and therefore occur only in anaerobic environment. In the earliest stage of evolution, when there was no oxygen atmosphere (more than 2 billion years ago), these bacteria could have existed everywhere. Their cell walls are periodic open structures ("mesh" phases) of self-assembled S-proteins, discussed in section 4.13. 

Ligrane, R. et al. (2002). Diversity in the distribution of polysaccharide and glycoprotein epitopes in the cell walls of bryophytes new evidence for the multiple evolution of water-conducting cells. New Phytologist, 156, 491-508. 

---