[Taxacom] Gloeobacteria and Prokaryota (was: All levels of organisation and manifestation ...)

Ken Kinman kinman at hotmail.com
Mon Nov 12 22:31:14 CST 2012

Dear All,                          I should note that the classification of prokaryotes which I posted yesterday (see below) is the phylogeny according to Cavalier-Smith.  Although I believe his phylogeny to be largely correct and far superior to other phylogenies and classifications (especially those simplistically showing Eubacteria as holophyletic, rather than very paraphyletic), my own personal view is that the earliest extant prokaryotes could actually be Gloeobacteria (which lack thylakoid membranes), usually merely classified as the earliest clade of Cyanobacteria.  I made a brief post about this here on Taxacom back in 2004, but began working on the hypothesis back in the mid-1990s.  Anyway, if such a view proves true, the higher Cyanobacteria (with thylakoid membranes) could conceivably be a chimaeric fusion of a member of Gloeobacteria with another photosynthetic bacterium (perhaps even a member of Chlorobacteria).    
     The earliest chimaeric cell is usually attributed to the origin of the eukaryotic cell, but a far, FAR earlier fusion could have created the thylakoid Cyanobacteria.  This would mean that early prokaryotic evolution (the first three extant clades shown by Cavalier-Smith) is even more complicated than even he envisaged.  Although I have long believed Cyanobacteria to be the most primitive prokaryotes, this could apply to Gloeobacteria alone, while the thylakoid-bearing Cyanobacteria could be slightly higher in the tree.  Of course, it would depend on whether one classified the chimaera as closer to Gloeobacteria or to the other parent of the chimaera.  Might be as arbitrary as which parent contributed the most genes to the chimaera.  With eukaryotes, the host cell clearly contributed more genes than organelles (like mitochondria or chloroplasts), but it could have been more equal in the proposed chimaera creating thylakoid Cyanobacteria.         
     This would also would have extremely important implications for the evolution of photosynthesis, as the chimaeric fusion of a Gloeobacterial cell with another photosynthetic bacterial cell would have independently brought together the two photosynethic reaction centers we know so well---NOT that they somehow evolved together in the same cell.  Anyway, when I present my own new classification of Prokaryota, don't be surprised if a  Phylum Gloeobacteria is at the base. 
            --------------------Cheers,                                          Ken Kinman    ----------------------------------------------------------------------------------------------I wrote: Kingdom Prokaryota     1   Chlorobacteria   2   Hadobacteria    3   Cyanobacteria (and chloroplasts)   4A  Spirochaetae    B   Sphingobacteria    C   Proteobacteria (and mitochondria)    D   Planctobacteria    5   Eurybacteria    6   Endobacteria    7   Actinobacteria    8   Archaebacteria (I still prefer Metabacteria)    9   {{Eukaryota}} (Protista, thence to Metazoa, Eumycota, and Metaphyta)


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