Date: Mon, 30 Apr 2001 20:59:01 -0700 Reply-To: Sustainable Agriculture Network Discussion Group From: Misha Subject: Cyanobacteria Howdy, all-- Frank held forth: >Bargyla Rateaver intoned: > > > bluegreens are bacteria, not algae > >To be precise, they are cyanobacteria, or were when last I acquired state of >the art reference materials. In the 1986 edition of Biology of Plants, Raven >et al, "blue-green algae" is used to refer one to cyanobacteria, and they >are discussed in various places in that text, most notably pp 183-184, where >the term "blue green algae" is indeed used: To be precise, Bargyla is right. Cyanobacteria are bacteria, not to mention quite likely the oldest ones on earth. Quoth the scientists at the UC-Berkeley Museum of Palaeontology: "Because they are photosynthetic and aquatic, cyanobacteria are often called "blue-green algae". This name is convenient for talking about organisms in the water that make their own food, but does not reflect any relationship between the cyanobacteria and other organisms called algae. Cyanobacteria are relatives of the bacteria, not eukaryotes, and it is only the chloroplast in eukaryotic algae to which the cyanobacteria are related." Source: http://www.ucmp.berkeley.edu/bacteria/cyanointro.html According to folks at /Scientific American/: "By comparing molecular sequences to infer genealogies, molecular phylogeneticists tell us that the two primary lines of descent lead to the eubacteria (or common bacteria, which include the photosynthetic bacteria) and to a second common lineage that subsequently divided to form the archaea (which like the eubacteria are prokaryotes) and the eukaryotes (which include all higher plants and animals). All these events appear to have preceded the oldest fossil stromatolites. So the eukaryotic lineage appears to be very ancient, about as ancient as the two prokaryotic lineages." Source: http://www.sciam.com/askexpert/biology/biology7.html What most of us on this list probably learned was the five-level organization of life forms: Monera Protista Fungi Plantae Animalia with all life being either "prokaryotes" (bacteria) or "eukaryotes" (protists, fungi, plants, animals). If I recall correctly the Reagan-era biological texts I studied, cyanobacteria fit into the Monera, subkingdom Eubacteriobionta, and were considered "primitive plants." Eeeww, what messy thinking--kind of like saying that iron ore is a primitive car, when you think about it. As people learned more about the history of life on earth, it became evident that the existing systems of organization were obscuring understanding by being based on relatively trivial things, like appearance/structure. A different system was needed to understand life's diversity and functioning more deeply. In the more recently developed biological classification system of cladistics, cyanobacteria are part of the Eubacteria branch of the three basic clusters of life: Archaea (methanogens, thermophiles, halophiles...) (oldest forms of life) | Eubacteria ("true bacteria"--heterotrophic bacteria, cyanobacteria) (fossils date back to 3.5 billion years) | Eukaryotes (basal protists, flagellates, rhodophytes, alveolates, chromists, plants, animals, fungi). The Eubacteria and Archaea comprise what used to be called the prokaryotes. The oldest known fossils (dating to 3.5 billion years ago) are those of cyanobacteria. These little beings are the mother of us all. Their forms are surprisingly conserved (stable), which suggests that they've been hugely genetically stable. Which is a dang good thing for the rest of life. (Hey! I know!!! Let's tinker with that stability and make it change and shape it to our whims--for profit--and call it science and claim it's truth!!!!!!) Cyanobacteria's contribution to life on earth at every level is huge. For starters, cyanobacteria created the earth's atmosphere. Cyanobacteria also gave plants a way to generate energy. Chloroplasts in plants are cyanobacteria which learned to live synergistically inside plant cells, and this is why plants, like cyanobacteria, create oxygen. This is similar to the fact that our own mitochondria were originally external organisms--a form of proteobacteria (purple bacteria). In other words, our ability to respire oxygen (created by cyanobacteria and later to plants) we owe to those critters who moved in and stayed. Otherwise we, like so many species in the history of life, would have died as the oxygen level of the atmosphere increased. I still hope to wake up one day and discover I have chloroplasts in place of mitochondria. peace misha ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Michele Gale-Sinex Home office: 510-525-5683 Home office fax: Same as above, phone first for enabling ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Nothing says "creativity" like a yard full of rusty car parts. --Red Green