For Chapter 25, review pages 593-601 but focus your attention on the cyanobacteria and chloroxybacteria on pages 601-604. We will not spend any time on viruses (pages 604-607) so you can avoid those pages.
This course focuses on organisms once called plants. Soon after bacteria were discovered, they were treated separately by botanists from the "blue-green algae" (cyanobacteria). Most bacteriologists were interested in human pathogens and so avoided the cyanobacteria. That left these organisms by default for the botanists. The obvious photosynthetic connection made this an imperative.
The reading is brief. The life cycle is simple (simple fission...NOT NOT NOT mitosis!) and there is little chance for recombination (NO NO NO syngamy NOR NOR NOR meiosis). Please note the book left mitosis off of this important NOT list on page 597.
At the top of page 601 you will notice it says "later in this chapter" referring to lichens...this is a hold-over from an error in the previous edition. This should say "in Chapter 26."
Cyanobacteria are one of the groups of organisms that can fix nitrogen! This is globally a critical process. Biologically fixed nitrogen is the chief source of nitrogen for plants to obtain through their endodermis. This plant nitrogen is the chief source of nitrogen for most animals...either directly in the case of herbivores, or indirectly in the case of carnivores. I'm sorry your book puts very little stock in this process. Nitrogen is the most limiting factor in plant growth and is a major problem in human malnutrition and starvation. Sounds important to me!
Figure 25.12 is not clear about whether this is its natural color. There are some red blue-greens, but I suspect this is a stained specimen.
Read carefully the nice section on Chloroxybacteria (page 601-2). I think this is very exciting news. Many years ago Lynn Margulis and others suggested the endosymbiont theory for the origins of eukaryotic organelles. Cyanobacteria were poor evidence; their photosynthetic pigments were wrong, their membranes were wrong. The more-recent finding of Prochloron and Prochlorothrix add further credibility to the endosymbiont theory. The pigments are right and the membranes are closer. I wish we could get some Prochlorothrix for class use. Please don't miss the important paragraph at the bottom of the left column on page 603!
The chapter ends for our case (page 603-604) with some interesting reading on uses for bacteria. From this botanist's perspective, Bacillus thuringiensis (BT) is a highlight from that reading. There are several different strains that are effective on different pests...especially Japanese Beetle larvae! I have used the bacterium on my lawn (where the larvae live) and they have wiped out my JB problem! It took about two years to eliminate them, but they are GONE! The genes from this bacterium have been cloned into plant genomes to produce plants that make their own insecticide. How we might use those plants is an interesting public health question.
The last few sentences under "The Origin and Evolution of Bacteria" on page 603 discuss recent discoveries about catalytic RNA. I'm sure there is more evidence and argument than is presented here. But, if you read only these last few sentences, ask yourself whether this represents belief based upon evidence (science) or belief based solely upon faith (i.e., almost a religion). Until we find a cellular organism with its life cycle independent of DNA, I'd say this interpretation is pretty speculative and faith based. Hey, proteins are catalytic, so are they the original hereditary molecule?
The mention of bacteria (page 604) as a source of pseudomycins and antimycotics is something I think we will be reading about in newspapers in the coming years. Fungal diseases are opportunistic and are common contributors to the cause of death in AIDS patients. These drugs may be important weapons against such fungi.
Go back to the Algae Chapter (27).
Go back to the Course Schedule.