VIRUSES AND PROCARYOTES

Viruses - (poisonous, noxious, venomous): non-cellular, infectious agents

        Nucleic acid core and a protective protein coat (capsid).
        Very host specific (animal, plant, microorganisms), and in many higher host forms,
            tissue specific.
        The nucleic acid, at least, must enter the host cell.
        DNA viruses have a double strand, RNA (also called retroviruses) viruses have a
            single strand.
        Varied morphology regular polyhedron, rod or combination.

        Generalized replication cycle:

                1.    Host recognition
                2.    Adhesion to host surface
                3.
    Enter host cell
                4.    Take over host genetic function
                5.    Form new virus parts
                6.    Assemble new, intact viruses
                7.    Release from host cell

        Cycle may be sequential and repetitious (full lytic cycle) or it may be interrupted at an
        early stage (temporate cycle) leading to a latent, lysogenic state.

Bacteria - monerians, procaryotes
        2 subgroups: eubacteria and archeabacteria
        metabolically very diverse
                1.    chemotrophs chemical energy source
                2.    autotrophs non-organic chemical energy source
                3.    heterotrophs organic chemical energy source
                4.    phototroph light as energy source
                5.    aerobes require molecular oxygen
                6.    anaerobes do not require molecular oxygen
                7.   
thermophiles heat loving
                8.    psychrophiles cold loving
                9.    halophiles salt loving
                10.  acidophiles acid loving

        general structure - nuclear area, cytoplasm, ribosomes, cell membrane, cell wall, and if
            motile, by flagella.

        Morphology - rods (bacilli), spheres (cocci), and curved or spiral (vibrios and spirilla)

        Reproduction - binary fission: simple duplication of the DNA and subdivision of the cell;
        some bacteria possess an extra bit of DNA called a plasmid which is very small and
        independent of the chromosome; often carries specialized genes, such as antibiotic resistance.

        Pathogenic bacteria - vast array of infectious diseases caused by bacteria; most are treatable
        with antibiotics; recent cause for concern about effectiveness of antibiotics.

Photosynthetic monerans - cyanobacteria (blue-green algae)

The Archaeans

In the 1970s and 1980s scientists discovered that some bacteria had rRNA quite different from other bacteria.

This group comprised a distinct category of bacteria, found also to have other differences:

Cell wall composition

Different membrane composition

Proteins associated with the DNA

Thus, this group of bacteria was more related to eukaryotes and it was suggested that the group should comprise a distinct kingdom.