2.3: Cellular pathogens and hosts- prokaryotes and eukaryotes

Unity and Diversity of Cellular Life

For cellular organisms, Carl Woese developed the taxonomic level of “Domain” based on ribosomal RNA sequences

• In Belk’s Biology, see the “Tree of Life” fig 2.19 on page 47 which illustrates how all cellular organisms evolved from common ancestral prokaryotic organisms.
• This common ancestry explains the unity of life (why all cellular organisms share many processes and structures).
• Evolution explains the great diversity of life (see chapter __ “Microbial Genetics” of the Reader for more info on genetic diversity)

Cellular organisms: prokaryotes and eukaryotes

1. Prokaryote: unicellular organisms which lack membrane bound nucleus and other membrane-bound organelles (no nucleus; unicellular= 1 cell). See fig 2.17 p 41 in Belk’s Biology

2 Domains of prokaryotic organisms

-Domain Archaea : few pathogens (maybe??)

-Domain Bacteria: contains the bacterial pathogens

e.g. Yersinia pestis/Bubonic Plague, Staphylococcus aureus/MRSA, Mycobacterium tuberculosis/TB, E. coli O157:H7, Bacillus anthracis/anthrax

-can treat bacterial pathogens with antibioticx

Contributors

• Karen Carberry-Goh, D.V.M., Ph.D. (Sacramento City College)