Bacteria - Defining Characteristics
♦ unicelluar prokaryote
♦ binary fission reproduction (no mitosis)
♦ diameter: 0.2 um (Mycoplasma species - smallest) to 5 um (Bacillus anthracis - largest) (compare RBC: 7um)
♦ nucleoid (DNA, but no introns, and RNA)
♦ plasmids (extrachromosomal circular DNA)
♦ 2000 genes on average (compare humans: 100,000 genes)
♦ 70S ribosomes (50S and 30S)
♦ no organelles (no mitochondria, lysosomes, or microtubules)
♦ cell wall, except Mycoplasma species
♦ no sterols in plasma membrane, except Mycoplasma species
Cell Wall
♦ Functions:
♦ rigid support
♦ maintains osmotic balance in hypotonic host environment
♦ prevents burst of bacteria
| Cell Wall type (memorize) | bacteria (memorize) |
|---|---|
| No Wall | Mycoplasma |
| Thin Wall | Spirochetes |
| Acid-Fast Wall | Mycobacteria, sometimes Nocardia asteroides |
| Thick Wall | All other bacteria... |
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