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Bacteria

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Updated 2007-03-12 07:41

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 typebacteria
No WallMycoplasma
Thin WallSpirochetes
Acid-Fast WallMycobacteria, sometimes Nocardia asteroides
Thick WallAll other bacteria...
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