Bacterial Shapes and Arrangements
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32 Terms
Average size of bacterial cells
1 µm
Most bacteria range from ___ to ____ in diameter
0.2 to 2.0 µm
Most bacteria range from ____ to ____ in length
1.0 - 8.0 µm
What is the significance of the size of mycoplasma cells?
ultra-small bacteria (0.15 to 0.3 µm)
Why is pleomorphism so extreme in the case of mycoplasms
because they lack a rigid cell wall and instead are bounded by a triple-layered “unit membrane & rely on sterols for stability
three major shapes of bacteria
Coccus
Rod-shaped (bacillus)
Spiral
What shape is this?
Coccus
What shape is this?
Bacillus
What shape is this?
Spirillium
Rigid Helix
Spirillum
Comma
Vibrio
What shape is this?
Vibrio
Flexible helix
Spirochete
Branching Filament
Branching rods
What is pleomorphism?
When cells of a single species vary in shape and size
What causes pleomorphism?
Individual variation in cell wall structure caused by genetic/nutritional differences
Example of a cells that exhibit pleomorphism
Corynebacterium diphtheriae
Rickettsia ricketsii
What impacts the arrangement of bacterial cells?
The pattern of division while it is growing and how the cell remains attached afterward
Which bacterial shape has the greatest variety in arrangement?
cocci
What arrangement is this
Diplococci (pair of cocci)
Where does division occur in diplococci?
One plane
Chains of a few to hundreds of cocci
Streptococcus
What arrangement is this?
Streptococcus
Where does division occur in streptococci?
One plane
Cocci in packets/groups of 4
Tetrads
What arrangement is this?
Tetrad
Where does division occur in tetrads
Division in two perpendicular planes
Cubical packet of 8,6 to 64 cells
Sarcina
Where does division occur in Sarcina
Two perpendicular planes
Arrangement typical of the Corynebacterium species
palisades
When cells of a chain remain partially attached by a small hinge region at the ends. The cells tend to fold (snap) back upon each other, forming a row of cells oriented side by side
Palisades
What is this arrangement?
Palisades