Module 2- Prokaryote Cell Structure

Bacteria

capable of all necessary life activities: reproduction, metabolism, nutrient processing

can act as group: colonies, biofilms

Size variation in Bacteria

Variety in size, shape, and colonial arrangement: average ~ 1 micron

Coccus

spheres, oval, bean-shaped, pointed

Bacillus

cylindrical rods

Spiral

rigid helix

Pleomorphism

Pleo-many, morphic- looks, variations in size & shape in cells of 1 species

Diplococci

pairs of coccus bacteria

Tetrads

groups of 4 of coccus bacteria

Staphylococci

irregular clusters of coccus bacteria

Streptococci

chains of a few to 100s of coccus bacteria

Sarcina

cubical packet of 8, 16, 32 of coccus bacteria

Diplobacilli

pairs, ends attached of bacillus bacteria

Streptobacilli

chains of bacillus bacteria

Palisades

side-by-side rows of bacillus bacteria

Spiral Bacterial Arrangements

include vibrios (curved rods), spirilla, spirochetes

sometimes found in short chains

Flagella

provide motility

Polar Flagellar

attached at 1 or 2 poles of cell

Monotrichous

sigle flagella on a pole

Lophotrichous

small bunches or tufts of flagella

Amphitrichous

flagella at both poles of cell

Hook

90 degree attachment for rod and filament of flagella

Rod

anchors flagella to the bacteria allows it to spin

Chemotaxis

movement in response to chemical

Positive chemotaxis

movement towards chemical (favorable)

Negative chemotaxis

movement away from chemical (harmful)

Phototaxis

movement in response to light

Run

counterclockwise turning of the flagella, cell swims in a straight line

Tumble

flagellum reverses direction

short: change direction, long: stay in 1 place

Spirochetes

bacteria that moves such as a cork screw, have periplasmic flagella (internal enclosed by cell wall & membrane, 2 or more long coiled threads)

Fimbriae

small, bristle-like fibers on cell surface

composition varies: most protein

function: stick to each other & to surfaces (help in formation of biofilms)

Pili (sex pilus)

long rigid tubular structure made of pilin protein

foind in G-bacteria

used in conjugation: transfer of DNA between cells

S layer

1000’s of copies of a single protein linked together, provides protection from environmental conditions, only hostile environments

Glycocalyx

glycoprotein-polysaccharide covering surrounding cell

slime layer: loose around cell, protects from loss of water & nutrients

capsule: tightly bound to cell, dense & thick, for protection from immune system + water loss + adherence