Prokaryotic Cells Morphology Specialized Structures Ultrastructure

Prokaryotic Cell l Size, Shape & Arrangement –0.2 µm to 2.0 µm diameter –2 µm to 8 µm in length –Three basic shapes »cocci (spheres) »bacillus (rods) »spirochete (twisted/spiral) –Pleomorphic shapes

Prokaryotic Cells l Characteristics –Smaller than eukaryotic cells –No nuclei or chromosomes –No membrane-bound internal organelles –Circular genomic DNA –70S Ribosomes –Cell division by binary fission –No meiosis; recombination by transfer of DNA fragments

Prokaryotic Cell l Cocci –spheres –Staphylo- clusters –Strepto- chains

Prokaryotic Cell l Bacilli –rods

Prokaryotic Cell l Spirochete –spirals

Prokaryotic Cells l Specialized Structures –Endospores – a structure produce primarily by Clostridia and Bacillus species to resist desication –Acid Fast Bacteria – a waxy sheet or coat produced by Mycobacteria –Club shape – produced by Corneybacteria

Prokaryotic Cells l Flagella l Capsules l Cell envelope l Fimbriae l Pili

Prokaryotic Cells

l Flagella –Long filamentous protein »filament »hook »basal body –Rotates to propel cell –Taxis (positive and negative)

Prokaryotic Cells l Capsules –Slime layer –Polysaccharide or polypeptide –Protection from phagocytosis by host –“Stickiness” permits adherence –Prevents desication

Prokaryotic Cells l Cell Envelope or Cell Wall –Gram positive »Peptidoglycan (Multi layer) »Teichoic acid –Gram negative »Peptidoglycan (single layer) »Outer membrane (lipopolysaccharide) –Primary function is resist changes in osmotic pressure; also functions in recognition

Prokaryotic Cells l Peptidoglycan –N-acetylglucosamine –N-acetylmuramic acid –Peptide composed of D- and L- amino acids

Prokaryotic Cells

l Lipopolysaccharide –Outer membrane of Gram negative cells –Composed of lipid and carbohydrate –Carbohydrate referred to as O- antigen –Associated with some endotoxins in pathogenic G- bacteria

Prokaryotic Cells

l Teichoic Acid –sugar alcohol plus phosphate

Prokaryotic Cells l Fimbriae –associated with the adhesiveness of cells to surfaces

Prokaryotic Cells l Pili –involved in the transfer of genetic material

Prokaryotic Cells l Internal Structures –Generally no internal structures –Some bacteria produce polyalkonate granules when carbon is in surplus and nitrogen is limiting