Prokaryotic Cell Structure

Bacterial Envelope comprises the inner cell membrane and the cell wall if present, may have an outer membrane such as in gram-negative bacteria May also be comprised of a capsule

Capsule or Slime Layer Made of polysaccharides (dextran, levan, cellulose) Outer part of cell envelope Not easily washed off (slime) Indicates virulence of organism Cannot be stained (must stain background) Helps them attach to other surfaces Prevents phagocytosis

Capsules Not all organism have capsules (nonencapsulated) On agar, encapsulated is smooth, glistening, and mucoid On agar, non-encapsulated is dry and rough Variation on capsule is glycocalyx

Cell Wall Gram Positive- thicker than gram negative because of peptidoglycan with amino acid bridges (NAG and NAM) to make interconnected mesh-like molecule; also has teichoic acids Gram Negative- peptidoglycan layer (inner wall) covered with lipoproteins

Cytoplasmic Membrane The bacterial cytoplasmic membrane is a fluid phospholipid bilayer that encloses the bacterial cytoplasm. Inward folding are called mesosomes- part of electron transport system; especially present during cell division Mesosomes not found in gram-negative bacteria

Nucleoid and Pasmids DNA not bounded by nuclear membrane Bacteria chromosome made from single strand DNA Coiled around RNA core Plasmids are found in some bacteria Considered extrachromosomal DNA Can transfer genetic information in process called conjugation

Flagella Threadlike extensions Four groups Monotrichous- single plar Amphitrichous- both ends Lophotrichous- tuft of flagella Peritrichous-flagella over entire surface area Made of protein flagellin Made of a hook and basal body Bacteria spins one way and flagella spins the other way

Flagellum

Pili (Fimbriae) Pili (hair) and fimbriae (fringe) are shorter and thinner than flagella Hair-like all over cell Fimbriae are like velcro so they can stick to things and help form biofilm Pili are a bit longer and help to transfer genetic material through conjugation over the pilus bridge

Pili and Conjugation

Endospore May lie dry and dormant for a while Germinate when conditions are right Sporogenesis when conditions are poor for bacteria Can be stained and seen with microscope