Main Groups of Microorganisms ••Prokaryotes (Bacteria and Archaea) ••Protozoa ••Fungi ••Viruses General Characteristics of Microorganisms ••Most are single celled organisms ••Two basic cell types ––Prokaryotic ––Eukaryotic ••Small Size Two Basic Cell Types Prokaryotic vs. Eukaryotic Cells Prokaryote Morphology and Structure ••Two Groups ––Bacteria and Archaea ••Use bacteria as our representative group ••Less complex compared to eukaryotic cells Size Thiomargarita “simple” morphology Shapes ••Not a lot of variation - described by one of three basic shapes: ––coccus - spherical ––bacillus – rod ••coccobacillus – very short and plump •• vibrio – gently curved ––spirillum - helical, comma, twisted rod, ••spirochete – spring-like Arrangements ••Arrangement of cells is dependent on pattern of division and how cells remain attached after division: ––cocci: ••singles ••diplococci – in pairs ••tetrads – groups of four ••irregular clusters ••chains ••cubical packets ––bacilli: ••chains ••palisades Major Components of a Typical Bacterium ••Appendages ••Cell envelope (covering) ••Cytoplasm/internal structures Appendages ••Flagella ••Fimbriae and Pili ••Monotrichous ••Lophotrichous ••PeritrichousAxial filament (endoflagellum) Fimbria Cell Envelope ••Glycocalyx ••S-Layer ••Cell Wall ••Cell Membrane Glycocalyx ••Varied chemical composition ––polysaccharides ––Proteins ••Function ––Attachment to surfaces ––Protection from phagocytic cells ––Prevent desiccation ––Other? S-Layer ••Found in some types of bacteria (common in Archaea) ••Composed of protein (some glycoprotein) ••Forms very regular pattern often crystalline structure ––Surface of cell wall ••Rigid support, adhesion, protection Cell Wall ••Semi rigid layer ••Function ––Shape and support ––Protect from osmotic lysis ••Two main types of cell wall ––Gram positive ––Gram negative Cell Wall & Osmotic Protection ••Terminology ––Gram (+) bacteria protoplasts ––Gram (-) bacteria spheroplasts Structural Components ••Peptidogylcan (murein) ––Main chemical providing strength ––Composition - Polysaccharide chains linked together with peptides ––Two monosaccharides ••N-acetylglucosamine (NAG) ••N-acetylmuramic acid (NAM) ––Peptides••Some D-configuration amino acids (L is found in most protiens) ••Some unique amino acids - DAP (diaminopimelic acid) Gram (+) & (-) Comparison Gram (+) & (-) Comparison Gram (+) Cell Wall Gram (-) Cell Wall LPS (endotoxin) Cell Membrane ••Similar in structure and function to eukaryotic cell membranes ••Phospholipid bilayer with embedded proteins ••Functions in: ––providing site for energy reactions, nutrient processing, and synthesis ––transport into and out of the cell Internal Structures ••Cytoplasm ––Gel-sol material, Suspends solid structures ––Contains dissolved substances ••Chromosome ••Plasmid ••Ribosomes ••Inclusions ••Internal Membranes ••Endospores Nucleoid and Chromosome ••Nucleoid ––Area in cell where chromosome is located •• Chromosome ––Main piece of DNA ––Single, circular ––E. coli ••4,639,221 bp ••~ 4,000 genes Plasmids ••Small circular pieces of DNA ••Independent from chromosome ••~ 1/20th size of chromosome ••May contain important genes ––Antibiotic resistance ––Toxin production ––Pilus formation••Used in genetic engineering (biotechnology) Ribosome ••Smaller than eukaryotic ribosomes ••Two pieces called subunits ••Medically important ––Site of action of many antibiotics Inclusions ••Accumulations of certain chemicals ••Inorganic or organic ••Energy rich compounds or substance needed for certain types of metabolism Internal Membranes ••Plasma membrane infoldings ••Bacteria with membrane dependent metabolic pathways ––Photosynthetic bacteria ––Nitrifying bacteria Endospores ••Internal structure ••Formed during adverse growth conditions ••Contains own DNA, ribosomes, membrane and tough external coating ••Produced primarily by some Gram (+) ––Bacillus, Clostridium ••Resistant to many chemical and physical forces ––Disinfectants and other chemicals ––Radiation ––Heat & Cold ––Desiccation ••Mechanism of resistance ––Precise mechanism unknown ––Chemical resistance due to spore coat ––Core contains: ••Calcium and dipicolinic acid ••Small acid soluble DNA binding proteins Archaea ••Major differences from Bacteria ––Cell Wall – pseudomurein or S layer only ––Cell Membrane – no phospholipids ••Isoprenoid lipids ether linked to glycerol ••Some types with lipid monolayer End ••Go to: Eukaryotic Morphology and
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