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Module 2 bacterial cytology & physiology
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Module 2 bacterial cytology & physiology


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  • 1. Bacterial Cytology & Physiology Bacterial Taxonomy Parts of a bacterial cell Specialized structures in bacteria
  • 2. Taxonomical Ladder• Kingdom Monera • Kingdom Plantae• Phylum • Kingdom Animalia• Class • Kingdom Protista• Order • Kingdom Fungi• Family • Kingdom Monera• Genus• Specie - Type & Strain
  • 3. New Classification:• Carl Woese – based on cellular organization (Domain above Kingdom) – Bacteria – cell wall w/ peptidoglycan – Archaea – cell walls, if present lack peptidoglycan – Eukarya – Protista, Fungus, Plants, Animals
  • 4. Characters used to classify Bacteria• Morphology- cell • Percentage of DNA shapes & struc. base pairs• Biochemistry & • DNA sequence Physiology - condi- • DNA hybridization tions & process • sequence of amino• Serology - FAT & acids in proteins slide agglutination • protein profiles• Phage typing • sequence of rRNA
  • 5. Prokaryote VS. Eucaryote
  • 6. Procaryotes• appendages: pili, flagella, • presence of plasma axial filaments in membrane spirochetes • undiff. cytoplasm• Usually glycocalyx is • non-membrane present bound organelles• outer membrane present • 1 circular DNA in gram (-) • binary fission• cell wall in all eubacteria • 1 to few u
  • 7. Eucaryotes• different flagella from • cytoskeleton & procaryotes cytoplasmic streaming• very few has glycocalyx • membrane bound• no outer memb. organelles• no cell wall • paired chromosome• plasma membrane- • mitosis & meiosis phospholipid bilayer • no endospores • > than 10 u
  • 8. Bacterial Cytology• Structures external to the cell wall• The cell Wall• Structures internal to the cell wall• General Structures• Specialized structures
  • 9. External to the cell wall:• Glycocalyx – sugar coat – Viscous, gelatinous polymer on the external of the cell, composed of polysaccharide, polypeptide or both• Capsule – If Glycocalyx is organized and firmly attached to the cell wall, capsule is formed – Determines virulence of the cell – Negative Staining
  • 10. • Slime layer - If the substance is unorganized & loosely attached to cell wall.• EPS ( Extracellular polysaccharide ) – – Glycocalyx made of sugar- enables the bacteria to attach to various surfaces in the natural environment in order to survive.• Flagella/Flagellum ( whip ) – Long filamentous appendages that propel bacteria
  • 11. Arrangements of flagella:• Monotrichous – single polar• Amphitrichous – tuft at each end• Lophotricous – 2 or more at one end• Peritrichous – entire cell• Atricous – no flagella• Flagellar rotation depend on cells continuous generation of energy• Flagellar motion – run, swim, tumble, swarm
  • 12. • Axial Filaments – Unique in spirochetes, also called endoflagella, which are bundles of fibrils that arise at the ends of the cell beneath an outer sheath and spiral around the cell. – Propulsion causes spiral motion or corkscrew movement
  • 13. Fimbriae & Pili:• Fimbriae/Fimbria – can occur at the poles of the cell or evenly distributed all over – Functions for cell attachment/ in the absence colonization cannot happen so no disease ensues• Pili/Pilus – Longer than fimbriae, only 1 – 2 per cell – Preparation for DNA transfer – sex pili
  • 14. The Cell Wall• Complex, semi rigid structure responsible for the shape of the cell• Composed of peptidoglycan (also known as murein) made up of NAG ( N- acetylglucosamine) and NAM (N-acetyl muramic acid). – Structures on the disaccharide portion is repeating.
  • 15. Gram + & - cell walls:• Most gram (+) bacteria have many layers of peptidoglycan in the cell wall forming a thick rigid structure while gram (-) only contain 1 thin layer of peptidoglycan.• Gram (+) contains teichoic acid consisting primarily of an alcohol & phosphate – Lipoteichoic Acid – Wall teichoic Acid• Gram (-) cell walls are susceptible to mechanical breakage because they contain only small amount of peptidoglycan
  • 16. Internal to the Cell Wall:• Plasma Membrane/Bacterial Membrane• Cytoplasm• The Nucleus• Ribosomes• Inclusions – Metachromatic granules – Magnetosomes• Endospores
  • 17. Bacterial Membrane• Functions: • Demonstrated by: – osmosis & – Plasmolysis permeability – Stain - Victoria – cell division Blue – primer for – Isolation - Diff. biosynthesis centrifuge – site of Ag – Ultrathin sections determinant
  • 18. Bacterial shapes & arrangements• Coccus - • Spirillus – single, diplo, tetrad, – wavy, corkscrew, sarcinae, strepto , comma-shaped staphylo. – Spiral bacteria may• Bacillus - have 1 or more – single, diplo, strepto twists
  • 19. Additional Shapes• Star shaped cells – Genus Stella• Rectangular flat cells – halophilic Genus Haloarcula• Triangular shaped cells
  • 20. Basis of Shape:• Shape of the bacterium is primarily dependent on heredity.• Generally bacteria are monomorphic, maintain 1 single shape• Due to environmental conditions, some bacteria tend to become pleomorphic which makes identification difficult. I.e. Rhizobium & Corynebacterium
  • 21. Trivia:• Is coccobacilli a coccus or a bacilli? Maybe both or neither of the two?• Why do bacillus not have tetrads or clusters?