Week 2.pdf

Prokaryote vs Eukaryote Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bacteria ▪ Prokaryotes ▪ Peptidoglycan cell walls ▪ Binary fission ▪ For energy, use organic chemicals, inorganic chemicals, or photosynthesis Copyright...

Prokaryote vs Eukaryote Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bacteria ▪ Prokaryotes ▪ Peptidoglycan cell walls ▪ Binary fission ▪ For energy, use organic chemicals, inorganic chemicals, or photosynthesis Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 1.1a  Bacterial cell morphology ▪ Average size: 0.2 -1.0 µm  2 - 8 µm ▪ Cocci (from kokkos meaning berry) are spherical or oval cells. ▪ Bacilli (from baculus meaning rod) are rod shaped cells ▪ Vibrios are comma shaped curved rods and derive their name from their characteristics vibratory motility. ▪ Spirilla are rigid spiral forms. ▪ Spirochetes (from speira meaning coil and chaite meaning hair) are flexuous spiral forms ▪ Actinomycetes are branching filamentous bacteria, so called because of a fancied resemblance to the radiating rays of the sun when seen in tissue lesions (from actis meaning ray and mykes meaning fungus) ▪ Mycoplasmas are bacteria that are cell wall deficient and hence do not possess a stable morphology. They occur as round or oval bodies and as interlacing filaments. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Cocci Vibrio Spirillium Bacilli Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bacterial cell morphology ▪ Unusual shapes ▪ Star-shaped Stella ▪ Square Haloarcula ▪ Most bacteria are monomorphic ▪ A few are pleomorphic Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Prokaryotic Cells ▪ Comparing prokaryotic and eukaryotic cells ▪ Prokaryote comes from the Greek words for prenucleus. ▪ Eukaryote comes from the Greek words for true nucleus. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bacterial Cell Arrangements Arrangement of Cocci Diplococci, Streptococci Division in one plane produces diplo- and streptococci Tetrad Division in two planes produce tetrads Sarcinae Division in three planes produce Staphylococci Division in multiple planes produce staphylococci Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figures 4.1a, 4.1d, 4.2c  Bacterial Cell Arrangements Arrangement of Bacilli Bacilli Single cell Diplobacilli Cells appear in pairs after division Streptobacilli Cells appear in chains after cell division Coccobacilli Cells have tapered ends or look like cocci * Bacilli only divide across their short Copyright ©axis 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Bacterial Cell Arrangements Vibrios Curved rods Spirilla helical, corkscrew like shape and fairly rigid bodies Spirochetes helical but flexible body Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Glycocalyx (capsule) ▪ Outside cell wall ▪ Usually sticky ▪ A capsule is neatly organized ▪ A slime layer is unorganized and loose ▪ Extracellular polysaccharide allows cell to attach ▪ Capsules can contribute to the virulence of bacteria by preventing from phagocytosis. Capsulated Bacillus anthracis or Streptococcus pneumoniea can only cause disease. Vibrio cholerae uses its capsule to attach to mucosal cells of intestine. ▪ An important component of biofilms. Glycocalyx in biofilms called extracellular polymeric substance (EPS) and Helps to attach to surfaces. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Flagella ▪ Outside cell wall ▪ Made of chains of a globular protein, flagellin ▪ No sheath covering the flagellum ▪ Three components, a filament, hook and basal body. ▪ Anchored to cell wall and membrane by the basal body. ▪ Basal body anchors the flagellum to cell wall. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.8a  Flagella ▪ Basal body is composed of a small central rod inserted into series of rings. Gram negative bacteria have 2 pairs of rings while gram positive bacteria have one pair of rings. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Classification of bacteria: Flagella Arrangement ▪ Atrichous: No flagella e.g. streptococci. ▪ Peritrichous: Distributed over the entire cell e.g. Salmonella Typhi. ▪ Polar: At one or both ends of a bacterium. ▪ Monotrichous: A single flagellum at one pole e.g. Vibrio cholerae. ▪ Lophotrichous: A tuft of flagella coming from one pole e.g. Spirillum. ▪ Amphitrichous: Flagella at both poles of a bacterium e.g. Alkaligens faecalis. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings