8_23 Fundementals II cell structures.pptx

Intro to cell structure Prokaryotic Cells Comparing prokaryotic and eukaryotic cells – Prokaryote comes from the Greek words for prenucleus. – Eukaryote comes from the Greek words for true nucleus.  Prokaryote Eukaryote One circular...

Intro to cell structure Prokaryotic Cells Comparing prokaryotic and eukaryotic cells – Prokaryote comes from the Greek words for prenucleus. – Eukaryote comes from the Greek words for true nucleus.  Prokaryote Eukaryote One circular Paired chromosomes, chromosome, not in a in nuclear membrane membrane Histones No histones Organelles No organelles Polysaccharide cell Peptidoglycan cell walls walls Mitotic spindle/mitosis Binary fission Separate Simultaneous transcription/translati transcription/translati on on Cellulose or Chitin Peptidoglycan  The Small World Surface-to-volume ratios, growth rates, and evolution advantages to being small more surface area relative to cell volume than large cells (i.e., higher S/V ratio). support greater nutrient and waste product exchange per unit cell volume tend to grow faster than larger cells Mutations lead to faster evolution. Eukaryotic cells adapt slower. Figure 2.3 Prokaryotic Cells Pilus Cytoplasm Ribosomes Nucleoid (DNA) Plasma membrane Cell wall Capsule Pili Flagellum 0.3  m  A Preview of Prokaryotic Cell Structure and Function procaryotes differ from eucaryotes in many traits including size and lack of internal membrane systems procaryotes are divided into – Bacteria – Archaea Bacteria: 2 main groups – Gram stain reaction Gram Positive Gram Negative  Major Shapes Cocci (Coccus) – spherical (round) Bacilli (Bacillus) – Rods (rectangular) Vibrio – Bent Rods spirilla (spirillum) – rigid helices spirochetes – flexible helices mycelium – network of long, filaments Pleomorphic – no set shape Figure 2.1  Morphology of Prokaryotic Cells Division along a single plane may result in pairs or chains of cells – Pairs = diplococci Example: Neisseria gonorrhoeae – Chains = streptococci Example: species of Streptococcus  Morphology of Prokaryotic Cells Division along two or three perpendicular planes form cubical packets – Example: Sarcina genus Division along several random planes form clusters – Example: species of Staphylococcus  Arrangements Pairs: Diplococci, diplobacilli Clusters: Staphylococci Chains: Streptococci, streptobacilli Figures 4.1a, 4.1d, 4.2c  Glycocalyx layers of material lying outside the cell wall – capsules usually composed of polysaccharides well organized and not easily removed from cell – slime layers similar to capsules except diffuse, unorganized and easily removed – S-layer Complex glycoprotein layer  The term… glycocalyx – network of polysaccharides extending from the surface of the cell – a capsule or slime layer composed of polysaccharides can also be referred to as a glycocalyx  Bacterial Capsules Figure 3.34  Bacterial Glycocalyx Streptococcus http://lecturer.ukdw.ac.id/dhira/BacterialStructure/BactStructImages/Capsule.JPG  Capsules, Slime Layers, and S-Layers S-layers – regularly structured layers of protein or glycoprotein – In bacteria the S layer is external to the cell wall – Common in some pathogenic bacteria C. difficile B. anthracis – common among Archaea, where they may be the only structure outside the plasma membrane Fagan, R., Fairweather, N. Biogenesis and functions of bacterial S-layers. Nat Rev Microbiol 12, 211–222 (2014). https://doi.org/10.1038/nrmicro3213  Functions of capsules, slime layers, and S-layers protection from host defenses (e.g., phagocytosis) protection from harsh environmental conditions (e.g., desiccation) attachment to surfaces – Biofilms – Host receptors  More functions… protection from viral infection or predation by bacteria protection from chemicals in environment (e.g., detergents) facilitate motility of gliding bacteria protection against osmotic stress  Biofilms Microbes attach to solid surfaces and grow into masses They will grow on rocks, pipes, teeth, and medical implants  Biofilms http://www.fei.com/resources/image-gallery/bacterial-biofilm-7330.aspx Figure 1.8 http://www.advancedhealing.com/blog/2009/10/18/biofilm-basics/  Microbial Appendages Flagella Locomotion – Fimbriae Attachment Movement ( – Pili – multiple types Exchange of genetic material = Sex Pilus or F pilus Movement (push or pull) Attachment (few cases) secretion  Pili and Fimbriae Fimbriae (s., fimbria) – short, thin, hair-like, proteinaceous appendages up to 1,000/cell – mediate attachment to surfaces – Genes on Chromosome Pili – Short hair-like fibers (tubular) Less than 10/cell – Attachment – Gene transfer (sex pilus for Conjugation) – Gene on plasmids Appendages Figure 4.11  Flagella and Motility Figure 3.4  Flagella Outside cell wall Made of chains of flagellin Attached to a protein hook Anchored to the wall and membrane by the basal body Figure 4.8a  Flagella Arrangement http://classconnection.s3.amazonaws.com/554/flashcards/618554/jpg/ lophotrichous1327193003993.jpg What is Figure 4.7  Motile Cells Rotate flagella to run or tumble Move toward or away from stimuli (taxis) Flagella proteins are H antigens (e.g., E. coli O157:H7) Motile Cells Figure 4.9  Cell Wall Prevents osmotic lysis Made of peptidoglycan (in bacteria) Figure 4.6a–b Next Time cell wall structure Read Chapter on Cell Walls