BIOSCI 1850 1st EditionExam 2 Study GuideChapter 2: Bacteria2.1: Morphology of Bacterial Cells The most common shapes/terms:Shape Microbiology TermSpherical CoccusRod BacillusCurved Rod VibrioSpiral Spirillum Shape of cell is determined by the organization of the cell wall Some cells remain separate from each other (E. coli), while others are grouped together in rods (B. anthracis), or in irregular clusters (Staphylococci)  Pleiomorphic: bacteria whose cells do not exhibit regular shapes—highly variable o Usually do not have a cell wall Hyphae: irregularly branching filaments Mycelia: networks that rise above the substrate/down in soil Trichomes: smoothed, unbranched chains of cells o Have polysaccharide sheath coating the entire filament  Most bacterial cells are between 0.5 μm—5 μm2.2: The Cytoplasm Nucleoid: convoluted mass of DNA coated in proteins and RNAo No membrane! Cations shield the negative charge of DNA Topoisomerases: enzymes that encourage chromosomal supercoiling Inclusion bodies: polymers used for storage of carbon/nitrogen/phosphorus  Sulfur globules: composed of elemental sulfur, usually a by-product of a cellular reaction Gas vesicles: provide buoyancy  Carboxysomes: contain key enzymes of photosynthesis  Magnetosomes: rare membrane-enclosed cytoplasmic organelle used to store magnetite2.3: The Bacterial Cytoskeleton Important for the internal organization of the cell Interact with plasma membrane and cell wall The FtsZ protein forms the Z-ring: pinches off the two cells during divisiono Directs synthesis of the bacterial cell wall  MreB: polymerizes into filaments resembling actino Forms long helical bands underlying the plasma membrane o Establish boundaries of cell before cell wall is synthesized to make it rigid o Rare in cocci, but in all bacillus  Helps guide cell wall formation into a rod-like structure ParM: found on certain plasmids, responsible for moving them to opposite sides of the cell during replication/division 2.4: The Cell Envelope Spatially defines the cell All cells have a plasma membrane “Optional” Membranes:o Semi-rigid cell wall of peptidoglycan Gram-positive Most cellso Outer membrane All three layers are referred to as the cell envelope Plasma Membrane: phospholipid bilayero Amphipathico Hopanoids: sterol-like molecules that stabilize the membrane  The membrane is fluid Roughly half of the membrane is protein o Control access of materials via permeabilityo Capturing and/or storing energy Oxidative electron transport, photosystems, maintaining gradientso Environmental sensing  Signal transduction of environmental signals usually results in changes in gene expressiono Signal transduction Aquaporins regulate osmosis  Facultative Diffusion: passive diffusion down a concentration gradient, no energy expended Active Transport Systems: move solutes against their concentration gradiento Symport: bringing the desired molecule into the cell along with another moleculethat’s going down its gradient Energy released by the gradient-following substrate is harnessed and used to carry the other Same directiono Antiporters: the energy-requiring uptake of one substrate is driven by the passiveejection of another Opposite direction o ABC Transporters: ATP-Binding Cassette  Have a nucleotide binding domain by which ATP is hydrolyzed to provide energy  The plasma membrane contains proteins for the general secretory pathwayo These proteins destined to leave the cell are marked with a signal peptide Recognizing apparatus for the protein and channel SecB binds to the protein as it leave the ribosome- Prevents it from folding in the cytoplasm and delivers it to SecA- SecA associated with SecYEG: membrane channel complex- SecA facilitates the protein through SecYEG o Uses energy- Signal peptidase removes the signal peptide and the protein can assume its functional conformation Cell wall: peptidoglycano Resists damage from osmotic pressure, mechanical forces, shearingo Gives bacteria their characteristic shapeo Net-like structure composed of a glycan backbone made up of alternating molecules of NAG and NAM Connected by β-1,4-glycosidic bonds Peptide crosslink OR pentaglycine interbridge to join strings together o Bactoprenol holds the peptidoglycan to the plasma membrane o Lysozyme: enzyme that degrades peptidoglycan  The peptidoglycan cell wall is a common target of antibiotic medication  The cell wall is NOT fused to the plasma membraneo Periplasm 2.5: The Bacterial Cell Surface Flagella provide motilityo Polar Flagella: only at one end of the cell o Monotrichous: bacteria with a single flagellao Lophotrichous: bacteria with more than one flagella at one or both endso Peritrichous: bacteria with multiple flagella spread all over the cell surface The flagella is anchored to the cell envelope by the basal body Cells with flagella change directions via tumblingo Random reorientation of the cello CheA, CheB, CheY ATP is utilized in eukaryal flagella NOT prokaryotic flagella!  Chemotaxis: process of using chemical signals from the environment to direct motilityo Ensures all motors in peritrichous/lophotrichous cells all rote in the same directiono Chemoreceptors o Chemotactic attractants are often productively metabolized molecules Sugars, amino acids, etc Some flagellar filaments are kept within the periplasm—the entire cell spins in order to move Gliding Motility: some bacteria can slide smoothly over surfaces Twitching Motility: movement via short pili that can quickly retract o Not an intrinsic property of all pili  Pili: fibers sticking out from the cello Twitching motilityo Allow bacteria to attach to other surfaces/cells Pathogenic importance o Sex Pilus/Conjugal Pilus: used to connect bacteria cells for the transfer of plasmids  Capsule: thick layer of polysaccharides surrounding cells o Common in pathogenic strains because it can be used as a shield against host defense systems  Cannot be recognized as foreignChapter 3: Eukaryal Microbes3.1: The Morphology of Typical Eukaryal Cells Have membrane-bound organelles!o Compartmentalization Organelle Main FunctionNucleus Contains DNA, site of transcription Mitochondrion Energy productionChloroplast PhotosynthesisRough Endoplasmic Reticulum Site of translation and protein foldingGolgi Apparatus Modifies,