Transcript Document
Bacterial Cell Structure Fig. 4.1 1 Cytoplasm • dense gelatinous solution of sugars, amino acids, & salts • 70-80% water • serves as solvent for materials used in all cell functions 2 Chromosome • single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell • DNA is tightly coiled around a protein, aggregated in a dense area called the nucleoid 3 DNA temperature melting Bacteria classification A +T G+C 4 plasmids • • • • • small circular, double-stranded DNA free or integrated into the chromosome duplicated and passed on to offspring not essential to bacterial growth & metabolism may encode antibiotic resistance, tolerance to toxic metals, enzymes & toxins • used in genetic engineering- readily manipulated & transferred from cell to cell 5 Ribosomes • made of 60% ribosomal RNA & 40% protein • consist of 2 subunits: large & small • procaryotic differ from eucaryotic ribosomes in size & number of proteins • site of protein synthesis • All cells have ribosomes. 6 7 Inclusions, granules • intracellular storage bodies • vary in size, number & content • bacterial cell can use them when environmental sources are depleted • Examples: glycogen, poly-b-hydroxybutyrate, gas vesicles for floating, sulfur and polyphosphate granules 8 9 Fig 4.10 10 Cytoplasmic membrane Protoplast Spheroplast L forms 11 4 groups based on cell wall composition 1. 2. 3. 4. Gram positive cells Gram negative cells Bacteria without cell walls Bacteria with chemically unique cell walls 12 Gram positive Gram negative 13 Gram positive Gram negative 14 Fig 4.16 Lipopolysaccharide n O-antigen Highly variable Core • Heptoses • Ketodeoxyoctonic acid Lipid A • Glucosamine disaccharide • Beta hydroxy fatty acids (Hydroxy myritic Acid) 15 LPS function Endotoxins Exotoxins 16 Gram positive wall 17 Gram negative cell wall 18 Peptidoglycan 19 Lipoteichoic acid Peptidoglycan-teichoic acid Cytoplasmic membrane Cytoplasm Porin Outer Membrane Lipopolysaccharide lipoprotein Inner (cytoplasmic) membrane Cytoplasm 20 Gram Positive Cell Envelope Lipoteichoic acid r Peptidoglycan-teichoic acid r r r r r r r r r Cytoplasmic membrane Cytoplasm 21 Glycocalyx • • Coating of molecules external to the cell wall, made of sugars and/or proteins 2 types 1. capsule - highly organized, tightly attached 2. slime layer - loosely organized and attached • Functions – – – attachment inhibits killing by white blood cells Receptor (K antigen) 22 2 Types of Glycocalyx 23 Biofilms 24 Flagella 25 Monotrichous lophotrichous amphitrichous 26 peritrichous Fig 4.2b 27 Fimbrae • Adhesion to other cells and surfaces 28 pili • rigid tubular structure made of pilin protein • found only in Gram negative cells • Functions – joins bacterial cells for DNA transfer (conjugation) – adhesion 29 Conjugation 30 endospores 31 Important components in endospore: Calcium Dipicolinic Acid 32 Sporulation The endospore 34 35 Major Taxonomic Groups of Bacteria • Gracilicutes – gram-negative cell walls, thin-skinned • Firmicutes – gram-positive cell walls, thick skinned • Tenericutes – lack a cell wall & are soft • Mendosicutes – archaea, primitive procaryotes with unusual cell walls & nutritional habits 36 Grwth in Bacteria • • • • Temperature Nutrients pH Osmotic pressure 37 Temperature • Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism • Maximum temperature – highest temperature that permits a microbe’s growth and metabolism • Optimum temperature – promotes the fastest rate of growth and metabolism 38 3 temperature adaptation groups 39 Bacterial Metabolism • Phototroph o Photoautotroph (Photolitotroph) o Photoheterotroph (Photoorganotroph) • Chemotroph o Chemoautotroph (Chemolitotroph o Chemoheterotroph (Chemoorganotroph) 40 Stages of metabolism in chemoheterotrophic bacteria • Digestion • Absorption (Passive and active transportation) • Preparation for oxidation • Oxidation 41 Oxygen requirements 42 43 Fermentation • Incomplete oxidation of glucose or other carbohydrates in the absence of oxygen • Uses organic compounds as terminal electron acceptors • Yields a small amount of ATP • Production of ethyl alcohol by yeasts acting on glucose • Formation of acid, gas & other products by the action of various bacteria on pyruvic acid 44 Fermentation 45 Binary division 46 Growth Curve Continuous Culture, Chemostat Chemostats are a means of keeping a culture in log phase indefinitely. Methods in bacterial identification 1. 2. 3. 4. 5. 6. Microscopic morphology Macroscopic morphology – colony appearance Physiological / biochemical characteristics Chemical analysis Serological analysis Genetic & molecular analysis • • • G + C base composition DNA analysis using genetic probes Nucleic acid sequencing & rRNA analysis 49 Bacterial Colonies • Standard Bacterial Count • Colony-Forming Units • Plaque-Forming Units •Spread Plate • Pour Plate • Soft-Agar Overlay Solid Medium 52 53