Chapter 4: A Survey of Prokaryotic Cells and Microorganisms PDF

Chapter 4 A Survey of Prokaryotic Cells and Microorganisms Talaro’s Foundations in Microbiology Twelfth Edition Barry Chess © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw...

Chapter 4 A Survey of Prokaryotic Cells and Microorganisms Talaro’s Foundations in Microbiology Twelfth Edition Barry Chess © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Characteristics of Life Reproduction and heredity – genome composed of DNA packed in chromosomes; produce offspring sexually or asexually Growth and development Metabolism – chemical and physical life processes Movement and/or irritability – respond to internal/external stimuli; self-propulsion of many organisms Cell support, protection, and storage mechanisms – cell walls, vacuoles, granules and inclusions Transport of nutrients and waste Cells exhibit these characterist Traditional Definitions of Cell Types Eukaryotic cells: animals, plants, fungi, and protists Contain membrane-bound organelles that compartmentalize the cytoplasm and perform specific functions Contain double-membrane bound nucleus with DNA chromosomes Prokaryotic (?) cells: bacteria and archaea No nucleus or other membrane-bound organelles * Please note that cells do not look like this!!!!! Is the term prokaryote valid? hylogenetic tree hree (current) domains of life Bacteria (Eubacteria) LUCA Viruses? Eukarya Archaea Focus on Bacterial Cells  Size, Shape, and Arrangement Size – varies but typically… S/V ratio Shape cocci and rods most common Others Arrangement determined by plane of division WHY?  Size Bacteria typically here Limits of light microscopy  Size smallest – 0.3 μm (Mycoplasma) average rod – 1.1 - 1.5 x 2 – 6 μm (E. coli) very large – 600 x 80 μm Epulopiscium fishelsoni 8  Size – Shape Relationship important for nutrient uptake surface to volume ratio (S/V) small size may be protective mechanism from predation S/V ratio of other shapes? 9  Bacterial Shapes Vary in shape but typically described by one of three basic shapes: Coccus – spherical Bacillus – rod Coccobacillus – very short and plump Vibrio – gently curved Spirillum – helical, comma, twisted rod, Spirochete – spring-like (flexible) Shape  All shapes and sizes found in Archaea Squares Triangles Stars Pleomorphic Variation in cell shape and size within a single species Again the shape is a valuable tool for identification Bacterial Arrangements Arrangement of cells is dependent on pattern of division and how cells remain attached after division: Cocci: Singles Diplococci – in pairs Tetrads – groups of four Irregular clusters Chains Cubical packets (sarcina) Bacilli: Diplobacilli Chains Palisades  Arrangements Cocci (s., coccus) – spheres diplococci (s., diplococcus) – pairs streptococci – chains staphylococci – grape-like clusters tetrads – 4 cocci in a square sarcinae – cubic configuration of 8 cocci  Arrangements Bacilli: Diplobacilli Chains Palisades  Structure/Function of Typical Bacterial Cell Compare contrast with what you have learned about typical eukaryotic cell – what’s the same/differe 3 “zones”  Structure of a Bacterial Cell Cell Envelope* – Plasma membrane and the cell wall External Structures Internal Structures External Structures Cell envelope (cell wall) Internal Structures  Structure of a Bacterial Cell Cell Envelope* – Plasma membrane and the cell wall External Structures Internal Structures External Structures Cell envelope (cell wall) Internal Structures Plasma membrane FUNCTIONS Look Ahead - Methods for Uptake of Nutrients Microbes can only take in dissolved particles across a selectively permeable membrane. Some nutrients enter by passive diffusion. Microorganisms use transport mechanisms. Passive diffusion. Facilitated diffusion. Primary and secondary active transport. Group translocation.  Bacterial Cell Wall The peptidoglycan of a cell wall is a huge, three- dimensional latticework that is actually one giant molecule to surround and support the cell. Structure/Function Dynamic Structure Evidence for Osmotic Protection Function of Cell Wall Lysozyme breaks bond between NAG and NAM. Penicillin inhibits peptidoglycan synthesis. If cells are treated with either of the above, they lyse in a hypotonic solution. Two basic organizations – not the only ones, just most common. Gram stain differentiates Draw them out  Gram-Positive Cell Walls Composed primarily of peptidoglycan May also contain teichoic acids (negatively charged) and lipoteichoic acids help maintain cell envelope protect from environmental substances may bind to host cells some gram-positive bacteria have layer of proteins on surface of 20-80 nm thick peptidoglycan peptidoglycan Some cells have a periplasmic space, between the cell membrane and cell wall hat is an Acid Fast cell wall?  Gram-Negative Periplasmic space differs from that in Cell Walls Gram-positive cells. More complex than Gram- May constitute 20 to positive 40% of cell volume. Consist of a thin layer of Many enzymes present in peptidoglycan surrounded by an periplasm. outer membrane Hydrolytic enzymes, Outer membrane composed of transport proteins and other proteins. lipids, lipoproteins, and lipopolysaccharide (LPS) No teichoic acids Lipopolysaccharide (LPS) Consists of three parts Contributes to lipid A negative charge on core polysaccharide cell surface. O side chain (O antigen) Helps stabilize outer Lipid A embedded in membrane structure outer membrane Creates a Core polysaccharide, O permeability barrier side chain extend out Host defense from the cell protection. Acts as an endotoxin Know your enemy Structures of Gram-Positive and Gram-Negative Bacterial Cell Walls Access the text alternative for slide images.  The Gram Stain Differential stain that distinguishes cells with a gram- positive cell wall from those with a gram-negative cell wall  Gram-positive - retain crystal violet and stain purple  Gram-negative - lose crystal violet and stain red from safranin counterstain Important basis of bacterial classification and identification Practical aid in diagnosing infection and guiding drug treatment Wikipedia.com  Size, Shape, Arrangement, and Gram-reaction All quickly assessed with a Gram-stain and very informative for diagnosis and treatment Nontypical Cell Walls Some bacterial groups lack typical cell wall structure, i.e., Mycobacterium and Nocardia  Gram-positive cell wall structure with lipid mycolic acid (cord factor)  Pathogenicity and high degree of resistance to certain chemicals and dyes  Basis for acid-fast stain used for diagnosis of infections caused by these microorganisms Some have no cell wall, i.e., Mycoplasma  Cell wall is stabilized by sterols  Pleomorphic  Structure of a Bacterial Cell Cell Envelope* – Plasma membrane and the cell wall External Structures Internal Structures External Structures Cell envelope (cell wall) Internal Structures  External structures Glycocalyx Flagella Fimbrae & Pili S-Layers 33 Glycocalyx Coating of molecules external to the cell wall, made of sugars and/or proteins Two types:  Slime layer - loosely organized and attached  Capsule - highly organized, tightly attached Functions of the Glycocalyx Protect cells from dehydration and nutrient loss Inhibit killing by white blood cells by phagocytosis, contributing to pathogenicity Attachment - formation of biofilms Flagella 3 parts: Filament – long, thin, helical structure composed of protein flagellin Hook – curved sheath Basal body – stack of rings firmly anchored in cell wall  Flagella Rotates 360o and functions in enabling motility of cell through environment No rudder? Guide bacteria in a direction in response to external stimulus: Chemical stimuli – chemotaxis; positive and negative Light stimuli – phototaxis Signal sets flagella into motion clockwise or counterclockwise: Counterclockwise – results in smooth linear direction – run Clockwise – tumbles Flagellar Arrangements Monotrichous – single flagellum at one end Lophotrichous – small bunches emerging from the same site Amphitrichous – flagella at both ends of cell Peritrichous – flagella dispersed over surface of cell Fimbriae and Pili Fimbriae Think attachment Fine, proteinaceous, hairlike bristles emerging from the cell surface Function in adhesion to other cells and surfaces Pili Rigid tubular structure made of pilin protein Found only in gram-negative cells Function to join bacterial cells for partial DNA transfer called conjugation  Structure of a Bacterial Cell Cell Envelope* – Plasma membrane and the cell wall External Structures Internal Structures External Structures Cell envelope (cell wall) Internal Structures  Internal Structures ytoplasm (next slide) ibosomes (following slide) nclusions Nucleoid ytoskeleton ndospores  Cytoplasm Cell cytoplasm: Dense gelatinous solution of sugars, amino acids, and salts 70-80% water Serves as solvent for materials used in all cell function Nucleoid Chromosome Single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell Plasmids Free small circular, double-stranded DNA Not essential to bacterial growth and metabolism Used in genetic engineering - readily manipulated and transferred from cell to cell Bacterial Ribosome Ribosomes Made of 60% ribosomal RNA and 40% protein Consist of two subunits: large and small Prokaryotic differ from eukaryotic ribosomes in size and number of proteins Site of protein synthesis Found in all cells Bacteri Eukaryot a es Total 70S 80S 50S Small Subun 30S 40S it Large 70S Subun 50S 60S 30S it  Bacterial Internal Structures Inclusions and granules Intracellular storage bodies Vary in size, number, and content Bacterial cell can use them when environmental sources are depleted  Cytoskeleton Cytoskeleton Many bacteria possess an internal network of protein polymers that is closely associated with the cell wall  Endospores Dehydrated, metabolically inactive Thick coat Longevity verges on immortality, 250 million years Resistant to ordinary cleaning methods and boiling Pressurized steam at 120oC for 20-30 minutes will destroy Endospores Inert, resting, cells produced by some G+ genera: Clostridium, Bacillus, and Sporosarcina Have a 2-phase life cycle: Vegetative cell – metabolically active and growing Endospore – when exposed to adverse environmental conditions; capable of high resistance and very long-term survival Sporulation - formation of endospores Hardiest of all life forms Withstands extremes in heat, drying, freezing, radiation, and chemicals Not a means of reproduction Germination - return to vegetative growth Sporulation Cycle  Bacterial Cells dvantages and disadvantages of structures Taxonomy Taxonomy “It is far more important to have a taxonomic system that reflects our current knowledge than to have a system that never changes.” Jacquelyn Black Things are a changin’ Phylogenetic tree Bacteria (Eubacteria) Three current domains of life LUCA How did we build this tree? Eukarya Archaea  Information in Biology Genotype DNA Ribosomal Genes RNA Environment Highly conserved Protein Phenotype  Taxonomy Definition – System for organizing, classifying and naming organisms Purpose - Identification – define systematic and specific criteria to determine identity of an organism Nomenclature– system of naming organisms that supports communication and reflects their classification Classification - Group related organisms that reflect and describe evolutionary relationships  What Information Do We Use? Replication Genotype DNA Transcription RNA Environment Translation Protein PheneticPhenotype  What Information Do We Use? Phyletic - Phylogenetic Replication Genotype DNA Transcription RNA Environment Translation Protein Phenotype Define a Bacterial species? 97% identity at rRNA gene? 70% ANI Apply these “rules” to big biology?  Taxonomy Definition – System for organizing, classifying and naming organisms Purpose - Identification – define systematic and specific criteria to determine identity of an organism Nomenclature– system of naming organisms that supports communication and reflects their classification Classification - Group related organisms that reflect and describe evolutionary relationships