Anatomy and Physiology of Prokaryotic Cells Microbiology Mrs. Hieneman

Bacterial Shape and Arrangement

Streptococcus chain

Sarcinae cube

Staphylococcus aureus cluster

Spiral-shaped bacterial cell

Prokaryotic Cell Structure

Cytoplasmic Membrane Surrounds cytoplasm and defines boundaries of cell Acts as barrier, but also functions as an effective and highly discriminating conduit between cell and surroundings Made up of phospholipid bilayer

Figure 4.14c

Phospholipid

Figure 4.14b

Movement of Molecules through Cytoplasmic Membrane Several ways for molecules to move through membrane 1.Simple Diffusion 2.Osmosis 3.Facilitated Diffusion 4.Active Transport

Simple Diffusion Does not require expenditure of energy Process by which some molecules move freely into and out of the cell Small molecules such as carbon dioxide and oxygen

Microbiology: An Introduction, 9e by Tortora, Funke, Case Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 4.18: The principle of osmosis - Overview. (a) At beginning of osmotic pressure experiment (b) At equilibrium (c) Isotonic solution — no net movement of water (d) Hypotonic solution — water moves into the cell and may cause the cell to burst if the wall is weak or damaged (osmotic lysis) (e) Hypertonic solution — water moves out of the cell, causing its cytoplasm to shrink (plasmolysis) Glass tube Rubber stopper Rubber band Sucrose molecule Water molecule Cellophane sack Cytoplasm SolutePlasma membrane Cell wall Water

Transport Proteins Transport proteins (or transporters) responsible for: Facilitated Diffusion Active Transport

Microbiology: An Introduction, 9e by Tortora, Funke, Case Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 4.17: Facilitated diffusion. Transported substance Transporter protein Outside Inside Glucose Plasma membrane

Cell Wall Composed of peptidoglycan Comprised of alternating NAG and NAM molecules Attached to each NAM is four amino acid peptide: tetrapeptide

Categories of Bacteria Two Major Categories: Difference due to difference in chemical structures of their cell walls –Gram positive: stains purple –Gram negative: stains red

Gram + Cell Wall Thick Layer of Peptidoglycan Contains techoic acid: chains of ribitol- phosphate or glycerol-phosphate to which sugars or alanine attached Techoic Acid sticks out above the peptidoglycan layer

Gram – Cell Wall More complex than Gram + cell wall Thin layer of peptidoglycan –Sandwiched between the cytoplasmic membrane and outer membrane Outside of peptidoglycan is outer membrane

Figure 4.13c

Outer Membrane Unlike any other membrane in nature A lipid bilayer with the outside layer made of lipopolysaccharides instead of phospholipids Also called LPS Contains Porins

Periplasm - Region between cytoplasmic membrane and the outer membrane - Gel-like fluid Filled with secreted proteins and enzymes

External Structures Glycocallyx Flagella Axial Filaments Fimbrae and Pili

Glycocallyx Gel-like structure –Functions in protection and attachment –Two types- capsule and slime layer –Involved in attachment, enabling bacteria to stick to teeth, rocks –Enables bacteria to brow as biofilm

Capsule in Acinetobacter species by gram negative staining

Filamentous Protein Appendages Anchored in membrane and protrude from surface Flagella: long structure responsible for motility Fimbrae and Pili: shorter, responsible for attachment

Four types of bacteria with flagella Montrichious- one flagella Amphitrichous- flagella at both ends Lophitrichous- many flagella at the end of the cell Peritrichous- flagella all over entire cell

Figure Overview

Axial Filament Present in Spirochetes Attach at end of cell, spiral around, underneath an outer sheath Move like a corkscrew

Figure Overview

Fimbrae and Pili Shorter and surround the cell Similar structural theme to filament of flagella Fimbrae- enable cell to adhere to surfaces, including other cells Pili- join bacterial cells in preparation for the transfer of DNA from one cell to another

Internal Structures of Prokaryotic Cells

Cytoplasm Substance of cell inside the cytoplasmic membrane About 80% water Thick, aqueous, semitransparent, elastic

Chromosome Found within a central location known as nucleoid Single, circular, double stranded Consists of all DNA required by cell

Plasmids Some bacteria contain plasmids- small circular double-stranded DNA Typically cell does not require genetic information carried on plasmid However, it may be advantageous

Ribosomes Site of protein synthesis Relative size and density of ribosomes and their subunits expressed as distinct unit (S) Two units of prokaryotic ribosomes: 50S + 30S= 70S Eukaryotic ribosomes: 80S

Microbiology: An Introduction, 9e by Tortora, Funke, Case Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 4.19: The prokaryotic ribosome. (a) Small subunit(b) Large subunit(c) 50S 30S (c) Complete 70S ribosome

Inclusions Store excess nutrients Examples: Polysaccharide granules- glycogen and starch Lipid inclusions Metachromatic granules- inorganic phosphate that can be used to synthesize ATP

Endospores Occurs in members of genera Bacillus and Clostridium Dormant cell produced by a process called Sporulation Germination- when they exit the dormant state and then become a vegetative cell Several species of endospore formers can cause disease