Prokaryotic Cell Structure

Transcription

1 Prokaryotic Cell Structure Chapter 3 Prokaryotes vs Eukaryotes DNA Prokaryotes Eukaryotes Organelles Size & Organization Kingdoms Where do viruses fit in? Acellular microorganisms Cannot reproduce outside of host cell No metabolism outside of host cell RNA or DNA never both Debate: living or non-living? 1

2 Prokaryotic Cell Shapes 3 Main Shapes Rods Cocci Spirals Spirochetes flexible Spirillum stiff Other Prokaryotic Shapes Coccobacillus Vibrio Pleomorphic Typical Prokaryotic Cell Fimbriae 2

3 Prokaryotic Cell Structures External structures Glycocalyx Flagella Pili / fimbriae Cell wall Gram-positive and Gram-negative Cell membrane Internal structures DNA, RNA, proteins Ribosomes Endospores Glycocalyx Made of polysaccharides, polypeptides, or both Two types Capsule Slime Layer Capsule Organized Firmly attached Functions: Protection Virulence factor 3

4 Capsule Slime layer Loosely attached Water soluble Functions: Protection Attachment Biofilms Flagella 4

5 Flagella Filament, hook, and basal body Filament made of flagellin Filament can rotate 360º Flagella arrangements Monotrichous Lophotrichous Flagella arrangements Amphitrichous Peritrichous 5

6 Function of Flagella Movement Rotate counterclockwise or clockwise Runs Tumbles Fimbriae Pili Hollow tubules Regular pili Conjugation pili 6

7 Fimbriae and Pili Bacterial Cell Walls Composed of peptidoglycan Polymer of N-acetylmuramic acid (NAM) and N-acetyl glucosamine (NAG) Attached by tetrapeptide crossbridges Types of bacterial cell walls Gram-positive Thick layer of peptidoglycan Gram-negative Thin layer of peptidoglycan plus an outer membrane 7

8 Gram-positive cell walls Gram-stain purple Thick layer of peptidoglycan Teichoic acids and lipoteichoic acids present Gram Stain (Gram-positive) Gram+ Genera Examples Bacillus Clostridium Streptococcus Staphylococcus Listeria Corynebacterium 8

9 Acid-fast cells Gram-positive cells Extra stuff in cell wall Mycolic acid Resistant Special staining procedure Acid fast stain Acid Fast Stain Acid-Fast Genera Examples Mycobacterium Nocardia 9

10 Gram-negative cell walls Gram-stain pink Thin layer of peptidoglycan Outer membrane Periplasmic space between inner & outer membranes Gram Stain (Gram-negative) Gram- Genera Examples Escherichia Salmonella Shigella Bordetella Neisseria Pseudomonas 10

11 Gram-negative outer membrane Also called cell envelope Phospholipid bilayer Lipopolysaccharides Porins Other proteins Lipopolysaccharide (LPS) Lipid + sugar Also known as endotoxin Lipid portion known as lipid A Released from dead/damaged cells May trigger fever, vasodilation, inflammation, shock, and disseminated intravascular coagulation (DIC) Can be released when antimicrobial drugs kill bacteria Sugar Lipid A Periplasmic space Between outer membrane and cell membrane Contains peptidoglycan and periplasm Periplasmic space 11

12 Bacteria without Cell Walls Mycoplasma Sterols in cell membrane Chlamydia Cell membrane + outer membrane No peptidoglycan Prokaryotic Cytoplasmic Membrane Functions of Cytoplasmic Membrane Selectively permeable Energy production Proton motive force (PMF) Photosynthesis photosynthetic prokaryotes 12

13 Internal Prokaryotic Structures Cytosol Inclusions Ribosomes Cytoskeleton Prokaryotic Ribosomes 70S 50S 30S S = Svedberg unit Endospores Formed by Bacillus and Clostridium Defensive strategy Metabolically inactive Germinate in favorable conditions 13

14 Endospore Formation Mother cell (keratin) Spore core (Dipicolinic acid + calcium) (peptidoglycan) Spore structure Outer Spore Coat (Exosporium) Spore Coat Outer membrane Cortex Inner membrane Spore Core Types of Endospores Central Terminal Subterminal 14

15 Endospore Stain Cell Division in Prokaryotes Asexual Binary fission is most common Cell Division Snapping division Palisades and V- hapes 15

16 Cell Division Budding Cell Arrangements Result from Plane of cell division Extent of separation of daughter cells Cocci multiple planes Bacilli single plane Coccus Bacillus Arrangements of Cocci 16

17 Arrangements of Bacilli What about Eukaryotes? Some have flagella Different structure than prokaryotes Similar to eukaryotic cilia Some have a glycocalyx Less organized than prokaryotes Some have cell walls Plants, fungi, algae Polysaccharides such as cellulose & chitin What about Eukaryotes? All have a cell membrane Phospholipid bilayer Capable of endo- and exocytosis All have ribosomes 80S ribosomes 40S + 60S 17

18 Eukaryotic organelles Membrane-bound organelles Nucleus Endoplasmic reticulum Golgi apparatus Lysosome Mitochondria Chloroplast Mitochondria & Chloroplasts Surrounded by phospholipid bilayer Contain a circular molecule of DNA Contain 70S ribosomes Cell Division in Eukaryotes Mitosis Meiosis 18

19 Last but not least... Nomenclature! Genus + species Escherichia coli E. coli 19