Prokaryotic Anatomy II: Cell Wall Structure, Sporulation Nestor T. Hilvano, M.D., M.P.H.

Learning Objectives You should be able to: 1.Describe the types of reproduction of prokaryotes. 2.Differentiate the cell walls of Gram-positive and Gram- negative prokaryotes in terms of structure and staining. 3.Describe the clinical implications of the structure of the Gram-negative cell wall. 4.Differentiate the cell walls of acid-fast bacteria with typical Gram-positive cell walls. 5.Describe types of archaeal cell walls with one another and with bacterial cell walls. 6.Diagram a phospholipid bilayer and explain its significance in reference to a cytoplasmic membrane. 7.Compare the passive and active processes by which materials cross the membrane. 8.Describe the formation and function of bacterial endospores.

Reproduction of Prokaryotes Binary fission- doubling cell # Snapping division- modification of binary Budding- outgrowth of parent cell

Prokaryotic Cell Wall Peptidoglycan, composed of NAG (N- acetylglucosamine) and NAM (N- acetylmuramic acid) chain linked to other chains by tetrapeptides

Gram Positive Cell Wall Thick layer cell wall (rigid peptidoglycan) Contain teichoic acids - anchor wall to CM - negative charge Wall retain crystal violet dye.

Gram Negative Cell Wall Thin layer cell wall Outer membrane of lipopolysaccharide (Lipid A) – protects bacteria from host’s immune system, protect bacteria from antibiotics Importance of lipid A = toxins (endotoxins); lead to coagulation (DIC- dessiminated intravascular coagulation), internal hemorrhage, inflammation, hypotension; heat stable Periplasmic space

Comparison of Exotoxin and Endotoxin Exotoxin: Produced by both Gram positive and Gram negative bacteria Released from cell Protein Heat labile Specific receptors on host target cells Specific effects in host Toxoids can be made by treating with formalin Endotoxin: Produced only by Gram negative bacteria Integral part of cell wall Lipid A of lipopolysaccharide Heat stable Diverse range of host cells and systems affected Diverse range of effects in host Toxoids cannot be made

Acid Fast Cell Wall Stain poorly w/ gram stain (weakly gram +) Thick lipid layer (waxy lipid, mycolic acid) Peptidoglycan thin Impermeable to most other stains acid fast cell wall is durable that the carbolfuschin must be driven into the cells with heat Grow slowly (lipid layer inhibits diffusion of nutrients)

Archaeal Cell Wall Lacks peptidoglycan; wall contain polysaccharides and proteins Gram + archaea – thick wall; stain purple Gram – archaea – have protein layer covering the wall; stain pink Archaea – found in deep sea vents (sulfur, over boiling point); no diseases

Protoplasmic Cell Membrane Phospholipid bilayer Selectively permeable Functions: diffusion, facilitated diffusion, osmosis, active transport

Endospores Dormant form (stable); formed when nutrients are limited; can survive under harsh conditions - resistant to drying, heat, radiation, and lethal chemicals Resistant to treatment Bacillus anthracis Clostridium perfringens Clostridium tetani

Sporulation Sporulation- the process of endospore formation; takes 8-10 hrs. A single bacterial (vegetative) cell transform into one endospore when nutrients are limited, which then germinates to grow into one vegetative cell. Endospore constitute a defensive strategy against hostile conditions

Homework 1.Define terms: phospholipid bilayer, peptidoglycan, lipid A, cell wall, group translocation, cell (plasma) membrane, and sporulation. 2.Differentiate the cell wall of gram +, gram -, and acid fast organisms. 3.Discuss why a person suffers a more severe condition as to symptoms with gram negative bacterial infection during treatment? 4.Explain why anthrax disease is difficult to control and discuss if steaming mail suspected of anthrax will provide protection?