Unit 6--Microbiology Chapter 19 Bacteria & Viruses

Early microbiologists Louis Pasteur Concluded that microorganisms cannot spontaneously generate Showed world how heat kills microorganisms (pasteurization)

Microscopic organisms Viruses = not living, but studied as micro- Bacteria = divided into 2 kingdoms; most are helpful, harmful tracked by CDC & WHO Protists = most diverse; show fungal, plant or animal characteristics Fungus = decomposers; most are helpful, some are disease-causing

(Eubacteria & Archaebacteria)

Bacterial characteristics: Prokaryotic (no nuclear membrane) –Ribosomes only –Pili = for attachment –Capsule = outermost layer for extra protection Unicellular (some colonial) Varied metabolism & nutritional types Often flagellated May contain endospores… to survive harsh conditions Binary fission to reproduce

Endospore formation

See page 465

Practice

Bacterial shapes Bacillus = rod-shaped (ex: Lactobacillus) Coccus = sphere (ex: Streptococcus) Spirillum = coiled (ex: Spirochete) Strepto- (chains) Staphylo- (clusters)

Blue = causes Lyme disease Black = causes syphilis

Metabolic diversity Obligate aerobes = –Must have oxygen to grow normally Facultative aerobes = –Prefers oxygen, but not necessary Facultative anaerobes = –Prefers no oxygen, but not necessary Obligate anaerobes = –May not have oxygen to grow normally

Nutritional diversity Autotrophs: –Photosynthetic = Cyanobacteria –Chemosynthetic = bacteria in deep ocean vents use sulfur instead of light for energy Heterotrophs: –Saprobes = decomposers feed on dead organic matter (nitrogen-fixing bacteria) –Parasitic = feed on living host (pathogenic)

Chemosynthetic bacteria in deep sea vents Photosynthetic Cyanobacteria in fresh-water ponds or streams

Binary fission Cell Replication (cloning) for prokaryotic cell Much simpler than mitosis (like cytokinesis without the 4 other stages)

Micro lab techniques How to study microorganisms safely & properly: How clean are you & the objects around you? Microorganisms are capable of spreading through many modes:

1) Direct Contact: 2) Air: 3) Fomites: (inanimate objects)

Gram-staining: Bacteria cell walls differ from plant cell walls which are made of cellulose Bacteria cell walls are made of peptidoglycan Bacteria have either thick or thin peptidoglycan cell walls Bacteria are classified as Gram positive (thick) or negative (thin cell walls)

See page 463

Staining techniques: Step 1 = smear thin layer of sample on slide. Step 2 = flame quickly to fix (stick) to slide. Step 3 = add Crystal Violet stain which adheres to peptidoglycan. Step 4 = add iodine to fix Crystal Violet. Step 5 = add alcohol to remove unfixed C.V. Step 6 = add Safranin O (a pink stain) to stain cell membrane. **Gram+ is purple and Gram- is pink.

negative