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