Z333 Lecture

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Chapter 19 The Hidden World of Microbes
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Chapter 19 Microbes
Virus Microscopic particles consisting of a
molecule of genetic material (e.g. DNA)
surrounded by a protein coat

• Can only reproduce inside an infected cell
  (host cell)

• Not alive
• Hijacks machinery of host cell

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Chapter 19 Microbes
How Viruses Replicate
1) Penetration Virus enters cell 2)
Replication Viral genetic material (DNA)
copied 3) Transcription Viral genetic material
(DNA) makes instructions (RNA) 4) Protein
Synthesis Instructions (RNA) used to make viral
proteins 5) Viral Assembly Viral genetic
material surrounded by viral proteins 6)
Release Viruses emerge from host cell
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Chapter 19 Microbes
Viruses specialized to attack specific cells

• Common cold Respiratory tract membranes
• Rabies Nervous system
• Herpes Mucosal membranes (mouth / genitals)
• HIV Immune system cells (T-cells)

Viruses are difficult to treat

• Antiviral agents often kill host cells
• along with virus

• Viruses mutate rapidly

Can not be treated with antibiotics
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Chapter 19 Microbes
Other Virus-like Agents

• 1) Viroids Particles consisting of
  short-stranded RNA (no protein)
• Attack plants
• 2) Prions Particles consisting of only protein
  (irregular form)
• Infects nervous tissue (Mad cow disease)

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Chapter 19 Microbes
Features of Prokaryotic Cells (no true nucleus)

• External features
• Cell walls
• Flagellum (movement)
• Pili (attachment and / or genetic exchange)
• Capsule / Slime Layer (host attachment)

• Internal features
• Plasma membrane
• Cytoplasm (w/ ribosomes)

• Nucleoid Central region of coiled
• DNA

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Chapter 19 Microbes
Bacteria Archaea (Prokaryotic Domains)

• Vary in basic structural / biochemical
  features (e.g. cell wall)
• Bacterial cell wall peptidoglycans (Gram
  stain / -)
• Archaea cell wall no peptidoglycans

Prokaryotes are difficult to classify...
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Chapter 19 Microbes
Prokaryotes Exhibit a Variety of Shapes and
Structures
Shapes
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Chapter 19 Microbes
Prokaryotes Exhibit a Variety of Shapes and
Structures
Structures

• Chemotaxis (chemical) / Phototaxis (light) /
  Magnetotaxis (magnetic field)

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Chapter 19 Microbes
Prokaryote Reproduction

• Ideal conditions - may divide every 20 minutes

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Chapter 19 Microbes
Prokaryotes Exhibit Diverse Metabolisms
1) Photosynthetic (produce food via sun - e.g.
cyanobacteria) 2) Chemosynthetic (produce food
via chemical reactions)

• Anaerobes Do not need oxygen to extract
  energy (e.g. tetanus)

Prokaryotes Enter Symbiotic Relationships
2) Breakdown Cellulose (animal (e.g. ruminants)
- bacteria symbiosis) 3) Synthesize Vitamins
(animal (e.g. human) - bacteria symbiosis)
Prokaryotes Function as Decomposers
(biodegradable)
Prokaryotes Cause Diseases (pathogens -
synthesize toxic chemicals)

• Tetanus / Botulism - Genus Clostridium
• Plague (Black death) - Yersinia pestis
• Pneumonia / Necrotizing fasciitis - Genus
  Streptococcus

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Chapter 19 Microbes
Features of Eukaryotic Cells

• Large and complex in structure (e.g. our cells)

• Internal Features
• Plasma membrane
• Cytoplasm (w/ ribosomes)
• Membrane-bound organelles

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Chapter 19 Microbes
Protista (Eukaryotic Domain)
Protist Reproduction
Modes of Nutrition
1) Autotrophs (plant-like) 2) Ingestive
Heterotrophs (animal-like) 3) Absorptive
Hetertrophs (fungi-like)
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Chapter 19 Microbes
Plant-like Protists Algae

• Widely dispersed in oceans / lakes

• Phytoplankton Single-celled algae
• 70 of Earths photosynthesis

• Named for 2 flagella present
• Found mainly in ocean (red tide)

• Protective shells of silica (glass)
• Pastures of the sea
• Remains form diatomaceous earth

• Moves via single flagellum
• Found mainly in fresh water
• Has eyespot sensitive to light

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Chapter 19 Microbes
Plant-like Protists Algae

• Widely dispersed in oceans / lakes

Seaweed Multicellular algae

• Color derived from red pigments
• Primarily inhabit clear tropical oceans
• Contribute to formation of coral reefs

• Color derived from brown-yellow pigments
• Primarily inhabit temperate (cool) oceans
• Form undersea forests (e.g. kelp forests)

• Include single / multi-cellular forms
• Primarily inhabit freshwater
• May have given rise to land plants

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Chapter 19 Microbes
Fungus-like Protists Water / Slime Molds

• Absorb nutrients from soil / water
• Decompose organic matter

• Inhabit water / damp soil
• Profound human economic impact
• Potato blight / downy mildew (grapes)

• Large cytoplasmic mass (plasmodium)
• Engulfs bacteria / decay as it oozes
• Brightly colored (yellows / oranges)

• Live as independent amoeboid cells

• Form multi-cellular reproductive structure
• (Pseudoplasmodium)

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Chapter 19 Microbes
Animal-like Protists Protozoa

• Ingest other organisms for nutrients

• Classified by locomotion method

• Move via flagella
• Free-living / symbiotic relationships
• Giardia (campers curse)

2) Sarcodines Move via pseudopods
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Chapter 19 Microbes
Animal-like Protists Protozoa

• Ingest other organisms for nutrients

• Classified by locomotion method

• No means of locomotion (parasitic)
• Form infectious spores
• Malaria (Plasmodium)

• Move via cilia (Hair-like outgrowths)

• Inhabit freshwater / marine environments

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Chapter 18 Systematics
The Prokaryotes
1) Bacteria
2) Archaea
Domains
3) Eukarya
A) Protists (single-celled eukaryotes)
B) Fungi (multicellular absorptive digestion)
Kingdoms
C) Plantae (Multicellular photosynthsis)
D) Animalia (Multicellular ingestion)