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PATHOGENS
BACTERIA, PROTISTS, FUNGI,
AND VIRUSES...
PROKARYOTAE; aka
Bacteria…
 Prokaryotic (no nucleus)
 Genetic code; one single circular strand of DNA
 Plasmids are DNA outside the chromosome
 No membrane bound organelles
 They do have ribosomes
 Cell wall made of an amino-sugar called
peptidoglycan
 Pili are hair like appendages on outside of the
bacteria; for attachment and reproduction
Structure…
Metabolism…
 Most are heterotrophs
 Feed off dead organic matter, symbiotic, and
parasitic
 Autotrophs; make their own food
 Photosynthetic
 Chemosynthetic
Respiration…
 Obligate aerobes; need oxygen
 Obligate anaerobes; oxygen kills them
 Facultative anaerobes; with or without
oxygen
REPRODUCTION
 Asexual = binary fission (mitosis)
 Sexual = conjugation; uses pili
 Can reproduce as quickly as 20 minutes
BACTERIA CAN EXCHANGE
GENETIC MATERIAL!!!
 Plasmid: giving a chunk of DNA
 Conjugation: swapping DNA via “pili”
Transfer of DNA…
 Conjugation
Classification by Shape
 Bacillis = Rod shaped
 Coccus = Spherical
 Spirillum = Spiral Shaped
SHAPES
 Coccus
 Spirillum
 Bacillus
Classified by Organization…
Strep
Staph
Diplo
Classified by Cell Wall
Structure…
 Gram Positive = Two layer membrane
 Thick peptidoglycan cell wall
 Plasma membrane under the cell wall
 Purple
 Gram Negative = Three layer membrane
 Thin peptidogycan cell wall
 Lipid membrane > petidoglycan cell wall > plasma
membrane
 Pink
Gram Positive vs. Gram
Negative…
BACTERIA: THE GOOD,
THE BAD, THE UGLY…
 Bacteria can be pathogens…
 Anthrax, tetanus, scarlet fever, strep throat…
 Bacteria can be useful…
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Nitrogen fixing; helps plants survive
Degrades wastes
Alternative energy sources
Produce plastics
Source of possible medicinal drugs
VIRUSES…
Characteristics…
 Nucleic acid core; either DNA or RNA but
never both
 Capsid; protein coat surrounding the
nucleic acid core
 No ribosomes or organelles of any kind
 No metabolism (doesn’t eat or breath)
 Host cell reproduces the virus
Structure…
Infection cycle…
 Lytic Cycle;
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Attachment of virus on cell membrane
Injection of DNA or RNA into cytoplasm
Cell replicates virus RNA or DNA
Assembly of viral structure (capsid & DNA)
Release; cell bursts and viruses escape
Lytic Cycle
Other ways…
 Lysogenic Cycle
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Virus attaches
Viral DNA is injected into cell
Viral DNA is incorporated into host DNA
Cell divides and daughter cells contain the
viral DNA; process continues
 May go into lytic cycle (scary)
Lysogenic cycle…
Retro-viruses
 Retrovirus is a virus that contains only
RNA.
 Virus has its own reverse transcriptase,
an enzyme that makes DNA from RNA.
 New DNA molecule is incorporated into
the hosts DNA.
 Example: HIV
HIV
HIV Anatomy
HIV Genes
HIV Gene Expression
HIV Infection
 Lytic cycle
 Viral load usually large enough at 6
months after infection to test positive on
ELISA or viral load tests
 Contracted through blood transfusions,
mothers milk, unprotected sexual
contact, dirty needles…affects ALL ages,
races, and genders!
Retrovirus…
HIV Therapies
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Docking Proteins (CD-4)
Reverse transcriptase (block action)
Proteases block building of Virus Proteins
Integrases block integration of vDNA into host
DNA
 AZT prematurely ends viral DNA replication
 Natural Immunities (CD-4 altered or super
immunity)
 Other? (vaccine?)
Viruses: The Good, The
Bad, The Ugly…
 Viruses can be pathogens…
 HIV, Influenza, Herpes, Chicken Pox…
 Linked to cancer: Mono, Herpes, Hepatitis
 Germ warfare: small pox
 Viruses can be useful…
 Can be used to inject useful genetic codes
 Example; bacteria produce insulin
 Vaccines; polio, measles, hepatitis…
Protists…
PROTISTA (protozoans)
 Eukaryote (has nucleus and membrane
bound organelles)
 Single-celled
 Two major categories
 Protists
 Blue-green algae
Are they plants?
Animals?? Fungi???
 Some protists are plant like!
 Blue-green algae are photosynthetic and are the
basis for aquatic food chains
 Protists are animal like!
 Carnivorous (ex. paramecium)
 Parasitic (ex. Plasmodium)
 Protists are like Fungi too!
 Slime molds digest decaying logs and leaves
Protists: The good, the
bad, the ugly…
 Good: Form the basis of food chains
 Ex. Algae
 Bad: Can cause crop damage
 Ex. Slime molds
 Ugly: Cause serious disease
 Ex. Malaria and Giardia
Giardia life cycle…
Giardia…
Malaria life cycle…
Malaria…
Fungi…
Fungi are biologically
“weird”…
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May be one simple cell or millions.
Have cell walls but are made of sugar.
Organelles can move from one cell to another
They can’t move nor can they make their own
food.
 They digest food outside themselves then
absorb it through their cell walls.
 Can reproduce sexually or asexually
Structure of Multicellular
Fungi…
 Cell Wall: Made of chitin, a complex
polysaccharide (sugar).
 Hyphae: Threadlike filaments that develop from
fugal spores.
 Mycelium: Network of hyphae.
 Anchor fungi, invade host cell, and reproductive
structures
 Septa: divide hyphae into individual cells
 Porous, cytoplasm and organelles can move freely.
Hyphae
Mycelium
The Septa…
Reproduction…
 Fragmentation: hyphae are severed and
grow into new mycelium
 Ex. Shoveling in a garden
 Budding: Single celled fungi splits in two
 Ex. Yeast
 Spores: hyphae grow away from fungi
and produce a case containing spores
 Ex. Mushrooms
Classified by eating habits
 Saprophytes: Feed off dead plants and
animals.
 Ex. Bread mold, mushrooms, bracket fungi.
 Symbionts: Live with other organisms,
mutual benefit.
 Ex. Lichen (fungi outside, algae inside)
 Parasites: Live off live organisms
 Ex. Cause of Athletes Foot, Ringworm, etc.
Fungi; The good, the bad,
the ugly…
 Good: decompose organic material,
make antibiotics (penicillin).
 Bad: destroys food, wood products,
shower curtains, etc…
 Ugly: Pathogenic (yeast infection,
athletes foot, ring worm, etc.)
Ring worm…
Athletes foot…
Questions???