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Bacteria
MAJOR Characteristics
• Found EVERYWHERE – Ubiquitous!
– Dominant the biosphere
– Found in ALL habitats
MAJOR Characteristics
• Different from Eukaryotic cells
– Smaller and lack nucleus & membrane bound
organelles
– Eubacteria has cells walls made of
peptidoglycan
– One single, double stranded circular DNA
Function of the Cell Wall
**Remember cell walls are only found in
bacteria in the Eubacteria domain**
• Maintains cell shape and structure
• Protection for the cell
• Prevents cell from bursting
• Composed of peptidoglycan
• Different from the cell walls of plants
(cellulose) and fungi (chitin)
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Bacteria Structure
Unicellular or can aggregate into groups
Pili – used in conjugation for DNA
(plasmid) transfer
Different shapes:
1. Cocci or coccus (spherical or round)
2. Bacilli or bacillus (cylindrical or rod shaped)
3. Sprilla or spirillum (spiral, helical,
spirochete)
Guess the Correct Shape!
Cocci
Bacilli
Spirilla
Bacilli
Cocci
Motility in Bacteria
• Structures may be
attached to the cell wall
of bacteria to aid in
motility:
– Flagellum: rotates like a
propeller to move the cell
– Pili: helps bacteria attach
to one another in
conjugation (transfer
plasmid) or helps attach
to surfaces
Bacterial Reproduction &
Survival
• Bacteria does NOT undergo Mitosis or
Meiosis
• Binary Fission
– Asexual reproduction
– Bacteria doubles its DNA, grows 2x its size
then splits in half
– Produces identical
offspring
Bacterial Reproduction &
Survival
• Spore formation
– Adaptation that allows bacteria
to survive in adverse conditions
– A hard protective wall forms
around the bacterial DNA (this
allows the bacteria to survive
for centuries!!!)
– When favorable conditions, the
spore disappears and the
bacteria revives
Benefits of Bacteria
• Decomposers & Recyclers
– Puts essential nutrients back into the ground
• Food Processing
– Used to produce yogurt, cheese, butter, pickles,
sauerkraut
• Mutualistic Inhabitants of our Digestive
Tract
– Aid in digestion; produce vitamin K – we give them a
warm, moist environment
Benefits of Bacteria
• Nitrogen Fixation
– convert nitrogen to a useable form that
plants can use
• Genetics & Medicine
– Bacterial genes are used in genetic
engineering of food and medicine
– Ex: insulin production
Bacteria & Disease
•
Mode of Attack – bacteria can cause
disease in two general ways:
1.
Direct Attack
– Bacteria attacks cells and tissues directly
– Breaks down cells & tissues and uses their
materials
– Ex: strep, gonorrhea, pneumonia
2. Toxin Production
– Toxins are poisons released by some bacteria
– Bacteria can release exotoxins that circulate
around the body and cause disease
Other Examples of Bacterial Disease
Lyme disease, scarlet fever, rheumatic fever,
whooping cough, tetanus, gangrene, leprosy,
syphilis, diphtheria, anthrax, Bubonic plague,
cholera, tuberculosis, necrotizing fasciitis
(flesh eating bacteria), toxic shock syndrome
Other Pathogenic Microorganisms
Kingdom Protista
1. Giardia lamblia
– Animal-like protist found in
freshwater streams & lakes
– Causes Giardiasis; symptoms
include diarrhea & abdominal
cramps
2. Plasmodium
– Parasitic animal-like protist that
causes malaria
– Parasite enters human via mosquito
bites
– Symptoms include fever, chills,
exhaustion
Other Pathogenic Microorganisms
Kingdom Fungi
• Fungal disease include:
–
Athletes foot, ringworm, yeast infections
Other Pathogenic Microorganisms
Kingdom Animalia
• Hookworm, tapeworm, mites (lice),
Ascaris