Bacteria

I. General Characteristics

A. Single-celled; no nucleus or complex organelles

What do we call this type of organism?

B. Earliest known life formsC. Smallest and simplest living

organismsD. Size 20 - 200 microns in

diameter and 50 – 1,000 microns long

E. Few hundred genes

Needle Tip

II. Bacterial StructureA. All bacteria have an outer cell wall

made out of glycoproteins or lipoprotein

II. Bacterial Structure (cont)

B. Some bacteria have a sticky envelope around the cell wall called a capsule or slime layer

II. Bacterial Structure (cont)C. Very simple internal organization 1) Cytoplasm with very few organelles 2) Nucleoid region (loosely coiled DNA)

1. Cell membrane

4. Cytoplasm

3. Nucleoid6. Cell wall

2. Ribosome

5. Pili (short flagella)

III. ClassificationA. Bacteria are placed into two

major kingdoms:1. Kingdom Archaebacteria - oldest

bacteria, found in harsh environments

2. Kingdom Eubacteria -True bacteria, the largest group.

Bacteria Overview Movie

B. Grouped according to their shape and arrangement:

1)Coccus (i) = Spherical shaped cellsa) single cocci

b) diplococci (pairs)

c) Streptococci (chains)

d) Staphylococci (clusters)

III. Classification (cont)Staphylococci (clusters)

III. Classification (cont)2) Bacillus (i) = Rod shaped cells

a) single bacilli

b) Diplobacilli

c) Streptobacilli

III.III. Classification (cont)Classification (cont)

StreptobacilliStreptobacilli

3. Spirillium = spiral shaped

III.III. Classification (cont)Classification (cont)

III.III. Classification (cont)Classification (cont)

C. Bacteria can also be grouped according to their living arrangements1. Saprophytes - live on dead things

(decomposers)2. Symbiotes - Two organisms living

and depending on each othera) Parasiticb) Commensulisticc) Mutualistic

III.III. Classification (cont)Classification (cont)

A. Warmth; 25-37 °C

B. Dark

C. Moisture

D. Food

Where can we normally find these

conditions?

IV.IV. Optimal Growth Optimal Growth RequirementsRequirements

V. MovementA. Many forms

have flagella for movement

B. Some bacteria have pili, which allow them to attach to other things

VI. Feeding and digestion

A. Autotrophic What does this mean?

1) Photosynthetic (e.g. cyanobacteria or blue-green algae)

VI. Feeding and digestion

2) Chemosynthetic (e.g. methanogens or halophiles)

VI. Feeding and digestion

B. Heterotrophic What does this mean?

C. Extracellular digestion1. Secret enzymes2. Digest their food3. They absorb the food back into their

cells by diffusion Why does food get mushy when it

rots? Rotting Watermelon Movie

VII.Circulation, Excretion and Respiration

A. By diffusion

B. Obligate aerobes 1. Must have oxygen to live

e.g. Mycobacterium tuberculosis

VII.Circulation, Excretion and Respiration

C. Obligate anaerobes

1. Can not live in the presence of oxygene.g. Clostridium botulinum spores can be

found in honey

VII.Circulation, Excretion and Respiration

D. Facultative anaerobes1. Can grow with or without O2 but do

better without O2 e.g. Escherichia coli

VIII.ReproductionA. Asexual

1. Binary fission - splitting into two equal cells

B. Sexual reproduction1. Conjugation-exchange of plasmids

a) plasmids are independent circular pieces of DNA in bacteria.

b) after plasmid is exchanged one bacterium usually dies.

IX. Harmful Effects of Bacteria

A. Pathogenic (cause diseases)1. By directly damaging cells as they

digest cells for food.2. Or by indirectly damaging cells by

releasing toxins which damage hosts.3. They also trigger body's immune

response, i.e. fever or inflammation.4. Examples: botulism, tuberculosis,

gonorrhea, typhoid fever, bubonic plague, diphtheria, cholera, tetanus etc.

IX. Harmful Effects of Bacteria

B. Other problems caused by bacteria

1. Food spoilage (many species)

2. Food poisoning Salmonella sp.

3. Disorders like boils, pimples, pneumonia, and some forms of arthritis.

X. Treatment of bacterial diseases

A. Antibiotics are usually made from fungi or other bacteria. why?

1. Examples: Penicillin, Streptomycin, tetracycline, and sulfa drugs.

B. Problems with Antibiotics

1. Antibiotic resistance.

2. Kills off good bacteria as well as bad.

3. Inhibits body's natural immunity.

C. Pasteurization and sterilization (UV & alcohol) help prevent the spread of disease.

XI. Beneficial effects of bacteria

A. Decomposition of organic material

B. Nitrogen fixation in some plants (legumes)

C. Used to make antibiotics

D. Food production: e.g. Yogurt, Cottage cheese, Blue cheese,Vinegar

E. Used as a tool in genetic engineering

F. Tanning leather

G. Curing tobacco

H. Bioleaching-extracting minerals from ore deposits