20.2 Prokaryotes

A. Classifying Prokaryotes

Smallest microorganism

Most abundant

Unicellular; lack nucleus

DNA located in cytoplasm

2 Domains: Bacteria & Archaea

1. Bacteria

Larger Domain

Found everywhere: land, water, on & w/in organisms

Cell Wall w/ peptidoglycan

E. Coli bacteria

2. Archaea

Small

Lack nuclei

Cell wall w/0 peptidoglycan

DNA sequence of key genes = eukaryotes

Live in harsh conditions—anaerobic methogens

Bacteria in hot springs

B. Structure & Function

1. Size, shape & mov’t

Size: Range in size from 1-5 µm

Shape

Bacilli: rod- shaped

Cocci: spherical

Spirilla: spiral/corkscrew

Mov’t:

Some don’t move

Flagella: whip-like structure

Glide: secrete slimelike material

2. Nutrition & Metabolism

NRG released from fuel molecules during cellular respiration, fermentation, or both

3. Growth, Reproduction, Recombination

Binary Fission: Asexual reproduction

DNA replicates & divides = 2 ident. Daughter cells

Endospore: Thick internal wall around DNA & cytoplasm

Unfavorable/harsh conditions

Remain dormant months-years ‘til conditions favorable

Recombination: pop evolve

Mutation:

Main way proks evolve

Mutations inherited by daughter cells thru binary fission

Conjugation:

Genetic material exchanged

Hollow bridge forms btwn 2 cells move in form of plasmid from 1 cell to another

C. Importance of Prokaryotes

A. Decomposers

Assist in breaking down or decomposing dead org

Help maintain equilibrium in envt

Assist in industrial sewage treatment help to produce purified H2O

B. Producers

Important producer—cyanobacterium Prochloroccus most abundant photosynthetic org

Provides food & biomass for others

C. Nitrogen Fixers

Convert N2 into useful form NH3

Plants need N for AA to make proteins

D. Human Uses

Food--yogurt

Commercial products

Digest petroleum

Remove human-made waste prod

Synthesize drugs & chemicals

BLOCKING OUT GAS. This wastewater-treatment tower bacteria-covered foam blocks (inset) to eliminate the hydrogen sulfide bubbling from treated sewage.

Solid waste digester takes solid organic waste and uses bacteria to turn it into methane, which is then used to generate electricity.

20.3 Diseases Caused by Bacteria & Viruses

A. Bacterial Diseases

Pathogen: anything disease causing (bacterial or viral)

1. Disease Mechanism

Bacteria disease: destroy living cells or release chem to upset homeostasis

Damaging Host Tissue

Tuberculosis (lungs)

Disease Tissue infected Organism

Diphtheria Throat epithelium Corynebacterium

diphtheriae

Gonorrhea Urogenital epithelium Neisseria gonorrhoeae

Cholera Small intestine

epithelium Vibrio cholerae

Pyelonephritis Kidney medulla Proteus sp.

Dental caries Oral epithelium

Streptococcus mutans,

S. sobrinus, S. sanguis,

S. mitis

Spontaneous abortion

(cattle) Placenta Brucella abortus

Acquired

immunodeficiency

syndrome (AIDS)

T helper lymphocytes

Human

immunodeficiency virus

(HIV)

Malaria Blood (erythrocytes) Plasmodium sp.

Releasing Toxins

Salmonella, diphtheria, tetanus, botulism

Tetanus: permanent contraction (death by respiratory failure)

Botulism: no contraction (death by respiratory failure)

Diphtheria : upper resp. tract infection

2. Controlling Bacteria

Physical Removal: wash hands/surfaces w/soap

Disinfectants: chem soln kills bacteria

Food Storage: refrigerate, heat, seal, preserve

Food Processing: boil/steam food

Sterilization by Heat: above 100◦C

3. Preventing Bacterial Diseases

Vaccine: prep of weakened or killed pathogen/inactive toxin

Stimulates body’s immune system

Active Immunity: immunity dev

b/c of deliberate exposure

4. Treating Bacterial Disease

Antibiotics: block growth & reprod

of bacteria

Ex: Penicillin

B. Viral Diseases 1. Disease Mechanism

Attack & destroys living cells

Ex: Poliovirus: kills cells in nervous system

Affect cellular processes that upsets homeostasis

2. Preventing Viral Diseases

Vaccinations: best way to protect

Personal hygiene

Wash hands

Avoid contact w/sick indiv

Cough/sneeze into tissue/sleeve

3. Treating Viral Diseases

Can’t be treated w/antibiotics

C. Emerging Diseases

Unknown disease appears for 1st time or well-known disease harder to control

Humans have little/no resistance & no vaccines have been dev.

1. Super Bugs

Resistant to whole grps of antibiotics

Transfer drug-resistant genes from 1 to another thru conjugation

Ex: MRSA

2. New Viruses

Replicate quickly & change genetic makeup

Ex: Flu Virus bird flu—mixing w/other flu strains

3. Prions

Protein particles that cause diseases

Can damage nerve cells