Chapter 23: Bacteria

Overview on Bacteria

-Microscopic-Unicellular

organism-Prokaryote:

– lack of membrane bound nucleus and organelles

– found everywhere– harmful and beneficial

types of bacteria– believed to have

existed 3.5 billion years ago

ClassificationBacteria are classified based upon the

following characteristics: structure, physiology, molecular composition and reaction to staining.

Two kingdoms…new version = Domains!

1. Archae

-ancient, living in extreme environments

-not commonly exposed to humans

2. Eubacteria

- “bacteria” and germs

-commonly exposed to humans

Domain: ArchaeCharacteristics:

Unusual lipid cell membraneIntrons in their DNANo Peptidoglycan *Lives in extreme environmentsrRNA is similar to rRNA in eukaryotesgenes are similar to eukaryotes

Peptidoglycan: protein carbohydrate found in cell walls

Archaeal Groups:1) Methanogens2) Halophiles3) Thermoacidophiles

Methanogens

• Harvest energy by converting H2 and CO2 into methane gas.

• Anaerobic environments• Facilitate fermentation• Location:

– Intestinal tracks, MARSH GAS, swamps and sewage

Extreme Halophiles• Found in salty

environments

• Use salt to generate ATP

Thermoacidophiles• Found in acidic and high

temperature environments• pH less than 2• Temp: up to 230oF

Domain: Bacteria

Characteristics:normal lipids in cell membrane

no introns

have peptidoglycan

live in a variety of environments

rRNA is different than rRNA of eukaryotes

genes are not like genes of eukaryotes

Eubacteria

Streptococci = chain of cocciStaphylococci = cluster of cocci

Gram StainingGram Positive

• Thick layer of peptidoglycan in cell wall.

• Cause: retains purple stain.

Gram Negative• Thin cell wall (very small

layer of peptidoglycan).• Cause: unable to retain

stain and appears pink.

Cell Membrane

Phylum• Cyanobacteria:

– Blue- green algae– gram –– Photosynthetic: capture sunlight to harvest energy

• Spirochetes:– Syphilis (STD and parasite)– Gram -

• Gram positive Bacteria:– Found in soil and used to produce antibiotics

• Proteobacteria:– Largest, most diverse– gram –– Heterotrophic, chemoautotrophic, nitrogen fixing

Structure

Structures• Cell wall

-Peptidoglycan

- Antibiotics (resistance)

• Cytoplasm-DNA, ribosomes, membrane for cell respiration

• Capsule and Pili-protective outer covering

-Glycocalyx: sticky covering used for attachment

- Pili: hair-like protein structures used for attachment.

Structures

•Endospore - Dormant - Protects DNA during harsh conditions (chemicals, radiations, temperature changes) - Bacillus and Clostridium

•Movement -Flagellum - Rotating (spiral-shaped bacteria) - Slime (myxobacteria)

Nutrition and GrowthAutotrophs

• Photoautotrophs: use sunlight as an energy source

• Chemoautrophs

Heterotrophs

• Saprophytes : feed on dead organic matter

• ANAEROBE = NO O2 AEROBES = YES O2

• Obligate Anaerobe (C. tetani)• Facultative Anaerobe (E. coli)• Obligate Aerobe (M. tuberculosis)

Reproduction and Recombination

•Transformation- Bacterial cells take DNA from an outside source and substitute for a similar DNA fragment in the chromosome of the cell.

•Conjugation- Two bacteria bind together and transfer genetic material to one another.- Conjugation Bridge: passageway used to transfer genetic material-Plasmids

•Transduction- a virus obtains a fragment of DNA from a bacterium.

Replication of the virus results in new bacterium.

PathologyThe study of disease

• Exotoxins : protein toxins – Gram positive bacteria

• ex: Tetanus

• Endotoxins: lipid and carbohydrate toxins– Gram negative bacteria– Released when bacteria die– Symptoms: fever, body aches and weakness

• ex: E. coli

What can we do to avoid diseases

caused by bacteria?

Name that pathogen!

Streptococcus mutans

Borrelia burgdorferi

Streptococcus pyogenes

Heliobacter pylori

Neisseria meningitidis

Antibiotics

Gram Positive Antibiotics

• Penicillin: inhibits cell wall synthesis

• Cephalosporin• Sulfa-drugs (synthetic):

inhibits cell metabolism Ex: bacterial meningitis

Broad Spectrum/ Gram Negative Antibiotics

• Tetracycline: Inhibits protein synthesis. Ex: skin infections (acne) and Lyme disease

• Ampicilin: Inhibits cell-wall synthesis

• Zithromax (Z Pack): inhibits protein synthesis

Benefits of Bacteria

Healthy flora (E. coli) in the intestinal trackEx: Enteric Bacteria

Lactobacillus found in sour dough bread.(Fermentation)

AcidophilusProbiotics

A mouse?