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The Infectious Agents of Disease

Infectious Infectious AgentsAgents

•VirusesViruses•BacteriaBacteria•Protozoa Protozoa

Bacteria (19-1)Bacteria (19-1)Kingdom Eubacteria/Kingdom Kingdom Eubacteria/Kingdom

ArcheabacteriaArcheabacteria

• Microscopic unicellular organismsMicroscopic unicellular organisms• Free living/ ProkaryoticFree living/ Prokaryotic• Self replicatingSelf replicating• Usually sensitive to antibioticsUsually sensitive to antibiotics• Responsible for the majority of Responsible for the majority of

human infectious diseaseshuman infectious diseases

Review of KingdomsReview of Kingdoms

ArchaebacteriaArchaebacteria• earliest moneransearliest monerans• found in extreme found in extreme

habitatshabitats• oxygen free, salty, oxygen free, salty,

and acidic and acidic environmentsenvironments

• Chemosynthetic Chemosynthetic metabolismsmetabolisms

• Diff. Membrane Diff. Membrane structures (p.472)structures (p.472)

EubacteriaEubacteria• modern bacteriamodern bacteria• found in diverse found in diverse

number of habitatsnumber of habitats• Heterotrophic Heterotrophic

(chemo and photo-) (chemo and photo-) & Autotrophic & Autotrophic (chemo and photo-)(chemo and photo-)

• Cyanobacteria Cyanobacteria group group

Structure of BacteriaStructure of BacteriaClassification by shape (morphology)Classification by shape (morphology)

Sphere Rod Spiral

Prefixes are added to the three basic shapes to further classify the bacteria according to their arrangement.

The three basic arrangements are:

A) Diplo-paired arrangement

B) Staphylo- clustered arrangement

C) Strepto- chained arrangement

A B C

More Ways to IdentifyMore Ways to Identify

• MovementMovement• FlagellaFlagella• Slime MovementSlime Movement• CiliaCilia• NoneNone

• Cell WallsCell Walls• Gram Positive Gram Positive

gives a purple gives a purple color after color after stainingstaining

• Gram Negative Gram Negative gives a pink color gives a pink color after stainingafter staining

-Hollow, hair like structures made of protein

-Allow bacteria to attach to other bacteria

-A specialized pilus, the sex pilus, allows the transfer of DNA from one bacterial cell to another

Pilus

-Long appendages which rotate for movement

-May have one, a few, or many flagella in different positions on the cell.

Flagella

Other specialized structural adaptations:Capsule

Gel like coating that protects bacteria from white blood cells and chemical agents.

Endospore Hard coating that is resistant to drying out, boiling, and many chemical agents

*Clostridium botulinium and Clostridium tetani forms endospores and toxic poisons

Structure of a Bacterial Structure of a Bacterial CellCell

Metabolic DiversityMetabolic Diversity

• HeterotrophsHeterotrophs

1.1. ChemoheterotropChemoheterotrophh: taking in of : taking in of organic moleculesorganic molecules

2.2. PhotoheterotrophPhotoheterotroph: : use use photosynthesis photosynthesis AND take in AND take in chemicalschemicals

• AutotrophsAutotrophs

1.1. PhotoautotrophPhotoautotroph: : require light to require light to perform perform photosynthesisphotosynthesis

2.2. ChemoautotrophChemoautotroph: no light : no light needed, undergo needed, undergo chemosynthesischemosynthesis

Please note: bacteria DO NOT have mitochondria or chloroplastsHow might they carry out metabolism (Cell Resp and Photosynthesis)??

Releasing EnergyReleasing EnergyAerobic• require oxygen for

cellular respiration• “obligate aerobes”-

without oxygen they will die

Anaerobic• do not require oxygen

for cellular respiration• “obligate anaerobes”-

will die in the presence of oxygen

“Faculties Aerobes/Anaerobes”

•Can live with or without oxygen

•Capable of switching metabolism

•Fermentation vs. Cellular respiration

ReproductionReproduction

• Binary fission

-Asexual form of -Asexual form of reproductionreproduction

-Produces identical -Produces identical clonesclones

-Rapid (20 min)-Rapid (20 min)

• Conjugation-Sexual form of -Sexual form of

reproductionreproduction

-Pilus is used to -Pilus is used to exchange genetic exchange genetic material material

-Produces a variant, -Produces a variant, making them hard to making them hard to treat with antibioticstreat with antibiotics

http://www.hhmi.org/biointeractive/animations/conjugation/conj_frames.htm

Economic Importance Economic Importance of Bacteriaof Bacteria

1.1. Nitrogen fixationNitrogen fixation- bacteria convert - bacteria convert atmospheric nitrogen (Natmospheric nitrogen (N22) to ) to ammonia (NHammonia (NH33) a fertilizer for plants ) a fertilizer for plants

2.2. RecycleRecycle organic material and organic material and oxygenoxygen

3. Food and and beveragesbeverages

4.4. MedicinesMedicines (antibiotics) (antibiotics)5. Industrial uses uses

AntibioticsAntibiotics

• Antibiotics work by blocking vital Antibiotics work by blocking vital processes in bacteria, killing the processes in bacteria, killing the bacteria, or stopping them from bacteria, or stopping them from multiplying. multiplying.

• This helps the body's natural immune This helps the body's natural immune system to fight the bacterial infection. system to fight the bacterial infection.

• Antibiotics differ in the types of bacteria Antibiotics differ in the types of bacteria they work against.they work against.

• Ex: PenecillinEx: Penecillin