BACTERIA (Ch. 24) AND VIRUSES (Ch. 25)

BACTERIA: Simplest & most primitive life forms (fossils from 3.5 bya)

2 Kingdoms: ArchaebacteriaEubacteria

Archaebacteria: “ancient bacteria” live in extreme environments

Thermoacidophile Thermoacidophile: thrives in hot, acidicenvironments

Halophile Halophile: thrives in saltyenvironments

Methanogen Methanogen: thrives in methane-richenvironment

Eubacteria “true bacteria” live in “normal” environments

Simple Structure: PROKARYOTE no nucleus or membrane-boundorganelles

Chromosome is in one loop, not in pairs Chromosome # 1

Have ribosomes; needed to make structural proteins and enzymes

Cell Wall: Some cell walls have a thick layer of peptidoglycan, a carbohydrate

Gram Positive: stains purple; stain is held by peptididoglyganlayer

Gram Positive

Gram Negative Gram Negative: Stains pink; stain resistant since there is a layer over the peptididoglycanlayer

Gram Negative

Cell Parts:

Classified by Shapes 1.Bacillus: ovals

2.Coccus: round

3.Spirillus: wavy or bent or bent

Configurations: Diplo: in pairs Diplococcus

Strepto: in chains Streptococcus Streptobacillus

Staphylo: in clusters

Reproduction: Binary Fission

Rapid life cycle since there is no mitosis

Some genetic recombination by three different methods:

1.Conjugation Two bacteria join up at the pili (conjugation bridge) and exchange a small loop of DNA that has detached from the main DNA (plasmid)

The plasmid is incor- porated into the DNA of the receiving cells conjugation conjugation bridge bridge

Transformation: Substitutes new DNA for a similar fragment in its original DNASubstitutes new DNA for a similar fragment in its original DNA

Transformation:

Transduction: A virus obtains a piece of DNA from host bacteriumA virus obtains a piece of DNA from host bacterium Virus transfers DNA to new cell that it infectsVirus transfers DNA to new cell that it infects

Transduction:

NUTRITION:AUTOTROPHIC by photosynthesis or chemosynthesis

Heterotrophic: many are saprophytic-- eat dead stuff

METABOLISM/ RESPIRATION: Obligate Aerobe Must have Oxygen to survive

Obligate Anaerobe: Can only survive in the absence of oxygen

Facultative Anaerobe: Can live with or withoutoxygen

Effects on Humans: DecomposersDecomposers Food & DrugFood & Drug industries industries

Clean up toxicClean up toxic waste naturally NaturalNaturalpesticides

Nitrogen fixation fixation Extract nitrogen from the environment for plants to use

Cause diseases by releasing toxins into host organism

Exotoxins: Produced by Gram positive cellsProduced by Gram positive cells Toxins constantly produced and steadily released by cellToxins constantly produced and steadily released by cell Protein-based toxinsProtein-based toxins

Endotoxins: Produced by Gram- negative cellsProduced by Gram- negative cells Toxins released when bacterium diesToxins released when bacterium dies Lipid or carbohydrate based toxinsLipid or carbohydrate based toxins

How can we control bacteria? Antibiotics! Wash hands! Good sanitation!Pasteurization Good sanitation!Pasteurization Immunizations! Safe sex!!! Immunizations! Safe sex!!!

Problem: ANTIBIOTIC RESISTANCE From overuse (antibiotics only From overuse (antibiotics only work on gram-positive work on gram-positive bacteria; doctors have bacteria; doctors have prescribed for any bacteria prescribed for any bacteria and also viruses and also viruses Patients don’t take all Patients don’t take all prescribed medication, as prescribed medication, as directed directed

Bacterial mutations occur that also result in resistance Bacterial mutations occur that also result in resistance Example: Tuberculosis used to respond to used to respond to penicillin but now it penicillin but now it doesn’t doesn’t