Viruses and Bacteria Chapter 18

Pathogen Anything that causes a disease.

What is a virus? Considered non-living particles by most biologists because they: Considered non-living particles by most biologists because they: –Do not carry out cellular respiration –Do not grow and develop –Cannot replicate on their own Viruses are named after: Viruses are named after: –The disease they cause (poliovirus) –The organ they infect (adenovirus)

Viral Structure 1. Genetic Material in the form of: –DNA –RNA 1. Capsid: -outer protein coat

Viruses Herpes virus Herpes virus Adenovirus Adenovirus Polio virus Polio virus

Bacteriophages “phage” “phage” Is a virus that attacks bacteria Is a virus that attacks bacteria

Viruses are Specific Each virus is specialized Each virus is specialized Most viruses are species- specific Most viruses are species- specific Many viruses are also cell- specific Many viruses are also cell- specific

Viral Replication Cycles Lytic Cycle Lytic Cycle –Kills the host cell Lysogenic Cycle Lysogenic Cycle –Similar to lytic cycle but does not immediately kill host cell –Viral genetic material recombines with host cell’s DNA –Provirus: Viral DNA that is integrated into host cell’s chromosome  Examples: HSV I & II, hepatitis B, and chicken pox

AIMAR Lytic Cycle AIMAR Lytic Cycle Step 1: A virus attaches to a host cell. Step 2: Virus injects its genetic material into the host cell. Step 3: The enzymes make parts for more new viruses. Step 4: The new parts assemble into new viruses. Step 5: The new particles lyse (burst) from the host

Lysogenic Cycle

Prokaryotes Unicellular organisms without membrane- bound organelles Unicellular organisms without membrane- bound organelles 2 Kingdoms 2 Kingdoms –Archaebacteria –Eubacteria

Archaebacteria Live in harsh environments Live in harsh environments 3 types 3 types –Methane-producers  “Methanogens”  Marshes  Lake sediments  Animal digestive tracts –Salt-dwellers  “Halophiles”  Dead Sea –Heat/Acid-dwellers  “Thermoacidophiles”  Deep ocean vents

Eubacteria: The Heterotrophs Bacteria that obtain their nutrients from elsewhere Bacteria that obtain their nutrients from elsewhere Some are parasites Some are parasites –Feed off of living organisms Some are saprophytes Some are saprophytes –Feed on dead organisms –Feed on organic wastes (recyclers)

Eubacteria: Photosynthetic Autotrophs Bacteria that convert solar energy into food Bacteria that convert solar energy into food Cyanobacteria or blue-green algae Cyanobacteria or blue-green algae Found in aquatic environments Found in aquatic environments Composed of chains of independent cells Composed of chains of independent cells

Eubacteria: Chemosythetic Autotrophs Break down and release energy from inorganic compounds such as H 2 S Break down and release energy from inorganic compounds such as H 2 S Important in converting atmospheric nitrogen into usable forms plants need Important in converting atmospheric nitrogen into usable forms plants need –Nitrogen Fixation

Structure

Identifying Bacteria: Gram Stain Gram staining reflects differences in cell wall composition Gram staining reflects differences in cell wall composition –Gram-positive bacteria stain blue/violet –Gram-negative bacteria stain pink

Identifying Bacteria: Shapes

Bacterial Reproduction Asexually by binary fission Asexually by binary fission Very rapid at optimal conditions Very rapid at optimal conditions –can double every 20 minutes

Bacterial Reproduction Sexually by conjugation Sexually by conjugation

Common Bacterial Diseases DiseaseAgentSymptomsTreatment Strep Throat Streptococcus pyogenes sore throat, fever antibiotic Tetanus C. tetani stiff jaw, muscle spasm, paralysis antibiotic, clean wound Tuberculosis M. tuberculosis chronic cough, chest pain, blood in sputum antibiotic Dental Caries S. mutans toothache remove decay Botulism C. botulinum blurred vision, paralysis, slurred speach antitoxins Cholera Vibrio cholera diarrhea, vomiting re-hydration, antibiotic Traveler's Diarrhea Escherichia coli stomach cramps, diarrhea re-hydration, antibiotic

Beneficial Bacteria Nitrogen Fixation Nitrogen Fixation N 2 → NO NO 3 - N 2 → NO NO 3 - Converts Nitrogen into a usable form for plants Food Food –Yogurt –Cheese –Pickles –Sour cream –Sauerkraut