Viruses and BacteriaViruses and Bacteria

Chapter 18Chapter 18

What is a virus?What is a virus?

Considered non-living particles by Considered non-living particles by most biologists because they:most biologists because they:– Do not carry out cellular respirationDo not carry out cellular respiration– Do not grow and developDo not grow and develop– Cannot replicate on their ownCannot replicate on their own

Viruses are named after:Viruses are named after:– The disease they cause (poliovirus)The disease they cause (poliovirus)– The organ they infect (adenovirus)The organ they infect (adenovirus)

Viral StructureViral Structure Genetic Material in Genetic Material in

the form of:the form of:– DNADNA– RNARNA

Capsid: outer Capsid: outer protein coatprotein coat– 4 common shapes4 common shapes

PolyhedralPolyhedral HelicalHelical EnvelopedEnveloped Bacteriophage or Bacteriophage or

phagephage

                                                                  

                    

Polyhedral VirusesPolyhedral Viruses

Herpes virusHerpes virus AdenovirusAdenovirus Polio virusPolio virus

Helical VirusesHelical Viruses

Tobacco Tobacco Mosaic VirusMosaic Virus

Enveloped VirusesEnveloped Viruses

Contain an Contain an envelope made of envelope made of – LipidsLipids– CarbohydratesCarbohydrates– Proteins Proteins

ExamplesExamples– Influenza VirusInfluenza Virus– HIVHIV

BacteriophagesBacteriophages

““phage”phage” Is a virus that Is a virus that

attacks bacteriaattacks bacteria

Viruses are SpecificViruses are Specific

Each virus is Each virus is specialized specialized

Most viruses Most viruses are species-are species-specificspecific

Many viruses Many viruses are also cell-are also cell-specificspecific

Viral Replication CyclesViral Replication Cycles

Lytic CycleLytic Cycle– Kills the host cellKills the host cell

Lysogenic CycleLysogenic Cycle– Similar to lytic cycle but does not Similar to lytic cycle but does not

immediately kill host cellimmediately kill host cell– Viral genetic material recombines with Viral genetic material recombines with

host cell’s DNAhost cell’s DNA– Provirus: Viral DNA that is integrated Provirus: Viral DNA that is integrated

into host cell’s chromosomeinto host cell’s chromosome Examples: HSV I & II, hepatitis B, and Examples: HSV I & II, hepatitis B, and

chicken poxchicken pox

                                                                        

Lytic CycleLytic Cycle A virus attaches to a host cell. A virus attaches to a host cell. Virus releases its genetic material Virus releases its genetic material

into the host cell. into the host cell. The injected genetic material The injected genetic material

recruits the host cell's enzymes. recruits the host cell's enzymes. The enzymes make parts for more The enzymes make parts for more

new viruses. new viruses. The new parts assemble into new The new parts assemble into new

viruses. viruses. The new particles lyse (burst) the The new particles lyse (burst) the

host cell and exit. host cell and exit.

Lysogenic CycleLysogenic Cycle

RetrovirusesRetroviruses

Type of RNA Type of RNA virus that virus that reverse reverse transcribes transcribes itself into DNAitself into DNA

The newly The newly transcribed transcribed DNA inserts DNA inserts into host’s DNAinto host’s DNA

Ex: HIVEx: HIV

ProkaryotesProkaryotes

Unicellular Unicellular organisms without organisms without membrane-bound membrane-bound organellesorganelles

2 Kingdoms2 Kingdoms– ArchaebacteriaArchaebacteria– EubacteriaEubacteria

ArchaebacteriaArchaebacteria Live in harsh Live in harsh

environmentsenvironments 3 types3 types

– Methane-producersMethane-producers ““Methanogens”Methanogens” MarshesMarshes Lake sedimentsLake sediments Animal digestive tractsAnimal digestive tracts

– Salt-dwellersSalt-dwellers ““Halophiles”Halophiles” Dead SeaDead Sea

– Heat/Acid-dwellersHeat/Acid-dwellers ““Thermoacidophiles”Thermoacidophiles” Deep ocean ventsDeep ocean vents

Eubacteria: The Eubacteria: The HeterotrophsHeterotrophs Bacteria that obtain Bacteria that obtain

their nutrients from their nutrients from elsewhereelsewhere

Some are parasitesSome are parasites– Feed off of living Feed off of living

organismsorganisms Some are Some are

saprophytessaprophytes– Feed on dead Feed on dead

organisms organisms – Feed on organic Feed on organic

wastes (recyclers)wastes (recyclers)

Eubacteria: Photosynthetic Eubacteria: Photosynthetic AutotrophsAutotrophs

Bacteria that Bacteria that convert solar convert solar energy into foodenergy into food

Cyanobacteria or Cyanobacteria or blue-green algaeblue-green algae

Found in aquatic Found in aquatic environmentsenvironments

Composed of chains Composed of chains of independent cellsof independent cells

Eubacteria: Chemosythetic Eubacteria: Chemosythetic AutotrophsAutotrophs

Break down and Break down and release energy from release energy from inorganic compounds inorganic compounds such as Hsuch as H22SS

Important in Important in converting converting atmospheric nitrogen atmospheric nitrogen into usable forms into usable forms plants need plants need – Nitrogen FixationNitrogen Fixation

Structure Structure

Identifying Bacteria: Gram Identifying Bacteria: Gram StainStain

Gram staining Gram staining reflects differences reflects differences in cell wall in cell wall compositioncomposition– Gram-positive Gram-positive

bacteria stain bacteria stain blue/violetblue/violet

– Gram-negative Gram-negative bacteria stain pink bacteria stain pink

Identifying Bacteria: ShapesIdentifying Bacteria: Shapes

Bacterial ReproductionBacterial Reproduction

Asexually by binary Asexually by binary fissionfission

Very rapid at Very rapid at optimal conditions optimal conditions – can double every can double every

20 minutes20 minutes

Bacterial ReproductionBacterial Reproduction

Sexually by Sexually by conjugationconjugation

Common Bacterial DiseasesCommon Bacterial Diseases

DiseaseDisease AgentAgent SymptomsSymptoms TreatmentTreatmentStrep ThroatStrep Throat StreptococcuStreptococcu

s pyogeness pyogenessore throat, feversore throat, fever antibioticantibiotic

TetanusTetanus C. tetaniC. tetani stiff jaw, muscle stiff jaw, muscle spasm, paralysisspasm, paralysis

antibiotic, clean antibiotic, clean woundwound

TuberculosisTuberculosis M. M. tuberculosistuberculosis

chronic cough, chest chronic cough, chest pain,pain,

blood in sputum blood in sputum

antibioticantibiotic

Dental CariesDental Caries S. mutansS. mutans toothachetoothache remove decayremove decay

BotulismBotulism C. botulinumC. botulinum blurred vision, blurred vision, paralysis, slurred paralysis, slurred speachspeach

antitoxinsantitoxins

CholeraCholera Vibrio Vibrio choleracholera

diarrhea, vomitingdiarrhea, vomiting re-hydration, re-hydration, antibioticantibiotic

Traveler's Traveler's DiarrheaDiarrhea

Escherichia Escherichia colicoli

stomach cramps, stomach cramps, diarrheadiarrhea

re-hydration, re-hydration, antibioticantibiotic

Beneficial BacteriaBeneficial Bacteria Nitrogen FixationNitrogen Fixation

NN22 → → NONO22-- + NO + NO33

--

Converts Nitrogen into a usable Converts Nitrogen into a usable

form for plantsform for plants

FoodFood– Yogurt Yogurt – CheeseCheese– PicklesPickles– Sour creamSour cream– SauerkrautSauerkraut