Chapter 20 PDF

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notes for chapter 20 from lecture...

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Chapter 20: Viruses, Bacteria, and Archaea Prokaryotes- “before a nucleus”   

Includes bacteria and archaea Abundant in air, water, and soil Pasteur- sterilized broth cannot have growth unless it is exposed to air

Structure       

Cell envelope (cell wall, plasma membrane, glyococalyx(extra protection)) Cytoplasm (nucleoid, ribosomes, thylakoids (to photosynthesize)) Appendages (flagella, conjugation pilus(bacteria linking and transferring DNA), fimbriae(hairlike attachments to attach to other bacteria or host)) Cellular membrane has infolds- where respiration and photosynthesis happens Have outer cell walls (helps them survive in a host) and could have rings of DNA (plasmids) Some move by flagella- tail that spins and allows to circulate and propel fowards Lack membrane bound nucleus and membranous organelles

Reproduction    

Asexual- binary fission- splitting into two daughter cells Generation time as short as 12 minutes, mutations generated rapidly HaploidSome bacteria form resistant endospores under unfavorable conditions

Genetic recombination 

Methods of genetic reconjugation: 1. Conjugation- conjugation pilus forms between two cells, donor cell passes DNA to recipient cell through the pilus 2. Transformation- occurs when bacterium pick up free pieces of DNA and incorporate it into their genome 3. Transduction- Occurs when bacteriophages carry portions of bacterial DNA from one cell to another, serve as vectors

Bacteria   

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Over 9,000 bacteria that have been named Most protected by cell wall- contains peptidoglycan Gram stain: positive [purple] retain dye, negative do not [pink] - have a second membrane which blocks antibiotic drugs making infections harder to treat (difference depends on cell wall) Gram positive have thicker peptidoglycan 3 shapes: spirilium (spiral), bacilli (rod), cocci (round)

Metabolism

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Obligate aerobes- unable to grow in absence of free oxygen (need oxygen) Obligate anaerobes- unable to grow in presence of free oxygen (butolism, tetanus) Facultative anaerobes- able to grow in either the presence or absence of free oxygen

Autotrophic Bacteria 

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Photoautotrophs -Use solar energy to reduce CO2 to organic compounds -Photosynthetic -Anoxygenic: Green sulfur and some purple bacteria living in oxygen poor conditions, does not produce O2 -Oxygenic: produces O2 Chemoautotrophs -Oxidize inorganic compounds to obtain energy, energy used to reduce CO2 to organic compounds -Live in environments such as deep sea vents- using chemicals instead of sunlight (chemosynthetic)

Heterotrophic Bacteria- does not use sun    

Chemoheterotrophs- take in organic nutrients Saprotrophs- Decompose most large organic molecules to smaller molecules, break down soil into nutrients Essential components of a healthy ecosystem May be free living or symbiotic (living together) -Commensalism: one benefits, other is unharmed -Mutualism: both benefit -Parasitism: one benefits, other is harmed

Antibiotics & Bacteria  

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EndosporesAntibiotic compounds fall into two classes Compounds that inhibit protein biosynthesis --Erythromycin, tetracycline Compounds that inhibit cell wall biosynthesis --bacterial but not animal cells --penicillin, ampicillin Bacterial resistance to antibiotics is increasing -Genes conferring resistance can be transferred by transformation, conjugation, or transduction -90% of staph are resistant to penicillin and increasingly to methicillin (MRSA) -MRSA is common in hospitals and nursing facilities

Cyanobacteria

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Gram negative bacteria that are photosynthetic (thin peptidoglycan layer) Believed to be responsible for introducing oxygen into the primitive atmosphere -Lack visible means of locomotion -Can live in extreme environments -In association with fungi, form lichens (cyanobacteria and fungi hook up) -Lichens- encrust rocks -Possess heterocysts, cells without nuclei, where nitrogen fixation occurs (turning nitrite to nitrate) -Cyanobacterial blooms result from pollution in lakes and ponds

Archaea   

Formerly considered bacteria- base sequence of rRNA differs from bacteria (Woese and Fox) Do not have peptidoglycan in their cell walls like bacteria Biochemically more like eukarya than bacteria

Types of Archaea 

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Anaerobic marshes (marsh with no oxygen) -Methanogens -Produce methane from hydrogen gas and carbon dioxide Salty lakes -Halophiles -Require high salt concentrations for growth/adapted to living in high salt area -Isotonic: equal to surroundings and environment -Maintain salt level inside their body to salt level outside their body Hot sulfur springs -Thermoacidophiles -High acidity and hot temperature environment -Reduces sulfides and survive best at temps above 80 C -Plasma membranes contain unusual lipids that confer tolerance of high temperatures...