1. Cell structure and function for microbiologistsProkaryotesEukaryotesBoth have the same types of biologicalmolecules metabolism, protein synthesis, ATP

2. Eukaryotes have organelles Much larger; more complex thanprokaryotes Processes compartmentalized intoorganellesNucleusProtein synthesis (ribosomes, RER, Golgi)Mitochondria; chloroplastsLysosomesPlasma membranes have different modificationsCytoskeleton 3. Eukaryotes may be multicellular Cells may be variable within theorganismTissuesOrgans 4. Prokaryotes:Have no nucleus; genome is circularNo histonesNo membrane-bound organellesCell wall usually contains peptidoglycan (cellwalls are more complex)Divide by binary fission 5. Prokaryotes include eubacteria and archaeHow do you tell them apart? Theyre all small!morphology chemical composition nutritional and energy requirements 6. Typical shapes of bacteriaMost bacteria retain a particular shape; a few are pleiomorphic 7. Characteristic grouping (or not grouping) 8. Even in groups, bacteria tend to be single- celled in structure and behaviorSome have colonial traitsWell-studied example: myxobacteria hunting colonies fruiting bodiesEtc. 9. Typical prokaryotic structuresWorking from the outside in 10. Extracellular componentsProtection dehydration immune mechanismsAttachmentGlycocalyx- polysaccharide, protein capsule if organized slime layer if notMay contribute to virulence 11. Some bacteria are motile (due to flagella)Bacteria vary in the way flagella are attachedHow they move: running, tumbling, swarmingCan move toward or away from light orchemical stimuliFlagellin protein is unique to prokaryotes 12. Cocci do not have flagellaPeritrichousmonotrichous(or amphi, or lophotrichous 13. Pili- attachment; motility; conjugation 14. Cell membrane structure is similar in structureand function to that of eukaryotesPhospholipid bilayer(everything moves through it, since thereare no organelles) carrier proteins generally involve proton motive force (i.e, require energy and moving against the concentration gradient) 15. Cell wall- hallmark of prokaryotesTheir reaction with Gram stain allows bacteria to be divided into two groupsPositive-lots of peptidoglycanNegative- thin layer, with an outer membraneand periplasmic space in betweenMany secreted proteins are found here 16. Structure of peptidoglycan 17. Gram-positive cell wall 18. Outer membrane is made of lipopolysaccharide (LPS)Porins allow molecules to pass through outer membraneLPS is protective lipid A- strong inflammatory response (endotoxin) O-linked polysaccharide- antigenic 19. Significance of Gram-positive vs Gram-negative antibiotic sensitivity sensitivity to lysozyme reaction with Gram reagentscrystal violetiodinealcoholsafranin 20. Mycoplasma do not have a cell wallLots of variety in Achaea- but none have peptidoglycan 21. Internal componentsNucleoid- with single, circular, supercoiled DNA moleculeMany bacteria have plasmidssmall, extrachromosomal, circularpiece of DNAgenes present are usually not requiredbut may be advantageous(antibiotic resistance, resistance to metals)Now used for genetic engineering 22. RibosomesInvolved in protein synthesisProkaryotic ribosomes are smaller thaneukaryotic (70S vs 80S)Some antibiotics bind to the 70S ribosomeHow does that affect bacteria? 23. No membrane-bound organellesSome have storage granulesSome aquatic bacteria have gas vesiclesSome have endospores (soil bacteria) thatenable them to lie dormant underunfavorable conditionsNOT a reproductive structure 24. Summary Eukaryotes have membrane-boundorganelles Eukaryotes may be multicellular with highlyspecialized cells Prokaryotes have simple shapes and areclassified according to their morphology Certain structures are unique to prokaryotes