Microbes : the most successful creatures on earth?

1. Microbes: the most successful creatures on earth? • Is evolution driving towards perfection or greater complexity? • Prokaryotes are the simplest form of what scientists usual consider life. • Prokaryotes have been around for 3.8 billion years and they are still here! • So what’s the most successful form of life?

2. Why you think bacteria are simple • Prokaryotic cells are only a fraction of the size of eukaryotes • Most bacteria are 1 – 5 µm in size; eukaryotes are 25x that size. • Bacteria have no internal organelles • No nucleus (but yes, DNA), no mitochondria, no endoplasmic reticulum (but they do have ribosomes) • We are smarter • We can kill them with disinfectants and antibiotics

3. Why bacteria are more clever than you • Nutrition • Give E. coli a simple nutrient source with mineral salts to supply N, P, S, and other elements, and only glucose as source of C, H, and O and it will grow. • You would die. You need: • 8 different amino acids • Vitamins (A, many B vitamins, C, D, etc.) • Habitat • Different bacteria can live in places with extremes in pH, temperature, with and without oxygen

4. How are bacteria classified? • Taxonomy of cellular creatures • Three domains • Eubacteria: prokaryotic cell structure • Archaebacteria: prokaryotes, but different • Eukaryotes: 4 kingdoms • Prokaryotes look alike • Archaea and eubacteria very similar • Differences are genetic, biochemical, and ecological

5. Why Study Microbes? • Major impact on health • Responsible for disease in humans, animals, plants • Major impact on environment • Major decomposers • Nutrient cycling, elemental cycling

6. Microbes are talented • Live under extreme conditions • Protect against disease • Eat oil, toxic waste (bioremediation) • Make plastic • Spoil food, make food • Use light, produce light

7. Bacterial Appearance • Size • 0.2 µm – 0.1 mm • Most 0.5 – 2.0 µm • Shape • Coccus (cocci); rod (bacillus, bacilli); spiral shapes; filamentous; various odd shapes. • Arrangement • Clusters, tetrads, pairs, chains http://smccd.net/accounts/case/biol230/ex3/bact.jpeg

8. How are bacteria put together? • A cell membrane • Separates inside from outside • Cytoplasm • No organelles • Nucleoid instead of nucleus • Ribosomes • Cell wall (usually) • In Eubacteria, made partly of peptidoglycan • Outer layers

9. Overview of prokaryotic cell.

10. Division of the Eubacteria:Gram Negative and Gram Positive • Gram stain invented by Hans Christian Gram • Gram positive cells stain purple; Gram negatives, pink. • Architecture: • Gram positives have a thick peptidoglycan layer in the cell wall; • Gram negatives have a thin peptidoglycan layer and an outer membrane. • Stain is valuable in identification.

11. Gram Negative Gram Positive http://www.conceptdraw.com/sampletour/medical/GramNegativeEnvelope.gif http://www.conceptdraw.com/sampletour/medical/GramPositiveEnvelope.gif

12. Function and Structure of peptidoglycan • Provides shape and structural support to cell • Resists damage due to osmotic pressure • Provides some degree of resistance to diffusion of molecules • Single bag-like, seamless molecule • Composed of polysaccharide chains cross linked with short chains of amino acids: “peptido” and “glycan”. • Many antibiotics work by preventing bacteria from producing this cell wall material.

13. Bacteria and Osmotic pressure • Bacteria typically face hypotonic environments • Insides of bacteria filled with proteins, salts, etc. • Water wants to rush in, explode cell. • Peptidoglycan provides support • Limits expansion of cell membrane • Growth of bacteria and mechanism of penicillin • Bacteria need different protection from hypertonic situations • Water leaves the cell; cell membrane shrinks • Lack of water causes precipitation of molecules, death

14. Effect of osmotic pressure on cells • Hypotonic: water rushes in; PG prevents cell rupture. • Hypertonic: water leaves cell, membrane pulls away from cell wall.

15. Glycocalyx: capsules and slime layers “Sugar covering”: capsules are firmly attached, slime layers are loose. Multiple advantages to cells: prevent dehydration absorb nutrients protection from predators, WBCs protection from biocides (as part of biofilms) attachment to surfaces and site of attachment by others. cell capsule www.activatedsludge.info/ resources/visbulk.asp

16. Fimbriae and pili Both are appendages made of protein Singular: fimbria, pilus Both used for attachment Fimbriae: to surfaces (incl. host cells) and other bacteria. Pili: to other bacteria for exchanging DNA (“sex”). www.ncl.ac.uk/dental/oralbiol/ oralenv/images/sex1.jpg

17. Fimbriae and pili-2 http://www.mansfield.ohio-state.edu/~sabedon/006pili.gif

18. Flagella • Flagella: protein appendages for swimming through liquid or across wet surfaces. • Rotate like propellers. • Different from eukaryotic flagella. www.ai.mit.edu/people/ tk/ce/flagella-s.gifwww.bmb.leeds.ac.uk/.../icu8/ introduction/bacteria.html

19. Energy and nutrition • Bacteria as a whole have several different ways of obtaining carbon and energy • Thus they are adapted to many types of environments. • Heterotrophs: use pre-existing organic molecules • Get energy aerobically or anaerobically (or both) • Some are autotrophs: get carbon from CO2 • Some get energy from light: photosynthetic • Some oxidize inorganic minerals • Play various roles in the cycling of different elements on the planet; play different roles in food webs

20. Archaea vs. Eubacteria:So what’s the difference? • Genetic • Ribosomal RNA genes different • Biochemistry • Cell wall polymer not peptidoglycan, but similar • Lipids in membranes unusual • Ecology • Tend to live in extreme environments • Very anaerobic, very salty, very acidic and/or very hot

21. Eubacteria: little disease-causing monsters? • Hardly. Most bacteria have never been grown in a lab, never mind on your tissues. • Live in soil, water, in association with other organisms. • Some do make you sick

22. Bacterial diseases • Staph infection, E. coli infection, Strep throat • Anthrax, tularemia, plague • Syphilis, gonorrhea, chlamydia infection • tuberculosis