1. 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. 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. 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. 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. 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. 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. 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. 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. 9 Overview of prokaryotic cell.

10. 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. 11 http://www.conceptdraw.com/s ampletour/medical/GramNegat iveEnvelope.gif http://www.conceptdraw.com/s ampletour/medical/GramPositi veEnvelope.gif Gram Negative Gram Positive

12. 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. 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. 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. 15 Glycocalyx: capsules and slime layers www.activatedsludge.info/ resources/visbulk.asp capsule cell “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.

16. 16 Fimbriae and pili www.ncl.ac.uk/dental/oralbiol/ oralenv/images/sex1.jpg 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”).

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

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

19. 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 CO 2 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. 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. 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. 22 Bacterial diseases Staph infection, E. coli infection, Strep throat Anthrax, tularemia, plague Syphilis, gonorrhea, chlamydia infection tuberculosis