Microbes: Diversity, Food Production and Disease

1. Microbes: Diversity, Food Production and Disease Topics F1, F4, and F6

2. F1: Diversity of Microbes • Domain = a broader classification than a kingdom. • DKPCOFGS • All organisms are classified in one of the 3 domains! • Eubacteria • Archaea (Archaebacteria) • Eukaryota http://www.ucmp.berkeley.edu/alllife/threedomains.html.

3. Evidence and Reasons • 3 Domain system of classification was first proposed relatively recently (1990). • Why? • Original evidence = rRNA sequences • Evolves slowly– so it is thought that it can give a glimpse into ancient evolutionary history. • More evidence = Gene sequencing • Also, various characteristics distinguish the domains.

4. Distinguishing the 3 domains

5. Archaea • “Extremophiles” (live in extreme habitats) • Halophiles– very high salt content • Dead sea… • Thermophiles– very hot (think boiling water) • Volcanic hot springs, hydrothermal vents • Methanogens – anaerobic habitats • Swamps, waterlogged soils, guts of ruminants… • Produce methane

6. Eubacteria • Shape • cocci (sphere) • Ex. Streptococcus sp. • bacilli (rod) • Ex. Bacillus thuringiensis (bt) • Escherichia coli • spirilla (spiral) • Vibrios (comma shaped) • Ex. Vibrio cholerae

7. Eubacteria • Cell Wall Structure • Gram-positive • Stain purple • Thick outer layer of peptidoglycan • Gram-negative • Appear pink (or red) when stained • Thin layer of peptidoglycan coated with an outer layer of lipopolysaccharide and protein. anthrax bacteria (purple rods) in cerebrospinal fluid sample. (The other cells are white blood cells). E. coli

8. Aggregates of Bacteria • Some bacteria form aggregates with characteristics not seen in individual bacteria • Examples: • Biofilms- • Ex.some produce toxins only when sufficient density is reached • Plaque on teeth • On rocks and other surfaces • Vibrio fischeri = bioluminescent only when aggregated

9. Viral structure • Virus: infectious particles consisting of a nucleic acid in a protein coat • Parts • Capsid (protein) made up of units called capsomeres; • Naked (no envelope) or enveloped • viral envelopes with glycoproteins on outside (bind receptors on host); • DNA or RNA • May be either single or double stranded. • Tail fibers (sometimes)

10. (SKIP)Viral reproduction: Lytic Cycle • The lytic cycle: 1- attachment 2- injection 3- hydrolyzation 4- assembly 5- release • Results in death of host cell • Virulent virus (phage reproduction only by the lytic cycle)

11. (SKIP) Viral reproduction: Lysogenic Cycle • Genome replicated w/o destroying the host cell • Genetic material of virus becomes incorporated into the host cell DNA (prophage/provirus DNA) and is reproduced with host DNA • Temperate virus (phages capable of using the lytic and lysogenic cycles) • May give rise to lytic cycle

12. Microscopic Eukaryotes

13. Saccharomyces • Yeast= a fungus • Nutrition– Heterotrophic (saprotrophic– absorbs sugar and other small molecules) • Locomotion – NO • Cell wall-- YES • Chloroplasts-- NO • Cilia-- NO • Flagella-- NO Saccharomyces cerevisiae

14. Amoeba Protists that move by crawling via pseudopodia • Nutrition– Heterotrophic (ingests living and dead organic matter using endocytosis) • Locomotion – Amoeboid movement (like a white blood cell) • Cell wall-- NO • Chloroplasts-- NO • Cilia– NO • Flagella--NO

15. Plasmodium genus of parasitic protozoa • Nutrition– Heterotrophic (Parasitize red blood cells) • Locomotion – YES • Cell wall-- NO • Chloroplasts-- NO • Cilia– YES? N/A • Flagella– YES? N/A For more info: http://www.cdc.gov/Malaria/ http://www.biology-questions-and-answers.com/protists.html http://www.hhmi.org/biointeractive/disease/malaria_anim/malaria-human.html cool animation This photomicrograph shows a mature Plasmodium malariae schizont within an infected RBC.

17. Paramecium • group of unicellularciliateprotozoa • Nutrition– Heterotrophic (ingests living and dead organic matter using endocytosis) • Locomotion – uses cilia • Cell wall-- NO • Chloroplasts-- NO • Cilia– YES • Flagella-- NO

18. Euglena • Nutrition– Heterotrophic (endocytosis) and Autotrophic (photosynthesis) • Locomotion – uses flagellum • Cell wall-- NO • Chloroplasts-- YES • Cilia– NO • Flagella-- YES

19. Chlorella • Single-celled algae • Nutrition– Autotrophic (photosynthesis) • Locomotion – NO • Cell wall-- YES • Chloroplasts-- YES • Cilia– NO • Flagella--NO

20. Assignment: Dichotomous Key • Now, make a dichotomous key to differentiate between the different groups of microscopic eukaryotes.

21. Microbes and Food Production • Saccharomyces (yeast) • Beer, wine, bread • Aspergillus oryzae (a fungus) • Soy and wheat mixed • Add in Aspergillus… • Tranfer to vats; add salt • Ferment for six months • Press the result to get the liquid (soy sauce) • Yogurt • Lactobacillus bulgaricus, Streptococcus thermophilus… • Yogurt Lab!

22. Microbes and Food • Harmful microbes can cause spoiling of food • Some ways to prevent this (preserve the food) include: • Acids • Ex. Vinegar-- Low pH prevents bacterial growth. • Ex. Yogurt– lactose  lactic acid • High salt concentration • Osmosis… • High sugar concentration • Osmosis… • Ex. Fruit preserves, honey • Others…

23. Food gone bad… Food poisoning • Symptoms • Nausea, Vomiting, and diarrhea develop within a few hours. • Method of transmission • Contaminated food • Treatment: • Replace electrolytes and fluids (ex. Pedialyte) • Named example: salmonella 

24. Microbes and Disease • Pathogen = disease causing organism. • Methods of entry • Droplets in the air e.g. Influenza Virus • Physical contact e.g. Ebola Virus • Exchange of body fluids e.g. Syphilis, HIV, Hepatitis • Animal bites e.g. Malaria, rabies, the plague • Contaminated food or water e.g. Salmonella, cholera, typhoid • Cuts e.g. Tetanus

25. Epidemiology • The study of the occurrence, distribution and control of diseases. • Epidemic = unusually high number of cases of a disease in a region. • Pandemic = occurs when an epidemic has spread very widely, affecting a large area such as a continent. • “pan-” means “all, every” • Ex. 1918 Flu, Asian flu pandemic of 1957 • http://www.pbs.org/wgbh/nova/sciencenow/3318/02.html • http://www.pbs.org/wgbh/nova/sciencenow/3302/04.html Pandemic flu

26. Influenza Virus Lytic Cycle • Binds glycoproteins • Endocytosis • Replication of viral RNA and virus assembly • Lysis of host cell • Spread of virus

28. Types of infection • Intracellular– pathogen inside the cell • Ex. Chlamydia • the most common bacterial sexually transmitted infections in humans, as well as the leading cause of infectious blindness worldwide.[1] • Extracellular- pathogen outside of the cell (in extracellular matrix) • Ex. Streptococcus • Usually infects upper respiratory tract • Would influenza be considered an intracellular or extracellular infection? Chlamydia trachomatis inclusion bodies (brown) in a McCoy cell culture Strep throat often includes a fever (greater than 101 degrees Fahrenheit), white draining patches on the throat, and swollen or tender lymph glands in the neck. Children may have headache and stomach pain.

29. Malaria • Cause: Plasmodium sp. (a genus of protozoan). • Transmission by infected Anopheles mosquitoes. • Effects: • Fever. • Chills. • Headache. • Sweats. • Fatigue. • Nausea and vomiting. Etc. • What other effects might malaria have (besides symptoms in individuals)?

30. Illness caused by Toxins • Endotoxins: lipopolysaccharides in the walls of Gram-negative bacteria that cause fever and aches.

31. Exotoxins: Specific proteins secreted by bacteria that cause symptoms such as muscle spasms (tetanus) and diarrhea (cholera). • Secreted toxins • Cholera, botox, diphteria, anthrax

32. A new type of disease? The Spongiform Encephalopathy Problem • Spongiform encephalopathies= “mad cow disease”, scrapie in sheep, Creutzfeld-Jacob disease in humans. • cause breakdown of brain resulting in: • Premature aging, dementia, and eventually death. • The Puzzle: What causes them? • Not affected by enzymes that digest DNA or RNA. • Very heat stable and not easily damaged by ionizing radiation • Not a living organism • It is affected by chemicals that denature proteins.

33. The Prion Hypothesis: Prions cause spongiform encephalopathies. • Prions:“infectious proteins”; trigger chain reaction conversions of normal protein to prion protein; a transmissible protein animation: http://health.howstuffworks.com/mad-cow-disease3.htm

34. Prevention and Treatment of microbial diseases

35. Evaluate Methods of Controlling Microbial growth • Irradiation- ionizing radiation kills microbes in food • Disadvantages: free radicals formed: may alter flavor, some bacteria survive it (ex. Clostridium botulinum), consumer reluctance. • Pasteurization– rapid heating, then rapid cooling • Kills all pathogens and most spoilage bacteria • Does NOT significantly alter flavor

36. Antiseptics– chemical substances that kill or prevent the growth of bacteria on skin or in wounds. • Help prevent infection • Can be used on surface of living tissues • Harmful if taken internally • Cannot be used in foods • Disinfectants– chemicals that kill or prevent microbial growth on NON-Living surfaces. • Sterilize med equipment, counters etc. • Too toxic for living tissues.

37. Antibiotics • Mechanisms of action: • Inhibit cell wall synthesis • Ex. Penicillin • Inhibit protein synthesis • Erythromycin, streptomycin • Inhibit nucleic acid synthesis • Rifampin and some others block RNA synthesis • Why don’t antibiotics do us harm if some block important processes like protein and nucleic acid synthesis? More info: http://www.hhmi.org/biointeractive/Antibiotics_Attack/frameset.html