IB Biology Option F SL

1. Investigating prokaryotes IB Biology

2. Label this cell!

3. Cell Wall Determine shape of bacteria Strength prevents osmotic rupture 20-40% of bacteria Unique to bacteria Some antibiotics effect directly Penicillin

4. Cell Wall Peptidoglycan polymer -amino acids + sugar Amino acids cross link sugars

6. Gram Staining Technique named after Hans Christian Gram (Danish scientist) Developed technique in 1884 Used to differentiate between bacteria that show same clinical symptoms

8. 5-10% peptidoglycan

9. No teichoic acids

10. 3 layers

12. The process includes the use of: a primary stain (crystal violet) a mordant (helper) iodine solution, a decolorizer (95% ethanol), a counterstain (safranin).

13. Patient No. 986214 Admitted at 01.03 this morning after complaining of severe stomach cramps and nausea Case history revealed that the patient bought a tamale from a street vendor on his way home from a late shift at the Jumex factory yesterday night After feeling okay for 24 hours after consumption of the tamale the cramping began

14. Your task The doctor wants to rule out bacterial food poisoning from Salmonella Bacterial cultures from the patient´s blood and stomach contents have been prepared Your job as the hospital microbiologist is to test the sample for presence of Salmonella

16. Salmonella toxins Enterotoxin: releasedbymicroorganism in thelowerintestine alterspermeability of intestinal wall waterleaksinto intestinal tractcausingdiarrhoea Endotoxin: Salmonella enters intestinal cellsthroughphagocytosis endotoxinsdamagethecellsfromtheinside cause fever and inflammation in largeamounts

17. Diagnosis Is the patient severely infected with Salmonella?? Or has he got something else?? You decide!! Lactobacillus acidophilus (G +ve) A good bacteria present in everybody’s digestive system Salmonella (G -ve) A bacteria that causes severe food poisoning

18. GRAM STAIN PROCEDURE 1. Gather all equipment and supplies Gram stain Microscope slides Heat source Sterile swab Culture or specimen Microscope

19. GRAM STAIN PROCEDURE 2. Sterilise your bench, wash your hands and light your bunsen burner

20. GRAM STAIN PROCEDURE 3. Choose an isolated colony off of the agar plate and obtain bacteria with a sterile swab.

21. GRAM STAIN PROCEDURE 4. Place the swab on the microscope slide and spread the colonies in a circular motion.

22. GRAM STAIN PROCEDURE 5. Heat fix the microorganisms to the slide by passing the slide through the bunsen flame a couple of times

23. GRAM STAIN PROCEDURE 6. Place slide on staining tray or hold with forceps above the sink.

24. GRAM STAIN PROCEDURE 7. Flood the surface of the slide with Crystal Violet stain and let sit for one minute.

25. GRAM STAIN PROCEDURE 8. Rinse the slide with distilled water.

26. GRAM STAIN PROCEDURE 9. Flood the slide with Gram’s Iodine and time for one minute.

27. GRAM STAIN PROCEDURE 10. Rinse the slide with distilled water.

28. GRAM STAIN PROCEDURE 11. Flood the slide with Gram’s decolorizer and time for 30 seconds.

29. GRAM STAIN PROCEDURE 12. Rinse the slide with distilled water.

30. GRAM STAIN PROCEDURE 13. Flood the slide with the counterstain, Safranin, and let sit for one minute.

31. GRAM STAIN PROCEDURE 14. Rinse the slide with distilled water.

32. GRAM STAIN PROCEDURE 15. Blot the slide and read with the oil immersion lens of the microscope. Look for Gram-negative and Gram-positive bacteria.

33. Diagnosis Is Patient No. 986214 severely infected with Salmonella Or has he just got something else! You decide!! Lactobacillus acidophilus (G +ve) A good bacteria present in everybody’s digestive system Salmonella (G -ve) A bacteria that causes severe food poisoning

34. Making Yoghurt

35. Fermentation of milk Lactobacillus Lactose lactic acid The milk becomes more and more acidic, lowering the pH and making it taste sour The souring of milk is a fermentation process which happens when the bacteria in the milk use the milk sugar (lactose). It is their food source during anaerobic respiration.

36. Product- yoghurt Yoghurt-making uses 2 species of bacteria to ferment milk (often low-fat). They are added as a starter culture and produce lactic acid. Lactobacillusacidophilus acidifies the milk Streptococcus thermophilus turns the milk creamy When the pH drops to 4.4 the proteins in milk coagulate (thicken) producing yoghurt.

37. Yoghurt production mixing Milk products Heat treatment at 90oC 1. 2. 3. Removes oxygen Kills harmful bacteria Changes milk proteins Cooled to 40oC Yoghurt bacteria added Best temperature for growing yoghurt bacteria Ferment milk sugar (lactose) into lactic acid. 1. 2. Give yoghurt its acid taste Credit: museum of brands Fermentation for 6 hours Storage tank at 4.5oC Slows down further bacterial fermentation

38. Make your own! You will need: Skimmed UHT milk (this milk is sterile!) Live yoghurt (starter culture) Dried milk powder(makes it creamy!

39. Method Take a clean pot and label with your name and the date Fill 2/3 of the pot with UHT Dissolve 1 teaspoon of milk powder into the milk Add 1 teaspoon of yoghurt to the milk Test the pH and make a note of it Put the lid on and place in the water bath at 35 degrees C