BIOLOGY This material is made freely available at www.njctl.org and - PDF document

Slide 1 / 61 Slide 2 / 61 New Jersey Center for Teaching and Learning Progressive Science Initiative BIOLOGY This material is made freely available at www.njctl.org and is intended for the non-commercial use of students and teachers. These materials may not be used for any commercial purpose without the written Bacteria Growth Lab permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course Prokaryotes & Viruses materials to parents, students and others. Click to go to website: www.njctl.org www.njctl.org Slide 3 / 61 Slide 4 / 61 Prokaryotes Unit Topics Click on the topic to go to that section · Bacterial Growth · Antibacterial Agents Bacterial · Analysis & Conclusion Growth Return to Table of Contents Slide 5 / 61 Slide 6 / 61 Bacterial Growth Bacterial Growth As previously mentioned, bacteria can live almost anywhere and do live almost everywhere! Bacteria reproduce by binary fission. In the lab, bacteria are grown in a medium that contains the This proliferation by nutrients necessary for growth and survival. cell division results in rapid bacterial population growth. Bacterial Growth Animation

Slide 7 / 61 Slide 8 / 61 Agar contains: Agar Water: Sugar: provides a Bacteria can also be grown on a gelatinous, polysaccharide solvent source of carbon substance called agar that is spread out on the surface of a petri dish. Bacteria are then "plated" on the agar. Salts: provide essential elements like magnesium, phosphorous, nitrogen, and sulfur needed for making proteins and nucleic acids. Slide 9 / 61 Slide 10 / 61 Plating Bacteria Bacterial Colonies Bacterial populations Different types of bacteria can typically form colonies - be distinguished by their distinct groups of millions or billions morphologies (shapes, of bacteria that live in a structures, colors, or patterns). tightly packed area. An individual bacterium can Plating bacteria on agar allows one only be seen with a to visualize the different types of microscope, but a bacterial bacteria that may be present in a colony growing on a petri solution and to isolate a particular dish is visible to the naked strain of bacteria for further use. eye. Streak Plating Demonstration Bacterial colonies growing on a plate of nutrient agar. Hans Knoll Institute. Jena, Germany Slide 11 / 61 Slide 12 / 61 Cultures Bacterial Growth A culture is a solution that is optimal When bacteria are placed in an environment that provides for the growth of a specific type of all of their metabolic needs, bacterial populations grow bacteria. rapidly until they have depleted all of the nutrients in their environment. Bacterial cultures are used primarily to grow isolated strains of bacteria in the lab.

Slide 13 / 61 Slide 14 / 61 Lag Phase Bacterial Growth Phases During the lag phase , the bacterial cell grows and prepares for There are four cell division phases to the bacterial growth cycle: *lag phase *log phase *stationary phase and *death phase. http://www.ryancshaw.com/Files/micro/Animations/BacterialGrowth/PLAY_bacterial_growth.html Slide 15 / 61 Slide 16 / 61 Log Phase During the log phase the bacterial population grows rapidly - doubling in size with each generation. watch the number of cells here http://www.ryancshaw.com/Files/micro/Animations/BacterialGrowth/PLAY_bacterial_growth.ht Slide 17 / 61 Slide 18 / 61

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Slide 31 / 61 Slide 32 / 61 watch the cell number take off! Slide 33 / 61 Slide 34 / 61 Slide 35 / 61 Slide 36 / 61 Stationary Phase The stationary phase is reached when the bacteria start to run out of nutrients and the number of bacteria dying is equal to the number of bacteria reproducing.

Slide 37 / 61 Slide 38 / 61 Calculating Bacterial Growth Death Phase It is possible to estimate the number of bacteria present in After nutrients a culture after a period of time using the following have been used formula: up and waste builds up, (2 n )(initial number of bacteria) = total number of bacteria bacteria begin to die in large n = the number of generations. numbers and This can be determined by using the following formula: only very few reproduce. total time generation time (time it takes the bacteria to divide) Slide 39 / 61 Slide 40 / 61 Calculating Bacterial Growth 1 Bacillus cereus divides every 30 minutes. You inoculate a At a fourth of July picnic, a bowl of potato salad was left out in the hot culture with exactly 100 bacterial cells. After 3 hours, how sun for 2 hours. If the salad originally contained 250 Salmonella many bacteria are present? enteritidis bacterial cells and Salmonella divides every 10 minutes, how many bacteria would be present at the end of 2 hours? Givens: Initial number of bacteria = 250 total time = 2hrs generation time = 10 minutes n = total time = 120 min. = 12 generation time 10 min. (2 n )( initial number of bacteria) = final number of bacteria 2 12 x 250 = 1,024,000 bacteria Slide 41 / 61 Slide 42 / 61 2 Staph. aureus , a disease causing bacteria, divides every 15 minutes at body temperature. A student gets a cut on her hand, is infected with 10 Staph. aureus bacterial cells, and does not clean the wound. After 1 hour, how many bacteria are present? Antibacterial Agents Return to Table of Contents

Slide 43 / 61 Slide 44 / 61 Antibacterial Agents Antibacterial Agents antiseptics: chemicals used to kill or inhibit growth on living tissues Antibacterial agents are chemical substances that either kill bacteria or ( examples - hydrogen peroxide, soap, mouthwash) inhibit growth. There are 3 main types: disinfectants: used to kill or inhibit growth on nonliving antiseptics objects ( examples - bleach and boiling water) disinfectants antibiotics antibiotics: chemicals produced by living organisms (fungi or bacteria) that inhibit growth of bacteria ( examples - penicillin and tetracycline) NOTE: some antiseptics are also disinfectants and vice versa Slide 45 / 61 Slide 46 / 61 How do we know they work? How do we know they work? Step 1 An experiment was done to test the effectiveness of various disinfectants and antibiotics. The experiment had 5 steps. A sterile cotton swab was inserted into a culture of E. Coli bacteria. Slide 47 / 61 Slide 48 / 61 How do we know they work? How do we know they work? Step 3 Step 2 The tip of the cotton swab was then placed on the agar 3 filter paper disks were dipped in 3 plate, streaking the sample of bacterial culture across the different types of disinfectants and plate as show below to inoculate the plate with bacteria. placed in the middle of each quadrant of the first petri dish. Distilled water was placed in the 4 th quadrant as a control Disinfectant 1: bleach Disinfectant 2: hydrogen peroxide Disinfectant 3: window cleaner

Slide 49 / 61 Slide 50 / 61 How do we know they work? How do we know they work? Step 4 Step 5 3 disks coated in 3 different Both petri dishes were then antibiotics were placed in the taped shut, flipped upside down middle of each quadrant of the to prevent condensation from second petri dish. Distilled water dripping onto the bacteria, and was placed in the 4 th quadrant as a placed inside a 37 degree control. incubator for 48 hours. Antibiotic 1: ampicillin Antibiotic 2: penicillin Antibiotic 3: tetracycline Slide 51 / 61 Slide 52 / 61 Predictions and Results Predictions and Results Make your prediction about whether bacteria is killed... Results Dish 2 Results Dish 1 The clearer areas 1 2 surrounding the disks 1 2 3 4 are called 4 3 zones of inhibition and indicate that bacterial growth was inhibited. Slide 53 / 61 Slide 54 / 61 Predictions and Results Fighting Bacteria with Viruses CHECK if a zone of inhibition is present on the plate Another mechanism of inhibiting bacterial growth is to infect the bacteria with a virus. A drop of solution containing bacteriophage viruses was added to the bacterial culture below resulting in several clear zones. These clear zones are called plaques . Viral plaques indicate that bacteriophages have infected and killed bacterial cells. Plaques may be counted and used to determine the number of viruses present in a bacterial culture.

Slide 55 / 61 Slide 56 / 61 Analysis and Conclusions 1). Which disinfectant most effectively inhibited the growth of E. coli? Analysis & Conclusions Return to Table of Contents Slide 57 / 61 Slide 58 / 61 2). Which antibiotic was most effective in preventing the 3). How do you know that any inhibition you have observed is growth of E. coli ? due to the disinfectants and antibiotics on the disk? Slide 59 / 61 Slide 60 / 61 4). If the same experiment was repeated using a different strain 5). You wake up one morning with a of bacteria and a zone of inhibition was observed around the severe sore throat and notice white disk soaked in window cleaner, what could account for the dots lining your tonsils. You quickly visit different results? the doctor, who diagnoses you with a Streptococcus infection (strep throat) and prescribes a 10-day antibiotic treatment. After 3 days, you begin to feel better. Why should you continue taking the antibiotic for the full 10 days?

Slide 61 / 61 6. What causes a zone of inhibition?