Metabolism Metabolism: Catabolism/Catabolic UNIT 3 CH.5 (pgs. 113-32) & 6 METABOLISM & GROWTH REQUIREMENTS Anabolism/Anabolic Properties of enzymes: Control Metabolic Pathways Enzymes (type of protein) Act as catalysts (they speed up chemical reactions up to a million times without changing) Activation energy is needed to get a reaction started One way to activate a reaction: heat (not good) Function #1: enzymes help lower the activation energy so that reactions happen at mild temperatures in cells Function #2: provide a spot for reactions to occur Properties of enzymes: Enzyme-substrate complex Active site: a binding site for the substrate Substrate: the substance the enzyme acts upon When they bind, the substrate undergoes chemical changes, the product is formed, & the enzyme detaches How enzymes work www.youtube.com/watch?v=ti69avrw0du Properties of enzymes High degree of specificity Catalyze only one type of reaction Work on only one particular substrate Recognized by the suffix ase Lipases breakdown lipids Peptidases break peptide bonds Many need the presence of a cofactor or coenzyme: Coenzyme: a nonprotein molecule associated with the enzyme (made by vitamins yep, they re important) Cofactor: an inorganic molecule that improves the fit of the enzyme & substrate (like Mg+) 1
Properties of enzymes Factors that affect enzymatic reactions ph Temperature Concentration (amount) of substrate, product, and enzyme Enzyme Inhibition: Competitive inhibitor: molecule similar to the substrate structure binds to the active site to prevent the binding of the substrate; reversible Noncompetitive inhibitor: bind to an allosteric site (a site other than the active site) and changes the shape of the active site; irreversible or reversible Feedback inhibition: when the amount of product influences the enzyme that started the process to stop Brain Check 1. Which of the following would influence the rate of an enzyme reaction? a. Temperature b. ph c. Concentration of substrate molecules d. Concentration of product molecules e. All of these 2. Where does a substrate bind to on the enzyme? a. active site b. allosteric site c. binding site d. key site Microbial Metabolism Microorganisms have to eat too Autotrophs: self-feeders that use CO2 to make organic molecules/food Photoautotrophs: use sunlight (don t usually cause disease) Chemoautotrophs: use inorganic substances/chemicals like sulfides & nitrites Microbial Metabolism Heterotrophs: other-feeders that use already made organic molecules/food Photoheterotrophs: use sunlight for nutrition, but have to supplement with organic molecules Chemoheterotrophs: use organic compounds like proteins, fats, & carbohydrates Microbial metabolism & energy Microorganisms have to capture energy for several things (movement, body functions, etc) Cellular respiration: process of organisms breaking down food into ATP C 6 H 12 O 6 + 6O 2 6CO 2 + 6 H 2 O + 38 ATP Purpose of ATP: energy is stored in this molecule ATP The Need for Energy Adenosine Phosphate Phosphate Phosphate ADP Adenosine High-energy bond: Stores a lot of energy that is released when the bond is broken Phosphate Phosphate Energy 2
Three Stages of Cellular Respiration in microbes Stage Aerobic/ Anaerobic Oxygen required? Location ATP Produced 1. Glycolysis Anaerobic No Cytoplasm 2 2. Krebs Cycle Aerobic Yes Cytoplasm 2 3. Electron Transport Chain Aerobic Yes Cell Membrane 34 Alcoholic fermentation Pyruvic Acid ethyl alcohol + carbon dioxide Carried out by yeast and some bacteria Used in brewing beer, making wine, and baking bread and cakes FERMENTATION o Occurs after glycolysis if oxygen remains absent o Doesn t yield a lot of energy o Glycolysis (2 ATP) + Fermentation (2 ATP) = 4 ATP Lactic Acid fermentation Pyruvic Acid lactic acid Occurs in lactobacilli, streptococci, and mammalian cells Used to make cheese (lactobacilli) and that burn you feel after working out 38 ATP Other types of fermentation Casu Marzu : Forbidden in the U.S. Fermentation Taken Too Far? Reason: Casu marzu, a traditional Sardinian cheese, develops when cheese fly larvae are introduced into Pecorino to promote advanced fermentation. As the larvae hatch and eat through the cheese, it softens. Diners have to dig in before the maggots die. Casu marzu, like many unpasteurized cheeses, is banned in the U.S. Anaerobic: no oxygen present Lactic Acid produces lactate Fermentation Makes 2 ATP Anaerobic Respiration = 4 ATP Cellular Respiration summarized Alcoholic produces alcohol & CO 2 1 molecule of GLUCOSE Glycolysis Anaerobic Makes 2 ATP Aerobic: oxygen is present Krebs Cycle Aerobic Makes 2 ATP Electron Transport Chain Aerobic Makes 34 ATP Aerobic Respiration = 38 ATP Brain Check 1. The major energy-exchange molecule in living cells is a. ADP b. AMP c. ATP d. Glucose 2. Why does fermentation occur? a. Because oxygen is absent b. Because oxygen is present 3
Microbial growth & cell division Microbial growth: the increase in the number of cells as they divide (not their actual size) GROWTH OF BACTERIA Unicellular organisms grow, but their process happens like this: The original cell, called the mother cell, grows to double its size and duplicates its contents (DNA) It then divides into 2 cells that are called daughter cells Microbial cell division Binary fission: www.youtube.com/watch?v=ytoii3-p-ni Budding: vimeo.com/39669636 Cell Division Binary Fission: when a cell duplicates or copies itself and then divides into 2 cells (how bacterial cells divide) Budding: when a small, new cell develops from the surface of an existing cell and then separates from it (how yeast & a few bacterial cells divide) Bacterial growth curve To help bacterial cells grow, you put them into a fresh, nutrient-rich mixture of substances on or in which microorganisms grow. This is called medium (media). The length of time required for one cell division is called the generation time. For most bacteria, it s between 20 min-20 hrs It happens at an exponential or logarithmic rate Ex. A culture with 1000 organisms per ml with a generation of 20 min would contain 2000/mL after 20 min, 4000 after 40 min, and so on Generation Times practice questions 1. If an E. coli culture has a doubling time of 20 minutes, how many cells will result after 1 hour from a single cell? 2. If an S. thermophilus culture has a doubling time of 30 minutes, how many cells will result after 3 hours from a single cell? 3. If an L. acidophilus culture has a doubling time of 25 minutes, how many cells will result after 2 hours from a single cell? 4
Bacterial growth curve Cells in a nutrient-rich environment will display 4 general phases of growth: Bacterial Growth Curve 1. Lag Phase: organisms are metabolically active growing and synthesizing various substances, but not increasing in number 2. Log Phase: organisms divide at an exponential or logarithmic rate with a constant generation time 3. Stationary Phase: the # of new cells = the # of cells dying; the medium contains limited nutrients and may even have some toxic waste materials; can still be saved if transferred to new media 4. Death Phase: many cells lose their ability to divide and eventually die a logarithmic decrease in cells is seen Brain check 1. Budding is seen in cells. a. Animal b. Bacteria c. Viruses d. Yeast 2. Binary fission is seen in cells. a. Animal b. Bacteria c. Viruses d. Yeast Brain check 3. When a cell divides, it is referred to as the. a. Daughter cell b. Dividing cell c. Father cell d. Mother cell 4. The newly created cells are known as. a. Daughter cells b. Dividing cells c. Father cells d. Mother cells Measuring bacterial growth: Counting Large Populations Serial Dilutions/ Standard plate counts: 1. Successive 1:10 dilutions of a liquid culture of bacteria are made and transferred onto an agar plate (start with 1:100 dilution) 2. Each colony that grows represents one live cell from the original sample 5
Measuring bacterial growth: Direct Counts Physical Influences on Growth 1. ph 2. Temperature 3. Oxygen concentration 4. Moisture 5. Hydrostatic Pressure 6. Osmotic Pressure 7. Radiation Physical Influences # 1: ph Remember that acidity or alkalinity of a medium is expressed in terms of ph Microorganisms have an optimum ph (when they grow best); this tends to be neutral (ph 7) Acidophiles: acid-loving; can make acids; exist from ph 0.1-5.4 Ex. Lactobacillus species (makes lactic acid) Neutrophiles: exist from ph 5.4-8 Ex. Most bacteria that cause human diseases Alkaliphiles: alkali (or base) loving; exist from ph 7-11.5 Ex. Vibrio cholerae Physical Influences # 2: temperature Most microorganisms can grow over a 30 o C range Psycrophiles: cold-loving; 15 o -20 o C (even 0 o C) *Obligates: can t grow above 20 oc *Facultative: grow best below 20oC, but can above that Habitat: soil & cold water (sea water can be below 0 oc) Mesophiles: moderate-loving; 25 o -40 o C Habitat: humans (our 37oC body temp is ideal) Thermophiles: heat-loving; 50 o -60 o C (even 110 o C) Obligates: have to grow above 37 oc Facultative: grow above or below 37 oc Habitat: compost heaps & hot springs Temperature continued Important for providing conditions for microbial growth, but also for preventing it Food refrigeration at 4 o C Food & other materials (like blood) can still grow so -30 o C is good for long term storage Sterilization: using extreme heat to kill microorganisms (most can survive extreme cold moreso than heat because heat denatures enzymes & proteins) Physical Influences # 3: Oxygen 1. Aerobes Use O 2 in their metabolic pathways 2. Obligate Aerobes: need free O 2 Ex. Pseudomonas (common nosocomial) 3. Microaerophiles: grow best in a small amount of free O 2 Ex. Campylobacter (causes intestinal disorders) 4. Anaerobes Do not use O 2 in their metabolic pathways Obligate Anaerobes: killed by free O 2 Ex. Clostridium tetani (lockjaw) 5. Facultative Anaerobes: can switch between aerobic metabolism if O 2 is present or anaerobic if it isn t Ex. Staphylococcus & E. coli 6. Aerotolerant Anaerobes: metabolize anaerobically, but aren t harmed by free O 2 Ex. Lactobacillus 6
Growth positions in Thioglycollate medium Other Physical Influences on Growth Moisture: all microbes need a water environment Hydrostatic pressure: exerted by standing water; some bacteria are the only things that can survive deep in the ocean Osmotic pressure: diffusion of water; halophiles love high salt contents that would cause our cells to crenate or shrink Radiation: can cause mutations to our DNA, but some bacteria have pigments that can screen radiation waves and even repair DNA Microbial growth There are a few microbes called fastidious microorganisms because it is hard to meet their needs in the laboratory setting such as N. gonnorheae which grow well in the body, but not on media. Nutritional Factors Affecting Bacterial Growth C, N, S, P availability: energy source, synthesis of organic molecules & cell components Trace elements: ions that serve as cofactors in enzymatic reactions Vitamins: used as coenzymes in enzymatic reactions; most microbes make their own. Microbes in our intestines make Vitamin K (blood clotting) and Vitamin B Nutritional complexity: determined by enzymes Brain Check 1. What are some physical requirements that must be satisfied to successfully culture bacteria? 2. What are some nutritional requirements that must be satisfied to successfully culture bacteria? CULTURING BACTERIA 7
Culture Media Bacteria have to be grown (cultured) for them to be identified. Applications of Culturing By appropriate procedures, they have to be grown separately (isolated) on culture media and obtained as pure for study (Koch s postulates) Stock cultures: maintained for keeping specimens viable for subculture into fresh medium for routine work Preserved cultures: maintained for storage to prevent contamination or change of characteristics Maintaining cultures Preserved cultures Diagnostic tests Limitations on Culture TYPES OF CULTURE MEDIA CONSISTENCY Solid media contains 2% agar Colony morphology & pigmentation Eg: Nutrient agar, Blood agar Liquid media no agar For inoculum preparation, blood culture, for the isolation of pathogens from a mixture Eg: Nutrient broth Semi solid medium 0.5% agar Eg: Motility medium CULTURING BROTH TECHNIQUE Culturing Plate techniques Streak Plates: spreading bacteria across sterile agar so that the progeny of a single cell can be picked up from the surface and transferred to the sterile medium 8
Culturing Plate techniques Pour Plate Method: using serial dilutions and transferring a portion of the solution to melted agar and then picking cells from a colony on agar. Brain Check 1. What is the difference between solid and liquid media? When should you use a solid media? A liquid media? 2. The pour plate method is used with serial dilutions to find out what? a. That bacteria are present b. The number of bacteria per dilution c. IDK I m tired I can t do this right now TYPES OF MEDIA DIAGNOSTIC Synthetic or defined media (most common) Media prepared from pure chemical substances and its exact composition is known Ex: Nutrient Broth (NB), Nutrient Agar (NA) - NB consists of peptone, meat extract, NaCl, - NB + 2% agar = Nutrient agar Complex media Media other than defined media They have added ingredients Provide special nutrients Selective, differential, and enrichment media are examples TYPES OF MEDIA DIAGNOSTIC Selective media Encourages the growth of some organisms and inhibits others Examples Mac Conkey s medium for gram negative bacteria TCBS for V.cholerae LJ medium M.tuberculosis Wilson and Blair medium S.typhi Potassium tellurite medium Diphtheria bacilli Mac Conkey s medium TCBS Thiosulfate Citrate Bile Salts Sucrose Agar Potassium Tellurite media LJ media 9
TYPES OF MEDIA DIAGNOSTIC Differential media A media which has substances incorporated in it enabling it to distinguish between bacteria. Eg: CHROMagar Candida TYPES OF MEDIA DIAGNOSTIC Enriched media Used to grow particular organisms that might not be present in sufficient numbers to allow it be isolated and identified. Substances like blood, serum, egg are added to the defined medium. Eg: Blood agar, Chocolate agar (used for growing fastidious respiratory bacteria, such as Haemophilus influenzae and Neisseria meningitidis) Application Questions 1. Which of the following statements is TRUE? A. An alga that produces energy from sunlight to reduce CO2 is a photoheterotroph. B. A purple nonsulfur bacterium that produces energy by using sulfur to reduce CO2 is a photoautotroph. C. A bacterium that metabolizes organic compounds to produce energy is a chemoheterotroph. D. A fungi that produces energy by capturing light to process organic compounds is a chemoautotroph. APPLICATION QUESTIONS 2. Phosphofructokinase (PFK) in glycolysis is controlled by the level of ATP in the cell. At high concentrations of the enzyme, ATP binds to the allosteric site and deactivates phosphofructokinase. Pick the answer that best explains why this occurs. A. ATP is a competitive inhibitor of PFK. B. ATP is a noncompetitive inhibitor of PFK. C. ATP is not an important regulator of glycolysis. D. PFK is not regulated by ATP levels inside the cell. 3. Streptococcus thermophilus can be used as a probiotic for digestive health and has a generation time of 25 min. A container of yogurt was inoculated with a single cell; calculate the number of cells present after 200 minutes. A. 8 B. 16 C. 108 D. 256 10
4. Lactobacilli are primarily found in the anaerobic colon of humans, but can also cause dental caries or cavities. Explain why this occurs. A. Lactobacilli are facultative anaerobes. B. Lactobacilli are microaerophiles. C. Lactobacilli are obligate aerobes. D. Lactobacilli are obligate anaerobes. 5. A bacterium has the following characteristics: mesophile, neutrophile, microaerophile, halophile. In which of the below environments could this bacterium grow? A. In the ocean which has a ph of 7, temperature range of 25-28 C and low dissolved oxygen. B. In the ocean which has a ph of 8, temperature range of 15-18 C and high dissolved oxygen. C. In a lake which as a ph of 7, temperature range of 25-28 C and low dissolved oxygen. D. In a lake which has a ph of 8, temperature range of 0-11