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Microbiology
Exam 02 - Culture of Bacteria: Growth Influencing Factors
| Question | Answer |
|---|---|
| What are the growth influencing factors of bacteria? | 1. Physical 2. Nutritional 3. Media |
| What kind of "growth" are we referring to when it comes to bacteria growth? | Population growth |
| What are the physical growth factors? | 1. temperature 2. pH 3. osmotic pressure 4. light 5. gases |
| What happens to bacteria when temperature is lower? | Bacteria continues to grow |
| What happens to bacteria when temperature is high? | Bacteria dies off more quickly |
| What are mesophiles? | Bacteria that grow best at human body temp (37 degrees C) 1. most disease-causing bacteria 2. contribute to food spoilage |
| How do you prevent food spoilage by mesophiles? | Refrigeration |
| What does the prefix "psychro" mean? | Cold |
| What are Psychrophiles? | bacteria that grow best at cooler places between 15-20 degrees C |
| What are Psychotrophs? | bacteria that grow best at cooler places between 20-25 degrees C |
| At what temperature do thermophiles grow best? | Hot temperature - 60 degrees C |
| At what temperature would hyperthermophiles grow best and where would you find them? | 80-100 degrees C; found in hot springs and on ocean floor |
| What is the definition of pH and what is neutral pH? | 1. Degree of alkalinity 2. neutral pH = 7 |
| What is the relationship between pH and protein structure? | pH greatly influences protein structure (can denature) |
| Describe the characteristics of the bacteria that we use in lab. | They like neutral pH |
| How do we keep the bacteria in lab from becoming too acidic? | We use buffers |
| What is the process of preserving food by making it more acidic? | Pickling |
| Why do bacteria in lab tend to make media more acidic? | Due to byproducts that they produce, and they can die |
| What are acidophiles? | Bacteria that love acid 1. prevents protein from denaturing 2. Ex: Fungi like a pH = 5 |
| What is osmotic pressure? | degree at which water will enter and exit cell |
| What factor influences osmotic pressure? | The amount of dissolved solutes |
| When it comes to osmotic pressure, under what condition will bacteria function best? | In isotonic solutions where there is no osomtic pressure either way |
| What does salting do for food? | Salting helps to preserve food |
| What are halophiles? | Bacteria that like HIGH salt concentration (ie: Dead Sea's salt concentration @ 30%) |
| Is light a problem for disease-causing bacteria? | No because 1. some use light as an energy source for photosynthesis to prduce oxgyen 2. other bacteria that can survive w/o light produce oxygen with other methods |
| What are the functions of bacteria pigments? | It allows for protection against UV light, which will denature DNA - baceria can lose their pigments when grown in lab |
| How is UV light used in the lab? | 1. To control bacterial growth 2. method of sterilization (when directly shined on area) |
| What are capnophiles? | Bacteria that like to have larger amounts of CO2 (ex: 1. Neisseria gonorrheae - gram negative cocci, aerobes 2. Streptococcus pneumoniae) |
| What is the candle-jar technique? | Method to create a CO2 rich environment - 1. put candle in jar with bacterial growth plates 2. close lid 3. candle builds up CO2 while decreasing O2 |
| Why is oxygen in the atmosphere toxic to bacteria? | Because of toxic byproducts made during its breakdown |
| T/F Some bacteria do not have sufficient amounts of enzymes to break down oxygen byproducts | TRUE |
| What kinds of toxic byproducts can enzymes be used to breakdown? | 1. hydrogen peroxide 2. superoxide radical 3. hydroxyl radical |
| What enzyme breaks down hydrogen peroxide? | 1. Catalase 2. Peroxidase (both found in aerobes and facultative anaerobes) |
| What kind of anaerobes does peroxidase work better against? | Aerotolerant anaerobes that don't do better with oxygen (ie: Staphylococcus) |
| T/F Many anaerobes have catalase or peroxidase therefore are immune to oxgyen | FALSE - many anaerobes don't have catalase and peroxidase, therefore oxygen kills them |
| How does peroxidase break down hydrogen peroxide? | With an additional proton to make 2 waters. (requies NaDH as a source of proton) |
| What is the chemical formula when catalase breaks down hydrogen peroxide? | 2 H2O2 ==catalase==> 2 H2O + O2 |
| What is the chemical formula when peroxidase breaks down hydrogen peroxide? | H2O2 ==peroxidase (NADH + H+ --> NAD)==> 2H2O |
| What is the chemical formula when superoxide dimutase gets rid of superoxide radical? | 2 O2- + 2H2+ ==superoxide dimutase==> H2O2 + O2 |
| How does nutritional factors affect bacterial growth? | It is provided directly in the media (ie: E. coli can get energy / electrons / carbon from glucose) |
| What are the nutritional factors in media that influences bacteria growth? | 1. energy 2. electrons 3. carbon 4. salts 5. vitamins/amino acid/purines/pyrimidines/etc 6. water |
| What is the role of energy as a nutritional factor? | To build bonds |
| What does the suffix "-troph" mean? | Feeding |
| What are bacteria that use "light" as its energy source called? | Phototrophs |
| What are bacteria that use "chemical" as its energy source called? | Chemotrophs |
| What is the role of electrons as a nutritional factor? | They transfer hydrogens |
| What are bacteria with inorganic electron H source called | Lithotrophs (ie: plants using photosynthesis to produce water) |
| What are bacteria with organic electron H source called? | Organotrophs (ie: E. coli) |
| When it comes to electron H source, what does the term "inorganic" mean? | No carbon, water, hydrogen sulfide |
| What are bacteria with inorganic carbon source called? | Autotrophs |
| What are bacteria with organic carbon source called? | Heterotrophs |
| When it comes to carbon source, what does inorganic mean? | Get carbon from CO2 |
| Based on the nutritional factors energy, electron and carbon source, describe plants | Photolithoautotrophs |
| Based on the nutritional factors energy, electron and carbon source, describe the bacteria (and our unknowns in lab) | Chemoorganoheterotrophs |
| Based on the nutritional factors energy, electron and carbon source, describe bacteria deep in the ocean | Chemolithoautotrophs |
| What are salts (inorganic molecules) sources of? | 1. nitrogen 2. sulfur/phosphorus 3. K, Mg, Fe & other elements |
| What is nitrogen used for? | To make amino acids & nucelotides (NAD/DNA/RNA) |
| What is sulfur/phosphorus used for? | 1. sulfur - for amino acids (ie: cysteine) 2. phosphorus (in the form of phosphate) - for phospholipids nucleic acids, buffers |
| What are K, Mg, Fe, & other elements use for? | 1. they are limiting/in trace amounts for most bacteria 2. iron is important in the electron transport chain (cytochromes have iron) |
| How do vitamins, amino acids, purines, pyrimidines, etc, influence bacterial growth? | They are provided to bacteria that can make those themselves |
| How does water influence bacterial growth? | Helps to keep bacteria moist & provide fluid for their cytoplasms (ie: slants don't dry out as fast) w/o water, endospores will not grow |
| What are the categories of media that influence bacterial growth? | 1. complex 2. defined 3. selective 4. differential |
| What are defined media? | built from scratch by adding different amounts of chemicals - can't e extracted from natural organisms |
| What are complex media? | 1. media made in the lab 2. easy to make 3. extracted from nutrient material |
| What are selective media? | Grows some organisms well, while others do not grow as well - good in isolating unknowns |
| What are differential media? | Helps to tell organisms apart because it separates groups/colonies |
Created by:
lophung
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