Micro final
Refer to the four steps in the scientific method in describing Pasteur's fermentation experiments.
) A group of observations leads a scientist to ask a question about some phenomenon. 2) The scientist generates a hypothesis 3) The scientist designs and conducts an experiment to test the hypothesis. 4) Based on the observed results of the experiment, the scientist either accepts, rejects, or modifies the hypothesis. " What causes fermentation"? 1st hypothesis:spontaneous fermentation He heated a flask of grape juice to kill microbes and sealed it. No fermentation occured, the grape juice had no microorganisms. He rejected his hypothesis. 2nd hypothesis: air causes fermentation He heated a flask of grape juice to kill microbes. Swan neck flasks were used to allow air. No fermentation occured. He rejected his hypothesis. 3rd hypothesis: bacteria ferments grape juice into wine He heated the grape juice in a flask and inoculated it with bacteria and sealed. The grape juice got cloudy as the bacteria grew. The bacteria fermented the grape juice into acid. He rejected his hypothesis. 4th hypothesis: yeast ferments grape juice He heated the flask of grape juice just enough to kill the bacteria, inoculated the juice with yeast, and sealed the flask.The yeast fermented and alcohol was produced. He accepted his hypothesis. In answering the question "What causes fermentation"? he learned that yeast ferments into alcohol, and that yeast could grow with or without oxygen. He also discovered pasteurization as a way of keeping foods from spoiling.
Why is agar used in microbiology?
- because most microbes cannot digest afar, therefore, agar media remain solid even when bacteria and fungi are growing on them - gives nutrients to bacteria that it needs to grow
Facultative anaerobes can live under either aerobic or anaerobic conditions. What metabolic pathways allow these organisms to continue to harvest energy from sugar molecules in the absence of oxygen?
- pentose phosphate pathway - entner-doudoroff pathway
Explain the mechanism of negative feedback with respect to enzyme action?
- self-regulating responses to changes experienced by an organism - control the action of enzymes -- end product of a series of reactions inhibits an enzyme in an earlier part of the pathway
If there are 47 cells in a microliter of sewage, how many cells are there in a liter?
1 microliter = .000001 = 1 X 10^-6 47 X 10^6 in a liter...aka 47,000,000 cells in a liter
List four major questions that drive microbiological investigations today.
1) How can we develop succesful programs to eradicate diseases such as tuberculosis, malaria, and AIDS? 2) What is it about the physiology of life forms known only by their nucleic acid sequences that presents those life forms from being grown in the laboratory? 3) Can bacteria and archaea be used in ultraminiature technologies, such as living computer circuit boards? 4)How can an understanding of microbial communitieshelp us understand the positive aspects of microbial action in preventing and curing diseases, recycling nutrients, degrading pollutants, and moderating climate changes? 5) How can we reduce the threat from microbes resistant to antimicrobial drugs as well as conquer emerging and reemerging infectious diseases?
List Koch's Postulates and explain why they are significant.
1) The suspected causative agent must be found in every case of the disease and be absent from healthy hosts. 2) The agent must be isolated and grown outside the host. 3) When the agent is introduced into a healthy host , the host must get the disease. 4) The same agent must be found in the diseased experimental host. His postulates provide a framework for proving the role of microbes in disease.They tell us how to definitively prove that a particular microbe causes a given disease.
Describe three types of microbes that are extremely resistant to antimicrobial treatment, and explain why.
1. Bacterial endospores - most resistant form of life, can survive more than 20 yrs in 70% alcohol 2. Mycobacterium - contains a waxy cell wall (mycolic acid) helps survive the drying & protects from chemicals 3. Cysts of Protozoa - protozoa cysts wall prevents entry of disinfectants, protects against drying & heat.
Put the following substances in the order they are used in a Gram Stain: counterstain, decolorizing agent, mordant, primary stain.
1. Primary Stain 2. Mordant 3. decolorizing agent 4. primary stain
What are 4 groups of microorganisms that are photosynthetic?
1. cyanobacteria 2. algae 3. chlorophyll 4. protozoa
List 3 indirect methods of counting microbes
1. metabolic activity 2. dry weight 3. turbidity
List 5 direct methods of counting microbes.
1. viable plate count 2. microscopic count 3. membrane filtration 4. electronic counters 5. most probable number
Describe the process of DNA replication, including the role of the origins of replication and replication forks
1.) In the beginning, a site called origins of replication has short stretches of DNA that have specific sequence of nucleotides. 2.) Proteins that initiate DNA replication separates the two strands which opens a replication bubble. At each ends of the bubble there is the replication fork. 3.) The enzyme helicase untwists the double helix at the replication forks. 4.) Once separated single-strand binding proteins bind to the unpaired DNA allowing stabilization. 5.) The topoisomerase relieves the strain from the untwisting of the double helix. 6.) Primase starts an RNA chain from a single RNA nucleotide and adds more RNA nucleotides. 7.) In E.coli, DNA pol III adds a DNA nucleotide to the RNA primer and continues adding till it reaches to the RNA primer to the right where a Okazaki fragment is formed. 8.) DNA pol I comes in and replaces the RNA nucleotides with DNA nucleotides. 9.) Lastly, DNA ligase comes in and joins the sugar-phosphate backbones of all the Okazaki fragments into a continuous DNA strand.
Why are alcohols now more effective in a 70% solution than in a 100% solution?
100% alcohol will dry bacteria and not kill it
Why is E. coli medium described as defined, whereas MacConkey medium and blood agar are defined as complex?
A defined medium (also known as synthetic medium) provides exact known amounts of nutrients for the growth of a particular microbe. Complex media contain a variety of growth factors.
Support or refute the following statement: Microbes cannot tolerate the low pH of the human stomach.
Acidophiles : bacteria and fungi that grow best in acidic habitats (1-2) -ex. stomach acid (pH 2)
What are some advantages and disadvantages to using ionizing radiation to sterilize food?
Advantages - kills microbes, larvae & eggs; also kill cells that spoil or over ripen fruits & vegetables Disadvantages - Can be cancer causing & change taste & nutritional value of fruit & vegetables
Compare and contrast the action of alcohols, halogens, and oxidizing agents in controlling microbial growth.
Alcohol - denatures proteins & disrupts cell membrane (ETOH) Halogens - denatures proteins including enzymes (Cl & iodine) Oxidizing agents - denatures proteins by oxidation (hydrogen peroxide & peracetic acid)
Given the resistant strains of pathogens are a concern to the general health of population, what can be done to prevent this development?
Allow your body to defeat pathogen on their own Combining antimicrobial agents (SYNERGISM VS ANTAGONISM) Limit the use of antimicrobials to necessary cases Use of new generation drugs Use full course of antibiotics
Given that both human cells & pathogens synthesize proteins at ribosomal sites, how can antimicrobial agents that target this process be safe to use in humans?
Antimicrobial agents have 70s rRNA and humans have 80s rRNA therefore it is safe for humans. Although, humans do have 70s rRNA in mitocondria their can be side effects.
Hyperthemophilic prokaryotes may remain viable in canned goods after commercial sterilization. Why is this situation not dangerous to consumers?
Because hyperthermophilic microbes grow at 85 degree C and not at 37 degree C where we store our food.
Why is it necessary to use strong disinfectants in areas exposed to tuberculosis patients?
Because tuberculosis cell wall has lots of waxy lipids mycolic acid, which allows bacteria to survive drying & protects it from most water-based chemical.
Why do warm disinfectant chemicals generally work better than cool ones?
Better penetration with heat
Explain quorum sensing and describe how it is related to biofilm formation?
Biofilms often form as a result of a process called quorum sensing, in which microorganisms respond to the density of nearby microorganisms, cells secrete molecules into their environment and act as their signals, many cells also posses receptors for these signal molecules
Discuss the significant difference between the flasks used by Pasteur and Spallanzani. How did Pasteur's investigation settle the dispute about spontaneous generation?
Both scientists boiled their infusion long enough to kill everything. Spallanzani used vials and sealed them by melting the necks closed, allowing no air to enter. Pasteur used swan neck flasks which allowed air to enter but not dust and microbes. Spallanzani's vials remained clear until he broke the necks off his vials. Though Spallanzani showed no spontaneous generation with his experiment, it was said that he sealed his vials and allowed no air for organisms to survive. Aristotle's 2000 year old theory was not disproved. Pasteur, after 18 months, had no microbial growth in his flasks. He tilted some of the flasks, allowing the dust settled in the curve of the neck to mix with the infusion. He also broke the neck off some other flasks, exposing the liquid to the air. The next day the flasks were cloudy with microbial growth. Pasteur said "Never will spontaneous generation recover from the mortal blow of this simple experiment."
What happens to the carbon atoms in glucose catabolized by E. coli?
Cell fission occurs and the carbon atoms create ribonucleic acid and protein around it like a protective shell. In some cases it crystallizes
What happens to the carbon atoms in sugar catabolized by E.coli?
Cell fission occurs and the carbon atoms create ribonucleic acid and protein around it like a protective shell. In some cases it crystallizes.
What is the difference between deamination and transamination?
Deamination frees up a nitrogen, but transamination only swaps nitrogen to another molecule - doesn't free it up.
Compare and contrast desiccation and lyophilization.
Desiccation - Inhibits growth by removing water that microbes need to metabolize Lyophilization - Uses freezing and drying to preserve microbes for many years, this is long term preservation of microbial culture.
Explain how the principle "electrons travel as waves" applies to microscopy.
Electrons are particles but also move as waves this is relevant to electron microscopes. While Light microscopes use visible light wavelengths to view specimens, Electron microscopes use the same principles to direct waves of electrons through lenses that allow scientists to view specimens using wavelengths between 0.01nm and 0.001 nm.
Define semiconservative replication.
Enzyme that catalyses the breaking of hydrogen bonds between nitrogenous base pairs
How can yeast cells make alcohol and cause bread to rise?
Ethanol & CO2 are waste products of yeast. Ethanol from yeasts is used in alcohol and CO2 made by yeasts causes bread dough to rise
Why would a macroscopic tapeworm be studied in microbiology?
Even though most of these worms are not microscopic as adults , many of them cause diseases that were studied by early microbiologists. Infections of tapeworms were diagnosed by finding microscopic eggs and immature stages in the blood, fecal, urine, and lymph specimens.
Describe what has been called the "Golden Age of Microbiology" with reference to four major questions that propelled scientists during that period.
For about 50 years, from the late 1800's to the early 1900's, during what is now called "The Golden Age of Microbiology", scientists were driven by the search for answers to the following 4 questions: 1- Is spontaneous generation of microbial life possible? 2- What causes fermentation? 3- What causes diseases? 4- How can we prevent infection and disease? During these years the question of spontaneous generation was studied by Redi, Needham, Spallanzani, and ended with the results of Pasteur finally disproving the theory. Fermentation was figured out by Pasteur while trying to figure out why wines sometimes spoiled. He learned pasteurization would kill the bacteria that caused spoilage and living yeast would ferment into alcohol. This began the field of industrial microbiology. Buchner proved that fermantation did not require living cells, but enzymes. This began the field of biochemistry and the study of metabolism. The question of what caused disease was previously though to be attributed to evil spirits, astrological signs, imbalances in body fluid and foul vapors. Pasteur's discovery that bacteria causes wine to spoil led to his hypothesis that microorganisms are responsible for disease, which became know as the germ theory of disease. Semmelweis, Lister, Nightingale, and Snow introduced aseptic techniques for treating patients in a hospital or clinical setting after it had been discovered that the health care givers were themselves infecting the patients. This began the field of infection control and epidemiology. Vaccinations were first discovered by Jenner with his vaccine of cowpox to prevent smallpox. This began the field of immunology. Ehrlich investigated the idea that chemicals could be used to kill microorganisms differentially. He discovered chemicals active against protozoans that caused African Sleeping Sickness and Syphilis. This began the field of chemotherapy.
Why are Gram-negative bacteria more susceptible to heat than Gram-positive bacteria?
Gram (+) bacteria has a thicker peptidoglycan layer than gram (-) & gram (-) has an outer membrane of LPS which contains lipid A
Where specifically does the most significant production of ATP occur in prokaryotic and eukaryotic cells?
In the Plasma membrane.
What does the term HAI (nosocomial infection) have to do with patient care?
Infection that patients acquire while they are receiving treatment for another health care issue.
How does a noncompetitive inhibitor at a single allosteric site affect a whole pathway of enzymatic reactions?
Inhibitors Enzymatic activity can be influenced by a variety of inhibitory substances that block an enzyme's active site. Allosteric (noncompetitive) inhibition results from a change in the shape of the active site when an inhibitor binds to an allosteric site. Noncompetitive inhibitors do not bind to the active site but instead prevent enzymatic activity by binding to an allosteric site located elsewhere on the enzyme. Binding at an allosteric site alters the shape of the active site so that substrate cannot be bound. Allosteric control of enzyme activity can take two forms: inhibitory and excitatory
A man has been given a broad spectrum antibiotic for his stomach ulcer. What unintended consequence can arise from this therapy.
It may allow secondary or superinfections to develop, by killing normal flora reduces microbial antagonism
A laboratory scientist notices that a certain bacterium does not utilize lactose when glucose is available in its environment. Describe a cellular regulatory mechanism that would explain this observation.
Lactose is not the preferred carbohydrate source for E. coli. If lactose and glucose are present, the cell will use all of the glucose before the lac operon is turned on. This type of control is termed catabolite repression. To prevent lactose metabolism, a second level of control of gene expression exists. The promoter of the lac operon has two binding sites. One site is the location where RNA polymerase binds. The second location is the binding site for a complex between the catabolite activator protein (CAP) and cyclic AMP (cAMP). The binding of the CAP-cAMP complex to the promoter site is required for transcription of the lac operon. The presence of this complex is closely associated with the presence of glucose in the cell. As the concentration of glucose increases the amount of cAMP decreases. As the cAMP decreases, the amount of complex decreases. This decrease in the complex inactivates the promoter, and the lac operon is turned off
Draw and label the 4 distinct phases of a bacterial growth curve. Describe what is happening within the culture as it passes through the phases.
Lag phase - microorganisms are introduced into fresh culture medium, usually no immediate increase in cell number occurs. Cells in the culture are synthesizing new components. Log (exponential) phase - microorganisms are growing and dividing at the maximal rate possible given their genetic potential, the nature of the medium, and the environmental conditions. Their rate of growth is constant during the exponential phase; that is, they are completing the cell cycle and doubling in number at regular intervals. Stationary phase - Population growth eventually ceases and the growth curve becomes horizontal. Bacteria at a population level of around 10 9 cells per ml. Death phase - For many years, the decline in viable cells following the stationary phase was described simply as the "death phase." It was assumed that detrimental environmental changes such as nutrient deprivation and the buildup of toxic wastes caused irreparable harm and loss of viability. That is, even when bacterial cells were transferred to fresh medium, no cellular growth was observed. Because loss of viability was often not accompanied by a loss in total cell number, it was assumed that cells died but did not lyse.
Defend this statement: "The investigations of Antoni van Leeuwenhoek changed the world forever."
Leeuwenhoek was a Dutch tailor, merchant, and a lens grinder. He had a stubborn desire to do everything himself. He learned to make his own magnifying lenses to examine the quality of cloth. He began looking at all kinds of things under his lenses out of curiosity. He began making simple microscopes and this became an over-whelming passion for him. He made a new microscope for each new specimen he viewed. One day he turned a lens to a drop of water. He discovered a previously unknown microbial world he called animalcules.This began the study of micrbiology.
How does the study of the nucleotide sequences of ribosomal RNA fit into a discussion of taxonomy?
Modern taxonomy uses nucleotide sequencing to look for relationships or shared DNA with ancestral species rather than relying on other characteristics for classification.
Describe 5 physical methods of microbial control.
Moist Heat - use to disinfect, sanitize, sterilize & pasteurize, kills cells by denaturing protein & destroying cytoplasmic membrane (disinfecting baby bottles) Dry heat - Used w/ powders, oils & metals. Hot air is used to denature protein & foster oxidation of metabolic & structural chemical. Refrigeration & Freezing - Used in food preparation & storage. Halts growth of most pathogens, because chemical reactions occur slower at lower temperatures. Ionizing radiation - denatures molecules DNA, which causes cell death & mutations Osmotic pressure - high concentration of salt & sugar. Used to preserve food like salted fish.
Why are vitamins essential metabolic factors for metabolism?
Most vitamins function as coenzymes in important metabolic reactions and are therefore essential factors
Why is the fact that drug Z destroys the NAM portions of a cell's wall structure an important factor in considering the drug for chemotherapy?
NAM is a component in bacteria cell wall & it is not present in human cell membrane, that is why drug Z only target NAM & we can use chemotherepy
Contrast narrow-spectrum and broad-spectrum drugs. Which one are more effective?
NARROW spectrum - Drugs that works against only few kinds of pathogens BROAD spectrum - Drugs that works against different kinds of pathogens
Why is Latin used in taxonomic nomenclature?
No country uses Latin as it's language so it is used as a universal language for science. (It was also used as the language of science in Linnaeus' time.)
Compare & contrast the actions of polyenes, azoles, allyamines & polymyxin.
POLYENES - Disrupts cytoplasmic membrane of cell & causing lysis to cell AZOLES - Inhibit synthesis of ergosterol, disrupts cytoplasmic membrane w/o ergosterol cell membrane does not remain intact & fungal cell dies ALLYAMINES - inhibits ergosterol synthesis POLYMYXIN - Disrupts cytoplasmic membrane (lipid bilayer) of gram (-) & toxic to humans
Defend the following statement: "Pasteurization is not sterilization."
Pasteurization allows thermophilic & thermoduric bacteria to survive (not pathogenic) & sterilization kills all microbes
Compare and contrast four tests that have been developed to measure the efficacy of disinfectants.
Phenol coefficient - Oldest method/efficiency against phenol; the greater the ratio the better Kelsey-Sykes capacity - Use in Europe/bacterial suspension added to chemical, lack of turbidity is lack of bacterial growth In-use - Checks real life situations/swab from a suspected site to media and check for growth, most realistic to determining efficacy of chemical Use - Use in US/Dip metal cylinders into broth culture of bacteria & dry 36 degree C
What are the differences between photoautotrophs, chemoautotrophs, photoheterotrophs, and chemoheterotrophs?
Photoautotrophs are microbes get their energy from light and their carbon for inorganic compounds. Chemoautotrophs are microbes that get their energy from chemicals and get their carbon from inorganic compounds. Photoheterotrphs are microbes that get their energy from light and carbon from organic compounds. Chemoheterotrophs get their energy from chemicals and carbon from organic compounds.
Support or refute the following statement: antimicrobial agents produce resistant cells.
Produce enzyme that destroys drug slow or prevent entry of drug alter the target of the drug, where drug can't attach to it alter metabolic chemistry pump the antimicrobial out of cell before drug can act biofilms retard drug diffusion and slow metabolic rate mycobacterium tuberculosis produce MfpA protein
What characteristics would an ideal chemotherapeutic agent have? Which drug has these qualities?
Readily available Inexpensive Non toxic & nonallergenic Chemically stable Selectively toxic against pathogens NO AGENT HAS ALL THESE QUALITIES
An atomic force microscope can magnify a living cell, whereas electron microscopes and scanning tunneling microscopes cannot. What requirement of electron and scanning tunneling microscopes precludes the imaging of living specimens.
Specimens must either be sliced up thin in viewing media and viewed in a vacuum or requires the use of a direct electron beam.
Why was the theory of spontaneous generation a hindrance to the development of the field of microbiology?
Spontaneous generation, proposed by Aristotle, was believed for 2000 years. Experiments with meat were done by Redi to disprove the theory and scientists began to doubt Aristotles theory. Needham tested the theory with boiled infusion in corked vials, only to show spontaneous generation was true. Spallanzani also tested the theory with boiled infusion and he sealed his vials by melting the necks to not allow any air to enter. Although his experiment showed no spontaneous generation it was said that his sealed vials did not allow air for organisms to thrive. The theory of spontaneous generation continued. Pasteur is the one who finally disproved the theory with his swan neck flask experiment in the 1800's. It was then that microorganisms began being studied in depth.
How do organisms control the rate of metabolic activities in the cell?
There is a wide variety of mechanisms such as controlling concentrations of enzymes or regulatory proteins through production or destruction changes, controlling flux through metabolic pathways in both directions through phosphorylation, controlling activity of enzymes, modifying transport or substances, changes in membrane potentials, and various methods of antagonism.
What is the difference between thermal death point and thermal death time?
Thermal death point is the lowest temperature that kills all cells in broth in 10 min Thermal death time is the time that it takes to sterilize volume of liquid at a set temperature.
Contrast the structures and actions of soaps and quats.
They are both detergents. SOAPS do not kill organism, they are washed off surfaces & QUATS disrupt cellular membrane where the affected cell lose internal ions
Why are enzymes necessary for anabolic reactions to occur in living organisms?
They catalyze reactions by lowering the activation energy, which is the amount of energy needed to trigger a chemical reaction. Whereas heat can provide energy to trigger reactions temperatures needed to reach activation energy for most metabolic reactions are often too high to allow cells to survive.
Why do cyanobacteria and algae take in carbon dioxide and give off oxygen?
They contain photosynthetic pigments and some even have chloroplasts. Substances such as chlorophyll absorb light at certain wavelengths and allow the following reaction to take place: 6CO2(g) + 6H2O(l) ------> C6H12O6(aq) + 6O2(g) Therefore CO2 is absorbed and oxygen is given off.
High temperature affects the shape of particular molecules. How does this affect the life of a microbe?
Too high temperature denatures proteins and cell membranes become too fluid - Too low temperature results in rigid and fragile membranes
Why are antiviral drugs difficult to develop?
Viruses are inside human cells, drugs have to pentrate human cells to get to viruse, viruses uses human enzymes & protein for themselves, therefore are harmful to humans.
Why do we breathe in oxygen and breath out carbon dioxide?
When oxygen is breathed in it goes to the alveoli and in to the bloodstream where it is picked up by a protein molecule called hemoglobin one molecule of hemoglobin can transport 4 oxygen molecules to anywhere in the body the hemoglobin transports the oxygen to another protein called Cytochrome C oxidase which makes two molecules of water for every molecule oxygen (water needs two hydrogen atoms and one oxygen) when a water molecule is made it releases energy the Cytochrome C oxidase harvests the energy then uses it for every day functions Carbon Dioxide is released because it is in most everything we eat and is toxic to humans so we breathe it out. You breath oxygen in order for you to live. You give off carbon dioxide in order for plants to live. Plants and animals are in a give and take process it's also know as "mutualism". Plants take in carbon dioxide in order for it to give off oxygen which can be very beneficial to us. While in humans and animals, it's in a complete opposite where in we take in oxygen and give off carbon dioxide.
What is the difference in drug action of synergists contrasted with that of antagonists?
antagonists - blocks attachment of viruses & defer infections Synergisms - enhances effects on 2nd drug
What is the difference between complex media and defined media?
defined media provides exact known amounts of nutrients while complex media contain a variety of growth factors of which we don't know for example sheeps blood and blood agar
List 6 types of microorganisms.
fungi protozoa algae bacteria archaea viruses
Critique the following definition of Magnification: "magnification makes things bigger"
magnification does not literally make things larger, rather it is the process by which lenses may be used to enlarge the image if something so that it can be viewed or be viewed with greater detail.
Give three characteristics of a specific epithet
must be expressed in lower case usually an adjective species specific
Why can electron microscopes only view dead organisms.
must be viewed in a vacuum (no oxygen)
How does oxidation of a molecule occur without oxygen?
they can occur with or without oxygen
Why must media, vessels, and instruments be sterilized before hey are used for microbial procedures?
to avoid contamination
