BIO 191 CH 24 HW

25 July 2022
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question
Classify each statement or picture as applying to gram-positive bacteria, gram-negative bacteria, or both. Drag each item to the appropriate bin.
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Gram-positive bacteria: -Appear purple after Gram staining -Have a thick peptidoglycan layer -Alcohol rinse does not remove crystal violet Gram-negative bacteria: -Appear pink after Gram staining -Have a thin peptidoglycan layer -Alcohol rinse easily removes crystal violet -Have an outer membrane as part of their cell wall structure Both: -Have a plasma membrane Gram staining is a technique for classifying bacteria based on differences in the structure of their cell walls. Gram-negative bacteria and gram-positive bacteria both have a plasma membrane surrounded by a cell wall that contains peptidoglycan. However, the cell wall of gram-negative bacteria is composed of a thin layer of peptidoglycan and an outer membrane, whereas the cell wall of gram-positive bacteria is composed of a thick layer of peptidoglycan. Gram-negative bacteria appear red or pink because the alcohol rinse washes away the crystal violet dye. Gram-positive bacteria appear purple because the alcohol rinse does not wash away the crystal violet dye.
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Label the diagram below to show the relationship between nutritional modes of bacteria. Drag the labels to their appropriate locations on the diagram.
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Nutritional Modes of Bacteria *Left side Require energy only from inorganic sources: (a) Autotrophs Use chemicals as energy source: (c) Chemoautotrophs Use light as energy source: (d) Photoautotrophs *Right side Require energy from at least one organic nutrient: (b) Heterotrophs Use light as energy source: (e) Photoheterotrophs Use chemicals as energy source: (f) Chemoheterotrophs *Center Photoautotrophs and Photoheterotrophs also classified as: (g) Phototrophs Chemoautotrophs and Chemoheterotrophs also classified as: (h) Chemotrophs Some bacteria obtain energy from light (phototrophs), whereas other bacteria obtain energy from chemicals (chemotrophs). Autotrophs (literally "self-feeders") require only an inorganic substance, such as carbon dioxide, as their carbon source; heterotrophs (literally "other-feeders") require at least one organic nutrient as their carbon source.
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Azotobacter is a genus of bacteria that live in soil and have the following characteristics: They are bacilli. They are gram-negative. They are obligate aerobes. They can fix nitrogen. (Unlike some other nitrogen-fixing bacteria, which associate with the roots of plants, Azotobacter species are free-living.) Select the four statements that are true for bacteria in the genus Azotobacter. -They appear purple after Gram staining. -They use O2 for cellular respiration. -They require amino acids or other organic molecules as a source of nitrogen. -They are poisoned by O2. -They can carry out anaerobic respiration in an environment that lacks O2. -They have a relatively thin layer of peptidoglycan in their cell wall. -They can convert atmospheric nitrogen to ammonia. -They have the appearance of coils or corkscrews. -They are shaped like rods.
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They use O2 for cellular respiration. They have a relatively thin layer of peptidoglycan in their cell wall. They can convert atmospheric nitrogen to ammonia. They are shaped like rods. Azotobacter is a genus of rod-shaped bacteria (bacilli). After Gram staining, bacteria in this genus appear pink due to the thin peptidoglycan layer in their cell wall. They require oxygen for cellular respiration and can convert atmospheric nitrogen to ammonia, which they incorporate into amino acids and other organic molecules
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The prokaryotic cells that built stromatolites are classified as _____. proteobacteria chlamydias spirochetes gram-positive bacteria cyanobacteria
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cyanobacteria Cyanobacteria built stromatolites.
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The prokaryotic cells that were the first to add significant quantities of oxygen to Earth's atmosphere are classified as _____. proteobacteria chlamydias spirochetes gram-positive bacteria cyanobacteria
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cyanobacteria Cyanobacteria are aerobic photosynthesizers.
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Streptococcus pyogenes is classified with _____. proteobacteria chlamydias spirochetes gram-positive bacteria cyanobacteria
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gram-positive bacteria S. pyogenes attracts the violet Gram stain.
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Organisms that can cause nongonococcal urethritis are classified with _____. proteobacteria chlamydias spirochetes gram-positive bacteria cyanobacteria
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chlamydias Chlamydia trachomatis causes nongonococcal urethritis.
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The chemoheterotroph Proteus vulgaris is a rod-shaped bacterium classified with _____. proteobacteria chlamydias spirochetes gram-positive bacteria cyanobacteria
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proteobacteria Proteus vulgaris is classified with proteobacteria.
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Spiral-shaped bacteria are likely to be placed with _____ proteobacteria chlamydias spirochetes gram-positive bacteria cyanobacteria
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spirochetes The name of these organisms provides the answer to the question.
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According to this phylogenetic tree, which of these pairs of prokaryotic subgroups share the most recent common ancestor? Euryarchaeota ... Cyanobacteria Proteobacteria ... Crenarchaeota Proteobacteria ... Euryarchaeota Euryarchaeota ... Crenarchaeota Crenarchaeota ... Cyanobacteria
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Euryarchaeota ... Crenarchaeota The branching pattern of the phylogenetic tree indicates that, of the pairs listed here, this is the one whose members are the most closely related.
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What hypothesis were the researchers testing in this study? Sugar beet seedlings have a higher rate of fungal infection in heated soils. Soils can be treated to reduce their ability to suppress fungal disease in seedlings. The disease-suppressive properties of soils are due to the activities of soil microorganisms. Sugar beet seedlings have a lower rate of fungal infection in disease-suppressive soils.
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The disease-suppressive properties of soils are due to the activities of soil microorganisms.
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What is the independent variable in this study? soil treatment percentage of seedlings with fungal disease number of seeds in each soil treatment
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soil treatment
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What is the dependent variable in this study? soil temperature percentage of seedlings with fungal disease number of seeds in each soil treatment
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percentage of seedlings with fungal disease
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What is the total number of pots used in this experiment, and how many plants received each soil treatment? 4 pots total, 5 plants per treatment 4 pots total, 8 plants per treatment 20 pots total, 32 plants per treatment 32 pots total, 20 plants per treatment
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20 pots total, 32 plants per treatment Total number of pots = 5 treatments Ɨ 4 pots each = 20 pots. 4 pots per treatment Ɨ 8 plants per pot = 32 plants per treatment. Using multiple pots per treatment and multiple plants per pot gave the researchers a larger sample size and reduced the chances that conditions in one particular pot or the condition or characteristics of one particular plant would drive the results of the experiment in a nonrepresentative way.
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Identify a controlled variable from the experiment. the amount of light the plants were exposed to the number of plants per treatment percentage of seedlings with fungal disease the amount of disease-suppressive soil the plants were grown in
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the amount of light the plants were exposed to
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How do the results shown in Figure 2 support this conclusion? Fungal infection rate increased in seedlings grown in disease-suppressive soil that had been heated. A high rate of fungal infection was found in seedlings grown in soil from the margin of the field. Fungal infection rate decreased in seedlings grown in soil from the margin of the field mixed with disease-suppressive soil. The lowest rate of fungal infection was found in seedlings grown in disease-suppressive soil.
answer
Fungal infection rate increased in seedlings grown in disease-suppressive soil that had been heated. Heating the disease-suppressive soil killed any microorganisms living in that soil. Because the infection rates for seedlings grown in heated soil were higher than the rates for seedlings grown in unheated disease-suppressive soil, the researchers concluded that microorganisms must account for the soil's disease-suppressive properties.
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Which of the following results would have disproved the hypothesis that microorganisms are responsible for the disease-suppressive properties of soils? if seedlings had similar fungal infection rates when grown in 100% and 10% disease-suppressive soil if seedlings had similar fungal infection rates when grown in heated and unheated disease-suppressive soil if seedlings had similar fungal infection rates when grown in disease-suppressive soil and soil from the margin of the field No results could have disproved the hypothesis that microorganisms are responsible for the disease-suppressive properties of soil.
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if seedlings had similar fungal infection rates when grown in heated and unheated disease-suppressive soil Unheated disease-suppressive soil contains living microorganisms, but heating the soil kills them. Therefore, if the researchers had found similar fungal infection rates when seedlings were grown in heated and unheated disease-suppressive soil, that would have indicated that microorganisms are not responsible for the soil's disease-suppressive properties.
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In one experiment, scientists raised mice in germ-free conditions so the mice lacked intestinal microbes. The mice were fed a low-fat diet rich in the complex plant polysaccharides, such as cellulose, that are often called fiber. When the mice were 12 weeks old, the scientists transplanted the microbial community from the intestine of a single "donor" mouse into all of the germ-free mice. Then they divided the mice randomly into two groups and fed each group a different diet. Group 1 (the control group) continued to eat a low-fat, high-fiber diet. Group 2 (the experimental group) ate a high-fat, high-sugar diet. Identify the components of this experiment by dragging the labels into the appropriate bins.
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Factor being tested (independent variable): Diet Factors controlled (kept consistent): -Age of the mice -Initial composition of the microbaial community Factors to be measured (dependent variables): -Change in body fat -Weight gain -Final composition of the microbial community In this experiment, the scientists intentionally varied only one factor (called the independent variable) -- diet. They standardized, or controlled, all other factors that might differ between the two groups of mice, including age and the initial composition of the microbial community (both groups of mice received microbes from the same donor mouse). Consequently, any differences in weight gain, body fat, or microbial community (the dependent variables) between the two groups can be attributed to diet. Now let's look at the results.
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After 8 weeks on the different diets, the scientists collected the following data on the two groups of mice: the amount of weight gained the amount of body fat the composition of the microbial community, especially the abundance of the two types of bacteria that dominate this region of the intestine -- Firmicutes and Bacteriodetes The results are shown in this data table. Group Weight gain Body fat (% of total body weight) Relative abundance of Firmicutes in intestine Relative abundance of Bacteriodetes in intestine Group 1 (control) Low-fat, high-fiber diet 1.5 grams 1.7% 75% 20% Group 2 (experimental) High-fat, high-sugar diet 5.3 grams 3.7% 97% 3% Which three statements are valid conclusions that can be drawn from these results? -People who consume a high-fat, high-sugar diet will have increased body fat. -A high-fat, high-sugar diet alters the composition of the microbial community. -A relative abundance of Bacteriodetes less than 25% results in obesity. -A high-fat diet is more likely to cause obesity than a high-sugar diet. -A microbial community dominated by -Firmicutes is associated with increased body fat. -Firmicutes cause obesity. -A high-fat, high-sugar diet results in greater weight gain than a low-fat, high-fiber diet.
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-A high-fat, high-sugar diet alters the composition of the microbial community. -A microbial community dominated by Firmicutes is associated with increased body fat. -A high-fat, high-sugar diet results in greater weight gain than a low-fat, high-fiber diet. In this experiment, mice that were fed a high-fat, high-sugar diet gained more weight and more body fat than did mice fed a low-fat, high-fiber diet. A high-fat, high sugar diet was also associated with increased abundance of Firmicutes in the microbial community of the large intestine.
question
Is the microbial community in the intestine a key to understanding obesity? To explore this question, scientists conducted another experiment. The scientists hypothesized that the microbial community of obese mice is more efficient at extracting energy from food, thus providing more calories to the host, and that it promotes more fat deposition than does the microbial community of lean mice. They decided to test this hypothesis by transplanting microbes from an obese donor mouse into lean mice. For this experiment, the scientists randomly divided lean germ-free mice into two groups. The experimental group received microbes from a genetically obese donor (the donor's obesity was due to genetic factors, not diet). The control group received microbes from a genetically lean donor. Both groups were fed the same low-fat, high-fiber diet. After two weeks, the scientists measured the increase in body fat in the mice. They also determined the amount of energy (in kcal/g) in the feces of both groups -- that is, the energy in the food molecules that was not extracted or absorbed by the mice. What experimental results would support the scientists' hypothesis? Label the bars on the graphs to match the results predicted by the hypothesis.
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Increase in Body Fat (%): Lean Donor Group Obese Donor Group Fecal Energy Contect (kcal/g) Obese Donor Group Lean Donor Group When this experiment was performed, the results supported the scientists' hypothesis: Mice that received microbes from an obese donor (the experimental group) had a significantly greater increase in body fat than the mice that received microbes from a lean donor (the control group). The mice that received microbes from the obese donor also had less energy (fewer kcal/g) in its feces. The microbial community had wrung more energy out of the food molecules, thus making more calories available to the mice. Do these results mean that obesity can be overcome by a few simple tweaks to the microbial community? Probably not. To understand a complex system -- and the interactions of hundreds of species of microbes with each other and with the human body are certainly complex -- scientists must isolate and study one small piece of the puzzle at a time. Many more years of research will be needed for definitive answers about the relationship of our microbial inhabitants to obesity.