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Chapter 22: Problem 44

A bacterium requires only a particular amino acid as an organic nutrient and lives in a completely lightless environment. What mode of nutrition (free energy and carbon) does it use? Justify your response. a. Chemoheterotroph, as it must rely on chemical sources of energy living in a lightless environment and a heterotroph if it uses organic compounds for its carbon source. b. Chemoorganotroph, as it must rely on chemical sources of energy living in a lightless environment and an organotroph if it uses organic compounds other than carbon dioxide for its carbon source. c. Chemolitoautotroph, as it must rely on chemical sources of energy living in a lightless environment and an autotroph if it uses organic compounds other than carbon dioxide for its carbon source. d. Chemoheterotroph, as it must rely on chemical sources of energy living in a lightless environment and a heterotroph if it uses organic compounds other than carbon dioxide for its carbon source.

Short Answer

Expert verified
d. Chemoheterotroph, as it uses chemical sources for energy and organic compounds other than carbon dioxide for its carbon source.

Step by step solution

01

Identify the energy source requirement

The bacterium mentioned is living in a completely lightless environment, so it cannot use light as its energy source (photo-). Therefore, it must rely on chemical sources for energy (chemo-).
02

Identify the carbon source requirement

The bacterium requires a particular amino acid as an organic nutrient. Amino acids are organic compounds, meaning it obtains its carbon from organic sources. This is a characteristic of a heterotroph. Therefore, the bacterium is a heterotroph.
03

Combine the two findings

Since the bacterium relies on chemical sources for energy (chemo-) and uses organic compounds for its carbon source (heterotroph), it must be categorized as a chemoheterotroph.
04

Justify the final choice

Option a and option d both indicate that the bacterium is a chemoheterotroph. However, option d is more precise because it specifies that the bacterium uses organic compounds other than carbon dioxide for its carbon source, which aligns with the details given about the amino acid requirement.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

bacterial nutrition
Bacterial nutrition refers to how bacteria obtain the energy and nutrients they need to survive, grow, and reproduce. There are various ways bacteria can meet these needs based on their environment and physiological capabilities.

Some bacteria can make their own food using light or inorganic compounds, while others must consume organic compounds. This distinction helps categorize bacteria into different nutritional groups. Knowing the type of nutrition a bacterium requires helps scientists understand its ecological role and its applications in medicine and industry.
chemical energy sources
When bacteria live in environments devoid of light, they depend on chemical sources of energy. This type of bacteria is termed chemo-meaning they derive their energy from chemical reactions.

Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environments. These can be organic (chemoorganotrophs) or inorganic (chemolithotrophs) molecules.

Chemotrophs are essential for nutrient cycling in ecosystems and can inhabit extreme environments where light is unavailable, such as deep-sea vents or underground caves.
organic carbon sources
Organic carbon sources are compounds composed of carbon atoms that are absorbed and used by organisms as a source of carbon. For bacteria, this can include things like sugars, fatty acids, and amino acids.

Heterotrophic bacteria, in particular, rely on organic carbon sources because they cannot fix carbon from inorganic sources. Instead, they consume carbon-containing compounds produced by other organisms. This is why heterotrophs play a critical role in breaking down and recycling organic matter in the environment.
heterotrophs vs autotrophs
Heterotrophs and autotrophs are two major categories of organisms based on their carbon sources.

Heterotrophs rely on organic compounds for their carbon needs; they cannot produce their own organic molecules and must ingest them. Chemoheterotrophs, for example, gain carbon and energy from organic substances.

Autotrophs, on the other hand, can produce their own organic molecules from inorganic carbon sources such as carbon dioxide. Phototrophic autotrophs use light energy, while chemolithoautotrophs use energy from inorganic chemical reactions.

Understanding these differences helps in identifying the roles organisms play in ecosystems and their methods of survival.

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Most popular questions from this chapter

Assuming that you could synthesize all of the nitrogen- containing compounds needed if you had nitrogen, what might you eat for a typical meal if you could fix nitrogen like some prokaryotes? a. My meal might be fruits or vegetables and water as nitrogen is present in the highest amount in water. b. My meal might be fruits or vegetables, water and air as atmospheric nitrogen could be simply absorbed. c. My meal might be fruits or vegetables, cheese, meat, water, and air as atmospheric nitrogen could be simply absorbed. d. My meal might be cheese or meat, water, and air as atmospheric nitrogen could be simply absorbed.

Why do scientists believe that the first organisms on Earth were extremophiles? a. Earth鈥檚 early environment was full of extreme places with much oxygen in the atmosphere, no ozone to shield Earth鈥檚 surface from mutagenic radiation, much geologic upheaval and volcanic activity. Extremophiles are bacteria and archaea that are adapted to grow in extreme environments. b. Earth鈥檚 early environment was full of extreme places with little oxygen in the atmosphere, no ozone to shield Earth鈥檚 surface from mutagenic radiation, much geologic upheaval and volcanic activity. Extremophiles are bacteria and archaea that are adapted to grow in extreme environments. c. Earth鈥檚 early environment was full of extreme places with little oxygen in the atmosphere, no ozone to shield Earth鈥檚 surface from mutagenic radiation, less geologic upheaval and volcanic activity. Extremophiles are bacteria and archaea that are adapted to grow in extreme environments. d. For the first two billion years of Earth's existence, the atmosphere had no molecular oxygen.

Describe briefly how you would detect the presence of a non culturable prokaryote in an environmental sample. a. Recombinant DNA techniques are used to detect the presence of a non- culturable prokaryote in an environmental sample. Polymerase chain reaction is used to amplify selected portions of prokaryotic DNA. b. Molecular biology techniques are used to detect the presence of a non- culturable prokaryote in an environmental sample. Electrophoresis is used to amplify selected portions of prokaryotic DNA. c. Molecular biology techniques are used to detect the presence of a non- culturable prokaryote in an environmental sample. Polymerase chain reaction is used to amplify selected portions of prokaryotic DNA. d. Recombinant DNA techniques are used to detect the presence of a non- culturable prokaryote in an environmental sample. Electrophoresis is used to amplify selected portions of prokaryotic DNA.

Explain the relationship between Earth's ancient atmosphere and the evolution of some of the first life forms on Earth. Use the terms anaerobicandphototrophic, and explain the effect of cyanobacteria on the atmosphere. a. Phototrophic organisms appeared during the first two billion years of Earth's existence. Anaerobic organisms appeared within one billion years of Earth's formation. From these organisms evolved the cyanobacteria which produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere. b. For the first two billion years of Earth's existence, the atmosphere had no molecular oxygen. Thus, the first organisms were anaerobic. Cyanobacteria appeared within one billion years of Earth's formation. From these evolved the phototrophic organisms which produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere. c. For the first two billion years of Earth鈥檚 existence, the atmosphere had no molecular oxygen. Thus, the first organisms were anaerobic. Phototrophic organisms appeared within one billion years of Earth鈥檚 formation. From these organisms evolved the cyanobacteria, which produce oxygen as a byproduct of photosynthesis, leading to the oxygenation of the atmosphere. d. For the first two billion years of Earth鈥檚 existence, the atmosphere had no molecular oxygen. Thus, the first organisms were anaerobic. Cyanobacteria which produce oxygen as a by-product of photosynthesis, leading to the oxygenation of the atmosphere, appeared within one billion years of Earth鈥檚 formation. From these organisms evolved phototrophic organisms

Gram-negative bacteria have an inner cytoplasmic membrane separated by a peptidoglycan layer from a second outer membrane. In addition, transport proteins called efflux pumps span this double membrane and actively eliminate chemicals such as antibiotics that pass through porins on the outer membrane. These efflux pumps can confer multi-drug resistance, a situation that is threatening human health. A. Explain how combining a drug that disrupts ATP synthesis in bacteria with antibiotics is a possible strategy for the treatment of bacterial infections caused by antibiotic-resistant gram-negative bacteria. ATP synthesis in prokaryotes is accomplished by a protein that connects the extracellular space to the cytoplasm. In gram-negative bacteria, the proton gradient that supplies the free energy to convert ADP into ATP is established across the inner membrane. B. Predict differences in the interactions of eukaryotic and prokaryotic cells with a drug molecule that successfully targets ATP synthesis and provide reasoning for your In gram-positive bacteria, ATP synthesis is accomplished by a protein that spans the single membrane and the outer cell wall. During the production of yogurt and wine, which rely on gram- positive bacteria, the pH is controlled. Sodium bicarbonate secretions from the pancreas maintain the pH of the human intestine, where many beneficial methanogens are gram-positive bacteria. C. Explain why homeostasis for gram-positive bacteria requires control of extracellular pH.
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