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Microbiology > Chapter 17 > Flashcards

Chapter 17 Flashcards

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1
Q

What does phylogeny study?

A

It studies the evolutionary relationships between organisms based on genetic changes over time.

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2
Q

How do genetic changes relate to evolutionary time?

A

Genetic changes accumulate over time, with more changes occurring in organisms that diverged longer ago.

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3
Q

How can we tell how distantly two organisms are related?

A

More genetic differences between their genomes indicate greater evolutionary distance.

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4
Q

What gene is commonly used to determine genetic relatedness in prokaryotes?

A

The 16S rRNA gene is used to assess relatedness in prokaryotes.

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5
Q

Why is the 16S rRNA gene useful for phylogenetic studies in bacteria?

A

It is highly conserved across prokaryotes but contains enough variation to distinguish between species.

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6
Q

What kind of environments can help us observe evolutionary changes over a short time period?

A

Strongly selective environments, which result in rapid evolution.

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7
Q

How does genome analysis help study evolution?

A

It allows us to compare genomes and track changes within and between species over time.

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8
Q

What is experimental evolution?

A

involves long-term experiments using rapidly dividing organisms (like bacteria) to observe how species change over time.

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9
Q

Why are rapidly dividing bacteria useful in evolutionary studies?

A

Because they evolve quickly, making it possible to observe genetic and trait changes across many generations in a short period.

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10
Q

What are three ways to study long-term evolutionary processes?

A
  1. Observe strongly selective environments
  2. Genome analysis
  3. Experimental evolution
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11
Q

What is a strongly selective environment?

A

An environment that promotes genetic changes for survival under harsh conditions.

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12
Q

How do antibiotics create a strongly selective environment?

A

Antibiotics kill susceptible organisms, allowing only mutants with resistance to survive.

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13
Q

What happens if an organism in a strongly selective environment develops a protective mutation?

A

That organism is more likely to survive and pass on the beneficial mutation.

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14
Q

determines what is
beneficial

A

the organism’s enviroment

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15
Q

What is reductive evolution?

A

It is the process where organisms lose genetic information over time, often to conserve energy.

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16
Q

Why might losing genetic information be beneficial?

A

Because replication, transcription, and translation require energy—less DNA means less energy needed.

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17
Q

Which types of organisms commonly undergo reductive evolution?

A

Intracellular pathogens and obligate symbionts, such as Treponema pallidum.

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18
Q

In what kind of environments is reductive evolution especially common?

A

Oligotrophic environments, where nutrients are limited.

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19
Q

What is symbiosis in biology?

A

Symbiosis is the intimate association of two unrelated species

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20
Q

What are the two main types of symbiosis mentioned in this slide?

A

Mutualism: both partners benefit

Parasitism: one partner benefits while the other is harmed

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21
Q

How does symbiosis influence evolution?

A

Symbiosis is a major engine of evolution that leads to coevolution.

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22
Q

What is coevolution?

A

Coevolution is the evolution of two species in response to each other.

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23
Q
A

T

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24
Q

What is the driving force of evolution in eukaryotic cells according to this slide?

A

The evolution of mitochondria and chloroplasts through endosymbiosis.

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25
From which type of bacterium did mitochondria evolve?
Mitochondria evolved from an alphaproteobacterium.
26
When did mitochondria evolve in relation to eukaryotic divergence?
Mitochondria evolved shortly after eukaryotes diverged from Archaea.
27
From which type of organism did chloroplasts evolve?
Chloroplasts evolved from cyanobacteria.
28
When did chloroplast evolution occur in relation to algae?
Before the divergence of red and green algae.
29
What is a key feature of mitochondrial and chloroplast genomes?
Both genomes show extreme reduction.
30
Which genes are typically retained in mitochondrial and chloroplast genomes?
Genes for rRNA, tRNA, and a few essential proteins related to respiration (mitochondria) or photosynthesis (chloroplasts).
31
Why do these organelles retain certain genes?
Because their gene products are essential for host survival, such as energy generation in mitochondria and photosynthesis in chloroplasts.
32
How does the retention of rRNA and tRNA genes support endosymbiotic theory?
It suggests that mitochondria and chloroplasts were once independent prokaryotes, which had their own functional genomes.
33
What defines a microfossil?
A microfossil has a size and shape consistent with modern-day bacteria.
34
Why is it difficult to confirm that a structure is a microfossil?
Because it's hard to prove that the structure doesn't have an abiotic origin.
35
What technological advances aid in analyzing microfossils?
Techniques like Raman spectroscopy and NanoSIMS provide chemical and isotopic evidence.
36
What does Raman spectroscopy measure in microfossil analysis?
It detects vibrational energy states to identify if chemical makeup is organic.
37
What is the purpose of NanoSIMS in microfossil studies?
NanoSIMS measures carbon isotope ratios, helping confirm biological origin.
38
I
39
Before the availability of molecular oxygen, how did early cells metabolize? 3 bullet points
o Oxidation reduction reactions o Light-driven ion pumps o Methanogenesis
40
What is the function of bacteriorhodopsin in microbial cells?
Bacteriorhodopsin is a light-driven proton pump that moves H⁺ ions across the membrane to generate a proton motive force.
41
How does bacteriorhodopsin contribute to ATP production?
The proton gradient created by bacteriorhodopsin powers ATP synthase, which synthesizes ATP from ADP + Pi.
42
What is the role of retinal in bacteriorhodopsin?
Retinal absorbs light and undergoes a conformational change, enabling the proton pump action.
43
How does bacteriorhodopsin differ from chlorophyll in light absorption?
Bacteriorhodopsin absorbs light best around 550–600 nm, while chlorophyll absorbs more at ~450 nm and ~675 nm (see graph on slide).
44
What are halorhodopsins and sensory rhodopsins?
Halorhodopsins pump Cl⁻ ions using light. Sensory rhodopsins help cells respond to light (e.g., swim toward red light, reverse motor in blue light).
45
What do HtrI and HtrII proteins do?
These are methylation helices involved in light signal transduction that affect flagellar motor behavior.
46
What is chemolithoautotrophy?
It is a form of metabolism where organisms use inorganic compounds (like H₂, H₂S, or FeS) as electron donors and CO₂ as a carbon source to build organic molecules.
47
Why is chemolithoautotrophy considered one of the earliest forms of metabolism?
It relies only on inorganic molecules, which would have been abundant on early Earth, and does not require complex biological molecules like chlorophyll or oxygen.
48
What role does FeS (iron-sulfur) play in early metabolism models?
FeS acts as an electron donor in redox reactions, helping reduce H₂S and generate H₂, which can then fuel energy-generating reactions.
49
What is the function of primitive hydrogenase in this model?
It catalyzes the oxidation of H₂, allowing electrons to enter the membrane system, creating a proton gradient.
50
How is ATP produced in this early metabolism model?
Protons (H⁺) flow back through a primitive ATPase, driving the conversion of ADP + Pi → ATP.
51
What is the end goal of this chemolithoautotrophic process?
The formation of organic compounds (like sugars or amino acids) from CO₂, supporting early cellular life through autotrophy.
52
What is the "prebiotic soup" hypothesis?
It suggests that life began from abiotic formation of small organic molecules in early Earth's oceans, sparked by lightning and fueled by simple reduced chemicals.
53
What basic ingredients were present in the prebiotic soup model?
Water (H₂O), methane (CH₄), ammonia (NH₃), and hydrogen gas (H₂), combined with electrical discharge, heat, and pressure.
54
What did the Miller-Urey experiment demonstrate?
That organic molecules like amino acids (e.g., glycine) can form spontaneously under simulated early Earth conditions.
55
How did small organic molecules contribute to the origin of life?
They eventually gave rise to complex macromolecules capable of self-replication and membrane compartmentalization—key steps toward cellular life.
56
What role did lightning play in the prebiotic soup theory?
Lightning provided the energy source needed to drive chemical reactions among simple molecules to form more complex organic compounds.
57
What is the "RNA world" hypothesis?
It proposes that RNA was the first informational molecule, capable of both storing genetic information and catalyzing chemical reactions before DNA and proteins evolved.
58
Why is RNA considered simpler than DNA?
RNA has a ribose sugar, is single-stranded, and uses uracil instead of thymine, making it easier and less energy-intensive to synthesize.
59
What modern evidence supports the RNA world hypothesis?
Some viruses use RNA as genomes, and ribozymes (RNA molecules with enzymatic activity) still exist.
60
What is a ribozyme?
A catalytic RNA molecule that can perform biochemical reactions, such as cleaving or joining RNA strands.
61
What role do proteins play in the RNA world model?
Proteins likely evolved to stabilize ribozymes, forming ribonucleoprotein complexes that led to modern ribosomes.
62
What is a riboswitch?
A riboswitch is a regulatory segment of an mRNA molecule that can bind a metabolite and influence gene expression
63
How do riboswitches regulate transcription?
When a metabolite binds to the riboswitch, it stabilizes a terminator structure in the mRNA, causing RNA polymerase to stall and end transcription prematurely.
64
What happens if the metabolite does not bind during transcription?
An antiterminator structure forms, allowing transcription to continue.
65
How do riboswitches regulate translation?
In translation, the bound metabolite causes the riboswitch to hide the Shine-Dalgarno sequence, preventing the ribosome from binding and blocking translation initiation.
66
What is the Shine-Dalgarno sequence?
It is a ribosomal binding site on bacterial mRNA necessary for the start of translation.
67
Why are methanogens considered important in origin theories?
Because they are a divergent group with simple metabolism, thrive in diverse habitats, and contribute to greenhouse gas production.
68
What characteristics make methanogens suitable for early life?
heir ability to survive in extreme environments and produce methane, a greenhouse gas that may have warmed early Earth.
69
What is the panspermia hypothesis?
It proposes that life or its building blocks originated in space and were delivered to Earth via meteorites.
70
What evidence supports panspermia?
Meteorites have been found with amino acids, and the theory suggests rapid RNA evolution once conditions allowed.
71
What is the implication of rapid RNA evolution in panspermia?
It suggests that once organic molecules arrived, self-replicating systems like RNA could have evolved quickly, jumpstarting life.
72
What are the three basic requirements for life to begin?
Essential elements (like carbon, hydrogen, nitrogen) Continual source of energy (e.g., sunlight or chemical reactions) Temperature range that allows liquid water
73
Why is a continual source of energy necessary for the origin of life?
It powers the chemical reactions needed to form and maintain biological molecules and structures.
74
What are three types of evidence scientists use to determine when life began?
Microfossils Carbon isotopes Biosignatures
75
What are stromatolites?
Stromatolites are fossilized microbial mats that form layered structures, offering evidence of ancient microbial life.
76
Why are stromatolites important in studying early life?
They help establish a timeframe for the existence of microbial life by preserving evidence in layered rock formations.
77
How old are the oldest stromatolite fossils found?
They have been found in rocks dating back 3.5 billion years.
78
What does carbon isotope fractionation help scientists determine?
It helps scientists identify biological activity by detecting a preference for lighter carbon isotopes (¹²C) over heavier ones (¹³C), which is typical of biological processes.
79
What is a biosignature?
a substance that provides scientific evidence of past or present life.
80
What is the significance of ¹³C-depleted carbon in ancient rocks?
It suggests biological carbon fixation, since life preferentially uses ¹²C, resulting in ¹³C-depleted organic matter.
81
Why are biosignatures and isotope data important in studying early life?
They provide indirect evidence of ancient microbial activity where fossils may not be preserved.
82
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83
Why is it hard to distinguish biotic from abiotic structures in ancient rocks?
Because non-living chemical processes can sometimes form structures that mimic the shape of microbes, making it difficult to confirm a biological origin.
84
Evidence of oxygen can be found in
Banded Iron Formations
85

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