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LF127: INFECTION BIOLOGY AND MICROBIOLOGY > Lecture 2: Microbial Evolution and Diversity > Flashcards

Lecture 2: Microbial Evolution and Diversity Flashcards

1
Q

What hypothesis suggests that cellular life originated from surface conditions like a ‘warm little pond’ or primordial soup?

A

Surface origin hypothesis.

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2
Q

What are the two main hypotheses regarding the origin of cellular life?

A

Surface origin hypothesis and subsurface origin hypothesis.

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3
Q

What conditions are associated with the subsurface origin hypothesis for the evolution of cellular life?

A

Stable conditions at hydrothermal vents with a constant energy source from reduced inorganic compounds.

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4
Q

What key features mark the transition from prebiotic chemistry to cellular life?

A

Self-replicating RNA, enzymatic proteins, DNA as genetic code, evolution of biochemical pathways, divergence of lipid biosynthesis, and divergence of cell walls.

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5
Q

What does LUCA stand for in the context of microbial evolution?

A

Last Universal Common Ancestor.

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6
Q

What was the early life likely dependent on for energy and carbon?

A

Hydrogen (H2) and carbon dioxide (CO2).

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7
Q

What significant metabolic processes diversified early in biological evolution?

A

Bacteria making acetate and Archaea making methane.

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8
Q

What is the significance of phototrophy in early life forms?

A

It involved using H2S as an electron donor and evolved into an oxygenic photosystem using H2O.

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9
Q

How did life alter the geosphere during early evolution?

A

Life contributed to the oxygenation of the atmosphere.

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10
Q

What was the impact of phylogenetic methods on our understanding of Archaea?

A

Before molecular biology, the existence of Archaea was unknown.

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11
Q

What characteristics must marker molecules have to be useful in phylogenetic analysis?

A

They must be universal, contain variable and conserved regions, not be subject to horizontal gene transfer, and be truly homologous.

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12
Q

Which molecular marker is considered universal and present in all forms of life?

A

Ribosomal RNA genes.

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13
Q

What does the 3 Domains Tree of Life represent?

A

It is a phylogenetic tree defined by comparative ribosomal RNA sequencing.

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14
Q

What are the three domains of life represented in the phylogenetic tree?

A

Bacteria, Archaea, and Eukarya.

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15
Q

What does the endosymbiont theory explain about the evolution of eukaryotes?

A

It explains the incorporation of aerobic chemo-organotrophic bacteria (mitochondria) and phototrophic cyanobacteria (chloroplasts) into host cells.

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16
Q

What is the hydrogen hypothesis in relation to eukaryotic evolution?

A

It suggests an association of an archaeal host using H2 as an energy source with an aerobic bacterium that produced hydrogen as a waste product.

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17
Q

When do fossils suggest that eukaryotes arose?

A

Approximately 2.5 billion years ago.

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18
Q

What are some examples of major phylogenetic groups discussed in microbial evolution?

A

Bacteria, Archaea, and Eukarya.

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19
Q

What role did energy and carbon metabolisms play in early life?

A

They diversified, leading to various metabolic pathways.

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20
Q

What is the significance of ribosomal RNA in understanding evolutionary relationships?

A

It serves as a universal molecular marker present in LUCA and all forms of life.

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21
Q

What is one of the major evolutionary events that occurred around 2.5 billion years ago?

A

The rise of eukaryotes.

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22
Q

What are the implications of the evolution of biochemical pathways in early life?

A

They led to the divergence of lipid biosynthesis and cell wall structures.

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23
Q

What is the endosymbiosis theory primarily used to explain?

A

The development of chloroplasts.

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24
Q

What does serial endosymbiosis refer to?

A

Subsequent endosymbiotic events suggested to explain the origin of the nucleus and multi-membrane chloroplasts.

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25
What is the hydrogen hypothesis (HH) in relation to eukaryotic cell evolution?
It proposes that an archaea and a bacterium in a syntrophic relationship merged, leading to the formation of the proto-eukaryotic cell.
26
What role does hydrogen gas (H2) play in the hydrogen hypothesis?
It is a waste product from bacteria that is utilized by archaea, creating a syntrophic relationship.
27
How does the hydrogen hypothesis challenge the original endosymbiosis idea proposed by Margulis?
It suggests an amalgamation of a bacterium by an archaea rather than engulfment of a bacterium by a proto-eukaryote.
28
What is the significance of syntrophy in the context of the hydrogen hypothesis?
Syntrophy describes the mutual reliance between the archaea and bacteria, leading to their eventual merger.
29
What is symbiogenesis?
The creation of a new form of life from a symbiosis, involving complete reliance between organisms.
30
Why is the hydrogen hypothesis considered a better explanation for the origin of eukaryotes than the endosymbiotic theory?
It provides a more plausible mechanism for the merging of cells and the complexity of eukaryotic evolution.
31
What does the term 'syntrophy' imply in biological relationships?
It implies a mutualistic relationship where organisms benefit from each other's metabolic processes.
32
What complexities are suggested by newer syntrophy hypotheses regarding eukaryotic evolution?
They propose that more than two organisms may have been involved and that multiple events may have contributed to the process.
33
What is the relationship between endosymbiotic theory and the origin of mitochondria?
Endosymbiotic theory suggests that mitochondria originated from engulfed bacteria, while the hydrogen hypothesis offers an alternative explanation.
34
How does the author view the complexity of eukaryotic evolution?
The author suggests it is likely more complex than current theories can explain, indicating a need for further research.
35
What is the primary focus of the lecture regarding eukaryotic evolution?
To discuss the limitations of endosymbiotic theory and the advantages of the hydrogen hypothesis.
36
What does the author imply about the relevance of the Syntrophy Hypothesis for Year 1 Biology students?
It is too complex to be relevant for introductory level studies.
37
What is the main argument against the endosymbiotic theory in explaining the origin of eukaryotes?
It does not adequately account for the complexity and the processes involved in the evolution of eukaryotic cells.
38
What is the significance of Margulis' original idea in the context of eukaryotic evolution?
It laid the groundwork for understanding endosymbiosis, though newer hypotheses have expanded on it.
39
What type of organisms are involved in the hydrogen hypothesis?
An archaea and a bacterium.
40
How does the hydrogen hypothesis describe the relationship between archaea and bacteria?
It describes a close physical interaction where archaea utilize hydrogen produced by bacteria.
41
What is a potential outcome of the close relationship described in the hydrogen hypothesis?
The archaea engulfing the bacteria, leading to the formation of a novel eukaryotic cell.
42
What does the author suggest about the future of research in eukaryotic evolution?
There is a need for more detailed studies to understand the complexities of eukaryotic origins.
43
What is the relationship between syntrophy and symbiogenesis?
Syntrophy is a form of symbiosis, and symbiogenesis refers to the creation of new life forms from such relationships.
44
What is Aquifex aeolicus known for?
It is isolated from a hot spring, is hyperthermophilic (grows up to 95°C), and is one of the deepest branching bacterial phyla.
45
What metabolic process does Aquifex aeolicus perform?
It is a chemolithoautotroph that oxidizes H2 to water using O2 as an electron acceptor and performs carbon fixation.
46
What is unique about Deinococcus radiodurans?
It is extremely radiation resistant and can rapidly reassemble radiation-damaged DNA.
47
From where was Deinococcus radiodurans isolated?
It was isolated from canned meat sterilized by gamma irradiation.
48
What are cyanobacteria also known as?
Blue-green algae.
49
What is the significance of cyanobacteria in relation to plastids?
Plastids (chloroplasts in plants) were originally cyanobacteria.
50
What role do cyanobacteria play in the environment?
They are oxygenic phototrophs important in the carbon cycle and may cause nuisance and toxic blooms.
51
What characterizes Actinobacteria?
They are high GC Gram positives with varied morphology/metabolism, and include important antibiotic producers like Streptomyces coelicolor.
52
Name two pathogens associated with Actinobacteria.
Mycobacterium leprae (leprosy) and M. tuberculosis (TB).
53
What are Firmicutes known for?
They are low G+C Gram positives, mostly heterotrophs, and some form spores.
54
What are some medically important genera within Firmicutes?
Lactobacillus, Lactococcus (food processing, probiotics), Listeria, and Staphylococcus (infections).
55
What diseases are caused by Clostridium species?
Clostridium botulinum (botulism) and Clostridium tetani (tetanus).
56
What defines Chlamydia?
They are obligate intracellular parasites with a distinct life cycle and are important human pathogens.
57
What disease does Chlamydia trachomatis cause?
It causes sexually transmitted diseases that can lead to infertility.
58
What are the characteristics of Spirochaetes?
They are helically shaped, motile, gram-negative heterotrophs with unusual flagella inside the cell.
59
Which human pathogens are classified under Spirochaetes?
Borrelia (Lyme disease) and Treponema (syphilis).
60
What are the main subdivisions of Proteobacteria?
Alpha, beta, gamma, delta, and epsilon.
61
What is notable about the metabolic diversity of Proteobacteria?
They include phototrophs, chemolithoautotrophs, and heterotrophs, with many important pathogens.
62
Name some important pathogens found in the Proteobacteria group.
Vibrio cholerae (cholera), Yersinia pestis (the plague), Salmonella (food poisoning), Escherichia coli (food poisoning), and Pseudomonas aeruginosa (in cystic fibrosis).
63
What are methanogens?
They are archaea that produce methane as a waste product and are at the bottom of the food chain.
64
What environments do halophilic archaea thrive in?
They can grow in saturated salt solutions, which are 20 times saltier than seawater.
65
What is a unique feature of the Walsby square 'bacterium'?
It can take very strange shapes and colors, found in salt lakes and ponds.

LF127: INFECTION BIOLOGY AND MICROBIOLOGY (1 decks)

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