Bacteria and Archaea Flashcards
1
Q
When did prokaryotes first appear?
A
Roughly 3.5 billion years ago
2
Q
What is the key benefit that prokaryotic cells have for survival?
A
The ability to rapidly adapt to changing (and extreme) environments
3
Q
Which 5 things allow prokaryotes to reach huge population sizes and thrive in diverse environments?
A
- Small size
- Rapid reproduction
- Mutations
- Diverse adaptations
- Rapid evolution
4
Q
What are the most common types of bacteria shape?
A
- Cocci
- Bacilli
- Spiral
5
Q
Cocci bacteria are ___ in shape
A
spherical
6
Q
Bacilli bacteria are ___ in shape
A
rod-like
7
Q
Which gram bacteria have a thick cell wall and what is it made of?
A
positive; peptidoglycan
8
Q
Which gram bacteria have a thin cell wall and a double membrane?
A
negative
9
Q
a) What is a slime layer?
b) What is it composed of?
c) What is its role?
A
- An outer, disorganised layer of:
- Polysaccharides or proteins
- To reduce dehydration
10
Q
a) What is a capsule?
b) What is it composed of?
c) What is its role?
A
- More organised structure surrounding prokaryotes
- Polysaccharides or proteins
- To reduce dehydration and protect against the host immune system
11
Q
Are slime layers or capsules more organised?
A
Capsules
12
Q
a) What are endospores?
b) Where is their DNA from?
c) What is their structure?
A
- DNA containing structures
- Copied from bacteria
- Surrounded by a multilayered, protective coat.
13
Q
Why and when do endospores form?
A
As a survival strategy when resources are limited
14
Q
How long can endospores survive?
A
They can lie dormant for centuries in soil
15
Q
What are fimbriae?
A
Hair like appendages that attach bacteria to surfaces
16
Q
What surfaces do bacteria attach to?
A
- Other bacteria
- Host cells like mucous membranes
17
Q
The hair like structure found on some bacteria is known as:
A
Fimbriae
18
Q
What type of movement are bacteria capable of?
A
Directed; towards or away from stimuli
19
Q
a) What structure do bacteria use to move?
b) What process makes this possible?
c) What is the power source for this process?
A
- Flagella
- Rotation of flagella using a complex motor protein embedded in the cell wall
- Proton gradient as protons are pumped out of the cell
20
Q
The difference in flagella movement in prokaryotes and eukaryotes is that..
A
- In prokaryotes flagella rotate
- In eukaryotes flagella move side to side like a whip
21
Q
What do prokaryotic cells lack?
A
Complex compartmentalisation
22
Q
What is structurally important for chemical processes?
A
They need to be structured near a surface so that enzymes can attach
23
Q
What type of DNA do prokaryotes have? (2)
A
- A single circular chromosome
- Small rings of DNA known as plasmids
24
Q
How short are bacterial reproductive cycles?
A
As short as 20 minutes
25
How do bacteria reproduce?
Binary fission
26
What happens as a result of high population and rapid reproduction in bacteria?
Rapid mutation creating genetic diversity
27
Bacteria are more ___ than eukaryotes
Adaptable
28
Name the three processes contributing to bacterial genetic recombination:
1. Transformation
2. Transduction
3. Conjugation
29
What happens during bacterial transformation?
- Foreign DNA uptake from the environment, absorbed and incorporated
- Production of a recombinant
30
What happens during bacterial transduction?
- Transfer of DNA from one prokaryote to another via a viral bacteriophage
31
What happens during bacterial conjugation?
- Bacteria temporarily join and one cell donates DNA to another
32
What is the energy and carbon source for photoautotrophs?
Light; CO2 and HCO3
33
What are the four main nutritional modes of prokaryotes?
1. Photoautotroph
2. Chemoautotroph
3. Photoheterotroph
4. Chemoheterotroph
34
What is the energy and carbon source for chemoautotrophs?
Inorganic chemicals; CO2 and HCO3
35
What is the energy and carbon source for photoheterotrophs?
Light; Organic compounds
36
What is the energy and carbon source for chemoheterotrophs?
Organic compounds; organic compounds
37
What are biofilms?
Large communities of bacteria that provide resistance
38
What are the five groups in the domain bacteria?
1. Proteobacteria
2. Chlamydias
3. Spirochetes
4. Cyanobacteria
5. Gram positive bacteria
39
Some archaea live in ___ environments
extreme
40
All known pathogenic prokaryotes are ___
bacteria
41
What is a key difference between prokaryotic and eukaryotic cells?
Prokaryotic cells lack a nucleus
42
What process causes genetic recombination during meiosis?
Crossing over
43
In a phylogenetic tree what term is used to describe two groups that share an immediate common ancestor?
Sister taxa
44
What is the primary difference between prokaryotic and eukaryotic cells?
- Prokaryotic cells lack a nucleus and membrane-bound organelles
- Eukaryotic cells have both.
45
How does crossing over cause genetic recombination?
Crossing over exchanges genetic material between homologous chromosomes leading to new combinations of genes.
46
What are sister taxa in a phylogenetic tree?
Sister taxa are groups of organisms that share an immediate common ancestor and are each other's closest relatives.
47
Prokaryotes
Organisms that lack a nucleus and membrane-bound organelles including bacteria and archaea.
48
Genetic recombination
The process by which genetic material is exchanged between homologous chromosomes during meiosis resulting in new allele combinations.
49
What is the typical diameter range of prokaryotic cells?
0.5–5 µm
50
What is a notable exception to the typical size of prokaryotic cells?
Thiomargarita namibiensis
51
How large can Thiomargarita namibiensis grow in diameter?
750 µm
52
What is the primary structural characteristic of most prokaryotes?
Unicellular
53
How do prokaryotes achieve all of an organism’s life functions?
Within a single cell
54
What were the first organisms to inhabit Earth?
Prokaryotes
55
How long ago did prokaryotes first appear on Earth?
3.5 billion years ago
56
What is one structural characteristic of most prokaryotes?
They are unicellular
57
Prokaryote
A unicellular organism that lacks a nucleus and other membrane-bound organelles
58
What is the primary function of the cell wall in prokaryotic cells?
- Maintains cell shape
- Protects the cell
- Prevents it from bursting in a hypotonic environment
59
What substance is primarily found in the cell walls of most bacteria?
Peptidoglycan
60
What is the main difference between gram-positive and gram-negative bacteria?
- Gram-positive bacteria have a thick layer of peptidoglycan
- Gram-negative bacteria have a thinner layer and an outer membrane with lipopolysaccharides
61
What is the purpose of the Gram stain technique?
To categorize bacterial species based on differences in cell wall composition
62
What is a capsule in the context of prokaryotic cells?
A dense and well-defined sticky layer of polysaccharide or protein that surrounds the cell wall
63
What are endospores?
Resistant cells formed by bacteria when they lack water or essential nutrients
64
What is the function of fimbriae in prokaryotic cells?
To help bacteria stick to their substrate or to one another
65
Why are gram-negative bacteria generally more resistant to antibiotics than gram-positive bacteria?
Because the outer membrane of gram-negative bacteria impedes the entry of some drugs.
66
Peptidoglycan
- A polymer composed of modified sugars cross-linked by short polypeptides
- Found in bacterial cell walls.
67
Gram-positive bacteria
Bacteria with relatively simple cell walls composed of a thick layer of peptidoglycan.
68
Gram-negative bacteria
Bacteria with less peptidoglycan in their cell walls and an outer membrane containing lipopolysaccharides.
69
Capsule
A dense and well-defined sticky layer of polysaccharide or protein surrounding the cell wall of many prokaryotes.
70
Endospore
A resistant cell formed by bacteria to withstand harsh conditions by halting metabolism and surviving extreme environments.
71
What is taxis in prokaryotes?
A directed movement towards or away from a stimulus
72
What is chemotaxis?
Movement in response to chemicals
73
What is the primary function of prokaryotic flagella?
Enabling movement
74
How do prokaryotic flagella differ from eukaryotic flagella?
They are one-tenth the width and typically not covered by an extension of the plasma membrane
75
What is an example of positive chemotaxis?
Movement towards nutrients or oxygen
76
What is the process called when structures originally adapted for one function take on new functions?
Exaptation
77
What is the similarity between bacterial and archaeal flagella?
Similar in size and rotational mechanism
78
What term describes structures that perform similar functions but are not related by common descent?
Analogous
79
What is a key structural difference between prokaryotic and eukaryotic cells?
Prokaryotic cells lack membrane-enclosed organelles
80
Where is the chromosome located in a prokaryotic cell?
In the nucleoid
81
What shape is the typical prokaryotic chromosome?
Circular
82
What are plasmids in prokaryotic cells?
Small rings of independently replicating DNA molecules
83
What allows certain antibiotics to target prokaryotic ribosomes but not eukaryotic ribosomes?
Differences in protein and RNA content
84
What kind of membranes do some prokaryotic cells have to perform metabolic functions?
Infoldings of the plasma membrane
85
How do prokaryotic ribosomes compare to eukaryotic ribosomes?
Prokaryotic ribosomes are slightly smaller
86
Eukaryotic cell
A complex cell type with membrane-enclosed organelles and multiple linear chromosomes.
87
What process do prokaryotes use to reproduce?
Binary fission
88
How often can many prokaryotes divide under optimal conditions?
Every 1-3 hours
89
What is one reason why prokaryotic cells cannot continue to divide indefinitely?
They exhaust their nutrient supply
90
What are the three key features that contribute to the rapid population growth of prokaryotes?
- Small size - Binary fission - Short generation times
91
Why can prokaryotic populations consist of many trillions of individuals?
They reproduce quickly and have short generation times
92
How quickly can some prokaryotic species produce a new generation under optimal conditions?
In only 20 minutes
93
What limits the exponential growth of prokaryotic populations in reality?
- Nutrient supply exhaustion - metabolic waste accumulation - competition - predation.
94
Binary fission
A method of asexual reproduction in prokaryotes where a single cell divides into two identical cells.
95
Generation time
The time it takes for a prokaryotic cell to divide and produce a new generation.
96
What are the three factors that promote genetic diversity in prokaryotes?
Rapid reproduction - mutation - genetic recombination
97
Why is genetic variation important for evolution?
Evolution cannot occur without genetic variation
98
What does the high level of genetic diversity in prokaryotes suggest about their populations?
Their populations have considerable genetic variation
99
What process primarily contributes to genetic variation in sexually reproducing species?
Meiosis and fertilisation
100
How do prokaryotes
such as Escherichia coli
101
What factor allows prokaryotes to adapt rapidly to new conditions?
Short generation times and large populations
102
What is genetic recombination in prokaryotes?
The combining of DNA from two sources
103
Which process involves the uptake of foreign DNA from the surroundings in prokaryotes?
Transformation
104
What is the role of bacteriophages in transduction?
They carry prokaryotic genes from one host cell to another
105
What is horizontal gene transfer?
The movement of genes from one organism to another
106
What structure forms between two prokaryotic cells during conjugation?
Mating bridge
107
What is the F factor in E. coli?
A piece of DNA required for the production of pili
108
What are R plasmids known for?
Carrying resistance genes against antibiotics
109
How can R plasmids spread rapidly through a bacterial population?
By enabling DNA transfer through conjugation
110
What term describes organisms that obtain energy from light?
Phototrophs
111
What term describes organisms that obtain energy from chemicals?
Chemotrophs
112
What term describes organisms that use CO2 or related compounds as a carbon source?
Autotrophs
113
What term describes organisms that require at least one organic nutrient to make other organic compounds?
Heterotrophs
114
How many major modes of nutrition are there in prokaryotes?
Four
115
What type of metabolism must use oxygen for cellular respiration and cannot grow without it?
Obligate aerobes
116
Which type of prokaryotes are poisoned by oxygen?
Obligate anaerobes
117
What can facultative anaerobes do in the absence of oxygen?
Carry out fermentation or anaerobic respiration
118
Which substances can obligate anaerobes use as electron acceptors in anaerobic respiration?
Nitrate ions or sulfate ions
119
What is the process called where atmospheric nitrogen is converted to ammonia?
Nitrogen fixation
120
Which organisms can convert atmospheric nitrogen to ammonia?
Cyanobacteria and methanogens
121
How do signals from Bacteroides thetaiotaomicron benefit humans?
They activate human genes that build the network of intestinal blood vessels
122
What is one way Bacteroides thetaiotaomicron may reduce the population sizes of competing bacterial species?
Inducing human cells to produce antimicrobial compounds
123
What type of bacteria causes tuberculosis?
Mycobacterium tuberculosis
124
Which disease is the most widespread pest-carried disease in the United States?
Lyme disease
125
What are the two types of poisons produced by pathogenic prokaryotes?
Exotoxins and endotoxins
126
Which bacterium secretes an exotoxin that causes cholera?
Vibrio cholerae
127
What type of bacteria releases endotoxins?
Gram-negative bacteria
128
Which bacterium causes typhoid fever?
Salmonella typhi
129
How can normally harmless bacteria become potent pathogens?
Horizontal gene transfer
130
Which strain of E. coli is a global threat due to its virulence?
O157:H7
131
How are virulence genes often transferred between bacteria?
Phage-mediated horizontal gene transfer
132
What is the main factor driving the rise of antibiotic resistance in bacteria?
The rapid reproduction of bacteria and natural selection
133
Which bacterial infection is highlighted as a major concern due to drug-resistant strains?
Tuberculosis
134
What new class of antibiotics was discovered using a metagenomic approach in 2018?
Malacidins
135
What is one traditional use of bacteria in food production?
Converting milk to cheese and yoghurt
136
Which bacterium is commonly used in gene cloning?
E. coli
137
What is the role of DNA polymerase from Pyrococcus furiosus in biotechnology?
Used in the PCR technique
138
What is the CRISPR-Cas system originally used for in bacteria and archaea?
Defending against attack by viruses
139
What is a potential application of the CRISPR-Cas9 system?
Altering genes in virtually any organism
140
What type of polymer do some bacteria synthesize that can be used to make biodegradable plastics?
PHA (polyhydroxyalkanoate)
141
What is the process of using organisms to remove pollutants from soil, air, or water called?
Bioremediation
142
How do anaerobic bacteria and archaea contribute to sewage treatment?
Decomposing organic matter into material that can be used as landfill or fertiliser
143
What process allows prokaryotes to reproduce quickly and form large populations?
Binary fission
144
What are the four modes of nutrition found in prokaryotes?
Photoautotrophy
145
Which type of prokaryote is poisoned by oxygen?
Obligate anaerobes
146
What process allows some prokaryotes to convert atmospheric nitrogen to ammonia?
Nitrogen fixation
147
What are the two largest groups of bacteria?
Proteobacteria and gram-positive bacteria
148
What role do heterotrophic prokaryotes play in ecosystems?
Decomposition
149
How do pathogenic bacteria typically cause disease?
By releasing exotoxins or endotoxins
150
What beneficial role do mutualistic prokaryotes play in the human intestines?
Helping to digest food
151
Biofilm
A surface-coating colony of one or more species of unicellular organisms that engage in metabolic cooperation; most known biofilms are formed by prokaryotes.
152
Symbiosis
An ecological relationship between organisms of two different species that live together in direct and intimate contact.
153
Peptidoglycan
A type of polymer in bacterial cell walls consisting of modified sugars cross-linked by short polypeptides.
154
R plasmid
A bacterial plasmid carrying genes that confer resistance to certain antibiotics.
155
Exotoxin
A toxic protein that is secreted by a prokaryote or other pathogen and that produces specific symptoms - even if the pathogen is no longer present.
156
Conjugation in:
a) Prokaryotes
b) Ciliates
(a) The direct transfer of DNA between two cells that are temporarily joined. When the two cells are members of different species conjugation results in horizontal gene transfer.
(b) A sexual process in which two cells exchange haploid micronuclei but do not reproduce.
157
Obligate aerobe
An organism that requires oxygen for cellular respiration and cannot live without it.
158
Pilus
(plural = pili) A structure in bacteria that links one cell to another at the start of conjugation; also called a sex pilus or conjugation pilus.
159
Endospore
A thick-coated resistant cell produced by some bacterial cells when they are exposed to harsh conditions.
160
Transduction
A process in which phages (viruses) carry bacterial DNA from one bacterial cell to another. When these two cells are members of different species
- transduction results in horizontal gene transfer.
161
Parasitism
Ecological interaction in which one organism benefits by feeding upon the host, which is harmed. Some parasites live within the host (feeding on its tissues) while others feed on the host’s external surface.
162
Parasite
An organism that feeds on the cell contents tissues or body fluids of another species (the host) while in or on the host organism. Parasites harm but usually do not kill their host.
163
F factor
In bacteria - the DNA segment that confers the ability to form pili for conjugation and associated functions required for the transfer of DNA from donor to recipient. The F factor may exist as a plasmid or be integrated into the bacterial chromosome.
164
Gram stain
A staining method that distinguishes between two different kinds of bacterial cell walls; may be used to help determine medical response to an infection.
165
Symbiont
The smaller participant in a symbiotic relationship - living in or on the host.
166
Fimbria
(plural
167
Gram-positive
The group of bacteria that have a cell wall that is structurally less complex and contains more peptidoglycan than the cell wall of gram-negative bacteria. Gram-positive bacteria are usually less toxic than gram-negative bacteria.
168
Commensalism
Ecological interaction that benefits the individuals of one species but neither harms nor helps the individuals of the other species.
169
Gram-negative
The group of bacteria that have a cell wall that is structurally more complex and contains less peptidoglycan than the cell wall of gram-positive bacteria. Gram-negative bacteria are often more toxic than gram-positive bacteria.
170
Taxis
An oriented movement towards or away from a stimulus.
171
Nitrogen fixation
The conversion of atmospheric nitrogen to ammonia. Biological nitrogen fixation is carried out by certain prokaryotes - some of which have mutualistic relationships with plants.
172
Pathogen
An organism or virus that causes disease.
173
Heterocyst
A specialised cell that engages in nitrogen fixation in some filamentous cyanobacteria; also called a heterocyte.
174
Methanogen
An organism that produces methane as a waste product of the way it obtains energy. All known methanogens are in domain Archaea.
175
Prokaryote
A single-celled organism of the domain Bacteria or Archaea.
176
Extremophile
An organism that lives in environmental conditions so extreme that few other species can survive there. Extremophiles include extreme halophiles (“salt lovers”) and extreme thermophiles (“heat lovers”).
177
Anaerobic respiration
A catabolic pathway in which inorganic molecules other than oxygen accept electrons at the “downhill” end of electron transport chains.
178
Host
The larger participant in a symbiotic relationship - often providing a home and food source for the smaller symbiont.
179
Extreme thermophile
An organism that thrives in hot environments (often 60–80°C or hotter).
180
Endotoxin
A toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die.
181
Mutualism
ecological interaction that benefits individuals of both interacting species.
182
Capsule
(1) In many prokaryotes - a dense and well-defined layer of polysaccharide or protein that surrounds the cell wall and is sticky to protect the cell and enable it to adhere to substrates or other cells.
(2) The sporangium of a bryophyte (moss; liverwort; or hornwort).
183
Extreme halophile
An organism that lives in a highly saline environment such as the Great Salt Lake or the Dead Sea.
184
Decomposer
An organism that absorbs nutrients from nonliving organic material such as; corpses, fallen plant material, wastes of living organisms and converts them to inorganic forms; a detritivore.
185
Bioremediation
The use of organisms to detoxify and restore polluted and degraded ecosystems.
186
What is the chemical formula for ammonia?
NH₃
187
Why are nitrogen-fixing cyanobacteria considered some of the most self-sufficient organisms?
They need only light CO₂ N₂ water and some minerals to grow
188
How do nitrogen-fixing prokaryotes benefit plants?
They increase the nitrogen available to plants by producing nitrogen compounds from ammonia
189
What is the primary function of heterocysts in Anabaena?
Nitrogen fixation
190
Why can't a single Anabaena cell perform both photosynthesis and nitrogen fixation simultaneously?
Oxygen produced during photosynthesis inactivates nitrogen fixation enzymes
191
What structure allows heterocysts to transport fixed nitrogen to neighboring cells?
Intercellular connections
192
What do cells in a biofilm secrete to recruit nearby cells?
Signaling molecules
193
What forms the capsule or slime layer in biofilms?
Polysaccharides and proteins
194
What is one major problem caused by biofilms in medical settings?
Contaminating medical devices
195
Why are biofilms difficult to treat with antibiotics?
They are extremely resistant
196
What has enabled prokaryotes to inhabit every environment known to support life?
Structural and metabolic adaptations
197
What recent scientific advances have begun to reveal the full extent of prokaryotic diversity?
Advances in genomics
198
What is a key characteristic of prokaryotic populations?
They have radiated extensively
199
What is the significance of prokaryotic adaptations?
They enable prokaryotes to inhabit diverse environments
200
What molecular marker did microbiologists start using in the 1970s to study evolutionary relationships?
Small-subunit ribosomal RNA
201
Which domain is more closely related to eukaryotes according to the genetic data?
Archaea
202
What technique did researchers begin using in the 1980s to analyze genes of prokaryotes from environmental samples?
Polymerase chain reaction (PCR)
203
What is the term for obtaining entire prokaryotic genomes from environmental samples?
Metagenomics
204
What process has played a key role in the evolution of prokaryotes by allowing them to acquire genes from distantly related species?
Horizontal gene transfer
205
What percentage of genes in an average bacterial genome have been transferred horizontally at some point in their evolutionary history?
0.75
206
What are the two separate lineages of prokaryotes that have evolved for billions of years?
Bacteria and Archaea
207
What type of organisms are bacteria classified as?
Prokaryotic
208
What is one use of beneficial bacteria?
Making Swiss cheese and yoghurt
209
How many phyla of bacteria are there approximately?
80
210
What is a key characteristic of bacterial nutritional and metabolic capabilities?
They are highly diverse
211
What characteristic is present in Eukarya but absent in Bacteria and Archaea?
Nuclear envelope
212
Which domain of life includes organisms that can grow at temperatures greater than 100°C?
Archaea
213
What is the initiator amino acid for protein synthesis in Archaea?
Methionine
214
Which type of extremophile thrives in highly saline environments?
Extreme halophiles
215
What is a by-product of energy production in methanogens?
Methane
216
Which clade includes many extreme halophiles and methanogens?
Euryarchaeota
217
What is the significance of the TACK supergroup?
It includes groups closely related to eukaryotes.
218
How crucial are prokaryotes to the biosphere compared to humans?
More crucial
219
What role do chemoheterotrophic prokaryotes play in ecosystems?
They function as decomposers - breaking down dead organisms and waste products.
220
Which process is performed by cyanobacteria?
Producing atmospheric O2.
221
How do prokaryotes affect soil nutrient concentrations?
They can both increase and decrease the availability of key plant nutrients.
222
What is the significance of Crenarchaeotes in marine environments?
They perform nitrification
223
What do autotrophic prokaryotes use CO2 to make?
Organic compounds such as sugars.
224
What is symbiosis?
An ecological relationship in which two species live in close contact with each other
225
In a symbiotic relationship what is the larger organism called?
Host
226
What type of symbiotic relationship benefits both species involved?
Mutualism
227
What is commensalism?
An ecological relationship in which one species benefits while the other is not harmed or helped
228
What is parasitism?
An ecological relationship in which a parasite feeds on the cell contents tissues or body fluids of its host
229
What are pathogens?
Agents that cause disease
230
What supports the diverse ecological communities at hydrothermal vents?
Metabolic activities of chemoautotrophic bacteria
231
What happens to the vent community when a hydrothermal vent stops releasing chemicals?
The entire vent community collapses
232
What fraction of prokaryotic species are known to cause human illness?
A small fraction
233
What is a common misconception about prokaryotes?
That most of them cause human illness
234
Approximately how many species of bacteria are estimated to live in the human intestines?
500–1000
235
What is the role of mutualistic bacteria in the human intestines?
Digesting food that human intestines cannot break down
236
What does the genome of Bacteroides thetaiotaomicron include?
Genes involved in synthesizing carbohydrates
