Microbiology Flashcards
1
Q
microorganisms
A
- organisms that are only visible using a microscope
2
Q
cellular microbes
A
bacteria, archaea, protists, fungi
3
Q
acellular microbes
A
viruses
4
Q
binary fission
A
- process where prokaryotes are only able to replicate via asexual reproduction
5
Q
What does ‘symbiotic’ mean in biology?
A
It refers to any close, long-term interaction between two different species. Includes mutualism, commensalism, and parasitism.
6
Q
What does ‘pathogenic’ mean?
A
It describes a relationship where one organism causes harm or disease to another—often a host-pathogen relationship.
7
Q
What is a ‘mutualistic’ relationship?
A
A type of symbiotic interaction where both organisms benefit.
8
Q
What does ‘commensal’ mean?
A
A relationship where one organism benefits and the other is neither helped nor harmed.
9
Q
Metabolism - energy source
A
- phototrophs gain energy from sunlight
- chemotrophs gain energy from inorganic and/ or organic compounds
10
Q
Metabolism - electron source
A
- organotrophs gain electrons from organic compounds
- lithotrophs gain electrons from inorganic compounds
11
Q
metabolism - carbon source
A
- autotrophs use CO₂ to make carbon compounds (primary producers)
- heterotrophs use organic compounds from their environment
12
Q
Niche
A
set of environmental conditions in which a species of microbe can replicate
13
Q
the conditions that determine where a microbe can live:
A
- Nutrient availability
- Oxygen concentration
- Temperature
- pH
- Light intensity
- Radiation
- Solute concentration (osmolarity) & water activity
14
Q
bacteria
A
- Single-celled prokaryotes
- Asexual reproduction by binary fission
- Lifestyles: Free-living, Commensals,
Mutualists, Pathogens - 1 circular chromosome (dsDNA), no
nucleus - May have one or more plasmids
- Cell morphologies:
- Spherical (cocci), Rods (bacilli), Spirals
- Peptidoglycan in cell wall
- Gram stain identifies 2 main groups
15
Q
Gram positive bacterium
A
Peptidoglycan traps the crystal violet – iodine stain (purple)
and so the cells are not decolourised by ethanol wash and this purple stain
masks the safranin counterstain.
16
Q
gram negative bacterium
A
The crystal violet - iodine stain is rinsed away with ethanol, and the cells are then stained red/pink with the safranin counterstain.
17
Q
capsule
A
some species of bacteria produce a capsule which can help them to attach to surfaces or evade the immune response
18
Q
fimbriae
A
- thread like appendages
- some bacteria produce fimbriae which help them to attach to surfaces
19
Q
flagellum
A
- tail like appendage that bacteria use to swim through liquid
- the rotational movement propels bacteria towards nutrients or away from toxicants via chemotaxis
20
Q
biofilm
A
aggregation of bacteria that are attached to each other and/ or a surface and embedded in an extracellular polymeric substances
21
Q
sex-pilus
A
thread-like appendage that bacteria use to exchange plasmids
22
Q
photorhabdus luminescens
A
bacterium that forms a mutualistic relationship with nematodes
23
Q
archaea
A
- Single-celled prokaryotes
- Asexual reproduction
- Lack peptidoglycan in cell wall
- Unique cell membrane lipids
- 1 circular chromosome, no nucleus
- May have one or more plasmids
- Forms: Spherical, Rods, Spirals, Rectangles/Squares, lemon-shaped
- Lifestyles: Free-living (many are extremophiles), Commensals,
Mutualists
24
Q
Pyrococcus furiosus
A
species of archaea that lives
in deep sea hydrothermal vents
25
fungi
* Single-celled & multicellular eukaryotes
* Asexual & sexual reproduction
* Chitin in cell wall
* Multiple linear chromosomes within the nucleus
* Forms: Yeasts, Moulds (or both)
* Lifestyles: Decomposers, Mutualists, Pathogens
26
Penicillium
mould commonly encountered
as a decomposer of food
27
Protists
* Single-celled & multicellular eukaryotes
* Slime molds, Algae, Amoebae
* Asexual or sexual reproduction
* Multiple linear chromosomes within the nucleus
* Forms: Most unicellular, some multicellular
* Lifestyles: Free-living, Pathogenic, Mutualistic
28
Viroid
non-translated ssRNAs, lack protein (infect plants)
29
Satellites
subviral infectious agents composed of nucleic acid and protein that require a helper virus to replicate
30
Prions
infectious proteins, cause spongiform encephalopathies (mad cow disease, scrapie, CJD)
31
Viruses
* Particles (virions): genome (DNA or RNA) in a protein coat
* May have an envelope
* Multiply only in living cells and often cause disease
* Are not living – no metabolism
* Do not grow – they are assembled from constituent parts
* Virus-specified proteins are synthesized using host ribosomes
32
Virus steps
1) entry and uncoating
2) replication
3) transcription and manufacture of capsid proteins
4) self-assembly of new virus particles and their exit from the cell
33
Covid replication cycle
1) attachment
2) uncoating
3) production of viral components
4) assembly
5) release
34
Global nitrogen cycle
* Microbial nitrogen fixation
is responsible for providing
>95% of the available
nitrogen in the biosphere
* Nitrogenase enzyme
coverts N₂ into ammonium
* Nitrifying bacteria reduce
the ammonium into nitrites
then nitrates
* Plants take up these
nitrogenous compounds
from soil
* Denitrifying bacteria use
nitrates as an energy
source and produce N₂
35
Global carbon cycle
* Methanogenic archaea
release methane (CH₄) -
a potent greenhouse gas
* Decomposers recycle
carbon from dead
organisms, enabling it to
re-enter the food chain
* Photosynthetic
microbes in the ocean fix
more CO₄ than all the
plants on land
* Viruses in the ocean play
an important role in
recycling carbon by
killing marine microbes
36
Microbiome
a host-associated community of commensal, mutualistic and pathogenic microorganisms
37
transmission of infectious diseases
* Direct contact
* Sexual contact
* Airborne
* Water/food-borne
* Vector borne
38
How do pathogens evade the immune system?
They can hide inside host cells, change their surface antigens, or suppress the immune response to avoid detection and destruction.
39
How do pathogens replicate and spread in the body?
They replicate using host resources and spread via the bloodstream, lymphatic system, or by directly invading surrounding tissues.
40
What causes the symptoms of an infectious disease?
Symptoms are caused by both the damage done by the pathogen and the host's immune response to the infection.
41
What methods are used to diagnose infections?
Infections can be diagnosed using culture methods or molecular techniques like PCR to detect the pathogen's genetic material.
42
How are infectious diseases treated?
They're treated with antimicrobial agents like antibiotics, antivirals, antifungals, or antiparasitics, depending on the pathogen type.
43
What strategies are used to prevent infectious diseases?
Prevention includes sanitation, good hygiene, protective measures, and vaccinations to reduce the risk of infection.
44
Penicillin
- natural product synthesised by the mould Penicillium
- B-lactam antibiotic.
- It inhibits bacterial enzymes that form cross links in peptidoglycan
45
What is the general function of antibiotics?
Antibiotics kill bacteria or stop them from growing by targeting parts of bacterial cells that human cells don't have.
46
How do antibiotics that inhibit cell wall synthesis work? Give an example.
They prevent bacteria from building their cell walls, causing them to burst. Example: Penicillin.
47
How do antibiotics that disrupt protein synthesis work? Give an example.
They block bacterial protein production, which is essential for growth and survival. Example: Tetracycline or Macrolides.
48
How do antibiotics that inhibit DNA or RNA synthesis work? Give an example.
They stop bacteria from replicating by interfering with DNA or RNA synthesis. Example: Ciprofloxacin or Rifampin.
49
How do antibiotics that damage cell membranes work? Give an example.
They disrupt the bacterial cell membrane, leading to leakage and death. Example: Polymyxins.
50
How do antibiotics that inhibit metabolic pathways work? Give an example.
They block enzymes in bacteria needed for metabolism, preventing growth. Example: Sulfonamides.
51
Alternatives to antibiotics
Phage therapy - using bacteriophages could be used to treat human infections
Metal ion based antimicrobials - Silver is being used as an antimicrobial in a wide range of domestic and medical products
52
53
What is antimicrobial resistance (AMR)?
AMR occurs when microorganisms become resistant to drugs like antibiotics, antivirals, or antifungals, making infections harder to treat.
54
How does antimicrobial resistance develop?
AMR develops when microorganisms evolve to survive exposure to drugs, often due to overuse or misuse of antimicrobials.
55
What causes antimicrobial resistance?
Causes include overuse, misuse, inappropriate prescriptions, and the agricultural use of antibiotics, leading to resistant strains.
56
How does overuse/misuse of antimicrobials contribute to AMR?
Taking antibiotics when not needed or not finishing a course can allow resistant bacteria to survive and spread.
57
What is the role of natural selection in AMR?
Bacteria with mutations that allow them to survive drugs are selected over time, and these mutations get passed to future generations.
58
How do resistant bacteria spread to others?
Resistant bacteria can spread through direct contact, contaminated food, or environmental exposure, making infections harder to control.
59
Eradication programmes
- Smallpox is the only human disease caused by a virus to have been eradicated through mass vaccination
- Polio is endemic in only 2 countries due to successful vaccination programmes
60
Food production and safety
- Microbes have been used for centuries to make fermented foods such as yoghurt, kimchi, vinegar, soy sauce, bread, beer & wine
- Microbes causing food spoilage lead to food waste
- Some microbes cause food poisoning e.g.
Bacillus cereus
61
Biofertilizers and biocontrol
- Bacteriophages could be used to increase food security by reducing bacterial diseases of crop plants and livestock
- Applying nitrogen-fixing bacteria to soils as a biofertilizer
- Insect pathogens (e.g. baculoviruses and EPN) can be used to control insect pests and reduce crop losses
62
biofuels
Algae can be used to make biofuels e.g. biodiesel or bioethanol, a promising alternative to fossil fuels
63
Bioremediation
Microbes have enormous metabolic diversity and some can be used to clean up pollution such as crude oil spills
64
Restriction endonucleases
enzymes produced by bacteria to defend themselves against bacteriophages. They cut DNA at specific sites and are widely used in molecular cloning techniques
65
Polymerase Chain Reaction (PCR)
- A heat stable DNA polymerases from the thermophilic bacterium
- Thermus aquaticus was the original source of Taq polymerase used in Polymerase Chain
Reaction (PCR)
