5. Infection Biology Flashcards
What are obligate aerobes?
Organisms that require oxygen for cellular respiration
What are obligate anaerobes?
Organism that produced energy for metabolism by fermentation or anaerobic respiration. They are poisoned by oxygen.
What are facultative anaerobes?
Organisms that use oxygen when it is present but respire anaerobically or use fermentation in anaerobic conditions, to survive.
What roles do prokaryotes play in chemical cycling?
Chemoheterotrophs = decompose waste products + dead material
Nitrogen fixers = fix N2 in the air into useable ammonia
Increase availability of N, P and K for plant growth
They can also immobilise / decrease nutrient availability
How are bacteria involved in agriculture?
Nitrogen fixing for fertiliser, nutrient recycling, organic material decomposition
How are bacteria involved in food?
Fermented food, preservation, meat substitutes
How are bacteria involved in energy?
Biofuels (methane), bioremediation, artificial photosynthesis
How are bacteria involved in biotechnology?
GMO, gene therapy
How are bacteria involved in disease?
Treatment and care, infection
What type of DNA do bacterial cells have?
A bacterial chromosome is a single, large, double-stranded molecule. Sometimes there are small circular plasmids which are additional DNA
What is the average overall size of bacterial cells?
<1-10um (micrometres)
Bacterial cells often lack membrane-bound organelles, what are some exceptions? (two examples)
Acidocalcisomes have membrane-bound acidic calcium storage compartments
Anammoxosomes have membrane-bound organelles that produce energy for anaerobic ammonia oxidation
What are the general components of a bacterial cell?
Cytoplasm
Cytoplasmic membrane
Cell wall
Capsule
Plasmid DNA
Single chromosome
Ribosomes
Flagellum
What is the general structure of flagella and how do they work to allow motility for bacterial cells?
What are fimbriae?
Relatively short extensions from the cells that allow them to stick to their substrate or others in the colony. AKA attachment pili
What are sex pili?
Extensions from the cells that allow prokaryotes to exchange DNA. They are longer than fimbriae.
What is the purpose of bacterial cell walls?
Shape / structure
Protect them from osmotic lysis and toxic substances
What is the composition of the bacterial cell wall?
Made of peptidoglycan (polymer)
How can the bacterial cell wall be used to classify bacteria into 2 groups?
Different compositions of the peptidoglycan polymer can be differentiated by Gram staining. (stain developed by Hans Christian Gram)
DESCRIBE DIFFERENCES
What is the capsule which covers many prokaryotes?
It is an additional polysaccharide or protein layer.
What do the colours produced by gram staining mean?
Purple = Gram positive bacteria. Peptidoglycan traps crystal violet.
Red-pink = Gram negative bacteria. Crystal violet is easily rinsed away.
LECTURE ON FRIDAY 25/10/24
How do microbes colonise
air, water, soil, food, animals
What makes a microbe beneficial or harmful?
Beneficial microbes have symbiotic mutual and commensal relationships.
Pathogens have symbiotic parasitic relationships, they damage the host during growth and have mechanisms of pathogenicity.
How do we provide microbes with good, diverse habitats for colonisation?
Factors important for growth are constant in a given niche:
Skin = dry and salty
Armpits = damp, warm, salty, low pH
Respiratory tract = moist, neutral pH, high in oxygen
GI tract = wet, warm, low pH, low in O2
Exposure?
What is the role of normal microbiota?
They protect surfaces from physical colonisation by pathogenic bacteria from animals, other humans, the environment, evolution of organisms.
What is the microbiome?
The microbes, their genomes and the environmental interactions in a define environment (e.g. GI tract in human microbiome)
How many cells / organisms make up the human microbiome?
number of human cells x10 = number of viruses and bacteriophages that make up the human microbiome
Gut microbiome
Are changes in human microbiome associated with human health or disease?
Yes, e.g. obesity, diabetes, asthma, cancer, autism, depression
How do we investigate the microbiome?
Whole genome sequences (e.g. Human Microbiome Project)
SLIDE 18 GUT MICROBIOME SLIDE
How can microbes be passed between humans?
Saliva
Aerosol transmission (sneezing)
Poor hygiene (not washing hands)
Insect bites
Cuts in skin
Sex
What is enteric bacteria
Bacteria that live in the GI tract
Describe the principles of pathogenesis
- Invade host
- Evade innate local defences + spread through host
- Multiply
- Evade adaptive immune defences long enough to complete life cycle
- Leave body and spread to new hosts
Give an example of how bacteria invade a host (tooth decay)
Bacterial micro-colonies grow attach to the tooth and grow on its surface. The bacteria then ferments sugar to lactic acid causing decalcification of enamel (tooth decay)
Describe how toxins work in relation to cholera
Toxin gene is phage encoded and induces severe diarrohea.
WHAT IS THIS SLIDE ABOUT
How is necrotising fasciitis caused?
Bacteria invade the body and produces a toxin that can lyse (split / break down) red blood cells
SLIDE 31 what is going on
How to prevent infection?
Good hygiene
Vaccines
Antibiotics
Anti-viral agents
How do vaccines work to prevent infection?
It stimulates / activates protective defences of the body. Body generates memory response so that if infected, it will clear infection rapidly.
How was the first antibiotic discovered and how does it work?
Alexander Fleming discovered the fungus Penicillium notatum which produces penicillin which kills bacteria by preventing peptidoglycan cross-linking and therefore bacteria lyse under osmotic pressure.
How do viral agents work?
They inhibit the multiplication of the virus without affecting the infected host cell
How does Acyclovir (zovirax) work?
How does AZT (zidovudine) work?
How does Oseltamivir (tamiflu) work?
What microbes are involved in the production of bread, beer, cheese and vinegar?
Bread = Yeast
Beer = yeast
Cheese = Rhizopus chinensi
Vinegar = Acetoobacter
How is beer produced?
- Ferment partially germinated malted barley
- Heat to 65C to kill dangerous microbes
- Add yeast which ferments sugar in barley
- Alcohol is produced after fermentation
- Yeast is removed, beer filtered, pasteurised, bottled
How is cheese produced?
Cheese used to be made by rennet but is now made by microbes.
- Rennet is added to pasteurised milk is separate it into curds and whey
or - Microbes separate pasteurised milk into curds and whey (Rhizopus chinensis = bread mold / CM Aspergillus niger)
- Flavour and form cheese by adding microbes during maturation + other processes
Rennet is mainly chymosin (aspartic acid protease) and was originally sourced from the the inner mucosa of 4th stomach of calf
How is vinegar produced?
- Expose wine to air contaminated with Acetobacter which oxidises alcohol to acetic acid
Commercial process:
1. ethanol is produced by yeast
2. Acetobacter converts it to acetic acid
Non-brewed condiment is a vinegar substitute made of water, acetic acid, flavourings and colouring
What is pruteen?
Pruteen was the 1st single-celled protein animal feed made from CONTINUE THIS
How are microbes involved in reducing pollution?
Break down organic matter in sewage.
Bioremediation
Produce biodegradable plastic
What is the activated sludge process and what does it involve?
The breakdown of sewage.
Autotrophs require CO2 and use inorganic compounds for energy.
Heterotrophs require
What is bioremediation?
The use of microbes to break down dangerous chemicals.
Give an example of bioremediation (Alcanivorax borkumensis = oil)
FINISH THIS
Talk about the plastics
How are microbes used in medicine?
Produce large quantities of useful compounds (already produced by the bacteria or GM for exoogenous molecules)
Produce vaccines, complex vitamins, antibiotics
Human gene therapy (viruses)
What does exogenous mean?
non-native molecules (e.g. useful products that are produced by bacteria which are not naturally encoded in the bacterial genome)
How can an exogenous
high pressure, lysozymes, sonification
How can exogenous proteins be produced by bacteria?
SLIDE 23