BIOL1997 Flashcards
Module 4
What did Robert Hooke do in 1664?
- Invented microscope
- Describes microscopic structure of blue molds, using 30x magnification microscope
- First to use the word ‘cell’ saw that all living things have the same structure
- Book Micrographia very influential due to excellent artwork
What did Leeuwenhoek do in 1684?
- Develops powerful microscopes (300x mag.), discovers “wee animalcules” in pond water
- First evidence of bacteria and protists
- He is considered the ‘father of microbiology’
What did Needham and Spallanzani do in the 1700s?
John Needham
-There is a “life force present in all matter that causes spontaneous generation
-Boiled hay in water to kill everything, left it to exposed air and microbial growth occurred
Lazzaro Spallanzani
-Repeated experiment but sealed the flask
-Microbes did not re-appear
What did Pasteur do in 1861?
- Vaccination
- Fermentation
- Pasteurization
- Disproved the theory of spontaneous generation (non-living objects can give rise to living organisms)
- Swan neck flask experiment:
- Boiled hay in swan neck flasks
- Broke neck of one of the flasks: bacterial growth in that one
- In the one with no broken neck which allowed air to pass, no bacteria growth
What did Koch do in 1876?
-Staining methods for microscopy
-use of solid growth media (agar)
-Identified bacteria which caused:
-Tuberculosis
-Cholera
-Anthrax
-Discovered spores and explained survival of anthrax in soil
-Germ theory: important in disproving spontaneous generation
-Koch’s postulates:
An organism that causes a disease must;
1. Be found in all cases of the disease
2. Be isolated from the diseased host in pure culture
3. Produce same disease in experimentally-infected host
4. Be re-isolated from the experimentally-infected host
What did Fleming do in 1928?
Found mold growing on a petri dish killed the bacteria around it
- Mold juice killed many bacteria, including agents of pneumonia
- Penicillin notatum
What did Florey and Chain do in 1935-1945?
- Purified penicillin and developed mass production
- First really effective antibiotic. Discovery helped the Allies to win WWII
- Still dependent on fungus to make penicillin as it is hard to make
How many trillion microbial cells does the human body have?
40
What is normal flora?
o Found at specific sites
o Specialised for that site
o Mostly bacteria
o Acquired at birth, from diet, from the environment
Where does microflora initially come from, and how does it develop?
- Concept of normal flora is flexible and differs between individuals, locations and times
- At the beginning, microflora comes from the mother
- It then develops based on diet, medicines, environment, people interacted with
- Broadscale similarities but individual differences
What are positives of having natural microflora?
‘Prime’ the immune system
Provide nutritional benefits
Compete with pathogens
What are negatives of having natural microflora?
Can cause disease if moved to the wrong location
Staphylococcus from nose to open wound can cause wound infection
Can cause disease even in normal habitat
Streptococcus can cause tooth decay
What is a pathogen?
Disease-causing microorganism
What are obligate pathogens?
pathogens that are always harmful
o Viral infection usually damages or destroys the host cell
What are opportunistic pathogens, and what factors do they depend on?
only cause disease under certain conditions
o Numbers- abnormally high cell density
o Location- get into the wrong place
o Host health- immune system compromised
o Virulence factors- gain antibiotic resistance
Bacteria can horizontally share genes and evolve extremely easily
What is the concept of the One Health concept?
- Healthy people Healthy environments Healthy animals
- Activities in homes and farms influence disease as a whole
- Consider animals and the environment when we are trying to manage human diseases
- Many human diseases originate in animals
- Use of antimicrobials in agriculture impacts on human pathogens
- Disease is influenced by urbanization, globalization, climate change, pollution
What are major infectious disease problems due to?
- Emerging infections due to new pathogens
- New problems with old pathogens
Describe what tuberculosis is?
- Bacterial cause
- How it is spread
- What it does
- Symptoms
- How many are affected
- Treatment
o Caused by bacterium Mycobacterium tuberculosis
o Spread person-person by airborne droplets (coughing)
o Infects lungs cough, chest pain, weight loss, death
o Disease can be ‘latent’ for many years (no symptoms)
o Symptoms are non-specific: difficult to diagnose
o One-third of world’s population is infected
o New strains of TB are resistant to antibiotic treatment
Drug resistant TB is difficult to treat and treatment is expensive
Describe the role of microbes in the production in the food production chain step
Good-
- Rumen microbes help cows digest grass
- Symbiotic fungi enhance plant growth
- Soil microbes recycle wastes into nutrients
Bad-
- Pathogens infect animals and plants
- Irrigation water can be contamined with human pathogens
- Post harvest contamination can ruin food crops
Describe the role of microbes in the processing in the food production chain step
Good-
Many foods require fermentation
Bad-
Factories can be contaminated by microbes
Describe the role of microbes in the distribution in the food production chain step
Good-
Some microbes are important food sources
Bad-
Refrigeration needed to stop microbial growth
Describe the role of microbes in the restaurant preperation in the food production chain step
Poor hygiene –> food poisoning
Describe the role of microbes in the restaurant consumer in the food production chain step
Good-
Good gut microflora beneficial to health
Bad-
Poor gut microbiota causes poor health
Describe the role of microbes in the retail in the food production chain step
-Poor hygiene –> food poisoning
Describe the role of microbes in the home consumers in the food production chain step
Good-
Good gut microflora beneficial to health
Bad-
Poor gut micriobiota causes poor health
What is the process of food production?
Production Processing Distribution Restaurant Restaurant preparation Restaurant consumer Retail Home preparation Home consumers
How do microbes maintain soil health?
o Fixing nitrogen from nitrogen gas to ammonia, which is extremely energy costly
o Breaking down organic wastes into inorganic nutrients
o Suppressing pathogenic microbes (animal+ plant pathogens)
o Breaking down toxic molecules like pesticides and pollutants
Why are microbes useful in animals? Use a specific example
o Cellulose: sugar polymer, abundant in plants, carbon-rich but difficult to digest
o Rumen microbes break down cellulose sugars organic acids, CO2, CH4
Rumen in cow
• Anaerobic environment
o Anaerobes killed by oxygen
• Not all living things need air
• Mutualistic relationship between cow and microflora
o Organic acids and dead microbial cells then digested by animals
o Methane is a potent gas –> cows farting contributes to climate change
Why are microbes useful in plants? Give two specific examples
• Microbes promote plant growth via mutualism
o Mutualism- ecological interaction where both partners benefit
o Mycorrhizal fungi (in most plants) enhance water + inorganic nutrient uptake, receive sugars from plant
o Rhizobium bacteria (in legume roots) fix nitrogen, receive sugars in return
What are the main plant pathogens?
• Just like humans and animals, plants are subject to disease caused by microbes
o Fungi and viruses are the main problems
o Crop pathogens cause global losses of about 30% of total yield
Talk about the Tobacco mosaic virus
Tobacco mosaic virus is a very simple entity (only 3 genes) but it can infect many crops
Remains infectious long after the virus has left the plant
What are the main animal pathogens?
• Pathogens can be viruses, bacteria, fungi or protists
Why are pathogens infecting farm animals a problem?
• Pathogens infecting animals inflict suffering, death, and massive economic losses (about 20% of total production)
Why was the foot and mouth disease so devastating, and how was it introduced?
o Devastating viral disease infecting many farm animals
o Infects cows, pigs, sheep and goats but not humans
o Resulted in huge economic losses
o Cause of UK outbreak was that pigs were fed waste products including meat illegally imported from infected animals
What is zoonosis and why is it a problem?
Human infection arising from animals
o Human pathogen may be normal flora for the animal (e.g. salmonella in chickens)
o Animal is a vector for disease (e.g. ticks and lyme disease)
Target shaped rash
High fever
Fatigued
What is fermentation?
Microbial transformation of foods
• Anaerobic metabolism of sugars –> alcohols, acids, CO2 due to the action of fungi and/or bacteria
Why is fermentation useful?
• Many products:
o Beer
Barley (source of sugars to support fermentation)+
Hops (natural preservative and provides bitterness)+
Water+
Yeast
• Saccharomyces (brewer’s yeast)
• Yeast is a unicellular fungi whilst mold is multicellular filamous fungi
=Beer
o Bread
o Cheese
Why does spoilage happen and how much food is lost to spoilage?
• Spoilage is due to the growth of fungi and bacteria, or due to enzymes these microbes secrete
-Approx 20% of all food is lost to spoilage
How is spoilage prevented?
• Spoilage is prevented by refrigeration, preservatives and fermentation
o Refrigeration double edged sword some microbes grow better at colder temperature
o Some preservatives such as sugar and salt are not great for human health
o Fermentation- curtails activity of pathogens by making good microbes ferment the food and reduce nutritional content for bad microbes
What does spoilage do?
• Spoilage makes food taste bad and reduces nutritional content
How does food poisoning occur?
• Food poisoning can occur from spoiled or fresh food- different sets of microbes are responsible for spoilage vs poisoning
What is a food-borne infection?
• Food-borne infection- microbes grow in gut
o Salmonella enterica
