1 - What is microbiology? Flashcards
What is microbiology?
• The study of organisms - too small to be seen clearly by the unaided eye, i.e. microorganisms (microbes):
o Viruses: non-cellular
o Prokaryotes: Bacteria/Archaea
o Eukaryotes: Protists, Algae, Fungi
estimate of the total number of microbial cells on earth
5x10^30
Microbiology revolves around two main themes
- The basic science of life – microbes can be easy to study
- Impact on humans either directly or indirectly –
o devise ways to increase the benefits of microbial activity or curtail their harmful affects.
o What are the impacts of microbes on humans?
Disease
- Infectious diseases are caused by pathogens
- Still the major cause of death in many lower income countries (malaria, tuberculosis, cholera, COVID-19)
- Controlled by combination of vaccination, antibiotics, personal hygiene
- Newly emerging diseases (COVID-19, Influenza, Nipah etc)
Benefit of Microbes: Food
• Food materials that benefit from or even require microbiological activity: yogurt, cheese, vinegar, sauerkraut, certain sausages, beer, wine …
problems of Microbes: Food
• Microbes grow well in food fit for human consumption: preservation to avoid
– Food spoilage
– Food borne disease
Benefits of Microbes: Agriculture
- Nutrient cycling – Microorganisms play a key role in nutrient cycling: convert nutrients into forms readily accessible to plants
- Animal husbandry – Microorganisms in the rumen of cattle and sheep degrade the cellulose present in grass and other plants
- N2 fixation – bacteria use atmospheric N to synthesise NH3: reduced need for costly and polluting fertilizer
Benefits of Microbes: Energy & Environment
- Methanogenic bacteria produce natural gas.
- Waste products and surplus grain can be converted to biofuels (methane, ethanol, butanol).
- Bioremediation: microbes clean up by degrading the pollutants eg. spilled oil, pesticides.
Industrial Microbiology & Biotechnology
Genetically modified microorganisms synthesise products of high commercial value (e.g. insulin, human growth hormone)
Robert Hooke first to describe microorganisms (1665)
- Renaissance man; “Jack of all trades”
- A drawing by Robert Hooke (1665) – a bluish coloured fungus growing on the surface of leather
- His first microscope had a magnification of 20-30x
Germ vs Miasma theory in the mid 1800s
- Miasma theory-’bad air’ origin of epidemics from rotting organic matter; get rid of the smells you get rid of the illness such as cholera or ‘plague’
- One prominent supporter of the miasma theory was Dr. William Farr. He was convinced that cholera was transmitted by air.
- Soil at low elevations, especially near the banks of the River Thames, contained much organic matter which produces ‘miasmata’. The concentration of such deadly ‘miasmata’ would be greater at lower down than in the surrounding hills.
Medieval PPE: Miasma personal protective equipment!
• PPE – Mask with scented herbs – Hat – Stick to prod people – Long hooded coat • Mal Aria -‘Bad air’
Summary about the Pasteurs
• Their work led to the development of methods for controlling the growth of microorganisms:
– sterilisation (killing of all microorganisms including dormant forms)
– pasteurisation (destruction of vegetative organisms, but not spores, by brief heating)
• Developed vaccines against anthrax and rabies
Where Did Viruses Come From?
- The progressive, or escape, hypothesis states that viruses arose from genetic elements that gained the ability to move between cells
- The regressive, or reduction, hypothesis asserts that viruses are remnants of cellular organisms; and
- The virus-first hypothesis states that viruses predate or coevolved with their current cellular hosts.
History of virus origin/identification
• Viruses were associated with precursors of mammals and coevolved with humans:
o Poliomyelitis
o Small Pox
o Tomato yellow leaf curl virus
History of polio and smallpox
- The first written record of virus infection consists of heirglyph from Memphis, the capital of ancient Egypt, drawn in about 3700 BC
- It depicts a temple priest called Ruma showing typical signs of paralytic polimyelitis
- Archeologists find “dome-shaped vesicles similar to those found in smallpox” on three mummies whose skin, bones and muscles were preserved in 1898
- One of these was Pharaoh Ramses V who died in 1157 BC
- The mummified head of Ramses V of Type showing the pustular eruption that may been due to smallpox
Robert Koch (1843-1910)
- What is the nature of infectious disease? Microbes were “suspects” but proof was lacking!
- Koch’s lab established germ theory of disease.
- Formulated criteria for proving that a specific microorganism causes diseases: “Koch’s Postulates”
- Developed simple methods for obtaining bacteria in pure culture
Koch’s Postulates
- Led to discovery of the causes for: Anthrax, Tuberculosis, Cholera
- Koch awarded Noble prize for Physiology and Medicine (1905)
Variolation
- It is the method first used to immunize an individual against smallpox
- Chinese practiced the oldest documented use of variolation. They implemented a method of “Nasal insufflaion” administered by blowing powdered smallpox material, usually scabs, up the nostrils
Modern Vaccination
- In 1796, Jenner took fluid from a cowpox blister on the hand of milkmaid, Sarah Nelmes and scratched it into the skins of James Phips, an eight-year old boy.
- Single blister rose up on the spot but James soon recovered
- Jenner inoculated the boy again, this time with smallpox matter, and no disease developed.
- Jenner had demonstrated smallpox immunization
