These are the notes from the Microbiology year 2 semester 1 at Rhodes university. It covers in-depth the basics, bacteriology, fungi, reproduction methods, different types and their individual life cycles.
• Study of microscopic organisms which are living cells, how they work, their
diversity, ecology and how they adapt and evolve.
- A microorganism exists as a single cell or cluster of cells and includes bacteria,
fungi, algae, and viruses.
Can be cultured or grown on artificial medium (agar plate)
Are observed under a microscope (viruses require a transmission electron
microscope)
Pros & Cons
Food
used in production of beer, fungi can cause food to go bad and
cheese, bread become harmful for consumption.
Agriculture
Nitrogen fixation for aqua- can cause plant diseases wiping-out.
Farms, bio-pesticides harvests
Medicine
Production of medicines like illnesses and antibiotic resistant
penicillin and Insulin variants
,Industrial and Environmental
Biofuels and water pollution from the production of
Purification systems toxins and reduction of oxygen
Basic History
Aristotle (384-322 BC) believed that living organisms developed from non-living
matter termed Spontaneous generation
Zacharias Janssen invented the microscope (1590)
In the mid 1600 Robert Hooke and Anton van Leeuwenhoek described and observed
microorganisms.
• Spontaneous generation
in 1861 Louis Pasteur disproved the concept and showed how to keep
solutions from going bad by using the swan-neck experiment
Swan-neck Experiment
- Clear nutrient solution was placed in a flask and after a while became
cloudy, indicating the growth of bacteria.
- Pasteur wanted to prove that the air containing particles
(microorganisms) was responsible for this.
- He bent the neck into an S shape, trapping the air particles in the bend.
, - He boiled the solution, so no particles were inside the flask or solution.
- He observed that if left the solution remained clear.
- If he tilted the flask the solution encountered particles and clouded.
- He concluded it was a living particle in the air that inoculated the
medium not spontaneous generation.
Methods used to kill microorganisms include:
Pasteurisation
- Process in which water and certain packaged / non-packaged foods are
treated with mild heat (<100˚C) to eliminate bacteria (potential
pathogens).
- The process deactivates microorganisms and enzymes that contribute
to spoilage / risk of disease.
Sterilisation
- Pasteurisation does not kill bacterial spores; this requires other
methods.
- Autoclaving is the use of pressurized steam and high temperatures to
kill microbes, spores, or viruses that are hard to destroy. This is
Sterilisation.
- There are other sterilisation methods such as filtration and use of gas.
, Did microorganisms cause disease / infections
• This relationship was recognized by Agostino Bassi (1836) through a silkworm
infection known as muscardine disease caused by the fungus Beauveria
bassiana.
- The white dust (fungal spores) that was left on the worm after it died
caused new infections to other worms.
• Joseph Lister (1867) reduced wound infections after surgery by introducing a
system of heat sterilising surgical instruments and treated dressings with
phenol.
- This antiseptic approach reduced the incidence of gangrene and the
death rate because of surgery.
• The Irish potato famine (1845-1852) resulted from the failure of up to ¾ of the
potato crop.
- Approximately 1 mil. People died of starvation / related causes & a
further mil. Emigrated.
- Reverend Miles Berkeley proved that this was caused by the fungus-like
oomycete, Phytophthora infestans.
The potato famine highlighted that low genetic diversity in monoculture crops are
susceptible to diseases.
- Potatoes of the “lumper” variety were vegetatively propagated,
meaning they we all genetically identical clones.
- Thus, all potatoes were infected due to low diversity. Diversity ensures
that there is less probability of all crops being infected.
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