LECTURE 18 - Microbiology Flashcards
viruses
a microorganism
The smallest and simplest biological entities
* Depend on host cell for replication & metabolism
Viruses are small in size and
genome content but have
large effects on other
organisms and ecosystems
e.g. hepatitis C virus, herpes virus, coronavirus, small pox, influenza, bird flu virus
bacteria
- Unicellular structure. Smallest free-living organisms.
- Have own metabolism and replication (unlike viruses)
Simple morphologies of
bacteria conceal complex
biochemistry and interactions
Fungi
- Large complex cells (Eukaryotes); nucleus, mitochondria
- Can be unicellular e.g. yeasts or multicellular e.g. moulds
Some fungi can have both
macroscopic and microscopic
parts: e.g. fruiting body
vs. spores of mushrooms
Protists
- Large complex cells (Eukaryotes); nucleus, mitochondria
- Protozoa: protists that are animal-like (predatory)
Protists are extremely
diverse in morphology,
lifestyles, and their
evolutionary histories
Algae
- Large complex cells (Eukaryotes); nucleus, mitochondria
- Algae: Plant-like protists. Photosynthetic
Some protists cannot
easily be classified as
‘algae’ or ‘protozoa’
Exceptions to rules are
very common in biology
Hooke. The idea of ‘cells’
- 1664 - Robert Hooke describes microscopic structure of blue
moulds, using a 30 x magnification microscope - First to use the word ‘cell’. His book “Micrographia” (1665)
very influential, due to the excellent artwork
who Discovers bacteria + protists
- Antonie van Leeuwenhoek develops powerful microscopes (300x mag.),
discovers “wee animalcules” - first evidence of bacteria and protists
- Antonie van Leeuwenhoek develops powerful microscopes (300x mag.),
- He is considered the ‘father of microbiology’
Pasteur spontaneous generation
- Louis Pasteur made many crucial
contributions to microbiology :
– Vaccination
– Fermentation
– Pasteurisation - 1861: Pasteur disproved the theory of
spontaneous generation – the idea that non-
living objects can give rise to living organisms
john needham boiled hay, which sterilised the microbes present in hay, left it there and “came back to life” when micrbes appeared again hence microbial growth occured.
lazzaro spallanzani did it as well with no holes and no microbes occured? caused controvery
pasteur used swanneck flasks to let air so it could grow with no bacteria entering the flasks. when boiled and left there with flasks, no microbial growth but when boiled and left there with no flasks, there were microbial growht!
therefore, life comes from the air and not spontaneously
Koch. Germ theory of disease, Koch’s postulates
- Robert Koch pioneered:
– staining methods for microscopy
– use of solid growth media (agar) - Used these methods to identify bacteria causing:
– Tuberculosis
– Cholera
– Anthrax
germ theory
- 1876: Koch’s most important contribution: definitive
proof that microbes cause disease (i.e. germ theory) - Along with Pasteur’s work, germ theory important in
disproving the idea of ‘spontaneous generation’
“As soon as the right method was found, discoveries
came as easily as ripe apples from a tree”
koch’s postulates
A microorganism that causes a disease must :
* must be absent from all healthy organisms but present in diseased organisms and be found in all cases of the disease
* Be isolated from the diseased host in pure culture
* Produce same disease when incoculated into a healthy/susceptible organisms experimentally-infected host
* Be re-isolated from the experimentally-infected host and grown in pure culture = identical to original causative agent
Penicillin
- 1928: Alexander Fleming (UK) found mould growing on
a petri dish killed the bacteria (Staphylococcus) around it - ‘Mould juice’ killed many bacteria, including causative agents
of scarlet fever, pneumonia, meningitis and diphtheria - 1935-1945. Howard Florey (Aus.) and Ernst Chain (German)
purified penicillin and developed mass production methods - Penicillin was the first really effective antibiotic
This discovery helped the Allies to win WWII
Normal flora:
Microbes that live in us and on us
* Your body: approx. 30 trillion human cells
but 40 trillion microbial cells !
* Normal Flora
– found at specific sites
– specialised for that site
– mostly bacteria
– acquired at birth, from diet,
and from the environment
* Concept of normal flora is flexible
Differs between individuals, locations, times
do we need normal flora
Positive effects:
* ‘prime’ the immune system: immune system to recognize and defend against harmful invaders.
* provide nutritional benefits : digest food and absorb nutrients
* compete with pathogens : help prevent infections
Negative effects:
* Can cause disease if moved to wrong location
e.g. Staphylococcus harmless on skin–> cause infection if in wounds
* Can cause disease even in normal habitat
e.g. too much Streptococcus –> tooth decay
Pathogen def
A disease-causing microorganism
