MBIO L1 - intro to microbiology

Lecture 1

what are microorganisms?

organisms that are too small to be seen with the naked eye

what are the three major groups of microorganisms?

• prokaryotes

• eukaryotes

• viruses (acellular microbes)

what are the three domains living organisms are classified by?

• what are they based on?

bacteria, archaea & eukarya

• they are based on their cellular composition and genetic relationships

what are prokaryotes?

unicellular organisms that lack a membrane-bound nucleus

• they also have a single circular chromosome

provide examples of prokaryotes

bacteria & archaea

describe archaea

unicellular organisms that are able to live in adverse environmental conditions

• ex: high salt concentrations, high temperatures and acidic environments

what are eukaryotes?

multicellular or unicellular organisms with a membrane-bound nucleus and organelles

provide examples of eukaryotes

protozoa & fungi

define:

• acellular, unicellular, multicellular

• acellular: not made of any cells

• unicellular: made of one cell

• multicellular: made of many cells

what are viruses?

acellular entities that require a living host cell to reproduce

how do viruses reproduce if they are acellular?

they do not grow or divide; they replicate by assembling new viral particles inside a living host cell

what system is used for naming microorganisms?

the binomial system of nomenclature which assigns each species a two-part Latin name

in the binomial system, which comes first: genus or species?

genus comes first followed by the species name

• ex: Staphylococcus aureus or Staphylococcus aureus

• the first letter of the genus is capitalized while the species name is in lowercase while both are italicized or underlined

can a genus contain multiple species?

• give an example

yes

• ex: the Bacteroides genus contains over 100 species

how can you abbreviate a microorganism’s scientific name?

use the first letter of the genus (capitalized) & the species name (not capitalized)

• ex: S. aureus

why is microbiology important for humans, animals and plant life?

they play essential roles in many areas of life including health, agriculture and the environment

how did microorganisms contribute to the development of higher life forms (complex, multicellular organisms)?

primitive photosynthetic microbes likely produced atmospheric oxygen, allowing higher life forms to develop

what role do microorganisms play in soil and plants?

they help degrade organic materials and perform atmospheric nitrogen fixation in plants

what impacts do microorganisms have on medicine?

they produce antibiotics that are used in clinical practice

how do normal bacteria in the human body help us?

normal bacteria within the body prevents the growth of harmful bacteria

how are microorganism used in the food industry?

they are used in fermentation for beer, wine and yogurt

who was the first to see and describe cells in 1665?

Robert Hooke

what invention allowed Robert Hooke to see cells?

the microscope

what scientific idea did Hooke’s observation of cells lead to?

the start of the cell theory (in which all living things are composed of cells and that cells are the basic unit of life)

who used the microscope to view live microbes in 1684?

Anthoni van Leeuwenhoek

what did Leeuwenhoek call the microbes he observed?

animalcules

what is spontaneous generation?

the theory that bacteria can arise spontaneously from non-living matter

what will happen to food left out for long periods of time according to spontaneous generation?

they will eventually spoil and may become contaminated with bacteria

what do microscopic examination reveal about spoiled food?

that spoiled food is crawling with bacteria

who rejected the theory of spontaneous generation?

Louis Pasteur rejected the theory of spontaneous generation

• he demonstrated that microorganisms come from other microorganisms

what is biogenesis?

the hypothesis that living matter arrises only from pre-existing living matter

according to biogenesis, can living matter come from non-living matter?

no, living matter arises only from pre-existing living matter

which theory (spontaneous generation or biogenesis) is currently accepted?

biogenesis

• this is because experiments demonstrates that bacteria only appears when pre-existing living organisms are present

what did Louis Pasteur demonstrate using a swan neck flask?

• what did he show about micro-organisms responsible for food spoilage?

he demonstrated aseptic technique and showed that microorganisms responsible for food spoilage came from the air and not from spontaneous generation

what was the main conclusion of Louis Pasteur’s swan neck flask experiment?

that spontaneous generation could not occur and that microorganisms came from the air

what are aseptic techniques?

practices used to prevent microorganisms from the air from contaminating materials, showing that microorganisms come from pre-existing living sources rather than spontaneous generation

describe this image by stages

stage 1:

• broth is placed in a flask

• broth is heated

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stage 2:

• the flask has a swan-neck shape

• air can enter the flask

• dust and microorganisms from their air gets trapped in the curve of the neck

• microorganisms cannot reach the broth

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stage 3:

• the broth remains clear and uncontaminated

• no microbial growth occurs, supporting the idea that microorganisms come from pre-existing living sources

what was first thought to convert sugar into alcohol?

it was first thought thought that air converted sugar into alcohol

what did Louis Pasteur show convert sugar to alcohol?

he showed that it is yeast that converts sugar into alcohol in the absence of air

what is the process called when yeast converts sugar to alcohol in the absence of air?

fermentation

what causes the souring of milk and beer/wine?

the souring occurs when the bacteria present coverts sugar into vinegar

how can you prevent the souring of milk and beer/wine?

you could heat the milk/beer/wine which would kill all of the bacteria present and prevent spoilage

what procedure involves heating milk, beer or wine to kill bacteria and prevent spoilage?

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is this procedure still used today?

pasteurization

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yes, it is still used today

how did Pasteur determine spoilage can be prevented?

by heating milk, beer or wine to kill bacteria (pasteurization)

differentiate fertilization and pasteurization

• fermentation is the process where yeast converts sugar into alcohol in the absence of air

• pasteurization involves heating milk, beer or wine to kill bacteria and prevent spoilage

what is the germ theory of disease?

the belief that micro-organisms are responsible for the cause of infectious diseases.

who developed the germ theory of disease, and on what basis?

Robert Koch on the basis that microbes alter the chemical and physical nature of organic material

what did the development of the germ theory lead to?

it lead to the development of Koch’s Postulates

what is Koch’s Postulates?

a set of criteria established to prove that a specific microbe is responsible for a specific disease

what are Koch’s Postulates used for today?

they are used in order to prove that a specific microbe is responsible for a specific disease.

based on this image demonstrating Koch’s Postulates, answer the following questions:

1. what is the first step shown in Koch’s Postulates?

2. what happens to the microorganisms after isolation?

3. what is done after the microorganisms are grown in pure culture?

4. what occurs in the laboratory animal after injection?

5. what happens after the disease is isolated?

6. what is shown at the final step of Koch;s Postulates?

1. microorganisms are isolated from a diseased or dead animal

2. the microorganisms re grown in pure culture

3. the microorganisms are injected into a healthy laboratory animal

4. the disease is reproduced in the laboratory animal

5. microorganisms are isolated from this animal

6. identical microorganisms are identified and grown in pure culture

what is pure culture?

a culture containing only one type of microorganism

who developed the small pox vaccine?

Edward Jenner

what observation was the small pox vaccine based on?

it was based on the observation that people previously infected with cow pox were immune to small pox

what did Edward Jenner do to test his observation? what happened after?

he injected a young boy with cow pox but the boy became mildly ill

what was later discovered that about the boy injected with cow pox?

it was later discovered that this boy was immune to small pox

what is the relevance of the discovery that the boy was immune to small pox?

it showed that infection with cow pox provided immunity to small pox and laid the groundwork for the development of vaccines

who developed the idea of selective toxicity?

Paul Ehrlich

what is selective toxicity?

the ability to either kill or inhibit the growth of pathogenic organisms while leaving the host unharmed

what did Paul Ehrlich discover that demonstrated selective toxicity?

the first effective anti-microbial Salvarsan which was used cure syphilis without damaging host cells

what are syphilis?

a sexually transmitted infection (STI) that can cause a serious disease if untreated

what are host cells?

the cells of the host organisms that can be infected by microorganisms

who made an important discovery in 1929 related to antimicrobials?

Alexander Fleming who discovered Penicillin

what did Alexander Fleming discover about the mold Penicillium chrysogeum?

he discovered that a product of the mold Penicillium chrysogeum was able to inhibit the growth of bacteria on plates contaminated with the mold

what was the product discovered from the Penicillium chrysogeum?

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what is it?

penicillin

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it is an antimicrobial agent (antibiotic) that inhibits bacterial growth.

what effect did penicillin have on bacteria?

It inhibited the growth of bacteria

how was the discovery of penicillin made?

this discovery was made by an accident

why was the discovery of penicillin important?

it revolutionized modern medicine