Exam 1 - Microbiology

Kitasato Shibasaburo’s contribution & Yersin got to name the bacteria

Shibasaburo found the bacteria that caused the bubonic plague, but he didn’t have enough scientific proof. However, Yersin did have enough proof, so he got to name the bacteria.

What is microbiology?

the study of microorganisms

What are considered microorganisms

Prokaryotes (bacteria & archaea), some small eukaryotes (fungi & yeast), viruses

Human Health

• they help to digest our food

• they make vitamins for us (they are an extension of our genomes)

• they help prevent infections by pathogenic microbes

Model systems

for basic studies of biological processes

because microorganisms can reproduce quickly

Nutrient Cycling/global economy

microbes help cycle nutrients and help with new species on our Earth

the process where microorganisms break down, transform, and regenerate essential chemical elements so they can be reused by other living organisms. Microbes act as the primary driving force behind global biogeochemical cycles, turning dead organic matter and rocks into available nutrients

Human use of microbes

Wastewater treatment - microbes are used to clean wastewater

Bioremediation - microbes are used to clean contaminated environments

Biotech applications - microbes can be genetically modified to produce high-values products such as pharmaceuticals and enzymes

Food fermentations - yeast/bread, food

Industrial fermentations - microbes are used at industrial scale to make chemicals, solvents, enzymes, and pharmaceuticals

Biofilms - microbes grow on surfaces and can foul pipes and pipelines

Biofuels - microbes are used to convert biomass into ethanol and wastes into natural gas (methane)

Important facts about microbes

• They contain the majority of the biomass on the planet (more than all plants and animals combined)

• There are about 10³⁰ microbial cells on Earth

• They can be found several kilometers up in the atmosphere and at least 10 km below the Earth’s surface

  • There are more microbial cells associated with your body than there are human cells

Key historical events

• Visual observation of microbes

• Defeat of the theory of “Spontaneous Generation”

• Demonstration of infectious disease and acquired immunity

Robert Hooke

• probably the first person to observe microorganisms

• Coined the term “cell”

  • Wrote the first book on microscopic observations: Micrographia

Antoni van Leeuwenhoek

• his hobby was lens grinding

• constructed his own single lens microscope

  • Royal society of London published his letters

Spontaneous Generation

• the idea that living organisms formed spontaneously from natural elements (i.e. germs, maggots, and mice would “magically” appear if you left food to rot)

• Early experiments showed that if the food was heated and then sealed from the air, then the rot

Vital force

organic compounds come only from living things because they need a special, God-given life energy that humans cannot make in a laboratory

Seed/germ theory

invisible "seed-like" particles spread infection

Louis Pasteur

• Swan-necked flask

  • to conclusively disprove the theory of spontaneous generation and prove that microorganisms come from other pre-existing microorganisms

Germ theory of Disease

• Edward Jenner → vaccination for small pox from cow pox

• Louis Pasteur → vaccines for anthrax, fowl cholerae, and rabies

• Joseph Lister → concept of disinfection of wounds and surgical rooms

Robert Koch

• Pure culture techniques

• Koch first used potato slices, gelatin, or starch under a bell jar

• Petri dishes, Julius Petri

• Gelatin (mp = 28C, metabolized) vs Agar (37C, not metabolized)

• Spread plate (dilute in liquid, then plate) vs Streak plate (dilute on plate itself using loop)

  • Each colony arises from a single cell! All the cells within a colony are identical! Each colony is a “Pure culture”

Koch’s Postulates

Rules for clearly demonstrating the cause of an infectious

1. The organism should be present in all animals suffering from the disease and should not be present in healthy individuals

2. The organism should be grown in pure culture away from the animal body

3. Cells from the pure culture, when inoculated into susceptible animals, should cause the disease symptoms

4. The organism should be re-isolated from these experimental animals and cultured again in the laboratory, after which it should still be the same as the original organism

Koch Postulates - FAILS

Viruses

Environmental microbiology

• not all bacteria cause infections

• the scientific study of microorganisms—such as bacteria, fungi, viruses, and algae—and their interactions with each other and their natural or artificial surrounding

Enrichment techniques

Place an environmental sample under conditions that select for optimal growth of an organism with specific metabolic capabilities

Martinus Beijerinck and Sergei Winogradsky

isolates specific microorganisms from environmental soil and water samples

Demonstrated:

• Chemolithotrophy

• Fixation of CO2 independent of photosynthesis (not always associated with photosynthesis)

• Fixation of atmospheric nitrogen into cellular nitrogen

Chemolithotrophy

the use of inorganic compounds (sulfur, ammonia, etc) to obtain energy

Magnification

the extent to which the image of an object is larger than itself

20x = 200x

40x = 400x

100x = 1000x

Magnification Calculation

Object lenses x Ocular lenses = magnification of an image

Resolution or resolving power

the degree to which details are retained in a magnified image; the ability to distinguish between two points

Resolution Equation

R = 0.5(wavelength) / NA

light wavelength (assume ~500 nm)

NA

numerical aperture

the light gathering ability of the lens

Best condition for standard light microscopes

with standard light microscopes, the best resolution with 1000x magnification is 200nm = 0.2 microns = 0.2 µm

Main limiting factor in light microscopy

Resolution

Why use oil in a 100X?

use of an oil immersion lens increases the NA (numerical aperture) of the lens

Bright field microscopy

• most common in general microbiology labs

• light is transmitted through the specimen

How do you generate contrast

contrast between the background and the cells is generated by absorption or scattering of light

Why cells end up dead

• staining of cells is generally required

  • staining tends to kill cells

  • dead cells take up more stains than live cells