Unit II - MicrobiologySources:

• Pelczar M.J. and Chan E.C.S., Elements of Microbiology, McGraw-Hill, Inc. 1981

• Paustian, T. , http://www.bact.wisc.edu/MicrotextBook/University of Wisconsin-Madison 2002 (Textbook on the web)

Student Objectives:

• 1. To become familiar with the ubiquitous nature of microorganisms.

• 2. To learn some basic bacteriological lab techniques.

• 3. To understand how bacteria grows.

• 4. To become familiar with major groups of microorganisms.

.

• 5. To know how microorganisms can be controlled.

• 6. To be familiar with diseases caused by microorganisms.

Section One

•History of Microbiology

The First Microscope.

• Invented in late 1500’s

• A simple microscope = like a magnifying lens

The discovery of microorganisms.

• Leeuwenhoek = Dutch naturalist in late 1600’s

– Ground lenses and made microscopes.

– First to record observations of microscopic organisms seen in rainwater.

– Called the little organisms “animalcules”.

• Basic kinds of bacteria as observed by Leeuwenhoek

–spirilla – spiral-shape

• cocci – spherical

• bacilli – rod-shaped

Spontaneous Generation

• Belief that organisms arose from non life

• Disproved by use of beef broth experiments

• Louis Pasteur – the gooseneck flask

Pasteur

Schulze acid base Schwann’s flame

Pasteur’s

Schroeder’s cotton plug

Fermentation

• Used for many years.

• Pasteur discovered microbes were responsible

Disease

• 1540’s – first theories that small organisms caused disease.

Key Discoveries

• Pasteur isolated anthrax –causing microbes

• Koch discovered anthrax was caused by bacilli bacteria

• Koch developed culture media

Koch’s postulates• A specific microbe is associated with a

given disease.

• That microbe can be isolated and grown.

• The pure culture can be used to infect a host organism.

• Microbes can be “recovered” from infected organism

Koch

Immunization

• Any process that develops resistance in a host to a specific disease.

Pasteur discovered immunization accidentally.

• By using old cultures, injected chickens remained healthy.

• He injected a new culture in those chickens and again they remained healthy.

Other breakthroughs• Jenner and smallpox

immunization • Vaccinations (from vacca =

cow)• Rabies vaccines.• Antisepsis• Many more !!

Today’s Microscope.• Bright field – dark objects in bright

area• Compound – multiple lenses. Up

to 2000 x• Electron – maximum magnification

because of short wavelengths. Up to 400,000 x

The oil immersion lens.

• is 100 X• Requires oil to prevent light

refraction • Gives maximum

magnification for compound light microscope.

Quiz – History of Microbiology

•COMING SOON

•GET READY !!!!

Section 2• Laboratory Techniques

Microscopes• Light microscopes – max 2000

X

• Electron microscopes – max 400,000 X

Bright-field Microscopy

• Light background and dark objects.

The Compound Light Microscope

• Main components for directing light.–Eyepiece, objectives, stage,

condenser, iris diaphragm, fine and course adjustment knobs, base, mirror, etc.

Resolving Power• Resolving Power = wavelength

NA objective + NA condenser

• NA = numerical aperature• Wavelength rane is 400 to 700 nm• NA for high dry is about 0.85• NA for oil-immersion objective: 1.2 to 1.4

• Whatever the resolving power, if two objects are closer together than the numerical resolving power, they appear as one.

• No doubt you have seen a sunrise and a sunset. The sky turns red, orange, yellow and even purple because the colored wavelengths of light travel farther through the air (atmosphere). When the sun is low in the sky, this long journey through the atmosphere means the colors with shorter wavelengths, like blue, have already scattered or bounced off in numerous directions.

• Orange sunsets (yellow and red light waves) appear when the air is clean. Sunsets that are the most spectacular occur when red wavelengths reflect off of overhead clouds.

• Spectators continue to see light in the sky long after it has turned dark on the ground. Why is this? Because night doesn't "fall". It actually rises from the ground as the sun goes farther below the horizon.

• Civil twilight occurs when the sun is 6° below the horizon. This is from the time that the sun drops below the horizon until artificial lights (street or home) are needed.

• Astronomical twilight occurs when the sun is 18° below the horizon. This is when there is no sunlight on the western horizon and stars can be seen.

• Twilight is shorter in the tropics because the sun's path is more perpendicular to the Earth's plane and it takes less time to go from 6° to 18° below the horizon at this angle.

• White nights occur in extreme northern latitudes where the evening twilight merges with the morning twilight.

• http://sci.odu.edu/sci/Scire/05Edition/sunset.html