Introductory Microbiology

Dr. Heather Townsend

Summer 2009

Microbiology• The study of of organisms

(microorganisms or microbes) too small to be seen without magnification

• This includes:1. Bacteria

2. Viruses

3. Fungi

4. Protozoa

5. Helminths (worms)

6. Algae

The Microbes

• 1. Bacteria– Single-celled

organisms – Various shapes

• Spherical• Rod• Spiral shapes

– Cellular– Lack membrane-

enclosed cellular structures

– Widely distributed in nature

Klebsiella pneumoniae, bacteria that causes

pneumonia in humans

The Microbes

• 2. Viruses– Acellular– Composed of nucleic

acid and a few proteins

– Replicate themselves to display other properties of living organisms when they invade living cells

Bacteriophages observed at 35,500X

The Microbes• 3. Fungi– Yeasts and molds

• Single-celled, microscopic

– Mushrooms• Multicellular,

macroscopic

– Cell nucleus and other cellular structures

– Absorb nutrients from their environment

– Widely distributed in water and soil

– Act as decomposers of dead organisms

Philobolus crystallinus, fruiting bodiesof this fungus

The Microbes• 4. Protozoa– Single-celled,

microscopic organisms

– Have at least one nucleus and many cellular structures

– Obtain food by engulfing or ingesting smaller organisms

– Most can move– Found in many

different environments

Amoeba

The Microbes

• 5. Misc.– Large, multicellular– Worms

• Helminths

– Arthropods• Insects

Tapeworm Head

The Microbes• 6. Algae– Single-celled

microscopic organisms

– Have a nucleus and many membrane-enclosed cellular structures

– Photosynthesize their own food

– Widely distributed in fresh and salt water

– Important source of food for other organisms

Micrasterias, a green algae living in fresh water.

Branches of Study Within Microbiology

• Immunology: – studies immune chemicals and cells that are produced in response

to infection

• Public health microbiology & epidemiology: – aim to monitor and control the spread of diseases (CDC)

• Food, dairy and aquatic microbiology: – examine the ecological and practical roles of microbes in food and

water

• Biotechnology: – ranges from bread making to gene therapy

• Genetic engineering & recombinant DNA technology: – altering the genetic makeup of organisms

Microbes Are Involved In:

• nutrient production & energy flow – i.e., photosynthesis

• decomposition and nutrient recycling• production of foods, drugs & vaccines• bioremediation • causing disease

Impact of Pathogens

• Pathogens – Diseases-causing agents

• Nearly 2,000 different microbes cause diseases in the human body

• 10 B infections/year worldwide• 13 M deaths from infections/year

worldwide killing about 1/3 of the U.S. population each year

Impact of Pathogens

• Emerging diseases– Becoming more prominent over the years– Zoonosis

• SARS

• Reemerging– Older diseases increasing in occurrence

• TB• Malaria• Hepatitis

• Noninfectious diseases

Characteristics of Microbes• Prokaryotic cells

– Smaller – Lack special structures such as a nucleus and organelles– All prokaryotic cells are microorganisms

• Only some microorganisms are eukaryotic

Lifestyles of Microorganisms

• Free existence

• Close associations– Parasites– hosts

Antonie van Leeuwenhoek

• First to observe living microbes

• His single-lens magnified up to 300X

(1632-1723)

Early Medical Microbiology

• Louis Pasteur: – Worked in the wine industry

• Had knowledge about yeast producing alcohol

– Swan-neck flasks– Tipping the flask would allow

the microbes to enter the infusion

• Cause them to become cloudy• Main experiment that helped

disprove spontaneous generation

•Pasteur discovered that some yeasts made good tasting wine

•Mixtures of microbes competed with yeast and made wine taste oily or sour

•Developed Pasteurization to deal with this problem

–Heated the wine to 56°C without oxygen present for 30 minutes

•Developed a rabies vaccine

Early Medical Microbiology

Early Medical Microbiology

• Robert Koch (~120 years ago, German) – Linked a microscopic

organism with a specific disease (anthrax)

– Developed method to grow bacteria in pure cultures (cultures containing only one kind of organism)

• Used solidified gelatin from potato slices mixed with agar

• Creates a firm surface that microbes could grow on

Koch’s Postulates

1. The specific causative agent must be found in every case of the disease

2. The disease organism must be isolated in pure culture

3. Inoculation of a sample of the culture into a healthy, susceptible animal must produce the same disease

4. The disease must be covered from the inoculated animal

Early Medical Microbiology

• Oliver Wendell (American physician) – observed mothers who gave birth

at home experienced fewer infections than those that gave birth in a hospital

• Ignaz Semmelweis (Hungarian doctor) – showed that women became

infected with puerperal fever during delivery by doctors coming directly from the autopsy room

Early Medical Microbiology• Joseph Lister (English surgeon)

– Introduced aseptic techniques • Aimed at reducing microbes in a medial setting

and preventing wound infections

– Improved sanitation • Promotes use of carbolic acid on bandages and

medical instruments

Spontaneous Generation Theory

• Germ theory of disease: – “Microorganisms can invade other organisms and

cause disease”– Many diseases are caused by the growth of microbes

in the body and not by sins, bad character, or poverty, etc.

• Spontaneous generation– “Living things arise from nonliving things”– Belief that some forms of life could arise from vital

forces present in nonliving or decomposing matter• Maggots found in rotting meat arose from a nonliving factor• Microorganisms found in broth that made it cloudy appeared

from a nonliving factor

What to expect……..

• Different microorganisms

• How to detect microorganisms

• Common disease caused by microorganisms

• How to control the spread of microorganisms

• Immune system