Microbiology for the Health Sciences

Chapter 1. Microbiology: The Science

Microbiology for the Health Sciences

Chapter 1. Microbiology: The Science

Chapter 1 OutlineChapter 1 Outline

• Introduction

• What is microbiology?

• Why study microbiology?

• First microorganisms on earth

• Earliest known infectious diseases

• Pioneers in the science of microbiology

• Careers in microbiology

What is Microbiology?What is Microbiology?

• Biology is the study of living organisms• Microbiology is the study of very small living organisms• Microorganisms are ubiquitous (they are everywhere!)• Categories of microorganisms include:

– Viruses– Bacteria– Archaeans– Protozoa– Some algae and fungi

Family Tree of MicroorganismsFamily Tree of Microorganisms

What is Microbiology?What is Microbiology?

• Viruses are technically infectious agents or particles

• “Germs” are the microorganisms that cause disease

• Disease-causing microorganisms are technically pathogens

• Microorganisms that do not cause disease are nonpathogens

Why Study Microbiology?Why Study Microbiology?

• Microorganisms live on and in our bodies (indigenous microflora)

• Some microorganisms are opportunistic pathogens

• Microorganisms are essential for life on this planet

• Microorganisms are involved in decomposition of dead organisms and waste (decomposers and saprophytes)

• Algae and bacteria serve as food for tiny animals

• Microorganisms participate in bioremediation and genetic engineering

• Microorganism are involved in elemental cycles

• Microorganisms aid in digestion of food

• Microorganisms are used in the food and beverage industry

Microbes as SaprophytesMicrobes as Saprophytes

Microbes and Nitrogen FixationMicrobes and Nitrogen Fixation

Why Study Microbiology?Why Study Microbiology?

• Some microorganisms produce antibiotics used to treat diseases

• Microbes are essential in the field of genetic engineering

• Microbes are used as “cell models”

• Microorganisms cause two categories of disease:

– Infectious diseases

– Microbial intoxications

Categories of DiseasesCategories of Diseases

First Microorganisms on EarthFirst Microorganisms on Earth

• Fossils of primitive microorganisms date back about 3.5 billion years ago.

• Candidates for the first microorganisms on earth are archaeans and cyanobacteria.

• Infectious diseases of humans and animals have existed for as long as humans and animals have inhabited the planet.

• Earliest known account of pestilence occurred in Egypt in about 3180 BC.

Pioneers in the Science of MicrobiologyPioneers in the Science of Microbiology

Anton van Leeuwenhoek (1632-1723)

– “Father of Microbiology”

– Not a trained scientist!

– Made many simple single-lens microscopes

– Observed ”animalcules” (bacteria and protozoa)

Pioneers in the Science of MicrobiologyPioneers in the Science of MicrobiologyLouis Pasteur (1822-1895)

– French chemist who made numerous contributions to microbiology

– Investigated different fermentation products

– Developed the pasteurization process

– Discovered life forms that could exist without oxygen – anaerobes

– Developed several vaccines, including rabies and anthrax vaccines

Pioneers in the Science of MicrobiologyPioneers in the Science of Microbiology

Robert Koch (1843-1910)

– German physician who made numerous contributions to microbiology

– Significant contribution to germ theory of disease

– Discovered that B. anthracis produced spores

– Developed method of fixing and staining bacteria

– Developed methods to cultivate bacteria

Koch’s PostulatesKoch’s Postulates

1. A particular microorganism must be found in all cases of the disease and must not be present in healthy animals or humans.

2. The microorganism must be isolated from the diseased animal or human and grown in pure culture in the laboratory.

3. The same disease must be produced when microorganisms from the pure culture are inoculated into healthy susceptible lab animals.

4. The same microorganism must be recovered from the experimentally infected animals and grown again in pure culture.

Koch’s PostulatesKoch’s Postulates

Koch’s Postulates (continued)Koch’s Postulates (continued)

• If an organism fulfills Koch’s postulates it is proven to be the cause of that particular infectious disease.

• Koch’s Postulates helped to prove the germ theory of disease

• Koch gave a tremendous boost to the development of microbiology by stressing lab culture and identification of microorganisms

• Circumstances do exist in which Koch’s Postulates cannot be fulfilled.

Careers in MicrobiologyCareers in Microbiology• A microbiologist is a scientist who studies

microorganisms.

• There are many career fields within the science of microbiology – bacteriology, phycology, protozoology, mycology, parasitology, and virology.

• Medical Microbiology

– Involves the study of pathogens, the disease they cause and the body’s defenses against disease.

– Concerned with epidemiology, transmission of pathogens, disease-prevention measures, aseptic techniques, immunology, and production of vaccines.

Review of Key PointsReview of Key Points

• Microorganisms, also called microbes, include viruses, bacteria, archaeans, certain algae, protozoa, and certain fungi

• Viruses are often referred to as “infectious agents” or “infectious particles”

• Microorganisms are ubiquitous; they are everywhere!

• Only a small percentage of known microbes cause disease; there are pathogens, nonpathogens and opportunistic pathogens

Review of Key Points (continued)Review of Key Points (continued)

• Microorganisms play essential roles in various elemental cycles

• Decomposers and saprophytes play important roles in the decomposing of dead animals and plants and organic wastes

• Many microbes are used in various industries, such as food, beverage, chemical and antibiotic industries. The use of microbes in industry is known as biotechnology.