The Main Themes of Microbiology

Chapter 1

THE SCOPE OF MICROBIOLOGYSection 1.1

Microbiology

• Specialized area of biology that deals with organisms too small to be seen with the naked eye– Microorganisms or microbes– Germs, viruses, or agents– “Bugs”

Major Groups of Microorganisms

• Bacteria• Algae• Protozoa• Helminths• Fungi• Viruses: non-cellular, parasitic, protein-

coated genetic elements

Study of Microbes is Easy AND Difficult

• Reproduce rapidly, large populations can be grown in the laboratory

• Can’t be seen directly, must be analyzed through indirect methods in addition to using microscopes

Aspects of Microbiological Study

• Medical Microbiology

• Public health Microbiology and Epidemiology

• Immunology

Aspects of Microbiological Study

• Industrial Microbiology

• Agricultural Microbiology

• Environmental Microbiology

Check Your Understanding

• What types of organisms are considered microbes? Provide some examples of these organisms.

• What types of cells can viruses infect?• List and describe three branches of microbiology.

Identify professions that make use of microbiology.

THE IMPACT OF MICROBES ON EARTH: SMALL ORGANISMS WITH A GIANT EFFECT

Section 1.2

The Impact of Microbes on Earth

• Microbes have shaped the development of the earth’s habitats and the evolution of other life forms for billions of years

• Single-celled organisms arose 3.5 billion years ago

• Bacteria, archaea, and eukaryotes arose from this ancestor

Types of Cells

• Eukaryotes: true nucleus– Cells with a nucleus are classified as eukaryotes

• Prokaryotes: “pre” nucleus– Bacteria and archaea do not have a nucleus and

have been traditionally classified as prokaryotes– This classification is no longer used because

bacteria and archaea are so distinct genetically

Bacteria are Ubiquitous

• Can be found:– Deep in the earth’s crust– Polar ice caps– Oceans– Inside the bodies of plants and animals

Photosynthesis

• Involved in the flow of energy and food through the earth’s ecosystems

• Photosynthetic microorganisms account for more than 70% of the earth’s photosynthesis– Production of oxygen by oxygenic

photosynthesis evolved later allowing a diversification of species

Decomposition

• Breakdown of dead matter and wastes

• Accomplished by bacteria and fungi

Microbes Are Vital In Shaping Earth

• Microbes are the main forces that drive the structure and content of soil, water, and atmosphere– Gas production by microbes– Microbes living within the earth’s crust– Bacteria and fungi living in complex

associations with plants

Check Your Understanding

• Describe the difference between a prokaryote and a eukaryote.

• Describe the role and impact of microbes on the earth.• Describe the basic tenets of the Theory of Evolution.• True/False: Microscopic organisms produce more

oxygen than plants.• True/False: More than 50% of the microbes on the

planet live below the Earth’s crust.

HUMAN USE OF MICROBESSection 1.3

Importance of Microbes to Humans

• Humans have been using microorganisms for thousands of years to improve life and even shape civilizations– Yeast for production of bread, wine, and beer– Other fungi used for cheese production– Moldy bread used in Egypt to treat wounds

Uses for Microbes

• Biotechnology– Manipulation of

microorganisms to make products in an industrial setting

• Genetic Engineering – Manipulates the genetics of

microbes, plants, and animals for the purpose of creating new products and genetically modified organisms (GMOs)

Uses for Microbes

• Recombinant DNA technology:– Techniques that allow

the transfer of genetic material from one organism to another and deliberately alter DNA

• Bioremediation: – introduction of microbes

into the environment to restore stability or to clean up toxic pollutants

Check Your Understanding

• Name three products produced by genetically modified organisms that benefit humans.

• Describe one method in which microbes are used for bioremediation.

INFECTIOUS DISEASES AND THE HUMAN CONDITION

Section 1.4

Pathogen

• Any agent (virus, bacterium, fungus, protozoan, or helminth) that causes disease– Nearly 2,000 different

microbes cause disease

Combating Infectious Diseases

• New (emerging) diseases as well as older (reemerging) diseases are increasing– AIDS, hepatitis C and viral encephalitis

• Polio, leprosy, and parasitic worm diseases have largely been eradicated

Knowledge of Diseases Is Improving

• Certain diseases once considered noninfectious are now found to be caused by microbes– Gastric ulcers caused by Helicobacter pylori– Link between certain cancers and bacteria and

viruses– Cocksackie virus has been associated with

diabetes– The Borna agent has been linked to schizophrenia

Clinical Work Against Disease Continues

• During the Golden Age of Microbiology, “obvious” diseases were characterized and cures or preventions were devised

• Today, we are discovering the subtler side of microorganisms and the quiet, slow, destructive diseases they cause

• An increasing number of patients with weakened immune systems are subject to infections by common microbes not pathologic to healthy people

• Drug-resistant microbes also contribute to the increase in infectious disease

Check Your Understanding

• True/False: All microbes cause disease.• Why is there a difference between the top 10 causes of

death in the U.S. versus worldwide?• Name three connections between diseases considered

to be noninfectious and a microbe.

GENERAL CHARACTERISTICS OF MICROORGANISMS

Section 1.5

General Categories of Microbes

Bacteria and Archaea

• About 10x smaller than eukaryotic cells• Lack organelles: small, double-membrane-

bound structures that perform specific functions

• All bacterial and archaeal cells are single-celled

Helminthes

• Not true microorganisms, but are included in the study of infectious disease:– They are transmitted similarly to bacterial

diseases– The human body responds to them in the

same way as it responds to bacterial diseases– Their identification requires use of

microscopes to view larvae and mouth parts

Five Types of Microbes