Chapter 1: Humans and the Microbial World

What is microbiology?

The study of organisms too small to be seen with the human eye.

Spontaneous generation

Worms and other forms of life arise from non-living material. Pasteur proved wrong with the swan neck flasks that the broth remained sterile even when broth was exposed to air.

Antony van Leeuwenhoek

First person to see bacteria and called them animalcules.

Francesco Redi

most famous for his excellent demonstration of the use of controlled experiments and his challenge to the theory of spontaneous generation.

John Needham

Showed that flasks containing various broths gave rise to microorganisms even when the flasks were boiled and sealed with a cork.

Bioremediation

Use of organisms to degrade environmental waste.

Endospores

Heat-resistant forms of bacteria.

Louis Pasteur

Defined pasteurization to prevent spoilage of food by bacteria, develop vaccines and disproved the scientific dogma of "Spontaneous Generation". He defined "Germ Theory" and demonstrated that germs were responsible for disease.

Semmelweis

Hand washing

Seemingly new diseases, actually not new

Legionnaire's, Lyme, West Nile virus disease, and Severe Acute Respiratory Syndrome (SARS)

Factors associated with emerging disease

Changing lifestyle and genetic changes (mutation of genes within the DNA)

Microbes

Microorganisms and other infectious agents

Biotechnology

The use of microbiological and biochemical techniques to solve practical problems.

Pathogens

Microbes that can cause disease

Normal microbiota

All surfaces of the human body are populated with characteristic communities of microorganisms. Also called normal flora.

Domains

All living organisms classified in one of 3 groups. Bacteria, Archaea, Eucarya

Prokaryotes

Single-celled organisms, no organelles, surrounded by a rigid cell wall.

Carl Woese

Created domains

Organisms that can be seen under a microscope.

Bacteria, Archaea, Fungi, Algae, and Protozoa

Eukaryotes

True nucleus, single and/or multicellular, contains internal organelles

Nomenclature

Two-word naming system, first word is genus name always capitalized and second word is species name not capitialized

Three basic shapes of bacteria.

coccus (sphere)

bacillus (rod)

spiral

Extremeophiles

Organisms that can live in very extreme environments.

Protozoa

Single-celled, found in water and on land, move by cilia/flagella, no rigid cell wall, complex.

Bacteria

Rod-shaped, spherical, and spiral, rigid cell walls made of petidoglycan, multiply by binary fission

Archaea

Same shapes as bacteria, multiply through binary fission, move by flagella, found in extreme environments, cytoplasm is surrounded by rigid cell wall

What are some infectious agents?

Viruses, viroids, and prions

How do viruses survive?

They have to be inside a cell to grow (a host)

What do viruses consist of?

Nucleic acid packaged within a protein coat and come in a variety of shapes. They cannot metabolize food or make energy. No cell membrane

Viroids

Single-stranded RNA, cause plant diseases, may cause diseases in humans but no evidence

Prions

Infectious proteins responsible for several fatal neurodegenerative diseases in humans and other animals. Abnormal protein (changes shape). This is found in the nervous system. Thought to cause Alzheimer's and Parkinson's diseases.

Viruses are measured in what?

Nanometers nm=10 to the -9m

Bacteria are measured in what?

Micrometers um=10 to the -6m

Robert Hooke

Saw the microorganism he called microscopical mushroom (common bread mold)

John Tyndall

Found that various types of broths required different boiling times to be sterilized. He concluded that some microorganisms exist in 2 different forms: a cell readily killed by boiling and one that is heat resistant.

Ferdinand Cohn

Developed the first classification scheme based on bacteria shape. He detailed and described the life cycle of Bacillus.

Robert Koch

Demonstrated that anthrax was caused by a spore-forming bacterium. Showed that microorganisms caused disease

Penicillin

Antibiotic that prevents the cross-linking of adjacent glycan chains. Most thoroughly studied of a group of antibiotics that interfere with peptidoglycan synthesis.

Gram stain

The most widely used procedure for staining bacteria. Gram-positive bacteria and Gram-negative bacteria

Lysozyme

An enzyme found in tears, saliva, and many other body fluids-breaks the bonds that link the alternating subunits of the glycan chain.

Capsule

Distinct and gelatinous cell wall

Slime layer

Diffuse and irregular cell wall

Glycocalyx

Capsules and slime layers are mostly composed of poly saccharides meaning sugar shell

Polar flagellum

A single flagellum at one end of the cell

Chemotaxis

Motile bacteria sense the presence of chemicals and respond by moving in a certain direction.

Pili

Shorter and thinner than flagella; a string of protein subunits arranged helically to form a long molecule with a hollow core.

Sex pilus

Used to join one bacterium to another for a specific type of DNA transfer

Carriers

Analogous to proteins in prokaryotic cells that function in facilitated diffusion and active transport

Channels

Form small pores in the membrane that allow only specific ion to diffuse through

Lysosomes

Organelles that contain a number of powerful degradative enzymes that could destroy the cell if not contained within the organelle.

Peroxisomes

Organelles in which O2 is used to help break down lipids and detoxify certain chemicals.

Diversity of microorganisms

Three domains-bacteria, archaea, and eucarya

Important roles of microorganisms

Decomposition, nitrogen fixation (giving plants the right form), help make food, bioremediation (turning harmful chemicals into non-harmful ones), antibiotics, insecticides, adhesives, cleaners, insulin, bacterial vaccinations.

Emerging vs re-emerging diseases

Emerging can come from changing lifestyles, rural areas where people are closer to animals that may be infectious. Re-emerging are diseases that were once under control but can increase again.

Why microorganisms are useful model organisms for study.

To study and treat disease, characterizing viruses that may be used to transport genes.

Major characteristics of bacteria

Unicellular, prokaryotic, asexual, rigid cell wall of peptidoglycon, multiply by binary fission

Major characteristics of archaea

Unicellular, prokaryotic, asexual, cell wall without peptidoglycon, multiply by binary fission, extremophile

Major characteristics of eucarya

Organisms contain membrane bound nucleus, contains internal organelles, may be single and/or multicellular

Microorganisms in bacteria

Staphylococcus aureus- frequently found in the human respiratory tract and on the skin. Escherichia coli- rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms.

Microorganisms in archaea

halophiles- salt-loving archaeon. Thermoacidophiles- heat and acid loving

Microorganisms in eucarya

Fungi- found in soil protozoas- live in water or as parasites, amoebas- one-celled aquatic or parasitic protozoans

The work of Tyndall and Cohn

Was used to explain why others investigating spontaneous generation had obtained results that were opposite of those obtained by Pasteur.

Microorganisms are involved in

Causing disease, curing/treating disease, preparing food, cleaning up pollutants.

Plants are dependent on microorganism

Changing atmospheric nitrogen to a usable form.

Bacteria are

Rods, spheres, or spirals, reproduce by binary fission, contain rigid cell walls made of petidoglycan, are single cells.

Which is not usually true of Archaea?

They contain peptidoglycan as part of their cell walls.

Outside a cell, viruses are

Inactive.

Eucarya

Have a more complex internal structure than Archaea or Bacteria and have a membrane around the DNA.

Organisms

May be classified in three domains.