Microorganisms

What are they?

What do they do?

What do they look like?

Microbiology• Study of microorganisms

– Organisms not visible with naked eye

– Require magnifying glass or microscope

– Includes wide variety of different organisms

Microorganisms are:

• Bacteria• Viruses• Fungi• Protozoa• Animals

Microorganisms are Ubiquitous

• Found virtually everywhere• Most are harmless• Some are beneficial

– Used in research– Used to make foods (yeast, mold)– Used to make antibiotics

Light Microscope

• Allows one to view most types of microorganisms (not most viruses)

• Magnifies 40x – 1000x• Works by passing light through a series of

glass lenses that bend or refract light rays• Microorganisms viewed may be living or

fixed and stained to enhance visibility

Microscopy: The Instruments

• A simple microscope has only one lens

• This is A. Van Leeuwenhoek’s microscope from the 1600’s

Figure 1.2b

Parts of a typical light microscope

Electron Microscopes

• Use beam of electrons, instead of light to magnify

• Magnify up to 100,000X or more• Allow us to look inside cells and even see

molecules

Units of Length

• Light microscope can view objects measured in millimeters and micrometers

• Electron microscope can view objects measured in micrometers and nanometers

Bacteria

• Prokaryotic cells– The genetic material in

their cells is not contained in a nucleus

• Appear as different shapes– Bacilli (rod-shaped)– Cocci (round)– Spirilla (spiral)

• Most ubiquitous microorganism

Stained Bacteria

• Average size: 0.2 -1.0 µm 2 - 8 µm• Basic shapes:

Bacterial Morphology

coccibacilli

spirals

Usefulness of Bacteria

• Decomposers: (“nature’s recyclers”) break down dead matter

• Clean up the Earth’s land & water• Help with digestion• Make vitamins your body needs• Used to make medicines (insulin)• Food production: cheese, yogurt, sour

cream, sauerkraut, pickles, etc.

Viruses

• Tiny, nonliving particle that enters and then reproduces inside a living cell

• Most are harmful

Characteristics of Viruses

• Does not have all the characteristics essential for life

• Viruses can only multiply when they are inside a living cell

• Acts like a parasite– Parasite: an organism that lives on or in a

host and causes it harm– Host: an organisms that provides a source of

energy for a virus

Usefulness of Viruses

• Gene Therapy– Take advantage of a virus’s ability to enter a

host cell– Gene therapy allows scientists to deliver

needed genetic material to cells

Viruses, Bacteria, & Your Health

Pathogenic Microorganisms

• Are harmful to humans• Able to cause pathology (damage) in host

- Invade host and damage tissue• Cause infectious disease

– Disease that is transmitted from one source to another

– Bacteria and viruses responsible for most infectious diseases

Infectious Diseases

• Can spread through contact with:– An infected person (touching, hugging, or

kissing)– A contaminated object (sharing drinks or

eating utensils)– An infected animal (an animal bite)– An environmental source (eating

uncooked eggs or meat)

Common Infectious Diseases

• Bacterial–Lyme Disease–Tuberculosis–Tetanus–Strep Throat

• Viral–The cold–The flu–Cold sores–Chicken pox–AIDS

Streptococcal Skin Infection

Anthrax Lesion

Rash From Lyme Disease

• Common Cold & The Flu Virus– Many different strains

• Round virus –Chicken pox:

causes an itchy rash on human skin

• Bullet-shaped–Rabies virus

infects nerve cells in certain animals

Viral Infection – Cold Sores

Treating Infectious Diseases

• Bacterial Diseases– Antibiotics– Antibiotic resistance

• Results when some bacteria are able to survive in the presence of an antibiotic

• Viral Diseases– No medications that can cure viral

infections

Vaccines

• Important tools that help prevent the spread of infectious diseases

• Vaccine: a substance introduced into the body to stimulate the production of chemicals that destroy specific viruses or bacteria– Made from dead or weak or altered viruses

and bacteria

Fungi

• Eukaryotic cells• Can be multicellular

molds or unicellular yeasts

Protozoa

• Unicellular eukaryotic organisms

• Show various forms of motility– Flagella– Cilia– Pseudopodia

Animals

• Multicelluar– Worms– Small arthropods

• Serve as vectors for disease transmission

• Ectoparasites– Feed on blood by

biting

Microscopy

• Microorganisms not visible with naked eye– Only visible with some method of

magnification– Most microorganisms require a microscope to

view them• Light microscope – provides 40X to 1000X• Electron microscope – provides 5000X to

500,000X

Measuring Microorganisms

• Microorganisms, because of their small size, require small units of measurement– Micrometer (um) – is 1x10-6 meter or 0.001

mm• Sufficient to measure bacteria, fungi, protozoa

– Nanometer (nm) – is 1X10-9 meter or 0.001um• Sufficient to measure viruses and sub cellular

particles

Units of Length

• Light microscope can view objects measured in millimeters and micrometers

• Electron microscope can view objects measured in micrometers and nanometers

TEM and SEM