Microbiology - BIOL 2516k - Ch 1 (Scientists) & 3 (Parts I and II) Mini Quiz

resolution

(also called resolving power) is the ability of the lenses to distinguish fine detail and structure.

Brightfield Microscopy

- Dark objects are visible against a bright background - Poor contrast unless you stain specimen

contrast

- Differences in intensity between two objects, or between an object and background - Staining increases contrast

Transmission Electron Microscope (TEM)

- Electrons pass through specimen - Can view internal structures of cells, small bacteria, and viruses - Cannot be used to study living organisms

Scanning Electron Microscope (SEM)

- Electrons scan outer surface specimen - Produces 3-D images of the whole specimen - Only magnifies external surface of specimen - Can only examine dead organisms

Dark-field microscopes

- Increases contrast in living specimens without using stains - Specimen appears light against dark background

Phase -contrast microscopes

- Useful for observing internal and external structures - Living specimens - Allows examination of living organisms and internal/external cell structures - Brings together two sets of light rays, direct rays, and diffracted rays to form an image

Electron Microscopy

- Uses electrons to magnify objects Electrons have small wavelengths Magnifies objects 10,000X to 100,000X - Gives detailed views of bacteria, viruses, internal cellular structures, molecules, and large atoms -Two Types *Transmission electron microscopes (TEM) *Scanning electron microscopes (SEM)

Explain how electron microscopy differs from light microscopy (including differences in resolution and magnification).

- While a light microscope uses light to illuminate specimens and glass lenses to magnify images, an electron microscope uses a beam of electrons to illuminate specimens and magnetic lenses to magnify images. - The resolution (the level of image detailing) is the main difference between these two microscopes.

Almost 70 years before Koch established that a specific microorganism causes anthrax, Edward Jenner, a young British physician, embarked on

- an experiment to find a way to protect people from smallpox. - First Jenner collected scrapings from cowpox blisters. - Then he inoculated a healthy 8-year-old volunteer with the cowpox material by scratching the child's arm with a pox-contaminated needle. - The scratch turned into a raised bump. - In a few days, the volunteer became mildly sick but recovered and never again contracted either cowpox or smallpox. - The protection from disease provided by vaccination (or by recovery from the disease itself) is called immunity.

Pasteur demonstrated that

- microorganisms are present in the air and can contaminate sterile solutions, but that air itself does not create microbes. - He filled several short-necked flasks with beef broth and then boiled their contents. Some were then left open and allowed to cool. In a few days, these flasks were found to be contaminated with microbes. The other flasks, sealed after boiling, were free of microorganisms. - From these results, Pasteur reasoned that microbes in the air were the agents responsible for contaminating nonliving matter. Pasteur next placed broth in open-ended, long-necked flasks and bent the necks into S-shaped curves. - The contents of these flasks were then boiled and cooled. The broth in the flasks did not decay and showed no signs of life, even after months. Pasteur's unique design allowed air to pass into the flask, but the curved neck trapped any airborne microorganisms that might contaminate the broth.

Louis Pasteur (1822-1895)

Demonstrated that life did not arise spontaneously from nonliving matter.

Fluorescent microscopes

Direct UV light at specimen; causes the specimen radiate visible light (glow) if stained with a fluorescent dye (fluorochromes)

Robert Koch (1843-1910)

Established experimental steps for directly linking a specific microbe to a specific disease

Alexander Fleming, a Scottish physician and bacteriologist, almost tossed out some culture plates that had been contaminated by mold. Fortunately, he noticed the curious pattern of growth on the plates—a clear area where bacterial growth had been inhibited encircled the mold . Fleming was looking at a mold that inhibited growth of a bacterium. The mold became known as

Penicillium chrysogenum (pen9i-SIL-le¯-um krI¯-SO-jen-um), and the mold's active inhibitor was called penicillin.

Joseph Lister (1827-1912)

Performed surgery under aseptic conditions using phenol. Proved that microbes caused surgical wound infections

The first proof that bacteria actually cause disease came from

Robert Koch (ko¯k) in 1876.

Explain how the transmission electron microscope is different from the scanning electron microscope

The most important differences between a transmission electron microscope and a scanning electron microscope are: Rather than the broad static beam used in TEM, the SEM beam is focused to a fine point and scans line by line over the sample surface in a rectangular raster pattern.

The first antibiotic was discovered by

accident by Alexander Fleming

Pasteur found instead that microorganisms called yeasts convert the sugars to

alcohol in the absence of air. This process, called fermentation, is used to make wine and beer.

Lister had also heard of Pasteur's work connecting microbes to

animal diseases.

Souring and spoilage are caused by different microorganisms, called

bacteria. In the presence of air, bacteria change the alcohol into vinegar (acetic acid).

Furthermore, Pasteur demonstrated conclusively that microbial life can be destroyed

by heat and that methods can be devised to block the access of airborne microorganisms to nutrient environments. - These discoveries form the basis of aseptic techniques, procedures that prevent contamination by unwanted microorganisms, which are now the standard practice in laboratory and many medical procedures. - Modern aseptic techniques are among the first and most important concepts that a beginning microbiologist learns.

total magnification of a specimen .

by multiplying the objective lens magnification (power) by the ocular lens magnification (power)

By the late 1930s, researchers had developed several other synthetic drugs that could

destroy microorganisms. - Most of these drugs were derivatives of dyes. - This came about because the dyes synthesized and manufactured for fabrics were routinely tested for antimicrobial qualities by microbiologists looking for a "magic bullet." - In addition, sulfonamides (sulfa drugs) were synthesized at about the same time

Koch discovered rod-shaped bacteria now known as Bacillus anthracis (bah-SIL-lus an-THRA¯ -sis) in the blood of cattle that had

died of anthrax. - He cultured the bacteria on nutrients and then injected samples of the culture into healthy animals. - When these animals became sick and died, Koch isolated the bacteria in their blood and compared them with the originally isolated bacteria. - He found that the two sets of blood cultures contained the same bacteria.

Koch thus established Koch's postulates, a sequence of experimental steps for

directly relating a specific microbe to a specific disease

Paul Ehrlich was the imaginative thinker who

fired the first shot in the chemotherapy revolution. .

As a medical student, Ehrlich speculated about a "magic bullet" that could

hunt down and destroy a pathogen without harming the infected host.

Thus, penicillin techniques to investigate

industrial applications and roles of microorganisms in the environment.

Disinfectants were not used at the time, but Lister knew that phenol (carbolic acid)

kills bacteria, so he began treating surgical wounds with a phenol solution. The practice so reduced the incidence of infections and deaths that other surgeons quickly adopted it. His findings proved that microorganisms cause surgical wound infections.

In 1665, after observing a thin slice of cork through a crude microscope, Englishman Robert Hooke reported that

life's smallest structural units were "little boxes," or "cells." - Using his improved microscope, Hooke later saw individual cells. - Hooke's discovery marked the beginning of the cell theory— the theory that all living things are composed of cells.

Pasteur's work provided evidence that microorganisms cannot originate from

mystical forces present in nonliving materials. - Rather, any appearance of "spontaneous" life in nonliving solutions can be attributed to microorganisms that were already present in the air or in the fluids themselves.

Pasteur showed that microorganisms can be present in

nonliving matter—on solids, in liquids, and in the air.

Lister was aware that in the 1840s, the Hungarian physician Ignaz Semmelweis had demonstrated that

physicians, who at the time did not disinfect their hands, routinely transmitted infections (puerperal, or childbirth, fever) from one obstetrical patient to another.

Van Leeuwenhoek made detailed drawings of organisms he found in

rainwater, feces, and material scraped from teeth. These drawings have since been identified as representations of bacteria and protozoa

In 1910, after testing hundreds of substances, Ehrlich found a chemotherapeutic agent called

salvarsan, an arsenic derivative effective against syphilis. - The agent was named salvarsan because it was considered to offer salvation from syphilis and it contained arsenic. - Before this discovery, the only known chemical in Europe's medical arsenal was an extract from the bark of a South American tree, quinine, which had been used by Spanish conquistadors to treat malaria.

During the past 100 years, these same criteria have been invaluable in investigations proving that

specific microorganisms cause many diseases.

Between 1673 and 1723, Anton van Leeuwenhoek wrote about

the "animalcules" he saw through his simple, singlelens microscopes.

Pasteur's solution to the spoilage problem was to heat

the beer and wine just enough to kill most of the bacteria that caused the spoilage. - The process, called pasteurization, is now commonly used to reduce spoilage and kill potentially harmful bacteria in milk and other beverages as well as in some alcoholic beverages.

Koch, a German physician, was Pasteur's rival in the race to discover

the cause of anthrax, a disease that was destroying cattle and sheep in Europe.

In the 1860s, Joseph Lister, an English surgeon, applied

the germ theory to medical procedures.

A general principle of microscopy is that the shorter the wavelength of light used in the instrument,

the greater the resolution.

Scientists now believe that a form of spontaneous generation probably did occur on

the primitive Earth when life first began, but they agree that this does not happen under today's environmental conditions.

Dutch merchant and amateur scientist Anton van Leeuwenhoek

was probably the first to observe live microorganisms through the magnifying lenses of the more than 400 microscopes he constructed.

List the units used to measure microorganisms.

we use the metric system.