chapter 3 observing microbes through a microscope biology 225: microbiology instructor: janie sigmon
TRANSCRIPT
Chapter 3 Observing Microbes through a Microscope
Biology 225: MicrobiologyInstructor: Janie Sigmon
Size of different cells/agents: Our cells: 10-100 mm
(micrometer)
Bacteria: 1-10 mm Viruses: less than 100
nm (nanometer)
“Cells alive” animationhttp://www.cellsalive.com/howbig
.htm
(View this animation to compare the sizes of different objects, animals, and microbes)
• Properties of light limit magnification/resolution to 2000X
Brightfield (compound light) microscope
• Most common
• Field of view is bright; specimen is darker
• Least expensive
• Requires staining of specimens usually
• Staining requires killing organisms
Light Microscopes
Brightfield (compound light) microscope
Images of an amoeba and a paramecium taken with our microscopes modified with darkfield capabilities
Fluorescence microscope --http://micro.magnet.fsu.edu/primer/java/lightpaths/fluorescence/fluorolightpathsjavafigure1.jpg
http://www.microbelibrary.org/Laboratory%20Diagnostics/details.asp?id=1345&Lang=English
Picture of bacteria taken with a fluorescence microscope
Meningitis-causing bacteria. The tiny yellow dots are Neisseria meningitidis bacteria living inside human airway cells. Although they live in the noses and throats of many people without leading to disease, if they break through into the bloodstream they can cause potentially fatal meningitis and septicemia. (Confocal image by Shao Jin Ong.)
http://images.google.com/imgres?imgurl=http://www.wellcome.ac.uk/en/wia/images/3.jpg&imgrefurl=http://www.wellcome.ac.uk/en/wia/gallery.html%3Fimage%3D3&usg=__zTlEYvtXqctVN-_UY9Xgq5o8EU8=&h=406&w=406&sz=54&hl=en&start=7&sig2=E9fSpwqRIkS3fw0NrJFujQ&um=1&tbnid=PieK57ZmEF8T-M:&tbnh=124&tbnw=124&prev=/images%3Fq%3Dconfocal%2Bbacteria%26hl%3Den%26rlz%3D1T4ADBS_enUS329%26um%3D1&ei=knYuSoz8BuaClAe-iejSCg
Confocal microscopy
Confocal micrographic image of Bacillus anthracis; cell walls appear green, while the spores appear red.
Taken by CDC/ Dr. Sherif Zaki/ Dr. Kathi Tatti/Elizabeth White
Electron MicroscopesBeware of artifactsStaining techniques require expertise and $$$Dehydration of specimenPlacing specimen under vacuum
Transmission electron microscope (TEM)
Magnify 10,000-up to 500,000X
View sections of organism
Can see inside viruses/cells
Scanning electron microscope (SEM)
Magnify 1,000-10,000X
See 3D image of structure
Under a high magnification of 12230x, this scanning electron micrograph (SEM) depicted some of the ultrastructural morphologic features displayed by this group of Gram-positive Micrococcus luteus bacteria.
Taken by CDC/ Betsy Crane
This negative-stained transmission electron micrograph (TEM) depicts the ultrastructural details of an influenza virus particle, or “virion”. A member of the taxonomic family Orthomyxoviridae, the influenza virus is a single-stranded RNA virus.
Taken by CDC/ Dr. Erskine. L. Palmer; Dr. M. L. Martin
Scanned-probe microscopes
Can “see” moleculesExpensiveUsed in research
Scanned-probe microscopy – Figure 3.11(a) is RecA (repair) protein from Escherichia coli and (b) is the O toxin from Clostridium perfringens.
The Gram staining technique
Acid-fast staining technique used to stain Mycobacterium leprae (bacteria responsible for leprosy)
THE END