About Microscopes
Most individual bacteria are too small to see with the unaided eye. Microscopes enlarge their appearance and, more importantly, improve resolution so nearby details can be distinguished. Different microscope types reveal different kinds of information.
Magnification
Magnification makes an object appear larger.
Learn MoreResolution
Resolution is the ability to distinguish two nearby points as separate.
Learn MoreLight Microscopes
Light microscopes use visible light and glass lenses.
Learn MoreStaining
Dyes can make transparent cells easier to see.
Learn MoreElectron Microscopes
Electron microscopes can reveal structures much smaller than light microscopes can resolve.
Learn MoreSlides and Samples
Good microscopy depends on careful sample preparation.
Learn MoreDigital Imaging
Modern microscopes often use cameras and computer software.
Learn MoreScale Bars
Scientific microscope images use scale bars to show actual size.
Learn MoreMagnification
A common classroom light microscope can magnify specimens hundreds or more than a thousand times. Magnification is useful only when the microscope also has enough resolution to reveal additional detail.
Resolution
A blurry image made larger does not reveal new information. Optical design, wavelength of light, lenses, sample preparation, and detector quality all affect resolution.
Light Microscopes
They can show bacterial shape, arrangement, movement, and stained structures. Living bacteria can be observed with certain methods, while stained preparations usually use fixed cells.
Staining
The Gram stain is a classic laboratory method that separates many bacteria into Gram-positive and Gram-negative groups based on cell-wall properties. Other stains highlight spores, capsules, acid-fast cells, or specific cell structures.
Electron Microscopes
Scanning electron microscopes show detailed surface topography, while transmission electron microscopes can reveal internal ultrastructure in very thin samples. These methods require complex sample preparation and do not image living cells in ordinary conditions.
Slides and Samples
Researchers may place a drop on a glass slide, grow cells on surfaces, preserve tissue, stain cells, or coat samples for electron microscopy. Preparation choices affect what can be observed.
Digital Imaging
Digital systems record images, measure cell size, count objects, create time-lapse sequences, and compare fluorescence or other signals. Computers help researchers analyze large numbers of images consistently.
Scale Bars
A scale bar might represent 1, 10, or 100 micrometers depending on the image. It is more reliable than guessing size from how large a picture appears on a screen.