Ex 1: Introduction to the microscope
So what exactly is a microorganism? Microorganisms = any living thing that is too small to be seen with the unaided eye fungus protist bacteria virus Parasitic worm
Microscopy allows us to study microbes! Microscopy refers to the use of light (or electrons) to magnify objects Simple: one magnifying lens Compound: multiple magnifying lenses
1 meter (1 m) Measurements 1 cm (1 cm) = 10-2 meters (or.01 m) 1 millimeter (1mm) = 10-3 meters (or.001 m) 1 micrometer (1μm) = 10-6 meters (or 0.000001 m) (a millionth smaller!) 1 nanometer (1nm) = 10-9 meters (or 0.000000001 m) Protozoan ~800μm Blood cell ~7μm Bacteria ~1-10μm Virus ~10-100nm
Sense of scale: How big are we really talking about? Ave woman: 5.5 ft (1.64m) Ave width of strand of hair (0.8mm = 0.008m) One thousandth the size of a person Ave length of E. coli (2μm = 0.000002m) One millionth the size of a person!! (~100 bacteria can stretch end to end across a human hair)
Observing microorganisms Electron microscope Light microscope
Microbes: How small are we really talking about?the E. coli cells measured here are: 4.4uM 6.31uM How big in cm? 4.4uM = 0.00044cm 6.31uM= 0.000631cm How big in meters? 4.4uM = 0.0000044m 6.31uM=0.00000631m
General principles of microscopy Wavelength of radiation Magnification Resolution Contrast
General principles: wavelength of radiation Visible light consists of electromagnetic waves Your eyes gather these wavelengths through the lens, that are then detected by specialized set of cells. The resulting signal is processed by your brain into an image. Figure 4.1
General principles: wavelength of radiation Figure 4.1
We see objects because light bounces off (reflects)objects and it is detected by our eyes. To see smaller objects, you need shorter wavelengths of light! Gram stained bacteria under a light microscope.
General principles: Magnification Magnification occurs when a beam of radiation refracts (bends) as it passes through a lens Degree to which image is enlarged depends on lens thickness, curvature, and speed of light through substance Magnification is written as number and x (10x)
General principles: Contrast Contrast is defined as a difference in intensity between two objects, or between an object and the background Staining enhances the contrast of colorless cells.
General principles: Resolution Resolution is the ability to distinguish objects that are close together Resolution is a function of: 1. Wavelength of light The smaller the wavelength, the smaller the object that can be seen 2. Numerical aperture (ability of a lens to gather light) Light microscope resolution= 0.2 um [.00000002m] Anything smaller than this cannot be visualized Electron microscopy image of mitochondria. This structure could not bee seen with a light microscope.
The light vs electron microscope Light microscope (LM) Scanning electron microscope (SEM) Transmission electron microscope (TEM)
A bright-field, compound light microscope Magnifying lens Magnifying lens Total magnification: Ocular lens X Objective lens Figure 4.4
The image you see is backwards and upside down RAT RAT
Immersion oil increases numerical aperture (light gathering) and prevents refraction (travels as same speed as glass) Figure 4.5
Electron Microscopes Elections have a wavelength of 0.01 nm or 0.001 nm depending on the energy supplied Have greater resolving power and magnification Magnifies objects 10,000 100,000X (TEM) (SEM)
Electron Microscopes TEM (transmission electron microscope): passes electrons through sliced specimens so you can see inside cells and cell objects at sliced images SEM (scanning electron microscope) bounces electrons off specimen so you can see the outside (makes a 3D image) (TEM) (SEM)
TEM images Golgi apparatus Smallpox in cell bms.brookes.ac.uk Commons.wikimedia.org
SEM images Figure 4.13
So what exactly is a microorganism? Microorganisms = any living thing that is too small to be seen with the unaided eye fungus protist bacteria virus Parasitic worm
All life is made of cells, including microorganisms There are TWO types of cells: Bacteria, Archaeans Everything else (Eukaryotes) No nucleus Has nucleus
The three domains of life Image from: www.learner.org
Most of the microbes we will discuss in class and lab are found in these two domains Domain Bacteria Domain Archaea All species in these two domains are single-celled and prokaryotic
Microorganisms are also found in the Domain Eukarya, which have a nucleus Protists Plants Animals Fungi Fungi Protozoans Algae
Nucleus Figure 1.6 Locomotive structures of protozoa. Pseudopods Protists Single celled eukaryotes Amoeba sp. Flagellum Have structures that give them locomotion.
Fungi Eukaryotic organisms Can be single (yeasts) or multicellular (molds)
Algae Eukaryotic organisms that harvest energy and make food from photosynthesis Often found in water Spirogyra sp.