Microbiology Exam 1 - Bacteria and Microscopes

What size are eukaryotes?

100x bigger than bacteria

What size are bacteria?

1-2 µm long

Describe bacteria.

no organelles, have nucleoids, and are prokaryotic

How are bacterial ribosomes different from eukaryotes?

eukaryotes have total of 80S ribosomes and bacteria only have 70S

Why is it important that bacterial ribosomes are different?

so antibiotics can target bacterial ones

What is the difference between eukaryotic and bacterial cell walls?

eukaryotes - made of cellulose and chitin

bacteria - made of peptidoglycan

What do bacteria do?

consume and grow

What do some bacteria consume?

sugars, light, toxins (H2S), metal

What are other things bacteria can do?

make alcohol, breathe uranium, and grow in extreme conditions

What are bacteria, structurally?

small, nucleoid, no organelles, peptidoglycan, 70S ribosomes

What are bacteria, metabolically?

diverse metabolism, extremophiles

What are bacteria, genetically?

circular chromosomes, operons of genes, sigma factors

What are the four requirements of microscopy?

magnification, resolution, light quality, contrast

What is magnification?

relative increase in image size

What is resolution?

the ability to distinguish 2 points that are close together

What is light quality?

sets limits of resolution

What is contrast?

the ability to detect objects against a background

What do lenses do?

refract visible light to focus light onto a single point

What is a refractive index?

a measurement of how much a lens will bend light

As the focal length decreases, the magnification...

increases

As numerical aperture increases, resolution...

increases

What is numerical aperture?

widest angle of light captured

What do stains do?

enhance contrast but kill/fix cells, some can be specialized/diagnostic

What does a Gram stain detect?

detects kind of cell envelope

What does a flagellar stain do?

detect flagella

What are the types of microscopy?

phase contrast, fluorescence, electron, atomic force

What is phase contrast microscopy?

uses diffraction and interference/refraction to generate contrast, no staining so cells still living and movement can be seen

What is fluorescence microscopy?

light excites fluorescent molecules which then emit light themselves, no light passes through specimen

What is resolution limited by?

light quality

The smaller the wavelength, the ____________ the resolution.

higher

What is GFP?

green fluorescent protein that genes fuse to which show where they go so we can determine what they do

What are the types of light emission?

fluorescence and luminescence

What is fluorescence light emission?

light required to work, emits light after excitation

What is luminescence light emission?

produces light by chemical reaction

What is electron microscopy?

uses a beam of electrons with a very short wavelength, allows very high resolution, specimen must be stained and killed

What are the 2 types of electron microscopy?

scanning and transmission

What is scanning EM?

coat with dense metal and use magnets instead of light, produces high resolution images of surface

What is transmission EM?

very high magnification, specimen must be extremely thin, shows intracellular structures

What is electron cryotomography?

freezing technique that preserves native state of structures examined in vacuum by taking pictures, tilting the stage, and 3D reconstruction

What is atomic force microscopy?

uses an ultra-fine prove to tap over sample and uses light to detect probe displacement and reflections, doesn't use light, so staining so cells living but can be damaged by probe