Microbiology Final A

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Types of microscopes and their utility (e.g., to observe stained vs. unstained objects, to observe motility, etc).

Brightfield: to observe stained material, general microscopy

Darkfield: background is dark, object is bright; especially good for motile cells

Phase Contrast: detailed examination of internal structures in living microorganisms, 3D, shows detail of non-stained cells

Fluorescent: uses UV light, fluorescent stained cells or structures will glow with color

Transmission electron microscope: shows internal cellular organelles greatly magnified, can also be used to observe viruses in sections

Scanning electron microscope: shows 3-D surface structures of cells or viruses highly magnified

What are fomites?

Any inanimate object or substance capable of carrying infectious organisms and hence transferring them from one individual to another

Examples: cloth or mop head, skin cells, hair, clothing, and bedding

Normal flora vs. transient flora: which ones does hand washing get rid of?

Normal flora: resident, live naturally and permanently on our skin, not readily removed by mechanical friction

Transient flora: microbes that are temporary also called non-colonizing or contaminating flora; easily removed by mechanical friction/hand washing

Terms associated with microscopes: resolution vs. magnification

A. Resolving power or resolution is defined as the closest distance two objects can be, where we can still see them as separate objects

Resolving Power= Wavelength/(2 X Numerical Aperture)

Numerical aperture is inscribed on the barrel of the objective lens


Magnification
4X Scanning= (4 X 10) Magnification
10X Low Power= (10 X 10) Magnification
40X High Dry= (40 X 10) Magnification
100X Oil Immersion= (100 X 10) Magnification

Purpose of various types of medium: selective, enriched, and differential medium

Selective: only allows certain species to grow and inhibits others
EMB agar—inhibits gram-positive bacteria and select gram-negative species

Enriched: contains added nutrients to enhance the growth of those finicky bacteria with a gourmet appetite
Blood agar—used for growing certain pathogenic microbes

Differential: has a diagnostic test built into it that changes colors with different species of microbes
Lactose broth will turn from red to yellow for species that can ferment lactose but not for those that can't
MSA agar

Shapes of bacteria and examples

-Coccus (plural: cocci, meaning berries)=spherical

Bacillus (plural: bacilli, meaning little staffs)=rod-shaped

Spiral or coiled

Cocci are usually round but can be oval, elongated, or flattened on one side
Diplococci—cocci that remain in pairs after dividing
Neisseria gonorrhoeae
Streptococci—cocci that divide and remain attached in chain-like patterns
Streptococcus pyogenes
Staphylococci—divide in multiple planes and form grapelike clusters
Staphylococcus aureus (abscesses)
Tetrad—cocci that divide in 2 planes, remain in groups of 4
Gaffkya tetragena
Sarcinae—cocci that divide in 3 planes, cube-like groups of 8
Micrococcus lutea

Bacilli are not usually subdivided by arrangement, only subdivided by other properties (e.g. Gram stain)
Gently curved
Vibrio cholerae (cholera)
Escherichia coli (urinary tract infections)
Bacillus anthracis (anthrax)

Spirally shaped
Rigid helix (twisted twice or more along its axis, like a corkscrew)
Campylobacter jejuni (diarrhea)
Flexible spirals (spirochetes)
Treponema pallidum (syphilis)

Structural components of bacteria and their function: capsule (role in pathogenesis), cell wall, flagella (what is an axial filament?), fimbria, and endospores.

Capsule—external to cell wall, organized and firmly attached to the cell wall, protect pathogenic bacteria from phagocytosis by the cells of the host; gummy consistency that gives colonies sticky (mucoid) characteristic)
Two types of Streptococcus pneumoniae
With capsule=pathogenic
Without capsule=nonpathogenic

Cell wall—prevents cell from blowing up by hypotonic solution, gram-positive and gram-negative, major target for drugs

Flagella—major function is motility
Axial filaments—spirochetes are flexible because of this (periplasmic flagella), contractile filaments, length of spirochete, flagella enclosed in the space between the cell wall and cell membrane
Fimbriae—hollow tubes of protein, not for locomotion
Shorter, numerous, for adhesion

Endospores—called endospore when still inside rod, made when essential nutrients are depleted, function for survival in heat, drying, chemical disinfectants, and radiation
Clostridium botulinum
Clostridium tetani
Clostridium perfringens
Bacillus anthracis

Cell wall is a good target for what anti-microbial drugs? What molecule on a Gram-negative bacterial cell wall acts as a deadly virulent factor?

Penicillin—blocks amino acid cross bridges in peptidoglycan

Lysozyme—digests bonds between NAG & NAM in peptidoglycan

Lipopolysaccharide (LPS) of the outer membrane of gram-negative bacteria is a large complex molecule that contains lipids and carbohydrates
When gram-negative bacteria die, they release lipid A, which functions as an endotoxin
A toxin that is a structural molecule of the bacteria that is recognized by the immune system

What are the reagents used in the steps of Gram stain?

Crystal violet (primary stain): stains all bacteria purple

Gram's Iodine (mordant): causes a stain to become more tightly bond to the cell by intensifying the ionic chemical bond between the crystal violet and the bacteria

Ethyl alcohol (decolorizer): removes the stain from gram-negative bacteria, which now becomes colorless

Safranin (counterstain): stains any colorless cells, stains gram-negative bacteria red

Transcription vs. Translation

Transcription: DNA to mRNA
Translation: mRNA to protein

Hypertonic vs. hypotonic solution (what happens to cells in each of these solutions?)

Hypertonic—solution has more solutes than the cell, plasmolysis (shriveling)

Hypotonic—solution has very little solutes, Plasmoptysis (swelling up of cell)

Eukaryotic cell components and functions: Cell membrane (phospholipid bilayer), RER (rough endoplasmic reticulum)

Cell membrane—two layers of phospholipids with proteins embedded and sterols (confer stability)

RER—site of protein synthesis, ribosomes

Viral structural components (envelope, nucleocapsid, peplomer, etc.)

Envelope—membrane that encloses virus, protein and lipid-sometimes called viral membrane
For enveloped viruses, this is the virion or virus particle

Nucleocapsid—capsid (viral protein) + genome (RNA or DNA)=nucleocapsid
For non-enveloped viruses this is the virion or virus particle

Peplomer—viral glycoproteins embedded in the envelope, receptor for virus

What determines the host specificity of a virus? (Why doesn't hepatitis virus infect muscle cells?)

Specificity normally resides at the cell surface virus receptor level

Human cells do not have receptors for viruses that infect cats

Muscle cells do not have receptor for hepatitis, the liver does

How do interferons protect a viral infection?

Interferons are natural compounds produced in the body during a virus infection. They inhibit virus replication and virus infection of adjacent cells. Cells make interferons even before immunity kicks in, part of the first line of defense. Can be made by every cell (except RBC); make proteins to chop virus

Definitions of phototroph, chemotroph, autotroph, heterotroph: pathogens are?

Phototroph—photosynthetic, sunlight as energy source

Chemotroph—organic chemicals as energy source

Autotroph—CO2 as carbon source
Heterotroph—organic chemicals as carbon source

Chemoheterotroph=man, animals, most bacteria: pathogenic bacteria

Definitions of aerobic, anaerobic, facultative aerobic (bacteria)

Aerobic—grows in the presence of oxygen
Pseudomonas aeruginosa

Anaerobe—grows best without oxygen
Clostridium sp.

Facultative anaerobe—use oxygen if its available, but they can also survive without it, grow all throughout the medium
Escherichia coli

What are halophiles? Saprobes (such as fungi)?

Halophiles: are organisms that require a high salt concentration for growth. Live in habitats with a high solute concentration, like the ocean

Saprobes: are organisms that obtain its nutrients from dead organic matter

Temperture range for: psychrophiles, mesophiles, thermophiles

Psychrophiles—cold loving, 0-20 C
Mesophiles—moderate temperature loving, 20-45 C

Thermophiles—heat loving, 45 and up C optimum growth temperatures

Binary fission is?

The way bacteria divide; one to two, two to four, four to eight

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