Micro. Chpt. 2,3,4

magnification

increase in the apparent size of the specimen

increases size of image, not object

10x

the magnification of the ocular lense

resolution

the minimum distance that 2 objects can be separated from one another, and still be recognized as distinct objects rather than 1 larger “fuzzy object”

100x

what magnification is used when viewing bacteria

oil

higher refractive index than air

decreasing illumination wavelength

done by putting a blue film over light source

oil, decreasing illumination wavelength, focusing illumination light

ways to increase resolution

better resolution

smaller wavelength means a

R= (constant)(wavelength)/numerical aperture

equation for resolution

smaller

which resolution is better

illumination brightfield

method of lighting the specimen from opposite the objective

specimen appears dark against a light background

common method of lighting

illumination dark field

illumination of the specimen without projecting light directly into the objective lens

used to examine specimens that can’t be distinguished from the background

used for unstained, living specimens

fixation

preservation of internal and external structures

organism is killed and firmly attached to a microscope slide

heat and chemical

methods of fixation

heat fixing

most common

preserved overall morphology (not internal structures)

heat evaporates the water, causing the organism to stick to the slide

organism is killed but not cooked

chemical fixing

protects fine cellular substructure and morphology of larger more delicate organisms

dyes

makes cell structures more visible

increases contrast

color

chromophore groups are

basic dye

positive charge

acidic dye

negative charge

basic dye

binds to negative molecules (DNA, RNA)

acidic dye

binds to positive molecules (cytoplasm)

simple staining

single agent

frequently used basic dyes

crystal violet, methylene blue

examples of basic dyes

differential stains

uses more than 1 dye

divides microorganisms into groups based on their staining properties

gram stain, acid-fast stain, staining of specific structures

examples of differential stains

gram staining

most widely used

2 groups ( positive and negative) based on cell wall structure

christian gram

invented gram staining

mordant

binds to dye, turning dye into a bigger complex

decolorization

occurs when cell wall isn’t sturdy enough to hold color

primary stain, mordant, decolorization, counterstain

steps of gram staining

primary stain

crystal violet

water rinse

mordant

gram’s iodine

water rinse

decolorization

wash with acetone

water rinse

counterstain

sofranine

water rinse

negative

pink

positive

purple

acid-fast staining

stains mycobacterium

negative staining

helps visualize capsules

capsules

easily destroyable

an extra layer that certain bacteria have

colorless against a stained background

spore staining

double staining technique

bacterial endospore vs. vegetative cell

endospore

dormant

vegetative cell

actively growing cell

flagellar staining

mordant is used to make the structure thicker and easier to see

phase-contrast light microscopy

visualization technique used with living cells and no stain

electron microscopy

two types: transmission and scanning

transmission microscope

only visualize 1 thin layer of structure

scanning microscope

helps visualize entire structure

cocci

spheres

diplococci

pairs of spheres

streptococci

chains of spheres

staphylococci

grape-like clusters

tetrads

4 cocci in a square

sarcinae

cubic configuration of 8 cocci

bacilli

rods

coccobacilli

very short rods

vibrio

comma shaped

spirilla

rigid helices

spirochetes

flexible helices

filamentus

form hyphae (multinucleated)

mycelium

branched hyphae

archaea

unusual shapes

pleomorphic

bacteria without a single characteristic shape

plasma membrane

selectively permeable barrier, mechanical boundary of cell, nutrient and waste transport, location of many metabolic processes (respiration and photosynthesis), detection of environmental cues for chemotaxis

gas vacuole

an inclusion that provides buoyancy for floating in aquatic environments

ribosomes

protein synthesis and process of translation occurs here

inclusions

storage of carbon, phosphate, and other substances; site of chemical reactions (micro compartments); movement

nucleoid

localization of genetic material (DNA)

periplasmic space

in typical gram-negative bacteria, contains hydrolytic enzymes and binding proteins for nutrient processing and uptake

In gram-positive bacteria, may be smaller or absent

cell wall

protection from osmotic stress, helps maintain cell shape

capsules and slime layers

resistance to phagocytosis, adherence to surfaces

Fimbriae and pili

attachment to surfaces, bacterial conjugation and transformation, twitching

flagella

swimming and swarming motility

endospore

survival under hard environmental conditions

bacterial cell envelope

plasma membrane + surrounding layers

peripheral membrane proteins

proteins on the plasma membrane

integral membrane proteins

proteins in the plasma membrane

macroelements

most of cell’s dry weight

required in relatively large amounts

C,O,H,N,S,P, K+,Ca2+,Mg2+,Fe2+/3+

what are the necessary macro elements

micronutrients

trace elements

enzyme cofactors

often supplied in water and media components

Mn,Zn,Co,Mo,Ni,Cu

what are the essential micronutrients

water and media components

what are micronutrients often supplied in

growth factors

essential cell components (or precursors)

macronutrients, micronutrients, growth factors

what are the three essential things a cell needs

amino acids, purines, pyrimidines, vitamins

classes of micronutrients include…

vitamins

function as enzyme cofactors

passive diffusion

higher concentration to lower concentration

not energy dependent

water, oxygen, carbon dioxide

molecules that can easily pass through plasma membrane

facilitated diffusion

not energy dependent

high concentration to low concentration

carrier molecules

rate reaches plateau

rate increases more rapidly and at a lower concentration

carrier saturation effect

when there is a plateau in facilitated diffusion, this represents

permeases

carrier molecules can also be called

transmembrane proteins

what type of proteins are carrier molecules

increase

in passive transport, the rate of transport and concentration gradient continues to…

active transport

works against concentration gradient (low to high)

energy-dependent

required carrier proteins(permeases)

proton motive force

difference in protons on either side of the cell creating an electrochemical gradient

ABC transporters, secondary active transport, group translocation

examples of active transport

ABC transporters

ubiquitously conserved

has a nucleotide binding domain and substrate binding protein

substrate-binding protein

scavenge in periplasm for food

require specific interactions

sugars, amino acids, some antibiotics

molecules that can be transported with ABC transporters

ATP binding cassette transporters

what does ABC transporters stand for