Virginia Tech BIOL 2614 Microbiology Lab Final - Spring 2024

germs

__________ can include bacteria, fungi, parasites, and viruses that are ubiquitous (found everywhere in nature, including water, food, the air, and on and in our bodies

pure culture

a culture that contains only 1 species of microorganism

sterilization

the destruction or removal of all forms of microorganisms (eukaryotes, prokaryotes, and viruses)

aseptic technique

the methods of obtaining and maintaining pure cultures

trypticase-soy

a type of media that contains glucose, enzymatically digested milk protein, enzymatically digested soybean meal, and a small amount of NaCl

SAB (sabouraud dextrose)

a microorganism like yeast and fungi that prefer an environment with a higher sugar concentration would like _________ media

stock

refrigerated slant cultures are examples of _________ cultures

slant cultures

cultures not used to characterize and identify microorganisms, but rather used for the growth and refrigerates storage of pure microbial cultures

agar deeps

type of stab culture made in either a solid (1.5-2% agar) or a semisolid (0.5-0.7% agar)

underlined

nomenclature

handwritten names should be _____________

italicized

nomenclature

typed named should be _____________

broth

any liquid medium used for growing microorganism is called a __________

turbidity

some microbes uniformly increase the _____________ (milkiness/cloudiness) of the broth as their numbers increase

pellicle

other species of microorganisms grow only at the surface of a static broth culture, forming a mat of cells called a _______________

sediment

other microbial species may settle to the bottom of the tube to form a _____________ or button of cells that stick together

mycelia

other microorganisms form intertwined ____________ during growth; these may form clumps of filamentous cells having the appearance of small cotton balls floating in clear broth

😁

know the parts of the microscope

eyepiece

total magnification = objective x ____________

heat fixation

a common method for killing cells prior to staining

simple stain

stain technique that colors the cell or the background in a way that enables you to observe whether the cell is a straight or curved rod or cocci and whether the cells are arranged in pairs or clusters

differential stain

stain technique that uses a combination of dyes that take advantage of chemical differences among cells; dyes the entire cell of only certain types of bacteria

simple

basic dyes and acidic dyes are types of __________ stain

differential

gram stain and acid-fast stain are types of _________________ stain (stains whole cells but only those of a certain type)

morphology

the study of the size, shape, and arrangement of cells

yeasts

a single-celled fungi eukaryotic microorganism

molds

a filamentous fungi eukaryotic microorganism

algae

a photosynthetic plant eukaryotic microorganism

protozoa

a single-celled animal eukaryotic microorganism

prokaryotic

bacteria are (prokaryotic/eukaryotic)

mordant

Gram Stain

the ___________, Gram's iodine, increases the affinity between the primary stain and the reactive substances in the cell

counterstain

Gram Stain

the ________________ can be any dye as long as it is a color that contrasts with the deep blue-violet of the stained gram-positive cells; common examples are basic fuchsin and safranin

endospore

a structure that is formed inside certain types of bacteria

vegetative

a cell that lacks an endospore is called a _______________ cell

capsule

term that is used to refer collectively to all extracellular polymers that are produced by the cell and accumulate (at least in part) around its outer surface

motility

the movement caused by the action of the flagella is called

positive chemotaxis

motility toward a favorable environment

flagella

long, narrow strands that are coiled into rigid helices (spirals) that revolve around their points of attachment and push against the surrounding medium for motility

polar flagellation

cells with flagella inserted only at the ends of a cell

peritrichous flagellation

cells with flagella inserted all over the surface

flagellin

all bacterial flagella are composed of a protein called _____________

streak plate

the most practical method for obtaining pure culture; start with a mixed culture and spread it over the surface of a solid medium until each cell is separated from all others; the colony that develops from one cell is a pure culture by definition because all cells in that colony were derived from that first single cell

😁

T-Streak Method

know how to T-streak

turbidity

the effect of light scattering by a colloidal suspension

optical density (OD)

it is traditional to record growth as the change in __________ ____________ with time, as it is directly proportional to cell concentration

cell number

growth = increase in ______ __________

serological pipettes

glass or plastic pipettes that are calibrated to deliver any amount within the graduated scale

Pasteur pipette

small, tapered glass pipette that is not graduated and is used to transfer liquid where the volume is not critical

micropipette

pipette used to dispense very small volumes of liquid usually between 1 µl and 1000 µl

500

0.5 ml is _______ µl

1

1000 µl is _______ ml

.50 ml, 500 µl

when the micropipette reads "050", that is _______ ml = ______ µl

1 ml, 1000 µl

when the micropipette reads "100", that is _______ ml = ______ µl

dilution factor

the denominator of the final dilution (100 or 10^2)

# of colonies • dilution factor

CFU/ml =

viable number

the number of cells capable of division on a solid medium

serial dilution and spread plating

the best method available for determining viable numbers

sampling error

error that occurs because of an unequal distribution of cells in the culture or dilution fluid

technical error

error that is most often due to some inaccuracy in preparing dilution blanks or in pipetting

spread-plate method

method that involves spreading a small, known volume (usually 0.1 ml) of a cell suspension onto the surface of a pre-poured agar plate followed by evenly spreading the cell suspension across the agar surface

spread-plate

preferred method for determining viable numbers of strict aerobes, to study the proportions of cell types in a mixed culture, or to check for culture purity; uses a "hockey stick" that is sterilized with burning ethanol

pour-plate

method where a known volume of cell suspension is inoculated into a tempered agar deep; satisfactory for growing either the facultative or the microaerophilic bacteria

300

plates with more than ______ colonies are considered TNTC

TFTC (too few to count)

plates with less than 30 colonies are considered

2 (example: 2.2 • 10^6)

your answer for CFU/ml should be how many sig figs?

all-purpose media

media used for maintaining pure stock cultures of many types of microorganisms and for growing these microbes for laboratory experiments

selective medium

media that contains at least one ingredient (selective agent) that can inhibit the growth of unwanted (more numerous) microorganisms without preventing the growth of the desired type

coliform bacteria

residents of the human intestine that, in their presence in water, indicate that the water is contaminated with fecal material

differential media

media that is designed to distinguish one type of microorganism from all others in a mixed culture; can be selective or nonselective

nutrient agar

name an example of an all-purpose medium

high-salt agar

name an example of a selective medium

mannitol-salt agar

name an example of a selective and differential medium

phenol red

dye used for mannitol medium

optimum growth temperature

the temperature at which the growth rate of a microbial species is closely correlated to the temperature of that organism's habitat

37°C

what is the optimum growth temperature for pathogenic microorganisms that infect humans?

mesophilic

most known microorganisms have optimum growth rates between 28°C and 38°C; these organisms are called _______________

psychrophilic

organisms that have optimum growth rates at temperatures lower than 16°C

thermophilic

organisms that have optimum growth rates around 60°C

tonicity

the normal osmotic pressure exerted by body fluids, which amounts to about the same as physiological saline (0.9% NaCl solution)

plasmoptysis

the result of placing a cell in a hypotonic solution (low osmotic pressure); exploding of the cell due to water rushing into the cell

plasmolysis

the result of placing a cell in a hypertonic solution (high osmotic pressure); shrinking of the cell due to water rushing out of the cell

osmophilic

osmotic-pressure loving

saccharophilic

sugar loving

halophilic

salt loving

obligate (strict) aerobes

organisms that grow only when oxygen IS present

microaerophiles

organisms that require only minimal amounts of oxygen to grow

obligate (strict) anaerobes

organisms that require NO oxygen for growth and oxygen is toxic; metabolism is fermentative

aerotolerant anaerobes

strict fermenters that do not find oxygen toxic but cannot use it in their metabolism

facultative aerobes/anaerobes

organisms that can grow either in the presence or the absence of oxygen, but grow faster in aerobic conditions; most microorganisms fall into this class

zone of hydrolysis

area that results from the enzymatic breakdown of the insoluble starch into smaller oligosaccharides and the disaccharide maltose

casein

insoluble protein found in milk secreted 3-5 weeks postpartum that can be readily attacked and solubilized by microbially produced extracellular proteinases

gelatin

as enzymes hydrolyze __________, it changes from a solid to a liquid, thus destroying its use as a solidifying agent

respiration

Fermentation Features

(1) can occur without oxygen

(2) energy-producing electron transport is absent

(3) much less energy efficient than ______________

(4) metabolic intermediates, often called fermentation end products, are excreted from the cell

lactic

Fermentation End Products

(1) acids: _________ or acetic

(2) neutral products: ethyl alcohol and butanediol

(3) gases: CO2 and H2

substrate-level phosphorylation

the way that fermentative microorganisms make all their ATP

Durham tubes

tubes used to detect gas production from fermentation

yellow

a positive reaction for sugar fermentation test is if the phenol red indicator turns _____________ in the ENTIRE medium and/or there is a bubble in the Durham tube

enteric bacteria

bacteria that grow aerobically on glucose (in broth cultures) and rapidly use all of the oxygen via respiratory metabolism; then they commonly shift to one of two types of glucose fermentation (mixed acid or butylene glycol)

methyl-red test

the test for mixed acid fermentation of glucose by enteric bacteria

Simmons' citrate agar

media used during the biochemical test used to determine utilization of citrate by enteric bacteria

green

Citrate Test

positive: growth and an alkaline reaction, turning the pH indicator (bromothymol blue) from _________ to blue