BIOL 351 Lab Exam 1

what does it mean that microorganisms are “ubiquitous in nature?”

found everywhere that other lifeforms exist

*doesnt apply to every species, but applies to microorganisms as a whole

Most organisms are _____ and ______

free-living and nonpathogenic

saprophytes

important role in decomposition

pathogens

cause damage to host

mutualism

both host and microbe benefit

commensals

microbe benefits but no effect on host

opportunistic pathogens

inhabit our bodies and are capable of producing a disease state if introduced into a suitable part of the body

reservoir

any area where a microbe with the potential to cause infection resides

purpose of blood agar

to differentiate bacteria based on their hemolytic characteristics

blood agar composition

includes 5% sheep blood in a tryptic soy agar (TSA) base

theory of blood agar

several species of gram-positive cocci produce exotoxins called hemolysins, which are able to destroy RBCs and Hb

beta hemolysis

complete destruction; results in clearing/yellowing of the medium

alpha hemolysis

partial destruction; results in greenish discoloration of the medium

gamma hemolysis

no hemolysis

identify the letters

A — beta hemolysis

B — alpha hemolysis

C — gamma hemolysis

germicide

refers to substances or systems, both chemical and physical, that prevent the spread of pathogens; most are broad-spectrum

3 categories of germicides

1. decontamination

2. disinfection

3. sterilization

decontamination

lowest level of control; reduction of pathogenic microorganisms to a level at which items are safe to handle without protective attire

disinfection

kill most, if not all, of the targeted pathogens but typically do not kill large numbers of spores

chemical sterilant

high-level disinfectants that have the ability to reduce or eliminate pathogens on or in living tissue

antiseptics

disinfectants designed to reduce or eliminate pathogens on or in living tissue

sterilization

highest level of control; complete elimination of viable organisms including spores

steam sterilization

most effective and most common method of sterilization

autoclave

device most commonly used for steam sterilization; use superheated steam under pressure to kill heat-resistant organisms

range for sterilizing temperature?

121-127 ºC

how long must something reach optimum temperature in the autoclave?

at least 15 mins (time varies according to the size and consistency of the material)

biological indicators

the only way, with certainty, to determine that sterilization has been achieved

*purple = success

aseptic transfer

transfer of living microbes from one place to another without contamination of the culture, the sterile medium, or the surroundings

culture

a medium that contains living microbes

pure culture

contains a single species

mixed culture

contains multiple species

*all cultures are assumed to be mixed prior to obtaining isolation

broths

used to grow microbes when fresh cultures or large number of cells are required

agar slants

generally used to grow stock cultures that can be refrigerated after incubation and maintained for several weeks

plated media

typically used for obtaining isolation of species, differential testing, and quantifying bacterial densities

3 methods of isolation

1. streak plate

2. pour plate

3. spread plate

who developed the concept of a pure culture?

Louis Pasteur

who developed a procedure for “streaking for isolation"?”

Robert Koch

whats the primary purpose for streaking for isolation?

obtaining isolated colonies

how is a pure culture obtained?

a single colony composed of identical cells is used to inoculate another culture

quadrant streak

used with samples suspected of high cell density

properly streaked

not sterilizing loops between quadrants

improperly streaked quadrants

not rotating plate properly

either loop was not cooled or loop did not pass through previous quadrant

growth characteristics are influenced by:

nutrient availability

temperature

incubation time

shape

round

irregular

punctiform

punctiform

tiny pinpoint dots

margin

entire

undulate

lobate

filamentous

rhizoid

entire

smooth with no irregularities

undulate

wavy

lobate

lobed

filamentous

unbranched strands

rhizoid

branched like roots

elevation

flat

raised

convex

pulvinate

umbonate

texture

moist

mucoid

butyrous

dry

shiny

dull

other properties of colony morphology

color and optical properties

agar slants

primarily used for cultivation, maintenance, and storage of stock cultures

filiform

dense and opaque with a smooth edge

friable

crusty

spreading edge

produced by motile organisms

pellicle

growth floats on top of medium

sediment

growth sinks to the bottom

flocculent

clumped growth

uniform fine turbidity

cloudy

spread plate technique

method of isolation in which a diluted microbial sample is deposited on an agar plate and spread uniformly across the surface

cell density formula

CFU/mL = # colonies / (volume plated (mL) x dilution)

1st dilution formula

1st dilution = volume transferred / total volume of tube

subsequent dilutions formula

nth dilution = concentration from the previous tube x (volume transferred (mL) / total volume)

bright field microscopy

produces an image made from light transmitted through a specimen

total magnification formula

total magnification = magnification of ocular lens x magnification of objective lens

dark field microscopy

light travels in a path past the objective unless scattered into it

phase contrast microscopy

make phase shifts visible as differences in brightness

fluorescence microscopy

high energy light outside the visible spectrum strikes the sample, molecules absorb that light and emit lower energy, visible light back to the viewer

cocci/coccus

spheres

bacilli/bacillus

rods

spirilla/spirillum

spirals

vibrios

slightly curved rods

coccobacilli

ovoid shape between cocci and bacilli

spirochetes

flexible spirals

pleomorphism

a single species that exhibits a variety of cell shapes within a given sample (ex: C. xerosis)

diplococci

sarcina

tetrad

staphylococci

streptococci

diplobacilli

palisades

streptobacilli

Diplococci

one plane of division

Streptococci

one plane of division, but cells do not separate and instead form a long chain

tetrad

two planes of division, one perpendicular to the other

Sarcina

three planes of division results in cube

Staphylococci

irregular division leads to a cluster of cells

diplo

diplococcus

strepto

streptococcus, enterococcus

tetrads

micrococcus

palisade and angular

corynebacterium

bacterial strains

solutions consisting of solvent (water/ethanol) and chromogen

chromophore

gives it color