Bio 15 Lab Quiz 1

colony

A visible mass of cells resulting from the division of a single cell.

agar liquifies and solidifies in what temperatures?

100ºC liquifies

room temp (40-45ºC) solidifies

3 reasons why a live microorganism might not be able to grow into a colony

-the medium did not provide the needed nutrients

-medium was incorrect for the microorganism

-incorrect growth conditions

why is it recommended that you turn the light to max brightness when using the highest powers?

light intensity decreases as magnification increases. by increasing magnification you see less light making the image dimmer

why do you need drawings of the micrometer in order to estimate the mm sizes size of the other objects?

there is a more accurate estimate of the mm sizes of the objects. can compare by scaling.

broths

sterile tubes of liquid nutrient medium

slants

liquid medium that has been set with agar so medium is at steep angle allowing larger surface area

slants are used for storing cultures over

longer periods of time

Deeps are used for

growing aerobic cultures and to test for the ability of an organism to grown with to without air

why is inoculating needle used for deep?

to introduce cells deep into the agar without introducing air

media used to store organisms

slants

media used to grow large numbers of organisms

broth

media used to best view individual colonies

agar plates

what limits which microbes can grown in the bottom of deeps?

the amount of oxygen available

a very important part of identifying any bacteria on a slide

getting the appropriate number of bacteria spread out evenly on a slide

heat fixing

kills cells, fixes cells on the slide and keeps cell on slide while staining

when making smear, what happens when you heat your sample which the cells are still wet?

It’s important for the slide to dry before heat-fixing to prevent cell lysis and preserve the cells’ morphology

aseptic technique purpose

be free from microorganisms and their toxins

prevents contamination

components of labeling fresh slide:

name, date, organism, class, lab exercise

a sign that culture was pure

if all colonies look exactly alike

what is done to assure purity once you gave well isolated colonies?

a single colony is chosen and a second isolation plate is done

streak plate is used to show?

show well isolated colonies

spectrophotometer

device that can measure light of specific colors or wavelengths

this device gives a qualitative number for the amount of light and is sensitive to small details

spectrophotometer

transmitted light

the amount of light passing through the object

absorbed light

light blocked by bacterial (or any other sample)

as the amount of light absorbed increases...what decreases?

amount of transmitted light

Optical Density (OD) is directly proportional to

the number of cells/mL

OD is on a ___ scale

log

log scales increase by

multiplying

Mesophiles

grows best at moderate temperatures (25-40ºC)

Thermophiles

grow best at high temperatures (55ºC)

Psychrophiles

grow best at low temperatures (0-20ºC)?

strict or absolute aerobes

only carry out respiration, no fermentation

found on surfaces, in dust, top layers of soil, skin and food surface

strict or absolute anaerobes

grow only when oxygen is absent

fermentation only, no respiration

aerotolerant anaerobes

do not utilize oxygen but can survive and grow in its presence

facilitative anaerobes

can live with or without oxygen, only become anaerobes when forced to do so

What is a complex medium?

medium in which the specific ingredients of unknown composition

What is a defined medium?

medium in which the specific chemical composition and amounts are known

What is a selective medium?

media that allows certain bacteria to grow but inhibits others from growing

What is a differential medium?

media that contains substances that helps distinguish some bacteria from others

What is the primary ingredient that is added in our liquid media?

agar

What is agar?

a complex polysaccharide isolated from seaweed (specifically, red algae)

What is the magnification of the ocular lens on the microscope?

10x

What are the magnifications and names of the objectives lenses on the microscope?

4x, 10x, 40x, 100x

scanning, low power, high power, oil immersion

Which objective lens can we adjust using the coarse knob?

4x

Which objective lens requires immersion oil?

100x

ways bacteria types can be defined on plate

morphology (color, shape), growth size

complex + defined media similarities

contain nutrients and carbon source

differential + selective media similarities

can be used to identify bacteria

pure culture definition and importance

contains only one species of microorganism

ensures accurate test results and prevents misidentification

Why can’t cells undergo infinite division

Nutrient depletion

Waste accumulation

Space limitations

Lag phase

Intense activity preparing for population growth, little to no increase in population

Log phase

Logarithmic (or exponential) increase in population, most metabolically active and vulnerable to antibiotics

Stationary phase

Equilibrium; microbial death rate equals production of new cells

Death phase

Population is decreasing (death rate more than production rate)

Ideal age for Gram stain specimen

16-18 hours