TAMU BIOL 206 Lab Exam 1

aseptic

free from disease-causing microorganisms; without contamination

Culture

a medium that contains living microbes

Pure culture

a culture containing a single kind of microorganism

aseptically

without contamination of yourself, others, the environment, the source culture, or the medium being inoculated

LAIs

laboratory acquired infections

Broths

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

agar slants

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

innoculating loop

used to transfer bacteria from one place to another

Innoculating needle

Wire straight, used when stabbing agar in semi-solid medium

mixed culture

microbial culture consisting of two or more species

isolation techniques

1. Streak Plate Technique

2. Pour Plate Technique

3. Spread Plate Technique

streak plate technique

A loop is used to streak the mixed sample over the surface of a solid culture medium

colonies

Collections of autonomously replicating cells.

colony forming unit (CFU)

term used to define the cell or group of cells that produces a colony when transferred to plated media

spread plate

A method to grow separate bacterial colonies by plating serial dilutions of a liquid culture.

colony morphology

the properties and characteristics of colonies such as shape, margin, and the elevation

isolated

colony not contacting another colony

free-living

Organisms that do not depend on one particular organism for food or a place to live.

host

an animal or plant that nourishes and supports a parasite

Nonpathogenic

Harmless microorganisms that may perform useful functions and are safe to come in contact with since they do not cause disease or harm.

Saprophyte

a plant, fungus, or microorganism that lives on dead or decaying organic matter.

Pathogen

a bacterium, virus, or other microorganism that can cause disease.

Mutualism

symbiotic relationship in which both species benefit from the relationship

commensals

organisms that live together in close association and may or may not benefit each other

opportunistic pathogen

a microorganism that does not ordinarily cause a disease but can become pathogenic under certain circumstances

reservoir

any area where a microbe resides and serves as a potential source for infection

shape of microorganisms

round

irregular

punctiform

margin of microorganisms

entire (smooth)

undulate (wavy)

lobate

filamentous (unbranched strands)

rhizoid (branched)

surface of colonies

smooth

rough

wrinkled

texture of colonies

moist

mucoid

butyrous (buttery)

dry

shiny

dull

Elevations of colonies

flat

raised

convex

pulvinate (very convex)

umbonate( raised in the center)

other colony morphology

color

opacity

filiform growth on a slant

dense and opaque with a smooth edge

Pigmented Growth on agar

Growth by bacteria on a solid media producing a color

friable growth

crusty

Spreading edge growth

solid growth seeming to radiate outward

Translucent Growth on agar

can see light through the growth

Pellicle growth in broth

a surface membrane produced by an organism that floats at the top of a liquid culture, often looks waxy

uniform fine turbidity (UFT)

fine growth throughout the broth

flocculent growth

small chunks of cells floating in the liquid

Decontamination

reduce pathogens to levels considered safe to handle - soaps or detergents

Disinfection

A process that eliminates many or all microorganisms, with the exception of bacterial endospores - low, medium, and high levels

heat, UV light, antiseptics

Sterilization

The process that completely destroys all microbial life, including spores.

chemicals, gases, incineration, ionizing radiation,

Autoclave

Piece of equipment used to sterilize articles by way of steam under pressure and/or dry heat 121-127F for 15 minutes

Biological indicators

test systems for sterilization that contain living organisms - used for testing autoclaves

bacterial endospores

most resistant, only extreme heat or chemical treatment destroys them

condenser lens

concentrates the light and makes illumination of the specimen more uniform

Refraction

Bending of light

objective lens

the part of a compound light microscope that is located directly above the specimen and that magnifies the image of the specimen

real image

an image that is formed by the intersection of light rays; a real image can be projected on a screen

ocular lens

Eyepiece of a microscope - 10x

virtual image

an upright image formed where rays of light appear to meet or come from

total magnification

objective lens x ocular lens

light microscope practical limit

1300x

Resolution

clarity of an image

limit of resolution (resolving power)

actual measurement of how far apart two points must be for the microscope to view them as being separate

Types of light microscopy

bright field

phase contrast

dark field

fluorescence

limit of resolution

D (minimum distance at which two point can be resolved) = λ (wavelength)/ NAc (numerical aperture of the condenser lens) + NAo (numerical aperture of the objective lens)

numerical aperture

measure of a lens ability to "capture" light coming from the specimen and use it to make the image

dark field microscopy

a special condenser is used so only the light reflected off the specimen enters the objective

phase contrast microscope

light microscope that enhances contrast; useful in examining living, unstained cells - looks 3D

flourescence microscopy

Uses UV light

Fluorescent substances absorb UV light and emit visible light

Cells may be stained with fluorescent dyes (fluorochromes)

ocular micrometer

a type of ruler installed in the microscope eyepiece, composed of uniform but unspecified graduations

stage micrometer

a transparent glass slide marked with a precise scale in micrometers and used to calibrate ocular micrometers by aligning the ocular scale with the stage scale - ruler with 10µm and 100µm graduations.

If 18 ocular divisions line up with two minor divisions of the stage micrometer, what is the diameter of a fungal cell that spans 3 ocular divisions?

2 x 10µm/18 OU = 3.3µm/OU

3 OU x 3.3µm = 9.9µm

A human RBC is approx. 7µm in diameter. An unknown bacterium measures 1OU using the oil immersion objective compared to 2 minor spaces on the stage micrometer

A) how big is the unknown bacterium?

B) How does its size compare to the RBC?

1OU = 20µm

2 x 10µm/1 OU = 20µm/OU

A) 20µm

B) 20µm/7µm = 2.9 = The bacterium is 2.9x larger than the RBC

When increasing the magnification what will happen to the number of spaces on the stage micrometer compared to the spaces on the ocular micrometer?

The spaces on the ocular micrometer will stay the same while the spaces on the stage micrometer will appear to increase in size and the number of spaces seen will decrease.

A) Bacterium A = 15 OU long

What is the length in µm?

B) Bacterium B = 3 OU wide

What is the width in µm?

10 OU = 60µm 6 x 10µm/10 OU = 6µm/OU

A) 6 x 15 = 90µm long

B) 6 x 3 = 18 µm wide

contrast

color differences between stained organisms and the microscope field behind them

Morphologies

the shape of an organism

Arrangements of bacteria

grouping of bacteria

Morphologies of Prokaryotes

spherical - cocci, coccus

rod - bacilli, Bacillus

spiral - spirilla, spirillum

curved rods - vibrios

short rods - coccobacilli

flexible spirals - spirochetes

Arrangement of Prokaryotes

Single cells

pairs of cells (diplo-)

chains of cells (strepto-)

tetrads

cube (sarcina)

irregular cluster (staphylo-)

palisade and angular

single cells

Cocci, bacilli, spirilla, spirochaetes, and vibrios

Pairs of cells ("diplo-")

cocci and bacilli

chains of cells ("strepto-")

cocci and bacilli

tetrads

cocci

cube (sarcina)

cocci

irregular cluster ("staphylo-")

cocci

Palisade and angular

bacilli

Chromogen

colored molecule in a stain

chromophore

the portion of the chromogen that gives it its color

auxochrome

charged portion of a chromogen and allows it to act as a dye through ionic or covalent bonds between the chromogen and the cell

Basic stains/dyes

dyes with positive charges, bind to negatively charged structures

Common basic stains

methylene blue, crystal violet, safranin

heat fixing

kills the bacteria, makes them adhere to the slide, and coagulates cytoplasmic proteins to make them more visible

structural stain

able to look for spore, capsule, flagellum

Gram stain

A staining method that distinguishes between two different kinds of bacterial cell walls.

primary stain

crystal violet

mordant

Iodine - forms the crystal violet-iodine complex

Decolorizer

ethanol - gram negative cells are decolorized

counterstain

safranin

over-decolorize

leaving decolorizer on too long and get reddish gram positive cells

under-decolorize

produce purple gram negative cells

Exotoxins

toxic substances that bacteria secrete into their environment

hemolysins

lyse red blood cells

beta hemolysis

complete lysis of red blood cells

alpha hemolysis

partial hemolysis

gamma hemolysis

no hemolysis

Streptolysins

hemolysins produced by streptococci