MicroLab Midterm Cram

Nutrient agar

a general purpose agar used for growing many types of bacteria

Enriched Media

contains extra nutrients necessary for bacterial growth

Contamination

the occurrence of microorganisms where you do not intend during an experiment

Fomite

objects that can transmit infectious agents to a new host

Fomite examples; 

door handles, cell phones, keyboard

Resident/normal flora

microorganisms that live naturally and permanently in various areas of our bodies

Resident/normal flora

not usually harmful but can cause problems if they get in the wrong area; essential to human health. Antibiotics, dietary changes, or illness can alter the composition

Transient flora

temporary microbes that can be removed by handwashing

Transient flora

will not cause harm unless resident flora is out of balance

Nosocomial infection

infection acquired during hospitalization

Nosocomial infection

most important procedure to prevent this is handwashing

Hypothesis

an unconfirmed and testable answer to your question

Independent/experimental variable

the condition/ parameter that’s changed during experiment

Experimental group

members that are subject to the change in an experiment

Control variable

conditions/factors that remain the same in an experiment

Control group

members of the experiment that are subjected to the control variable

Simple microscope

a microscope with one magnifying lense

Compound microscope

microscope with two magnifying lenses

Lenses in a compound microscope

objective and ocular lense

Objective lense

magnifies the image of the specimen we are looking at

Ocular lense

compounds the magnification of the image created by the objective lense

Bright field microscope

The background is bright while the specimen appears as darker objects, used for observing stained specimens

Dark field microscope

negative image, the background is dark while the specimen appears bright, useful for observing live motile cells

Phase contrast microscope

increases the contrast between cells or portions of cells that vary only slightly in density, used for studying details of unstained cells with a similar density to water

Fluorescent microscope

allows detection of fluorescence through the use of ultraviolet light

Ocular lense

lense which we look through, the standard magnification is 10x

Scanning objective lense

magnification 4x, widest field of view, always start with this to find areas for closer observation

Low power objective lense

magnification 10x

High dry objective lense

magnification 40x

Oil immersion objective lense

magnification 100x, use a special oil, smallest field of view and very difficult to focus without oil

Stage

holds the slide/specimen for viewing

Condensor

focuses light onto the specimen

Numerical Aperture for scanning lens

.1

Numerical Aperture for low power lens

.25

Numerical Aperture for high dry lens

.65

Numerical Aperture for oil immersion lens

1.25

Resolving power for scanning lens

2.5 um

Resolving power for low power lens

1.0 um

Resolving power for high dry lens

.38 um

Resolving power for oil immersion lens

.20 um

Parafocal

image remains in focus when objectives are changed

Total magnification

product of the magnifications of the ocular lenses (10x) and the objective lenses

Resolution

the closest distance two objects can be, where we can still see them as separate objects

Simple stain

a procedure that stains all cells the same color regardless of the type of bacteria or its characteristics

Simple stain pt. 2

a quick method for observing the basic bacterial morphology or shapes of micro-organisms

Cocci

sphere shaped

Bacillis

rod shaped

Helicoidal

divided into two groups

Flexible helicoidal

bacteria called spirochetes

rigid helicoidal

divided into spiral or comma shapes

Coccus

single celled

diplococci

occur in pairs

tretrad

group of four

sarcina

cube-like morphology

streptococci

chain-like morphology

staphylococci

grapelike cluster

Differential stain

procedure used two different dyes to stain bacteria in contrasting colors, targets specific chemical and structural differences in kinds of bacteria

what are differential stains used to visualize

endospores, flagella, or inclusion bodies

Gram stain

a type of differential stain, the most important stain in microbiology

Gram Stain: primary stain

crystal violet and stain all bacteria purple

Gram Stain: Mordant

causes a stain to bind more tightly to cell, iodine intensifies the ionic bond between crystal violet and the bacteria

Gram Stain: Decolorizer

ethyl alcohol removes the stain from some bacteria (gram negative) which becomes colorless

Gram Stain: counterstain

safranin is a red dye that will stain any colorless cell present

Gram negative is stained

pink/red

Gram positive is stained

purple

Difference between gram positive and gram negative

gram positive has a thicker peptidoglycan cell wall which shrinks upon addition of ethyl alcohol and locks in purple stain. Gram negative has a thinner layer of peptidoglycan surrounded by layers of lipids which are dissolved by the decolorizer (washes purple out)

Aseptic technique goals

protect yourself and others and to prevent unwanted microorganisms from contaminating a culture or patient

Forms of bacterial media

broth (liquid medium), petri plate (solid medium), slant (solid medium)

Synthetic media

made from scratch with every single ingredient listed and added separately

Non-synthetic media

composed of nonspecific ingredients (beef extract or peptone)

General purpose medium

used to grow bacteria and keep them alive

Enriched medium

allows certain species of microorganisms to grow and inhibits others

Differential medium

has a diagnostic test built into it so that it changes colors with different species of microbes

Transport medium

used to transport microbes from one place to another

Sterile

completely devoid of life

Pure culture

medium growing only one intended species of microorganism

Mixed culture

medium growing two or more intended species of microorganisms

Contaminated culture

medium or article that has accidental or unwanted microorganisms in it

Differential stain

uses an acidic stain and a basic stain in order to detect capsule production

Negative stain

what we want to see will not be stained

Slimer layer

unorganized and loose

capsule

neatly organized, extracellular polysaccharide allows cell to attach, prevents phagocytosis, protects from desiccation

Congo red

will stain entire cell and the background red

acid alcohol

will fix the cells to the slides and change the color of the red dye to grey, water removes stain from cells and capsule

acid fuchsin

stains the cells red but not the capsule

What staining technique is used to visualize endospores

differential

Bacterial spore developed in the middle

central spore

Bacterial spore developed at the end

terminal spore

Bacterial spore developed in between

subterminal spore

Structure of an endospore provides resistance to 

heat, desiccation, radiation, and chemical disinfectants

Endospore staining: primary stain

malachite green

Endospore staining: mordant

heat

Endospore staining: decolorizing agent

water

Endospore staining: counterstain

safranin

Streak plate is used for generating

pure cultures, culture is derived from one species or strain of bacteria

Mixed culture is derived from

more than one species or strain of bacteria

Advantages agar has over gelatin

higher melting temperature, resistant to microbial degradation

First koch postulate

pathogen must be in every single case

second koch postulate

pathogen must be isolated from disease in host and grown in pure culture

third koch postulate

pure culture must cause same disease in a susceptible host