Micro 2051 Lab Midterm

Front 1

mixture of nutrients in which a microorganism can grow

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medium (pl. media)

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liquid media

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broth

Front 3

types of solid media

Back 3

-agar plate

-agar slant

-agar deep tube

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type of medium composed of many different extracts

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complex medium

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type of medium that has a precise chemical composition

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defined medium

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the killing and removal of all living organisms and their viruses from a growth medium

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sterilization

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method of sterilization that involves a sealed device that allows the entrance of steam under pressure

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autoclave

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autoclaving is frequently used to sterilize ______

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liquid media and other items that are heat-resistant

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type of sterilization that kills by oxidation effects

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dry heat sterilization

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simplest method of dry heat sterilization

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flaming

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useful sterlization method for glassware in which items are placed in an oven and heated to 170 degrees celsius for 2 hours

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hot-air sterilization

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heat-sensitive liquids or gases can be sterilized by _____ in which a device has pores too small for microorganisms but large enough to allow passage of liquid or gas

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filtration

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type of cold sterilization used for Petri dishes and other heat sensitive objects

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gaseous chemosterilizers (ex: ethylene oxide)

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UV causes damage to _____

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DNA

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disease-causing microorganisms

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pathogenic

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hospital-acquired infections

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nosocomial

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the number of microorganisms or viruses sufficient to establish an infection

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infectious dose

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occur naturally in or on the body; don't cause infection under normal conditions

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normal (resident) microbiota/flora

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why must resident flora have to be removed in a surgical scrub if it is not harmful?

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it can cause disease if introduced into the bloodstream or tissues

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temporarily on body; can't grow and multiply on skin because it is too acidic and dry

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transient microbiota

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handwashing removes _______

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transient flora

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common normal flora

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Stapylococcus, Acinetobacter, Propionibacterium

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a group of genetically identical bacteria arising from a single cell on an agar plate

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colony

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colony characteristics such as shape that are visible with the naked eye and are used to differentiate between organisms

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colony morphology

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unwanted organism which has been accidentally introduced into the culture

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contaminant

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the colony morphology is dependent on the ______ on which it is growing

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medium

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categories of colony morphology

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whole colony shape, margin shape, elevation, optical properties, surface characteristics, pigmentation

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different types of whole colony shapes

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round, irregular, rhizoid

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different types of margin shapes

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smooth, lobate, filamentous

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types of elevation

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convex, umbonate, flat

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types of optical properties

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opaque or translucent

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types of surface characteristics

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dull or shiny

Front 33

how do colonies form?

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a single cell replicates and gives rise to a single colony

Front 34

laboratory technique used to prevent contamination or errors

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aseptic technique

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type of culture that contains only one type of organism

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pure culture

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technique used for diluting bacteria on agar plates; can be used to isolate bacteria from a mixture

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streak plate

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what does TSA stand for?

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Trypticase soy agar

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purpose of a streak plate

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to isolate and identify colonies

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why must the loop be flamed between each quadrant?

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to get separation between quadrants

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kills cells, destroying autolytic enzymes, and causes the cells to adhere to the slide

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heat fixation

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why is staining a cell useful?

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cells consist mostly of water and staining makes them more visible (more contrast)

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unstained cells are hard to see even under high magnification because of ______

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lack of contrast

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first step in staining cells

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smear

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staining allows the _____ of a cell to be observed

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morphology

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basic cell shapes

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cocci, bacilli, spiral

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round, spherical cells

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cocci

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rod shaped cells

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bacilli

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cell grouping arrangements

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single, diplo, strepto, staphylo

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diplo-

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pairs

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strepto-

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chains

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staphylo-

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clusters

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groups of four cocci

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tetrads

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why is there no such thing as staphylobacillus?

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bacillus cells only divide across the short axis

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curved rod shaped cells

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vibrio

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cells that have one or more twists

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spiral

Front 56

difference between colony and cellular morphology

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colony - seen with the naked eye on a streak plate; help differentiate bacteria without a microscope

cellular - physical characteristics of a cell as seen under a microscope

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method of making a smear

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-label slide

-liquid broth - aseptically obtain loopful; spread on slide; let air dry; flame a few times

-solid media - loop of water on slide; aseptically obtain loopful; spread thin layer on slide; air dry and flame a few times

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aqueous or alcohol solution of a single basic dye

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simple stain

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primary purpose of a simple stain

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highlight entire microorganism so cellular morphology and grouping/arrangement are visible; dyes all cells the same color

Front 60

possible grouping of cocci cells

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diplo, strepto, staphylo, tetrads

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possible grouping of bacilli cells

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strepto or diplo

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types of spirals

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spirilla or spirochete

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vibrio shape

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curved rods

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cellular appendages that increase cell surfacearea and help transport nutrients into the cell

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prosthecate cells

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some actinomycete bacteria produce filaments or hyphaethat form a mycelium (network of hyphae) that later differentiate and fragmentto produce spores

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filamentous growth

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microscope that consists of a series of ocular and objective lenses

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compound microscope

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type of light microscope used in lab

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bright-field microscope

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term describing a microscope that has an ocular containing a magnifying lens for each eye

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binocular microscope

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part of the microscope on the revolving nosepiece above the stage of the microscope

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objective lenses

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closest spacing between two points at which the points can still be seen as separate entities

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resolving power

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maximum resolution of a compound light microscope

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0.2 micrometers (um)

Front 72

reduces the amount of light that is lost and increases resolution

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immersion oil

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only objective to be used with immersion oil

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100x

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part of the microscope that holds the slide

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stage

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moves stage up and down

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coarse focus adjustment knob

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where is the light source located?

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in the base

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controls amount of illumination

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light intensity knob

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move stage along x or y axis

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vertical and horizontal adjustment knobs

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collects and concentrates light onto the object on the stage

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condenser

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within the condenser; can be opened or closed to allow more or less light through to the stage; regulates light

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iris diaphragm

Front 81

light passes through the slide on the stage and through one of the _______

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objective lenses

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three objective lenses

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10x, 40x, 100x

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eye piece through which light passes into the eye

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ocular lens

Front 84

order of light traveling through a microscope from the light source to your eye

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-light source, condenser, slide on stage, smear, objective, ocular lens, your eye

Front 85

order of focusing a microscope

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-10x objective, use coarse adjustment to raise stage all the way, find line on slide or some cells with x/y-axis knobs, move until in focus, fine focus, move revolving objectives halfway to put immersion oil, move to 100x objective, fine focus (DO NOT MOVE COARSE FOCUS)

Front 86

term that describes a microscope that: as the objective lens changes, the specimen should remain in focus

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parfocal

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what to clean 100x objective lens with?

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lens paper only

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utilize a combination fo dyes to demonstrate a chemical or structural component of a cell

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differential stain

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type of differential stain

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Gram stain

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primary stain of Gram stain

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crystal violet

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mordant of Gram stain

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iodine

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decolorizer of Gram stain

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ethanol

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counterstain of Gram stain

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safranin

Front 94

cells that have a thick layer of peptidoglycan in their cell walls

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Gram positive

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contain only a few layers of peptidoglycan surrounded by an outer membrane

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Gram negative

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Gram positive will stain _____ because the primary dye remains inside the thick cell wall

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purple

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Gram negative will stain _____ because the ethanol decolorizer disrupts the outer membrane and washes the crystal violent and iodine out and the safranin can change the color

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red

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specialized dormant structures commonly found in certain Gram positive rods

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endospores

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examples of genera that produce endospores

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Clostridium and Bacillus

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when does an endospore form?

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when nutrients are depleted; harsh conditions

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cell that can grow and divide under optimal conditions

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vegetative cell

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process of endospore formation within a vegetative cell

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sporulation

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peptidoglycan layer between the two plasma membranes of an endospore

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cortex

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do endospores reproduce?

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no, they are survival structures

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spore coat is formed by

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spore proteins

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responsible for resistance of the endospore to harsh chemicals

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spore coat

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possible locations of endospores

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central, terminal, subterminal

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complex believed to play a role in the heat resistance of endospores

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dipicolinic acid and calcium

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occurs when an endospore returns to a vegetative state

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germination

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why are organisms that form endospores good for indicating the effectiveness of autoclaves?

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because endospores aare extremely heat resistant, if the endospores are killed, it is assumed that all other organisms would be killed as well

Front 111

organism that causes botulism

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Clostridium botulinum

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endospores usually form in cells that are ______ and of what cell morphology

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Gram positive rods

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examples of organisms that produce endospores

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Bacillus megaterium; Bacillus sphaericus

Front 114

what will the endospore stain look like under a microscope?

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vegetative cells are red; endospores are green and on the inside of the red cells or free endospores

Front 115

how to find total magnification of the microscope

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magnification of the ocular lens (10x) times the objective lens (4x, 10x, 40x, or 100x)

Front 116

stain that can distinguish cell types

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differential stain

Front 117

type of differential stain that distinguishes between thick and thin peptidoglycan cell walls

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Gram stain

Front 118

Gram reaction of cells with thick peptidoglycan layer

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Gram positive

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Gram reaction of cells with thin layer of peptidoglycan

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Gram negative

Front 120

Gram positive cells will stain ____; why?

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purple because the crystal violet and iodine mordant form a complex inside the cell and is too large to be washed out of the thick peptidoglycan layer by the decolorizer

Front 121

Gram negative cells will stain _____; why?

Back 121

red because the ethanol decolorizer disrupts the outer membrane and the crystal violet-iodine complex is washed out of the thin peptidoglycan layer and the safranin turns them red

Front 122

problem caused if too much time has passed before performing a Gram stain on a culture

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the Gram positive cells lose the ability to retain the dye and appear Gram negative

Front 123

Staphylococcus epidermidis Gram reaction and color

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Gram positive, purple

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Spirosoma linguale Gram reaction

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Gram negative, red, spirals

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movement of bacterial flagella

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spinning; rotating by a "rotary engine" in which a proton gradient provides the energy

Front 126

part of the flagella that connects the basal body to the filament

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hook

Front 127

filament of flagella is made of _____

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flagellin proteins

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when one or more flagella are attached at the ends of cells

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polar

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form of polar attachment in which a single flagellum is attached at one end

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monotrichous

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tuft of flagella attached at one or both ends

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lophotrichous

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one flagella at each end

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amphitrichous

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flagella found at multiple locations

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peritrichous

Front 133

used to determine whether microorganisms possess flagella and thus are capable of motility

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motility test medium

Front 134

what is special about the motility test medium?

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-it contains a low agar concentration to allow movement of motile bacteria

-also has tetrazolium salt (TTC)

Front 135

what is the purpose of tetrazolium salt in the motility test medium?

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-it is used as an electron acceptor; in its oxidized form, it is colorless; when it is reduced, it is red and insoluble

Front 136

what will the test look like if the bacteria are motile?

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red color will radiate in all directions from the stab line

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test result if bacteria are not motile

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red line only where you stabbed the deep

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motility test result for Enterobacter aerogenes

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motile

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motility test result for Bacillus megaterium

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nonmotile

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movement of cells with polar flagella

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rapid, spinning from place to place

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movement of cells with peritrichous flagella

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slow, typically in a straight line

Front 142

examples of species with monotrichous flagella

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Vibrio, Pseudomonas

Front 143

species with lophotrichous flagella

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Rhodosporillium

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species with amphitrichous flagella

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Spirillum

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species with peritrichous flagella

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Proteus, Salmonella, Escherichia

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pH at which organism grows best

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optimum pH

Front 147

grow best at pH less than 6; examples

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acidophiles (Saccharomyces cerevisiae, other normal microbiota on the skin)

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grow best at pH close to 7; examples

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neutrophiles (Echerichia coli)

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grow best at pH greater than 7; examples

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alkalinophiles (Agrobacterium; Vibrio, Alcaligenes faecalis)

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organisms that resist rigorous decolorization

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Mycobacterium

Front 151

Mycobacterium are called ____ because they resist decolorization

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acid fast

Front 152

what is the unique lipid component of Mycobacterium called?

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mycolic acids

Front 153

group of branched-chain hydroxy lipids complexed to peptidoglycan of mycobacterial cell wall

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mycolic acids

Front 154

primary stain in acid fast

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carbol-fuschin

Front 155

decolorizer for acid fast stain

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acid-alcohol

Front 156

counterstain in acid fast stain

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methylene blue

Front 157

how does Myco look on solid media and why?

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wrinkled appearance because of the cell wall's hydrophobic nature that renders the cell stronly impermeable to nutrients

Front 158

why is acid fast staining useful?

Back 158

Myco grows slowly, and acid fast stain quickly determines if Myco is present to diagnose the infected individual

Front 159

what must be used instead of water to make a smear for Myco? why?

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egg albumin because Myco has surface lipids that cause celsl to form tight aggregates and don't disperse in aqueous solution; egg albumin is high in protein content

Front 160

results of acid fast stain

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E. coli - blue rods

Myco - red rods because they cannot be decolorized

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countable plate

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30-300 colonies

Front 162

as the number of cells in a broth increases, the turbidity _____

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increases

Front 163

direct microscope count

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counts all cells living and dead (hemocytometer)

Front 164

standard plate count

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aka viable count; cfu/mL; assumption that one living cell will give rise to one colony

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pour plate method

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sample poured first, the the medium is added on top

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fewer than 30 colonies

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not statistically significant

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more than 300 colonies

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insufficient nutrients for all of them to grow

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coliforms

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Gram negative rods; don't form endospores; ferment lactose and produce CO2 gas; aerobic

Front 169

why are E. coli called indicator organisms?

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they indicate the possibility of other bacterial species

Front 170

nutrient medium designed to favor growth of certain microbes and inhibit undesirable competitors

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selective medium

Front 171

medium which provides a visible indication of a physiological characteristic

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differential medium

Front 172

EMB

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selects for Gram negative; differentiates lactose fermenters from non lactose fermenters

Front 173

used for the presumptive test of MPN

Back 173

lauryl sulfate lactose broth (LSL)