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organisms that can grow over a wide range of water activity or osmotic concentrations


organisms that grow optimally in high salt concentrations


organisms that can tolerate high levels of salt but do not grow optimally in them


organisms that grow optimally in high sugar concentrations


where the cell membrane pulls away from the cell wall. this results in dehydration in many organisms and growth ceases. it happens in hypertonic solutions when water exits the cell, causing the cell to shrink. osmotolerant organisms have mechanisms that prevent their proteins from aggregating in hypertonic environments.


organic compounds that accumulate in the cytoplasm and act as solutes that balance the osmotic pressure.

antibiotic resistance

pump toxin out of cell


organisms that grow optimally between pH 0 and pH 5.5


organisms that can tolerate acidic pH even though growth is not optimal there


organisms that grow optimally between pH 5.5 and pH 8.0


organisms that grow optimally between pH 8.5 and pH 11.5


organisms that do not grow optimally in basic conditions but can tolerate pH in this range

obligate aerobes

organisms that will only grow in the presence of O2


organisms that require a small amount of O2 for growth but are inhibited by the amount of O2 normally present in the atmosphere

facultative anaerobes

organisms that grow better in the presence of O2 but will also grow in its absence ex. e. coli

aerotolerant anaerobes

organisms that grow equally in the presence or absence of oxygen

obligate anaerobes

organisms that cannot survive in the presence of oxygen because it is toxic to them


organisms that require elevated levels of CO2 for optimal growth


produces methane

cardinal temperatures

the characteristic temperature dependence with distinct minimum, maximum, and optimum temperatures for every microbial species


growth is the best/fastest/most efficient


organisms that grow optimally at cold temperatures between O degrees C and 15 degrees C


organisms that do not grow optimally at cold temperatures but will exhibit some growth at these temperatures. these organisms include many organisms responsible for food spoilage, like lactic acid bacteria


grow optimally at ambient temperatures between 20 and 40 degrees celsius. many organisms in our lab fall into this range. (also human inhabitants and pathogens)


grow optimally at warmer temperatures between 50 and 80 degrees celsius


organisms that do not grow optimally in warmer temperatures but are able to survive them (ex. endospore formers)


organisms that grow optimally in extremely hot temperatures, above 80 degrees celsius (ex. archaea)


a dormant form of bacteria that produce them, which allow bacteria to survive harsh conditions including temperatures, chemicals, irradiation, pH changes, and dessication. endospores are produced within the cells in a process called sporulation

vegetative cells

metabolically active cells, cells that are capable of growth and reproduction

structural stains

stains used to classify or assist in identifying organisms based on the presence or absence of specific structures

negative structural stain

a stain that requires the background to be contrasted with the capsule in order to visualize it.


a structure that is composed of polysaccharides or polypeptides that are mucoid and give cells a sticky outer surface


capsules that are composed of polysaccharides, means sugar shell

acid-fast stain

stains groups of bacteria differently that have different morphological characteristics with respect to cell wall structure and composition.

mycolic acids

contained in the cell wall of acid-fast bacteria which are waxy substances that lead to differences in staining behavior. they confer a higher affinity for the primary stain used and also add resistance to decolorization

gram stain

the staining procedure used most often in microbiology that is based on morphological characteristics with respect to cell wall structure.

gram + bacteria

possess a thick cell wall composed of many interconnecting layers of peptidoglycan. it contains teichoic acids which increase the degree of cross-linking between peptidoglycan layers

gram - bacteria

posess a thin layer of peptidoglycan only a few layers thick and lack teichoic acids in their cell wall. the cell walls have a lesser degree of cross-linking and possess an outer membrane that surrounds the cell wall which is composed of lipopolysaccharides (LPS)

acidic dyes

utilized when performing negative stains (congo red and nigrosin). they contain negatively charged chromophores which are repelled by cellular surfaces that are negatively charged, and therefore stain the background

negative stains

results in a colored background while the cells remain clear. it does not involve heat-fixing specimens, and is used when the sample is too delicate to withstand heat-fixing.

basic dyes

utilized when performing positive stains (crystal violet, methylene blue, safranin). they contain positively charged chromophores which are attracted to cellular surfaces that are negatively charged, and therefore stain the cells

positive stain

results in colored cells against a clear background. it involves heat-fixing specimens which kills the bacteria and helps them adhere to the slide, making it easier to stainthe specimen without washing it away. heat-fixing can sometimes distort cell shape






random clusters

micro (tetrad)

square groups of 4 cells


cubical groups of 8 cells

bright field microscopy

produces an image from light that is transmitted through a specimen and utilizes a compound light microscope

compound light microscope

contains two types of lenses where specimens are magnified


concentrates the light on the specimen

objective lense

the first place the specimen is magnified. usually 4x, 10x, 40x, 100x


the image should remain in focus when switching between objective lenses

ocular lense

inside the eyepiece, it magnifies the image a second time by a power of 10x. this creates a virtual image of the specimen that appears below or within the microscop

total magnification

the magnification of the objective lens in use multiplied by the magnification of the ocular lens


the clarity of an object. the limit is the length two points must be away from each other in order to be viewed as separate. light miscroscopy can not distinguish between two points that are closer together than 0.2 micrometers

0.2 micrometers

the limit for a light microscope


dial that controls the intensity of the light coming through to the specimen

substage condenser

located beneath the stage and collects, controls, and concentrates light from the lamp onto the specimen

iris diaphragm

part of the substage condenser. it is an aperture that controls the angle of light emerging from the top of the condenser.

numerical aperture

measure of a lenses ability to capture light coming from the specimen and use it to make the image. it indicates the resolving power of the lens

immersion oil

used with the 100x objective lens. it allows more light to pass through to the specimen since it has a higher refractive index than air. less light is scattered by refraction. it improves the numerical aperture of the lens and increases resolution

ocular micrometer

a ruler inside the eyepiece that has gradations corresponding to a specific length

stage micrometer

contains a ruler on a slide with gradations of a known width.


the unit of measure that microorganisms are always measured in, with the exception of viruses


the process of growing organisms on media under controlled laboratory conditions


can use visible light from the environment to create ATP


require chemicals in the media that they can break down from ATP


macronutrients needed by cells


a polysaccharide from seaweed that is not metabolized by most microorganisms. it does not provide any nutrients for organisms but can serve as a solid surface for colony growth

aseptic technique

a set of procedures necessary to maintain the purity of a culture while working with microorganisms.

streak plate

allows one to isolate individual cells from a pure or mixed culture. performed on solid media contained in petri dishes. they are often used to analyze colony morphologies of organisms.

pure culture

contains only one species


a large number of bacterial cells on a solid medium that is visible to the naked eye as a discrete entity. all cells are genetically identical.

colony form

refers to the shape of a colony

colony elevation

refers to the presence and type of height

colony margin

refers to the edge of the colony


colonies that are barely within the limits of resolution of the naked eye and are less than 0.1 mm in diameter


organisms that form colonies greater than 4 mm within 48 hours


organisms that spread from the original locations on an agar plate as slightly raised, concentric waves of thin filmy growth over large surface areas of the medium after short periods of incubation

surface texture

can be described as smooth or wrinkled

surface appearance

describes how light bounces off the colony, can be dull, shiny, or glistening

mold colony

will appear cotton-like and "fuzzy"

quadrant method

involves using four areas on a solid surface to create a dilution gradient where cells are separated more and more in each quadrant. many streaks are performed to dilute the culture slowly, and the stock culture is used only once.


cloudiness in the broth


formed by organisms that are non-motile and will sink to the bottom of the tube in a broth culture


formed by organisms that grow better in the presence of oxygen or require oxygen for growth which will grow at the top of the test tube where the concentration of oxygen is greatest


growth where organisms appear as clumps in the broth

broth culture

used to grow organisms quickly and in large amounts for immediate use. can be used to observe growth patterns or to perform additional tests on organisms

slant culture

used to store already purified cultures for extended periods of time. can be sub-cultured to broths or new slants if needed for further study or testing


process used by organisms to generate energy from food

true motility

individual cells exhibit independent movement over large distances. the movement often described as non-random and with a purpose, and is usually due to the presence of extracellular appendages that enable the organisms to travel in the environment autonomously


the appendage responsible for bacterial movement. in prokaryotes, it moves in a spinning motion and results in a characteristic tumble and run pattern

brownian motion

sometimes confused for true motility but is not actually a result of self-directed movement by the cell. it si a result of collisions with water molecules, organisms appear to be jiggling and not moving over large distances

wet mount

constructed by placing an aqueous sample of a specimen on a microscope slide and covering it with a cover slip. viewed with as little illumination as possible in order to improve the contrast.

hanging drop

contructed by placing an aqueous sample of a specimen on a cover slip and placing it on top of a washer. the sample will hang from the cover slip. they are a little more difficult to focus because they are three dimensional


the portion of a dye that confers color. it can be positively or negatively charged which influences the type of staining pattern achieved

cellular morphology

cell shape and cell arangement


species that have a variety of shapes


how individual cells are oriented with each other


kills the bacteria and helps them adhere to the slide, making it easier to stain the speciment without washing it away. however it can distory cell shape


used to bind to the crystal violet to form an insoluble complex


used to remove dye from certain cells.






curved rod


short rod


rigid spiral


flexible spiral


describes an organism that remains attached to a surface for its entire life


a tiny cell that is able to grow into a new organism


the total mass of living matter in a given unit area


A form of a colony where the growth is most dense in the middle, and branches outward

teichoic acids

may make gram positive cell walls more rigid and connects cell wall to the plasma membrane


free floaters


is a component of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different wavelength


having deeply indented margins but with lobes not entirely separate from each other


process of forming an endospore within a vegetative cell


tryptic soy broth


elevation; raised with a convex center

osmotic pressure

the external pressure that must be applied to stop osmosis


form of growth, rootlike structure


organisms that have strict nutritional requirements

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