Flashcards in Chapter 2 Deck (190)
Microbiologists use ____ basic techniques to manipulate, grow, examine, and characterize microorganisms in the laboratory.
The five I's
It is not necessary to cultivate a microoganism to ___ it anymore, though it still remains a very common method.
Sometimes growing microbes in isolated cultures can tell you very little about how they act in a mixed species environment, but being able to isolate them and study them is also valuable, as long as you keep in mind that it is an ____ state for them.
To grow, or _____, microorganisms, one introduces a tiny sample (the inoculum) into a container of nutrient _____ which provides an environment in which they multiply. This process is called ____.
Any instrument used for sampling and inoculation must initially be ___.
The observable growth that appears in or on the medium after ____ is known as a culture.
Clinical specimens for determining the cause of an infectious disease are obtained from body fluids, discharges, anatomical sites (ear, eye, throat) or _____.
Other samples subject to microbiological analysis are soil, water, sewage, foods, air and _____.
Once a container of medium has been inoculated, it is _____, which means it is placed in a temperature-controlled chamber (______) to encourage multiplication.
Although microbes have adapted to growth at temperatures ranging from freezing to boiling, the usual temperatures used in laboratory propagation fall between ___ and ___.
20C and 45C
Incubators can also control the content of atmospheric gases such as oxygen and carbon dioxide that may be required for the _____ of certain microbes.
During the incubation period (ranging from one day to several weeks), the microbe multiplies and produces growth that is observable ____.
Microbial growth in a liquid medium materializes as cloudiness, sediment, scum, or ____.
The most common manifestation of growth on solid media is the appearance of ____ especially with bacteria and ___.
Culturing microbes is analogous to gardening. Cultures are formed by "seeding" tiny plots (____) with microbial cells. Extreme care is taken to exclude weeds (_____).
A ____ is a container of medium that grows only a single known species or type of microorganism.
The ____ is the most frequently used for laboratory study, because it allows the systematic examination and control of one microorganism by itself.
A ____ is a container that holds two or more identified, easily differentiated species of microorganisms, not unlike a garden plot containing both carrots and onions.
A _____ was once pure or mixed but has since had contaminants (unwanted microbes of uncertain identity) introduced into it, like weeds into a garden.
_____ get into cultures when the lids of tubes or Petri dishes are left off for too long, allowing ____ to settle into the medium. They can also enter on an incompletely sterilized inoculating loop or on an instrument that you have inadvertently ____ or touched to the table or your skin.
Some microbes require only a very few simple inorganic compounds for growth; others need a complex list of ____ inorganic and organic compounds. This diversity is evident in the types of media that can be ____.
Culture media are contained in test tubes, flasks, or ___ and they are inoculated by such tools as loops, needles, pipettes, and ___.
Media are extremely varied in nutrient content and consistency, and can be specially formulated for a ___.
a particular purpose
Culturing microbes that cannot grow on artificial media (all viruses and certain bacteria) requires ___ or hose animals.
____ media are the most frequently used type in clinical situations.
Agar, the main component of media, is commonly harvested from ____.
For an experiment to be properly controlled, sterile technique is ___.
Media can be classified according to three properties; physical state, chemical composition, and ____.
functional type (purpose)
Liquid, Semisolid, Solid (can be converted to liquid), solid share what property of media.
chemically defined, complex; not chemically defined share what property of media
general purpose, enriched, selective, differential, anaerboic growth, specimen transport, assay, enumeration share what property of media.
Liquid media are ___ based solutions that do not solidify at temperatures above freezing and that tend to flow freely when the container is ___.
In liquid media growth occurs ___ the container and can then present a dispersed, cloudy, or ____ appearance.
____ broth is used to show a biochemical reaction in which the enzyme urease digests urea and releases ammonium. This raises the pH of solution and causes they dye to become increasingly pink.
___ media have more body than liquid media but less body than solid media. They do not flow freely and have a soft, clotlike consistency at ______.
Semisolid media are used to determine the ____ of bacteria and to localize a reaction at a specific site.
The semisolid medium is stabbed with an inoculum and incubated. Location of growth indicated ____ or _____.
nonmotility or motility
____media containing 1% - 5% ___ are solid enough to remain in place when containers are titled to inverted.
Nutrient gelatin contains enough gelatin (___%) to take on a solid consistency.
_____, a complex polysaccharide isolated from the alga Gelidium, is a critical tool in the microbiology lab.
Agar is solid at room temperature, and it melts at the ____ temperature of water.
boiling (100 C)
Once liquefied, agar does not resolidify until it cools to ___, so it can be inoculated and poured in liquid form at temperatures that will no harm the microbes or the handler.
Agar is ___ and moldable, and it provides a basic framework to hold moisture and _____. Importantly, it is not itself a ____ nutrient for most microorganisms.
Media whose compositions are precisely chemically defined are termed _____ also known as synthetic.
Defined media contain contains pure organic and inorganic compounds that vary little from one source to another and have a ___ content specified by means of an exact formula.
Standardized and ___ media are most useful in research when the exact nutritional needs of the test organisms are known.
If even one component of a given medium is not chemically ___, the medium belongs in the complex category.
____ media contain extracts of animals, plants, or yeasts, including such materials as ground-up cells, tissues, and secretions.
Blood, serum, and meat extracts or infusions are examples of ____ media.
Milk, yeast extract, soybean digests, and peptone are other possible ingredients are _____.
Nutrients broth, blood agar, and MacConkey agar, though different in function and appearance, are all complex media that present a ___ mixture of nutrients for microbes that have complex nutritional ___.
Depending on what is added, a microbiologist can fine-tune a medium for nearly ___.
Unit recently, microbiologists knew of only a few species of bacteria or ____ that could not be cultivated artificially. However, ___ detection technologies have shown us that there are many more microbes that we don't know how to cultivate in the lab than those that we do.
Now we can study some vital ___ of bacteria without actually growing the bacteria, developing new media is still important for growing the bacteria that we are discovering using ___ methods.
General-purpose media are designed to grow ____ .
as broad a spectrum of microbes as possible
General-purpose media are a complex variety and contain a mixture of nutrients that could support the growth of a variety of _____.
Examples of general-purpose media include nutrient agar and ____, brain-heart infusion, and trypticase soy agar (TSA).
An ____ contains complex organic substances such as blood, serum, hemoglobin, or special growth factors that certain species must have in order to grow.
_____ such as specific vitamins and amino acids are necessary for certain species to grow.
Bacteria that require growth factors and complex nutrients are termed ____.
____ agar, which is made by adding sterile sheep, horse, or rabbit blood to a sterile agar base is widely used to grow fastidious ____ and other pathogens
Pathogenic Neisseria (one species of gonorrhea) are grown on either Thayer-Martin medium or "___" agar which is a blood agar with added hemin and nicotinamide adenine dinucleotide.
Enriched media are also useful in the clinical laboratory to encourage the growth of ____ that may be present in very low numbers, such as in urine or blood specimens.
Selective and differential media are designed for special ____ groups, and they are extremely useful in isolation and ____.
Selective and differential media can give the preliminary identification of a ___ or even a ___ in a single step.
A _____ contains one or more agents that inhibit the growth of a certain microbe or microbes, but not others and thereby encourages, or selects a certain microbe to grow.
Selective media are very important in primary isolation of a specific type of microorganism from samples containing ____ of different species - for example feces, saliva, skin, water, and soil.
Selective medium speed up ____ by suppressing the unwanted background organisms and favoring growth of the desired ones.
Media for isolation intestinal pathogens such as ______, contain bile salts as a selective agent.
Agents that have selective properties are ___, such as methylene blue and crystal violet, and antimicrobial drugs.
_____ allow multiple types of microorganisms to grow but are designed to display visible difference in how they grow.
Differentiation shows up as variation in ___ size or color, or in the formation of gas bubbles and ___.
colony size and color
The variation in differential media often come from the type of ____ these media contain and the ways that microbes react to them.
selective agent : sodium azide, tetrazolium
used for: isolation of fecal enterococci
Tomato juice agar
selective agent: tomato juice, acid
used for: isolation of lactobacili from saliva
selective agent: bile, crystal violet
used for: isolation of Gram-negative enterics
Salmonella/Shigella (SS) agar
selective agent: bile, citrate, brilliant green
used for: isolation and maintenance of Salmonella and Shigella
selective agent: Malachite green dye
used for: isolation and mantenance of Myobacterium
selective agent: pH of 5.6 (acid)
used for: isolation of fungi-inhibits bacteria
MacConkey agar selects against ___ bacteria. It is also ____ between lactose-fermenting bacteria and lactose-negative bacteria. So it is ____ and ___.
selective and differential
The simplest differential media show ___ reaction types, such as the use or nonuse of a particular nutrient or a color change in some colonies but not in others.
Some differential media are sufficiently complex to allow for ___ or ___ different reactions.
3 or 4
Media that are both selective and differential allow for microbial isolation and ____ to occur at the same time, which can be very useful in the screening of patient specimens as well as food and water samples.
Dyes are frequently used as ___ agents because many of them are ____ indicators that change color in response to the production of an acid or a base.
MacConkey agar contains neutral red, a dye that is yellow when natural and ___ or ___ when acidic.
pink or red
A common intestinal bacterium such as Escherichia coli that gives off acid when it metabolizes the lactose in the medium develops ____ colonies, and one like Salmonella that does not give off acid remains its ____ color.
red to pink
natural off white
A _____ contains a substance that absorbs oxygen or slows the penetration of oxygen in a medium, thus reducing its availability.
Reducing media are important for growing ___ bacteria or for determining oxygen ____ for isolates.
_____ media contain sugars that can be fermented (converted to acids) and a pH indicator to show this reaction.
_____ media are used to maintain and preserve specimens that have to be held for a period of time before clinical analysis or to sustain delicate species that die rapidly if not held under stable conditions.
___ media are used by technologists to test the effectiveness of antimicrobial drugs and by drug manufacturers to assess the effect of disinfectants, antiseptics, cosmetics, and preservatives on the growth of microorganisms.
____ media are used by industrial and environmental microbiologists to count the numbers of organisms in milk, water, food, soil, and other samples.
Certain ___ techniques are based on the concept that if an individual bacterial cell is separated from other cells and provided adequate space on a nutrient surface, it will grow into a discrete mound of cells called ____.
If it was formed from a single cell, a colony consists of ___ species
Proper isolation requires that a small number of cells e inoculated into a relatively large volume or over a large area of ___. It generally requires a medium with a relatively ____, a Petri dish, and _____.
In the ____ method, a small droplet of culture or sample is spread over the surface of the medium with an inoculating loop in a pattern that gradually thins out the sample and separates the cells spatially over several sections of the plate. The goal here is to allow a ___ cell to grow into an isolated colony.
In the loop dilution, or ___, technique the sample is inoculated serially into a series of cooled but still ___ agar tubes so as to dilute the number of cells in each successive tube in the series. Inoculated tubes are then plated out (poured) into sterile Petri dishes and are allowed to ____. The end result, usually in the 2nd or 3rd plate is that the number of cells per volume is so _____ that cells have ample space to grow into separate colonies.
harden or solidify
One difference between the loop dilution or pour plate method versus the streak plate technique is that in the loop dilution some of the colonies will develop ____ in the medium itself and not just on the ___.
The ____ technique, a small volume of liquid, diluted sample is pipetted onto the surface of the medium and spread around evenly by a sterile spreading tool. Like the _____, cells are pushed onto separate areas on the surface so that they can form individual colonies.
The dimensions of macroscopic organisms are usually given in _____ and _____, those of microorganisms fall within the range of millimeters to _____ to _____.
centimeters and meters
micrometers to nanometers
The size range of most microbes extends from the smallest bacteria, measuring around ___, to protozoa and algae that measure ___ to ___ and are visible with the naked eye.
3 to 4 millimeters
Viruses, which can infect all organisms including microbes, measure between ___ and ___, and some of them are thus not much bigger than large molecules, whereas others are just a tad larger than the smallest bacteria.
20 nanometers to 800 nanometers
The objective lens forms the initial image of the specimen, called the ___.
When the real image is projected up through the microscope body to the plane of the eyepiece, the ocular lens forma a second image, the ___.
The virtual image is the one that will be received by the ___ and converted to a retinal and visual image.
The magnifying power of the objective lens usually ranges from __x to ___x, and the power of the ocular lens is usually __x.
4x to 100x
The total power of magnification of the final image formed by the combined lenses is a product of the separate powers of the two lenses: ____ x ___ = total magnification
objective x ocular
Depending on the power of the ocular, the total magnification of standard light microscope can vary from ___x with the lowest power objective (scanning objective) to ____x with the highest power objective (the oil immersion objective)
40 x with the scanning objective
1000x with the oil immersion objective
The ___ or ____ is the capacity of an optical system to distinguish or separate two adjacent objects or points from one another..
resolution or resolving power
The oil immersion lens uses oil to capture some of the light that would otherwise be lost to scatter. Reducing this scatter increases the ___.
The oil immersion lens can resolve any cell or cell part as long as it is at least ____ in diameter, and it can resolve two adjacent objects as long as they are at least ___ apart.
2 um (micrometer)
In general, organisms that are ___ um or more in diameter are readily seen. This includes fungi and protozoa, and some of their ____, and most ___.
A few bacteria and most __ are far too small to be resolved by the optical microscope and require _____.
The factor that most limits the clarity of a microscope's image is its ___. Even if a light microscope were designed to magnify several thousand times, its ____ power could not be increased and the image it produced would simply be enlarged and fuzzy.
The degree of ____ from its surrounding is the thirds quality of a good microscope.
The contrast is measured by quality called the ____.
The refractive index refers to the degree of ____ that light undergoes as it passes from one medium, such as water or glass, to another medium, such as a bacterial cell.
The higher the difference in refractive indexes (the more bending of light), the ____ the contrast that is registered by the microscope and the eye.
Because too much light can ____ contrast and burn out the image, an adjustable iris diaphragm on most microscopes controls the amount of light entering the condenser.
The lack of contrast in cell components is compensated for by using special lenses (the phase-contrast microscope) and by adding ___.
Optical microscopes that use visible light can be described by the nature of their ___, meaning the circular area viewed through the ocular lens.
There are four types of visible-light microscopes: bright-field, dark-field, ____, and ____.
phase-contrast and interference
A fifth type of optical microscope, the ____ microscope, uses ultraviolet radiation as the illuminating source, another the ___ microscope, uses a laser beam.
The manner in which a slide specimen, or mount, is prepared depends upon the ____ of the specimen, either in a living or preserved state; the ___ of the examiner, whether to observe overall structure, identify or see movement; and the ___ of microscopy available, whether it is bright-field, dark-field, phase-contrast, or fluoresecence.
Live samples of microorganisms are placed in ___ mounts or in hanging drop mounts so that they can be observed as near to their natural state as possible.
The live sample cells are suspended in suitable fluid (water, broth, saline) that temporarily maintains ____ and provides space and a medium for locomotion.
A wet mount consists of a ____ of the culture placed on a slide and overlaid with a coverslip.
drop or two
The hanging drop preparation is made with a special concave (depression) slide, ______, and a coverslip with which a tiny drop of sample is suspended.
a vaseline adhesive or sealent
These wet short term mounts provide a true assessment of the size, shape, arrangement, color, and ____ of cells.
If you need to visualize greater cellular detail, you will have to use phase-contrast or _____ microscopy with live samples.
A more permanent mount for long-term study can be obtained by preparing ____, stained specimens.
The smear technique, developed by ____ more than 100 years ago, consists of spreading a thin film made from a liquid suspension of cells on a slide and _____ it.
Once a slide has been air-dried, the smear is usually ___ gently by a process called _____ that simultaneously kills the specimen and secures it to the slide.
Like images on undeveloped photographic film, the unstained cells of a fixed smear are quite indistinct, no matter how great the ___ or how fine the ____ power of the microscope.
The process of "developing" a smear to create contrast and make inconspicuous features stand out requires ____.
____ is any procedure that applies colored chemicals called dyes to specimens.
____ impart a color to cells or cell parts by becoming affixed to them through a chemical reaction.
Dyes can be classified as basic (cationic) dyes, which have a ____, or acidic (anionic) dyes, which have a _____.
Because chemicals of opposite charge are attracted to each other, cell parts that are negatively charged will attract ___ dyes, and those that are positively charged will attract ____ dyes.
Many cells, especially those of bacteria, have numerous ___ substances on their surfaces and thus stain more readily with ____.
negatively charged acidic
Acidic dyes on tend to be repelled by cell, so they are good for ___.
safranin malachite green
Two basic types of staining techniques are used depending upon how a dye reacts with the ____.
Most procedures involve a ___ stain, in which the dye actually sticks to the specimen and gives it color.
A ____ stain when dyed does not stick to the specimen but settles some distance from its outer boundary, forming a silhouette.
____ and India ink are the dyes most commonly used for negative staining. The cells themselves do not stain, the dyes are negatively charged and are repelled by the negatively charged surface of the cells.
The value of negative staining is its relative simplicity and the reduced ___ or ____ of cells, as the smear is not heat fixed.
shrinkage or distortion
Negative staining is also used to accentuate the ____ that surrounds certain bacteria.
Two basic types of staining
positive and negative
Positive staining methods are classified as ___, ____, or special.
____ stains require only a single dye and an uncomplicated procedure.
____ stains use two differently colored dyes, called the ___ and the ____ to distinguish between cell types and parts.
Simple stains cause all cells in a smear to appear more or less the same color, regardless of ____, but they can still reveal bacterial characteristics such as shape, size, and ______.
A satisfactory differential stain uses differently colored dyes to clearly ____ two cell types or cell parts.
Common combinations for differential stains are red and ___, red and __, or pink and ____.
red and purple
red and green
pink and blue
Typical examples of differential stains include Gram, ____, and endospore stains.
Some staining techniques (endospore, capsule) which are differential also are considered in the ____ category.
The ___ stain is one type of differential stain that can help to identify bacterial species and guide ____.
In 1884, ____ discovered a staining technique that could be used to make bacteria in infectious specimens more visible.
Hans Christian Gram
Gram's technique consisted of timed, sequential applications of crystal violet (_____), Gram's iodine (_________), an alcohol rinse (________), and a contrasting counterstain.
the primary dye
Using the gram stain technique, bacteria that stain purple are called _____, and those that stain red/pink are called ____.
The different results in the Gram stain are due to differences in the structure of the cell wall and how it reacts to the series of ____ applied to the cells.
The ___ method remains the universal basis for bacterial classification and identification.
The Gram stain is practical in aiding diagnosing infection and in guiding ____.
The Gram stain remains an important first tool in ___.
The ___ stain differentiates acid-fast bacteria (pink) from non acid-fast bacteria (blue).
The ____ stain originated as a specific method to detect Mycobacterium tuberculosis in specimens.
The acid-fast stain was originated because some bacterial cells have a particularly impervious outer wall that ____ to the dye even when washed with a solution containing acid or acid alcohol.
The acid-fast stain is performed when a ________ result is seen in a specimen.
The ___ stain or ____ is similar to the acid-fast method in that dye is forced by heat into resistant bodies called _____.
endospore or spore stain
The endospore stain is designed to distinguish between endospores and ____.
the cells they come from also called vegetative cells
In medical microbiology are the gram-positive ____ members of the genus Bacillus (the cause of anthrax) and Clostridium (the cause of botulism and tetanus).
___ stains are used to emphasize certain cell parts that are not revealed by conventional staining methods.
_____ staining is a method of observing the microbial capsule, an unstructured protective layer surrounding the cells of some bacteria and fungi.
The capsule does not react with most stains, it is often negatively stained with ___, or it may be demonstrated by special positive stains.
The fact that not all microbes exhibit capsules is a useful feature for identifying _____.
Cryptococcus, causes a serious form of fungal meningitis in AIDS patients and this bacteria does not have a ____.
_____ staining is a method of revealing fagella, the tiny, slender filaments used by bacteria for locomotion.
Because the width of bacterial flagella lies beyond the ____ of the light microscope, in order to be seen, they must be enlarged by depositing a coating on the outside of the filament and then staining it.
The presence of flagella as well as the number and ____ on a cell are useful for identification of the bacteria.
____ cultures are defined as containing two or more identifiable species of microorganisms.
_____ is a designation given to cultures when unwanted microbes are present. These intruders have been introduced to the specimen through poor collection, handling, or ____.
Urine specimens are one of the few specimens collected by patients themselves and may become _____ easily due to poor collection technique.
The papanicolaou test (commonly referred to as a (_______) is a test used to screen for precancerous and cancerous conditions occurring in the female endocervical canal.
A pap smear may also detect some vaginal and uterine infections caused by bacteria, fungi, or ____.
The Papanicolaou test was developed by Dr. George Papanicolaou in 1942 and is still widely ___.
During a Pap smear, cells are collected from the cervical os (entrance to the uterus) using a swab, brush or ___.