Common Terms and Definition in Microbiology Laboratory

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aerosol – a spray of live microbes ejected from sputtering
brightfield microscope – a microscope which the general background or field of view is bright while dense specimens appear darker objects; used for stained materials
capsule – thick layer of substance found on the surface of some bacteria that inhibits phagocytosis by white blood cells
capsule stain – involves the process of negative staining the slide and staining the cytoplasm of the bacteria making the capsule only the colorless structure which appears as a light halo around the bacteria
carbol fuchsin – the primary stain used in acid fast staining
citrate test – detects species of bacteria that survive on citrate as its carbon source
coagulase – a bacterial enzyme which brings about the coagulation of blood or plasma and is produced by disease-causing forms of staphylococcus
colony – visible mass of microorganisms originating from a single mother cell
compound microscope – microscope with two magnifying lens
conclusion – logical judgment or analysis we make from our results
condenser – lens system in microscope whose function is to focus the light onto the specimen
conjugation – joining of two bacteria or unicellular organism for the transfer of genetic material by direct cell to cell contact or by bridge like connection called sex pilus
contamination – the presence of undesirable microorganism that accidentally gets into a culture
control group – the group in the experiment that does not receive treatment; used to compare how the experimental group do
controlled variable – the factors in the experiment that we control and keep the same
crystal violet – primary stain used in Gram staining
darkfield microscope – creates the effect of a negative image; field of view is dark while cells and other objects are lit up; used to observe live, motile cells
decolorizer – removes the primary stain from the gram-negative bacteria making it colorless
dependent variable – the variable being tested, observed, and measured
differential medium – a medium with diagnostic test built into it that changes color with different species of microbes
differential staining – procedure that will dye different kinds of bacteria in contrasting color
double blind – a type of experiment which neither the subjects nor the experimenters know which subjects are in the test and control groups
electron microscope – a microscope that uses beam of electron rather than beam of light to observe a specimen
endemic – when a disease prevalence is fairly stable in a location
epidemic – occurs when a disease is spreading rapidly in a particular population
ethyl alcohol – the decolorizer used in Gram staining
fluorescence – the ability of a substance to absorbed UV light and emit back the light as a visible color
Gram’s iodine – mordant used in Gram staining
HCG – is a hormone that prevents menstruation from occuring during pregnancy
Hfr cell – a bacterial cell with conjugative plasmid integrated into its chromosomal DNA
immunocompromised – means more susceptible to infections
independent variable – also called the experimental variable; anything that can be changed or manipulated
lysozyme – an enzyme that dissolves the chemical bond between the NAG and NAM within the backbone of the peptidoglycan molecule in gram-positive bacteria
malachite green – primary stain in spore staining
methylene blue – counterstain used in acid fast staining
microbial hot spots – warm and moist areas where the number of microorganisms is usually the highest
minimum inhibitory concentration – lowest concentration of drug which prevent visible growth of bacteria
mordant – a substance which causes the primary stain to become more tightly bound to the cell
negative stain – a stain which involves staining the background of the slide
nosocomial infection – infectious disease acquired during hospitalization
nutrient agar – a general purpose medium that will support growth of many common bacteria
ocular lens – also called eyepiece; the top lenses of the microscope which you look through
ocular micrometer – also called the microscopic ruler inscribed into the eyepieces on the microscope
opsonin – an antibody which binds to foreign microbes making them susceptible to phagocytosis
pandemic – occurs when a disease is spreading globally or over one continent
parfocal – means when one lens is focused, the others are also focused
phase contrast microscope – a microscope that increases the contrast between cells or portions of cells that vary only slightly in density; used to observe unstained bacterial cells
pour plate – is made by inoculating melted agar with bacteria and then pouring the agar into an empty petri plate to harden, thus the microbes are distributed evenly throughout the agar; creates an evenly distributed lawn of bacteria to be use for phage typing
pseudopodia – extension of cytoplasm use for movement; also called false feet
pure culture – a medium growing with only one intended species of microorganism
refraction – the bending of light
resident or normal flora – microorganisms that live naturally and permanently in various areas of the human body
resolving power – defined as the closest distance two objects can be where you can still see them as separate objects
results – refers to the actual data that you collect such as the number of colonies
R-plasmid – is a plasmid in bacteria that contains the antibiotic resistant gene
Sabouraud agar – medium that are slightly acidic and have extra glucose; also used for fungal growth; used to check fungal spores in the air
safranin – the counter-stain used in Gram staining
scanning electron microscope – a microscope that reflects beam of electrons off the exterior of the specimen; produces 3D view of specimen’s surface
selective medium – a medium that only allows certain species of microbes to grow and inhibits others
simple microscope – microscope with single magnifying lens
simple staining – defined as a procedure that stains all cells with the same color
Snyder test – measures the amount of acid produced by normal flora in a medium containing sugar
sporadic – occurs when a disease is infrequent and in scattered location
stage – the platform below the objective lenses of a microscope used to hold the slide
stage micrometer – term typically referring to a slide that comes with a known scale on its surface
sterile – a term which means free of bacteria or living things
streak plate – is performed by spreading an inoculum of bacteria across the surface of an agar plate in such a way as to produce isolated colonies
Streptococcus mutans – oral bacteria involve with the development dental caries or tooth decay
super-infection – second infection with microbial agent that is resistant to the treatment used against the first infection
synthetic medium – medium made from scratch with every single ingredient defined and listed separately
thermal death point – minimum temperature required to kill a bacteria with a given amount of time
thermal death time – time required to kill a bacteria at a particular temperature
transduction – is the process by which foreign DNA is introduced into a cell by a virus or viral vector
transformation – is a process of horizontal gene transfer by which some bacteria take up foreign genetic material from the environment
transient flora – microbes that are temporary and can be removed by handwashing
transport medium – is a medium used to transport microbes from one place to another and limits the overgrowth of microbes

Sources:

Alderson, Gary D. Microbiology Experiments and Lab Techniques 14th Edition. Palomar College. Fountainhead Press. Accessed November 26, 2019.

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