“Aseptic” means free from contamination caused by anymicroorganism that is not of interest to the scientist. Aseptic technique meansusing practices and procedures to prevent contamination from microorganisms,including the use of sterile media and equipment, as well as proper handlingprocedure. Aseptic technique is used in microbiology because it is essential foridentification of a microbe; in order to study an organism, it must first beisolated. Media, or singular medium, is a broth-like liquid or gel-likesolid designed to support the growth and/or selection of cells. Most commonly,agar petri plates or tubes of liquid broth are used. Specialized media aresometimes required for microorganism and cell culture growth.
Media is used inmicrobiology to grow enough cells for characterization or experimentation. Mediacan also be utilized, such as in the streak-plate method, to obtain purecultures. Media are used to make microbial cultures, which are used todetermine the type of organism, its abundance in a sample, and for selective ordifferential growth.
If media is not kept sterile, microorganisms other thanthe microbe of interest can be introduced; if aseptic technique is notmaintained, there is no guarantee that the culture/colonies grown are from thespecies of interest. Good scientific method requires that experiments should bedesigned to minimize possible errors, especially through the use of appropriatecontrols, such as aseptic technique to isolate the independent variable. The lid of a petri dish or culture tube should never be laidon the table or benchtop when inoculating because contamination may beintroduced to the culture. The bottom of a petri dish should be labeled, rather thanthe lid; lids can accidentally be switched.
Labelling on the bottom ensuresthat the written information stays with the intended culture, even if the lidgets accidentally exchanged with another plate. Petri dishes are incubated in an inverted position toprevent condensation that can disturb a culture, and to lessen the risk ofcontamination from airborne particles settling on them. An inoculating loop is an instrument used to transfer bacteriafrom one medium to another. Visible bacterial growth in a culture tube is referred to asa _____culture______. A colony is a visible, discrete clump of bacteria growing onthe surface of solid media.
Each individual colony represents the descendantsof a single cell. Colony morphology is a method that scientists use todescribe the characteristics of an individual colony of bacteria growing onagar in a petri dish; it can be used to help to identify them. Colonies aredescribed according to size, shape, texture, opacity, elevation, pigmentation,effect on growth medium, etc.