<P> A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions . Microbial cultures are foundational and basic diagnostic methods used extensively as a research tool in molecular biology . </P> <P> Microbial cultures are used to determine the type of organism, its abundance in the sample being tested, or both . It is one of the primary diagnostic methods of microbiology and used as a tool to determine the cause of infectious disease by letting the agent multiply in a predetermined medium . For example, a throat culture is taken by scraping the lining of tissue in the back of the throat and blotting the sample into a medium to be able to screen for harmful microorganisms, such as Streptococcus pyogenes, the causative agent of strep throat . Furthermore, the term culture is more generally used informally to refer to "selectively growing" a specific kind of microorganism in the lab . </P> <P> It is often essential to isolate a pure culture of microorganisms . A pure (or axenic) culture is a population of cells or multicellular organisms growing in the absence of other species or types . A pure culture may originate from a single cell or single organism, in which case the cells are genetic clones of one another . For the purpose of gelling the microbial culture, the medium of agarose gel (agar) is used . Agar is a gelatinous substance derived from seaweed . A cheap substitute for agar is guar gum, which can be used for the isolation and maintenance of thermophiles . </P> <P> There are several types of bacterial culture methods that are selected based on the agent being cultured and the downstream use . </P>

What is meant by the term pure culture