Global challenges Study Guide

Aseptic techniques are a set of practices used when culturing microorganisms to prevent contamination from unwanted microbes and to ensure the safety of the experimenter. The goal is to create and maintain a sterile environment for the desired microorganisms, allowing them to grow without competition or interference from other bacteria, fungi, or viruses present in the air, on surfaces, or on skin. These techniques are crucial in microbiology for accurate scientific results, as contamination can lead to misleading data or experimental failure. For example, when transferring bacteria from a culture plate to a sterile broth, the inoculation loop must first be sterilised, usually by heating it in a flame until red hot. This kills any microorganisms on the loop. After cooling, the loop is used to pick up the desired bacteria. The neck of the culture vessel and the new sterile broth tube are also flamed just before and after opening and closing, respectively. This creates an upward current of air, preventing airborne contaminants from entering. The lid of the Petri dish or cap of the broth tube should be held downwards to minimise exposure to the air. Petri dishes are often sealed after inoculation to prevent airborne microorganisms from entering and to contain the cultured microbes, which is important for safety. Incubating cultures at appropriate temperatures, typically 25°C for school labs, ensures optimal growth of the desired organism while reducing the risk of culturing harmful human pathogens, which often thrive at higher body temperatures like 37°C.

Monoclonal antibodies are identical antibodies that have been produced from a single clone of B-lymphocytes. These antibodies can be manufactured in a laboratory to target specific antigens, which are unique molecules found on the surface of cells, such as pathogens or cancer cells. The process of creating monoclonal antibodies involves several key steps. First, an animal, typically a mouse, is injected with a specific antigen. This stimulates the mouse's immune system to produce B-lymphocytes that make antibodies against that antigen. These B-lymphocytes are then extracted from the mouse's spleen. However, B-lymphocytes do not divide indefinitely in culture. To overcome this, they are fused with myeloma cells, which are a type of cancer cell that can divide rapidly and indefinitely. The fusion of a B-lymphocyte and a myeloma cell creates a hybrid cell called a hybridoma. These hybridoma cells possess the desired characteristics: they can produce specific antibodies (from the B-lymphocyte) and they can multiply indefinitely (from the myeloma cell). The hybridoma cells are then screened to identify and select the ones that are producing the desired monoclonal antibody. Once identified, these specific hybridoma cells are cultured to produce large quantities of identical antibodies. These monoclonal antibodies have a wide range of applications, including disease diagnosis, imaging, and treatment, particularly in cancer therapy and autoimmune diseases, by specifically targeting disease-causing cells or molecules without harming healthy cells.