must

Examples of must in the following topics:

• Industrial Production of Antibiotics

  • Oxygen concentration, temperature, pH, and nutrient levels must be optimal and are closely monitored and adjusted if necessary.
  • Once the process is complete, the antibiotic must be extracted and purified to a crystalline product.
  • Otherwise it must first be removed by ion exchange, adsorption, or chemical precipitation.
  • This process must be closely linked with retesting of antibiotic production and effectiveness.
  • Most antibiotics identified in such a screen are already known and must therefore be disregarded.

• Koch's Postulates

  • The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
  • The microorganism must be isolated from a diseased organism and grown in pure culture.
  • The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

• Antibiotics and Selective Toxicity

  • Most antibiotics identified in such a screen are already known and must therefore be disregarded.
  • The remainder must be tested for their selective toxicities and therapeutic activities, and the best candidates can be examined and possibly modified.
  • In antibacterial production, microorganisms must be isolated, cultured, and tested for growth inhibition of target organisms and for their selective toxicity.

• Filtration

  • Quite often when biological samples are processed, viruses must be removed or inactivated.
  • The filtration equipment and the filters may be purchased as pre-sterilized disposable units in sealed packaging, or must be sterilized by the user, generally by autoclaving at a temperature that does not damage the fragile filter membranes.

• Medical Importance of Viruses

  • Once inside a cell, all viruses must uncoat, replicate, and transcribe their genomes, and then repackage their genomes into viral progeny that are released from cells.
  • RNA viruses in particular must coordinate the switch between plus and minus strand synthesis and between replication and transcription while protecting their genomes from cellular nucleases.

• Synthesizing DNA

  • DNA) must be understood.
  • DNA must be synthesized to study genes, the sequence of genomes, and many other studies.

• Complementation

  • If not, the two alleles must be defective in the same gene.
  • If the combination of two haploid genomes containing different recessive mutations yields the wild type phenotype, then the mutations must be in different genes.

• Koch and Pure Culture

  • These postulates stated that to establish that an organism is the cause of a disease, it must be found in all cases of the disease examined.
  • Additionally, it must be absent in healthy organisms prepared and maintained in a pure culture capable of producing the original infection, even after several generations in culture retrievable from an inoculated animal and cultured again.

• Osmotic Pressure

  • Osmotic pressure is the pressure which must be applied to a solution to prevent the inward flow of water across a semipermeable membrane.

• Purification of Drinking Water

  • In order to purify drinking water from a source (such as a lake, river, reservoir or groundwater), the water must go through several steps to remove large particles and different types of pathogens .
  • Disinfection: Before water is considered potable, it must be disinfected to remove any pathogens that passed through the membrane filter.