MICR 2123 Lecture Notes - Lecture 8: Quorum Sensing, Signal Transduction, Sigma Factor
Document Summary
All cells need to monitor two environments, the intracellular (their cytoplasm) and the extracellular (their environment) Intracellularly, the concentrations of micromolecules, macromolecules, and required growth factors must be enough to support growth. Cells must achieve a balance between biosynthesis and/or import, and catabolism. Cells also need to know whether conditions outside the cell are hazardous, or whether there is pleny of food or not so much food in the surroundings. This is called sensing the environment: intracellular control of gene expression. A bacterial genome encodes thousands of different proteins needed to handle many types of environmental contingencies. To compete successfully with others, the microbe will not waste energy making unneeded proteins. It uses elegant mechanisms to control gene expression at various levels: dna level, transcription, post-transcription (mrna, translation, post-translation (protein, controlling gene expression at the dna level. Microbes can program a mutation of dna so as to activate or disable a particular gene.