Expression in microorganisms

As depicted in Fig. 8.9 [5], plant alkaloid genes can be functionally expressed in microorganisms to produce either single biotransformation steps or short biosynthetic pathways. 

Screening of enzymes expressed in microorganisms, which are found in the environment and cultivated in laboratory, has the merit of finding novel enzymes because the method does not use the sequence information of already-known enzymes. However, an enzyme cannot be found if the microorganism cannot be cultured under laboratory cultivation conditions, or the microorganism does not express the enzyme under certain laboratory cultivation conditions. 

Enzymes expressed in microorganisms found in the environment and cultivated in the laboratory... 

Aquaporins are central players in mammalian physiology, but are also important in microorganisms and plants. The number of AQPs in plants is quite high angiosperms species, for example, express approximately 35 different AQPs divided into four families on the basis of their sequence. Moreover, plant AQPs might be considered multifunctional channels for their different transport properties. 

Iron homeostasis in mammalian cells is regulated by balancing iron uptake with intracellular storage and utilization. As we will see, this is largely achieved at the level of protein synthesis (translation of mRNA into protein) rather than at the level of transcription (mRNA synthesis), as was the case in microorganisms. This is certainly not unrelated to the fact that not only do microbial cells have a much shorter division time than mammalian cells, but that one consequence of this is that the half-life of microbial mRNAs is very much shorter (typically minutes rather than the hours or often days that we find with mammals). This makes it much easier to control levels of protein expression by changing the rate of specific mRNA synthesis by the use of inducers and repressors. So how do mammalian cells... 

Resistance of pathogenic microorganisms to beta-lactam antibiotics can result from one or a few of the mechanisms listed below inability of the drug to directly find an active site a change in PBP function, which is expressed in the reduction of affinity to the drag or inactivation of the drug by bacterial enzymes. 

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