Wild-type organisms

Forward mutation refers to mutation of the natural ( wild-type ) organism to a more stringent organism. By contrast, reverse (backward) mutation is the return of a mutant strain to the wild-type form, i.e. it is a heritable change in a previously mutated gene that restores the original function of that gene. 

The overall rate of desulfurization for enabling commercialization has to be greater than 1.2mmol/g dcw/h [1,12,13], The rates of desulfurization of model compounds such as DBT is usually higher than that achievable for real feedstocks such as diesel and other middle distillates. Thus, it is estimated that a more than 100-fold improvement in rates for removal of total sulfur (not just DBT) over wild-type organisms is necessary to achieve rates suitable for commercialization. 

Comparison of the relative amounts of pathway intermediates and final products in normal and mutant organisms containing a defective enzyme in the pathway. The precursor, intermediates, and final product of the pathway are labeled A, B-D, and E, respectively. The enzymes 1, 2, 3, and 4 are indicated by the numbers over the reaction arrows. A cross through the reaction arrow indicates a defective enzyme. In the wild-type organism with no defective enzymes (top),... 

In addition, NR is a very convenient genetic marker, that has the potential to be selected or counter-selected in many organisms, whether they be plants (Caboche Rouze, 1990 Nussaume et al., 1991) or microorganisms (Unkles et al., 1989). NR-deficient (NR-) mutants will not grow on nitrate, but unlike wild-type organisms will not be killed by chlorate, a nitrate analogue that is toxic when reduced by NR. 

MUTANT An organism that possesses an alteration in its DNA that makes its genetic function or structure different from that of a corresponding wild-type organism. 

PROTOTRQPH An organism able to carry out a given chemical synthesis a wild-type organism able to grow on minimal medium. (See also AUXOTROPH)... 

None of the carbon sources can be utilized by the wild-type organisms. 

Cellulases are found in fungi and bacteria. Of commercial interest are fungal enzymes from Aspergillus or Trichoderma and a few bacterial enzymes. They are either used as a multicomponent, which contain all enzyme types and are found in Trichoderma reesei (Hypocrea jecorina), or as a monocomponent enzyme product, which consists of only one of the three types of enzymes. The multicomponent enzyme preparations can be produced from a selected cellulose overproducing strain of the wild-type organism, whereas the monocomponent cellulases are mainly produced in recombinant production systems. 

Many mutant microorganisms are known to require, as a supplement to the medium in which they are grown, a substance that is synthesized by the corresponding wild-type organism (the normal strain). An example is the pyridoxine-requiring mutant of Neurospora sitophila reported by G. W. Beadle and E. L. Tatum in their first... 

The site of the metabolic block can be further ascertained by measurement of the appropriate enzyme activity. This will be absent or greatly decreased, compared with that in the wild type organism. Sometimes, serologically similar, but enzymically inactive protein is produced, i. e. the mutation has not prevented transcription and subsequent translation of a protein, but small changes (sometimes replacement of a single amino acid) have occurred which destroy catalytic activity. Such proteins are known at CRiM proteins (Cross Reacting Materia the i is added for pronunciation purposes). 

Class I products are deemed to have no new or unusual safety concerns, and are reviewed without special precautions. Class II products, however, involve the introduction of r-DNA constructions into live organisms and additional information is needed for full review. Issues include the competitiveness of the organism in the environment, its survivability and persistence, and whether it will transplant the wild-type organisms from the environment. The added genetic information must be well characterized, and the full nucleotide sequence may be requested. The fully documented identification of the entire insert from the foreign source is essential. Concerns for safety to humans and animals, and impact on the environment, must be addressed in an environmental assessment or environmental impact study to be evaluated by an ad hoc committee before live products can be considered for a limited field trial or licensing. 

Move the gene coding for an interesting enzyme from a wild-type organism to a high-yielding production strain (heterolog expression)... 

The stainless steel-made fermentation tanks are designed to allow easy cleaning and proper sterilization of the substrate. The sterilization of the substrate is performed in the tank by heating with direct injection of steam. Every step in the process is carefully designed to protect the cultures from contamination with foreign wild-type organisms, since the intrusion of such organisms would ruin the whole batch. 

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