Degradation and recovery of microbial strains.

Degradation of the species With the extension of the shelf life of the species or the multiple transfer of the species, the excellent genetic characteristics of the species themselves may be continued or may mutate.
variants have positive (spontaneous mutation) and negative variation, where negative variation is the deterioration of the strain's productive symptoms or the loss of some genetic markers are called the degradation of the strain.
in production practice, however, it is necessary to distinguish between the morphological and physiological variations and the degradation of strains due to changes in culture conditions.
because the production performance of good strains is closely related to fermentation process conditions.
If the culture conditions change, such as the lack of certain elements in the medium, it will lead to a decrease in the number of spores produced, will also cause changes in spore color, temperature, pH changes will also cause fermentation yield fluctuations.
all of this, as long as conditions return to normal, the original properties of the species can return to normal, so these causes of species changes can not be called species degradation.
Common bacteria degradation phenomenon, the most easily detected is the fall morphology, cell morphology and physiology and other aspects of changes, such as changes in the color of the fall, the appearance of malformed cells, etc. ; After the production of "bare" phenomenon, resulting in the production of spores inoculation difficulties, as well as the metabolic activities of the species, the production capacity of metabolites or its parasitic capacity to the host significantly decreased, such as the decline of the ability to carbasin glycerin, the reduction of antimicrobial fermentation units, the decline of the starch enzyme production capacity of herb.
all of this is detrimental to fermentation production.
, in order for the good character of the bacteria to last, it is necessary to do a good job in the recovery of the bacteria.
that is, thoroughbred separation and performance determination are carried out on a regular basis before the excellent characteristics of each strain are degraded.
the main cause of the degradation of these strains is the negative mutation of the gene in question.
when a negative mutation occurs in the gene that controls production, it causes a decrease in yield, and when a negative mutation occurs in the gene that controls spore production, the spore production performance of the species decreases.
generally speaking, the degradation of bacteria is a gradual evolution from quantity to quality.
At the beginning, only individual cells in the group have negative mutations, when not timely detection and use effective measures and the transfer of species, will cause the proportion of negative mutant individuals in the group gradually increased, and finally dominant, so that the whole group showed serious degradation.
Therefore, the performance of the mutation in quantity depends on the transmission, that is, the strain is under certain conditions, the group multiplys many times, can make the degenerative cells gradually dominant in the number, so the degenerative character of the performance is more obvious, gradually become a degraded strain.
At the same time, the frequency of mutation is relatively low for a particular gene of a strain, so it is not easy for individuals in the group to have mutations in production performance, but in the case of a cell that is often in a state of vigorous growth, the risk of mutation is much greater than that of cells in hibernation, so the metabolic level of cells is closely related to gene mutations, and efforts should be made to control the cell storage environment, so that cells are dormant, thereby reducing the degradation of bacteria.
Reasonable measures to prevent degradation when breeding and breeding the cells should use monocytes, avoid the use of multi-nucleal cells, reasonable selection of mutagenic agent types and doses or increase mutation points to reduce separation response, after mutagenic treatment to carry out adequate post-culture and separation purification, to ensure the preservation of pure bacteria.
these can effectively prevent the degradation of strains.
the selection of suitable culture, it has been found that the cultivation of "5406" anti-biobacteria - fine yellow chain mold can prevent its degradation with the old root juice culture.
In the culture medium of erythromycin-vine erythromycin, when adding substances such as molasses, tianmentin, glutamine, 5-nucleotides or glycol, it also has the effect of preventing the degradation of bacteria.
There are also selected relatively poor nutrients of the medium as a seed preservation medium, such as the medium appropriate restrictions easy to use of sugar source glucose, etc. , because the mutation is mostly produced through the growth and reproduction of strains, when the medium is rich in nutrients, strains will be in a state of vigorous growth, higher metabolic levels, providing good conditions for variation, greatly improving the rate of degradation of strains.
to create good culture conditions In production practice, creating and discovering a condition suitable for the growth of the original species can prevent the degradation of bacteria, such as low temperature, drying, hypoxia and so on.
in perched on the soil 3. In the culture of 942, measures to change the culture temperature (from 20-30 degrees C to 33-34 degrees C) were used to prevent the degradation of its spore production capacity.
control the number of transmissions due to the existence of spontaneous mutations in microorganisms, and mutations are occurring in the reproductive process and manifest.
, we should try to avoid unnecessary transfer and transmission, to reduce the necessary transmission to a minimum, in order to reduce the risk of spontaneous bursts.
the number of transmissions, the higher the chance of mutation, and therefore the greater the chance of germ degradation.
this requires that the number of transfers of strains must be strictly controlled, both in the laboratory and in production practice, and that appropriate time intervals for the transfer of species should be established according to the different methods of species preservation.
such as slope preservation and other preservation methods (vacuum freeze-dried preservation, sand pipe, liquid nitrogen preservation, etc.) to extend the shelf life of the species.
Using different types of cells for transfer of species in some microorganisms, such as line bacteria and mold, because the cells of their bacteria often contain several nuclei or even foreign nucleosomes, so the use of mycelium inoculation will appear incomplete and declining, and spores are generally monocyte, with it when inoculated, there is no such phenomenon.
Some people have found in practice that nest-building craylomy is easy to degenerate if passed down by spores, while the use of cystic spores to transfer the species is not easy to degrade, and some people use sterilized cotton cysts lightly contaminated with "5406" spores for slope transfer, because of the avoidance of the access of mycelium, thus achieving the effect of preventing degradation.
the use of effective species preservation methods for industrial production of some microbial strains, the main characteristics are quantitative characteristics, and these characteristics are the most easily degraded.
, it is necessary to study and develop more effective methods of species preservation to prevent species degradation.
The rehabilitation of the compound degenerative strains of the degenerative species can be achieved through such methods as thoroughbred separation and performance determination, one of which is to identify a small number of individuals who have not yet degenerated from the population of the degenerative species in order to achieve the original typical characteristics of the restored species.
the other is to carry out regular and conscious determination of thoroughbred separation and production performance before the production performance of the species has not deteriorated, in order to achieve a gradual improvement in the production performance of the species.
so this is actually a job of constantly selecting species from production using spontaneous mutations.
the following measures for the recovery of specific strains: pure-bred separation using flat-line separation method, diluted flat-panel method or coating method can be.
isolated single cells that still maintained the original typical good character, and restored the typical fine characteristics of the original strain through expanded culture, it would be better if performance measurement could be carried out.
can also be isolated using a microscope manipulator to separate well-growing single cells or single spores and culture them to restore the original strain."
the degenerative strains of resusced parasitic microorganisms carried out by the host can be inoculated into the corresponding parasite to enhance the vitality of the strains.
combined with resuscing the degenerative strain can also be compounded with high doses of UV radiation and low doses of DTG combined treatment.
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