Analysis of common causes of bacterial decline
Last Update: 2020-06-20
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Microbial fermentation technology channel: the reasons for the decline of the bacteria are two folds: first, the bacteria species is not properly preserved, and second, the conditions for the growth of the bacteria species are not met, or encounter adverse conditions, or lose some of the needs of the conditionsIn addition, new strains that have been induced to return to mutation, resulting in the loss of new characteristicsthe decline ofspecies will change all aspects of microbial individual and group characteristics, the most important of which is to reduce the production of the desired products, nutrient metabolism and growth and reproduction capacity, fermentation cycle extended, anti-adverse environmental conditions, such as reduced performanceThe degradation of the strains is different from the superficial and temporary changes caused by changes in environmental conditions during culture, but rather a genetic variation process from quantitative to qualitative change caused by the decline of individual and minority bacterial cellscontinuous transmission of strains is the direct cause of the decline of the bacteriaBecause the continuous transmission of bacteria often in a strong growth state, and each transmission of nutrition and the environment and other culture conditions are constantly changing, compared with the dormant bacteria, the rate of spontaneous mutation of cells is much higherTherefore, after the continuous transmission of strains, individuals with mutant genes gradually prevail in number, and degradation gradually appearsThe difference between the increase and cooling of the medium sterilization, the different storage time of the medium, the use of aging bacteria and polynucleic micro-transmission, etcare relatively easy to cause the decline of the bacteriaspecies preservation is mainly through the control of low temperature, drying, hypoxia and other conditions, so that microbial nutrition or sleep in an inactive state, maintain the minimum metabolic level, as far as possible to ensure vitality and no variationHowever, the preservation method of various species is not the same effect on preventing the variation of the strains, with poor conditions to protect the bacteria species, the bacteria are more prone to declineIn addition, improper preservation operation will also affect the preservation effect, and even lead to the mutation of bacteriabacteria's own mutation causes the bacteria to declineSpontaneous mutations and regenerative mutations of bacteria are the main causes of the decline of the bacteria themselvesMicrobial cells in each generation of mutation probability is generally 10-8 to 10-9, hidden in 0 to 4 degrees C when the probability of this mutation is smaller, but still can not rule out the possibility of bacterial declineFor example, if there is not sufficient supply of nutrients for nutrient-deficit strains, the bacteria will mutate and lose their existing properties the recovery mutation of the strains refers to the rehabilitation of the mutant strains due to the self-repair of the genetic composition, so that the original genetic barriers are lifted, the metabolic pathways change, thus restoring the original characteristics, showing the degradation of the excellent traits acquired in the original breeding process mutation does not completely cause differences in the genetic composition of the bacteria For the strains of mononucleic cells, there is only one chain of DNA in the double chain of the bacteria where the site mutation occurs, and the DNA chain of the mutant bacteria is copied, and the unaltered chain of the DNA is copied into the DNA chain of the original bacteria, resulting in the formation of impure colonies, which shows the decline of the bacteria after transplantation the same, for strains with more than two nuclear cells, if only one or a few nuclear mutations, will produce heteronuclear mycelium, impure hexaxaxax, will form different characteristics of mycelium, and once the characteristics of different mycelium advantage, will show the decline of the strain, and no longer have excellent characteristics if the colonies are not formed by a spore or a cell, when there is only one high-yielding mutation of spores or cells, after transplantation, the number of high-yielding strains is relatively small, showing a decline in the bacteria
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