What are the main factors that affect the growth of microorganisms

What are the four major factors that affect the growth of microorganisms?

The main factors that affect the growth and reproduction of bacteria include:

1. Temperature: The optimal growth temperature for most microorganisms is 25 37; In the optimal growth temperature range, the microbial growth rate accelerated with the increase of temperature. When the optimal growth temperature is exceeded, the growth rate of microorganisms decreases sharply due to irreversible damage to intracellular proteins and nucleic acids.

2. pH value: the optimal pH of each microorganism is different, and beyond the optimal pH, it affects the enzyme activity, cell membrane temperature, etc., thereby affecting the absorption of nutrients by microorganisms.

3. Oxygen: According to the demand for oxygen, microorganisms are divided into aerobic microorganisms (such as most bacteria, most fungi), anaerobic microorganisms (such as some streptococcus, some methanogens), and facultative anaerobic microorganisms (such as yeast).

4. Chemical environment: some chemicals and antagonistic bacteria can affect the growth and reproduction of microorganisms, physiological and biochemical processes.

1.Temperature. Value.

3.Oxygen and redox potential.

eh）4.Water activity and osmotic pressure.

5.Other environmental factors: the influence of microorganisms.

The main environmental factors that affect the growth of microorganisms are: temperature, pH, oxygen.

The microbial culture process (growth phase) is divided into four phases.

1. The adjustment period is also called the adaptation period and the hysteresis period. After microorganisms enter a new growth environment, it takes some time to adapt to the environment. During this period, the growth of microorganisms is slow, and the OD value (bacterial density value) is basically unchanged.

2. The logarithmic growth period is also called the logarithmic period. At this stage, because the microorganisms have adapted to the growth environment, coupled with the rich nutrients in the medium, the harmful substances discharged by the microorganisms are less, and the impact on the growth and reproduction of microorganisms is small, and the microorganisms enter the stage of rapid growth and mass reproduction. The OD value basically increases logarithmically.

3. The equilibrium period, also known as the stability period. After a period of rapid growth and reproduction, the consumption of nutrients in the medium is increasing, the harmful substances are gradually accumulating, the growth and reproduction of microorganisms are restricted, the bacteria die, the number of newly reproduced individuals and the number of deaths tend to be balanced, and the OD value tends to be stable.

4. Decay period. The nutrients in the medium are depleted, a large number of harmful substances are accumulated, the microorganisms can no longer grow and reproduce normally, and a large number of bacteria die. There was a significant decrease in OD values.

Lag Period: 1The growth rate constant is 0; 2.

The cell morphology becomes larger or grows, and many bacilli can grow into filaments; 3.The content of RNA in cells, especially RRNA, is increased, and the protoplasm is basophilic; 4.Anabolic is very active; 5.

Sensitive to adverse external conditions.

Exponential phase: the growth rate constant r is the largest and the shortest generation time; 2.Cells grow in balance; 3.The enzyme system is active and the metabolism is vigorous.

Stable period: The growth rate constant r is equal to 0.

Decay period: The rate of individual death is greater than the rate of rebirth, and the whole population shows a negative growth state.

1. The effect of temperature on the growth of microorganisms: the optimal growth temperature of most microorganisms is 25 37; In the optimal growth temperature range, the microbial growth rate accelerated with the increase of temperature. When the optimal growth temperature is exceeded, the growth rate of microorganisms decreases sharply due to irreversible damage to intracellular proteins and nucleic acids.

2. Effect of oxygen on the growth of microorganisms: According to the demand for oxygen, microorganisms are divided into aerobic microorganisms (such as most bacteria, most fungi), anaerobic microorganisms (such as some streptococcus, some methanogens), and facultative anaerobic microorganisms (such as yeast). 3. Effect of pH value on microbial growth:

The optimal pH of each microorganism is different, and beyond the optimal pH, it affects the enzyme activity, cell membrane temperature, etc., thereby affecting the absorption of nutrients by microorganisms.

Specifically, it affects enzyme activity, temperature changes affect the rate of enzymatic reactions, and ultimately affect cell synthesis. Affect the fluidity of the cell membrane, high temperature, high fluidity, conducive to the transport of substances, low temperature, reduced fluidity, is not conducive to the transport of substances, therefore, temperature changes affect the absorption of nutrients and the secretion of metabolites.

It affects the solubility of substances and has an effect on growth.

Microbial growth is influenced by a variety of factors, including self-factors and external environmental factors. Here are the common self-factors:

1.Nutrient requirements: Microorganisms need to absorb nutrients to maintain life activities, which are closely related to their metabolic pathways. Different types of microorganisms have different requirements for the type and proportion of nutrients required.

2.Metabolic pathways and rates: The metabolic pathways and rates of microorganisms affect the rate at which they grow and reproduce. For example, anaerobic microorganisms require specific metabolic pathways to produce ATP, while aerobic microorganisms can produce more ATP through oxidative phosphorylation.

3.Enzyme activity: Enzyme activity in microorganisms directly affects their metabolic pathways and energy production processes.

4.Antimicrobial resistance: Some microorganisms are resistant to antimicrobials, meaning they can still grow and multiply in the presence of antibiotics.

5.Gene expression: The regulatory mechanisms of microbial gene expression directly affect the rate at which they grow and reproduce, as well as their adaptation to the external environment.

Empirically, the amount of microbial growth depends on a number of factors:

1. Types of carbon sources;

2. The pathway of substrate alienation and catabolism;

3. The first of any cofactor of complex substrate (avoiding the need for anabolic improvement);

4. Absorb energy from other nutrients, especially nitrogen**;

5. Different efficiencies of ATP generation reactions;

6. Inhibition of the existence of the fifth, unfavorable ion equilibrium, or the forced additional demand for the medium component in the transport system;

7. The physiological characteristics of organisms, almost all microorganisms will change their growth status according to the external environment, and different metabolic processes (such as primary and secondary metabolism) will have a large amount of energy balance. Further influencing factors can be obtained in the medium in which the growth rate and nutritional status of cells are regulated.

8. Limit the type of substrate, carbon-restricted other pathways, such as how to grow more efficient with nitrogen-restrictive, in which excess catabolism will become a positive "waste" pathway. (However, they are useful for biotechnology);

9. Allowable growth rate: Once the cell growth rate slows down, the proportion of substrates used to maintain the cells increases, thus reducing the substrate access to other pathways. Because the last factor determines all the performance traits of microorganisms, one can be added;

10. The role of microbiology.

Temperature: The optimal growth temperature for most microorganisms is 25 degrees to 37 degrees; In the optimal growth temperature range, the growth rate of microorganisms accelerated with the increase of temperature. When the optimal growth temperature is exceeded, the growth rate of microorganisms decreases sharply due to irreversible damage to intracellular proteins and nucleic acids. pH:

The optimal pH of each micro-buried token is different, and beyond the optimal pH, it affects the enzyme activity, cell membrane temperature, etc., thereby affecting the absorption of nutrients by microorganisms. Oxygen: According to the demand for oxygen, microorganisms are divided into aerobic microorganisms, anaerobic microorganisms, and facultative anaerobic microorganisms.

Chemical environment: Some side-wheel chemicals and antagonistic bacteria can affect the growth and reproduction of microorganisms, physiological and biochemical processes.

a.Temperature. b.Water Lap Cave comma.

c.Oxygen. d.Ph.

Correct Answer: Temperature; Sell water in rotation; Oxygen. Ph.