Dilution plate method: soil sample dilution - shaking - gradient dilution - culture (pour the culture medium and spread it - coating method; pour the bacterial liquid into the agar medium and mix it - pouring method)

The plate streaking method (three-zone streaking) requires burning and sterilizing the first streak, and then drawing again, aiming to form a single colony. A single colony is called a pure colony.

Indirect separation method: measuring microorganisms, as well as physiological indicator methods and turbidimetric methods.

slow period Characteristics: The growth rate constant is zero, the bacteria are thick, the RNA content is increased, the metabolic activity is strong, and the resistance to adverse environments is reduced. Cause: The microorganism has just been inoculated onto the culture medium, and its metabolic system needs to adapt to the new environment and synthesize enzymes, coenzymes, and other metabolic intermediate metabolites, so the number of cells does not increase during this period.

Logarithmic period Characteristics: The fastest growth rate, vigorous metabolism, active enzyme system, the number of viable bacteria and the total number of bacteria are roughly close, and the chemical composition, morphology, and physical and chemical properties of the cells are basically the same. Cause: After the preparation of the adjustment period, sufficient material basis is provided for the growth of microorganisms during this period, and the external environment is also in the best state.

stable period Features: The number of viable bacteria remains relatively stable, the total number of bacteria reaches the highest level, the accumulation of cell metabolites reaches the highest peak, it is the harvest period of production, and Bacillus begins to form spores. Cause: The consumption of nutrients leads to imbalanced nutrient proportions, accumulation of harmful metabolites, unsuitable physical and chemical conditions such as PH value and EH value.

period of decline Characteristics: The death rate of bacteria is greater than the rate of new generation, the entire population experiences negative growth, cells begin to become deformed, and cell death occurs with autolysis. Cause: The main reason is that the external environment is becoming more and more unfavorable for continued growth, and the catabolism of cells is greater than anabolism, which in turn leads to the death of a large number of bacteria.

Lactic acid fermentation occurs in both animal microorganisms and plant alcoholic fermentation. When we run like crazy, we produce a lot of lactic acid, and a person's lactic acid tolerance determines how fast or slow they run. Lactic acid and pyruvate are converted into each other. Northeastern sauerkraut, Korean kimchi, spicy cabbage all have lactic acid bacteria. Acid-resistant and bile-resistant lactic acid bacteria. Fungi produce lactic acid and have lactate dehydrogenase, and some cancer cells can use lactic acid. If a person's lactate dehydrogenase is not good, lactic acid will not be degraded and lactic acidosis will occur. Analysis: Lactose is converted into lactic acid using β-galactosidase. E. coli in the intestine has this enzyme. This enzyme in humans is induced. In addition to inducible enzymes, there are also housekeeping genes - constitutive enzymes.

The growth curve is the logarithm of the amount of bacteria, because bacteria grow exponentially. The first step is to adapt to the environment - the lag phase, and then enter the logarithmic growth phase after adaptation (the bacterial growth cycle is the same, which is very rare, and there is a certain mechanism between bacteria to inform each other). Why does it enter the stable phase after the waiting formula? After 10 vaccinations and a delay period of 1 hour, 320 were detected. How long will it take? The number of bacteria does not increase during the delay period, and is reduced by 1 in the end.

Question: If we get a strain of lactic acid bacteria that can withstand oxygen and survive in the human body for a long time, what should we do if the company asks us to get this strain of bacteria, which involves the laws of growth and reproduction? Question: The boss asked at which point in the growth curve to harvest this bacteria? Answer: The point before the stationary period and after the logarithmic period. Question: The company wants to produce drugs or enzymes? Answer: It needs to be a point after the stable period and before the decline period.