实验三－七 大分子物质的水解实验和IMVIC实验 一、教学要求 了解微生物一些生化反应的原理及其在微生物鉴 定中的应用。 二、简介 To identify bacteria, we must rely heavily on biochemical testing. The types of biochemical reactions each organism undergoes act as a "thumbprint" for its identification. This is based on the following chain of logic:
实验三－七 大分子物质的水解实验和IMVIC实验 一、教学要求 了解微生物一些生化反应的原理及其在微生物鉴 定中的应用。 二、简介 To identify bacteria, we must rely heavily on biochemical testing. The types of biochemical reactions each organism undergoes act as a "thumbprint" for its identification. This is based on the following chain of logic:
•Each different species of bacterium has a different molecule of DNA (i.e., DNA with a unique series of nucleotide bases). •Since DNA codes for protein synthesis, then different species of bacteria must, by way of their unique DNA, be able to synthesize different protein enzymes. •Enzymes catalyze all the various chemical reactions of which the organism is capable. This in turn means that different species of bacteria must carry out different and unique sets of biochemical reactions
•Each different species of bacterium has a different molecule of DNA (i.e., DNA with a unique series of nucleotide bases). •Since DNA codes for protein synthesis, then different species of bacteria must, by way of their unique DNA, be able to synthesize different protein enzymes. •Enzymes catalyze all the various chemical reactions of which the organism is capable. This in turn means that different species of bacteria must carry out different and unique sets of biochemical reactions
When identifying a suspected organism, you inoculate a series of differential media After incubation, you then observe each medium to see if specific end products of metabolism are present. This can be done by adding indicators to the medium that react specifically with the end product being tested, giving some form of visible reaction such as a color change. The results of these tests on the suspected microorganism are then compared to known results for that organism to confirm its identification
When identifying a suspected organism, you inoculate a series of differential media After incubation, you then observe each medium to see if specific end products of metabolism are present. This can be done by adding indicators to the medium that react specifically with the end product being tested, giving some form of visible reaction such as a color change. The results of these tests on the suspected microorganism are then compared to known results for that organism to confirm its identification
1、Macromolecules hydrolysis •Exoenzymes diastase（amylase）、protease、 lipase • endoenzymes • Starch hydrolysis Some bacteria are capable of using starch as a source of carbohydrate but in order to do this, they must first hydrolyze or break down the starch so it may enter the cell. The bacterium secretes an exoenzyme which hydrolyzes the starch by breaking the bonds between the glucose molecules. This enzyme is called a diastase （amylase）
1、Macromolecules hydrolysis •Exoenzymes diastase（amylase）、protease、 lipase • endoenzymes • Starch hydrolysis Some bacteria are capable of using starch as a source of carbohydrate but in order to do this, they must first hydrolyze or break down the starch so it may enter the cell. The bacterium secretes an exoenzyme which hydrolyzes the starch by breaking the bonds between the glucose molecules. This enzyme is called a diastase （amylase）
Starch hydrolysis
Starch hydrolysis
•protein hydrolysis Proteins are made up of various amino acids linked together in long chains by means of peptide bonds. Many bacteria can hydrolyze a variety of proteins into peptides (short chains of amino acids) and eventually into individual amino acids. They can then use these amino acids to synthesize their own proteins and other cellular molecules or to obtain energy. The hydrolysis of protein is termed proteolysis and the enzyme involved is called a protease
•protein hydrolysis Proteins are made up of various amino acids linked together in long chains by means of peptide bonds. Many bacteria can hydrolyze a variety of proteins into peptides (short chains of amino acids) and eventually into individual amino acids. They can then use these amino acids to synthesize their own proteins and other cellular molecules or to obtain energy. The hydrolysis of protein is termed proteolysis and the enzyme involved is called a protease
protein hydrolysis
protein hydrolysis
2、fermentation of carbohydrates Facultative anaerobic and anaerobic bacteria are capable of fermentation, an anaerobic process during which carbohydrates are broken down for energy production. A wide variety of carbohydrates may be fermented by various bacteria in order to obtain energy and the types of carbohydrates which are fermented by a specific organism can serve as a diagnostic tool for the identification of that organism. We can detect whether a specific carbohydrate is fermented by looking for common end products of fermentation. When carbohydrates are fermented as a result of bacterial enzymes, the following fermentation end products may be produced: • acid end products. • acid and gas end products
2、fermentation of carbohydrates Facultative anaerobic and anaerobic bacteria are capable of fermentation, an anaerobic process during which carbohydrates are broken down for energy production. A wide variety of carbohydrates may be fermented by various bacteria in order to obtain energy and the types of carbohydrates which are fermented by a specific organism can serve as a diagnostic tool for the identification of that organism. We can detect whether a specific carbohydrate is fermented by looking for common end products of fermentation. When carbohydrates are fermented as a result of bacterial enzymes, the following fermentation end products may be produced: • acid end products. • acid and gas end products
In order to test for these fermentation products, you inoculate and incubate tubes of media containing a single carbohydrate (such as lactose or maltose), a pH indicator (such as phenol red) and a durham tube (a small inverted tube to detect gas production). If the particular carbohydrate is fermented by the bacterium, acid end products will be produced which lowers the pH, causing the pH indicator to change color (phenol red turns yellow) .If gas is produced along with the acid, it collects in the durham tube as a gas bubble
In order to test for these fermentation products, you inoculate and incubate tubes of media containing a single carbohydrate (such as lactose or maltose), a pH indicator (such as phenol red) and a durham tube (a small inverted tube to detect gas production). If the particular carbohydrate is fermented by the bacterium, acid end products will be produced which lowers the pH, causing the pH indicator to change color (phenol red turns yellow) .If gas is produced along with the acid, it collects in the durham tube as a gas bubble
acid- acid- no acid- -no gas no gas -gas Durham Durham Durham tube tube tube