"Microorganisms Everywhere" PPT

Hunan Education Edition fifth grade science volume 2, microorganisms everywhere PPT courseware

Part One: Microorganisms

1. Definition of microorganisms

What are microorganisms?

In addition to common animals and plants in nature, there is also a very complex group of organisms with tiny individuals. They are small in size and have a certain morphological structure. The structure is simple and invisible to the naked eye. They must be magnified thousands or even tens of thousands of times using a microscope to see them. Tiny organisms that can grow, reproduce and undergo genetic variation in a suitable environment are called microorganisms.

2. Classification of microorganisms

According to the differences in morphology, structure and biological properties of microorganisms, they can be divided into bacteria, fungi (including molds and yeasts), and viruses.

Microorganisms everywhere PPT, part 2: bacteria

Definition of bacteria

The definition of bacteria: It is a type of prokaryotic microorganism that is cellular, thin and short, has a simple structure, has a tough cell wall, reproduces by second-class division, and is highly aquatic.

Bacterial morphology

Bacteria are very small individuals, usually measured in microns (μm, 1μm=10-3mm). Most bacteria are about 1-5μm long and 0.2-1.0μm wide. Under certain conditions, bacteria have a relatively stable basic form. According to different shapes, bacteria can be divided into three categories: Spiral bacteria, cocci, and bacilli.

Fungi – an overview

Fungi are widely distributed and come in many varieties, with more than 100,000 species. Most of them are harmless to humans, while some are beneficial to humans.

Fungi are eukaryotic cell-type microorganisms. Their main feature is that they have a complete nucleus (i.e., a nuclear membrane and a nucleolus) in the cell. The nucleus is composed of DNA and protein and forms several chromosomes. However, fungi have no chlorophyll and can be heterotrophic. In life, most are saprophytic, and a few are parasitic or symbiotic. Fungi include molds and yeasts. Molds account for the majority of fungi, and yeasts are single-celled eukaryotic microorganisms without true mycelium.

fungal culture

Fungi do not have high nutritional requirements, and the temperature for cultivating fungi is 22 to 28°C. However, the optimal growth temperature for some deeply infected fungi is 37°C. The optimal pH is: pH4.0~6.0.

Ubiquitous Microorganisms PPT, Part 3: Viruses

Viruses – size and shape

Viruses are a type of non-cellular microorganisms that are very small in size, simple in structure, contain one type of nucleic acid (DNA or RNA), and must grow and reproduce within living cells. A substance between life and non-life, a genome composed of one or more nucleic acid molecules, with a protective shell of protein or lipoprotein, so a virus is regarded as a "package of genes". Not sensitive to antibiotics but sensitive to interferon.

The largest viruses such as vaccinia virus are 330nm × 230nm × 100nm and can be seen under an optical microscope, while small viruses such as poliovirus are only 27nm in size. The size of most viruses is around 1050nm and can only be seen under an electron microscope. You can only see it by magnifying hundreds of thousands of times. Can pass through sterilizing filter.

Microorganisms everywhere PPT, Part 4: Sterilization and disinfection

Sterilization and Disinfection – Concepts

Sterilization: The use of physical or chemical methods to kill all microorganisms on objects or in the medium, including all pathogenic and non-pathogenic microorganisms and bacterial spores, is called sterilization. Sterilized items are sterile.

Disinfection: Chemical or physical methods to kill non-spore pathogenic microorganisms on objects or in media are called disinfection to prevent the spread of germs.

Bacteriostasis: A method of inhibiting the growth and reproduction of bacteria inside or outside the human body. Commonly used bacteriostatic agents are various antibiotics.

Anticorrosion: It is to prevent the growth and reproduction of microorganisms to prevent items from spoiling, also known as bacteriostasis.

Sterility: means it does not contain viable bacteria. The aseptic operation technique of microbial testing is to operate under specific conditions to strictly prevent viable bacteria from invading the experimental materials. The utensils and materials used in aseptic operations must be sterilized in advance.

Microorganisms everywhere PPT, part 5: thinking

think:

1. What problems did the winery encounter?

Answer: The fragrant and fragrant wine suddenly turned sour.

2. What causes wine to go bad?

Answer: It is the result of a tiny gray-white rod-shaped organism - Lactobacillus.

3. How did Pasteur solve this problem?

Answer: Warm the wine to 55°C to kill the lactobacilli in the wine.

Microorganisms everywhere PPT, Part 6: Physical methods commonly used for sterilization and disinfection

Physical methods commonly used for sterilization and disinfection

Thermal sterilization method:

Heat can break the DNA, an important component of microorganisms, disintegrate ribosomes, irreversibly denature proteins and enzymes, and destroy membrane structures, leading to the death of microorganisms.

Ultraviolet sterilization method:

Ultraviolet light with a wavelength of 200-300nm has a bactericidal effect, and the wavelength of 260-280nm has the strongest bactericidal effect. Ultraviolet light can cause a variety of damages to DNA. The main reason is that nucleic acid absorbs ultraviolet light and causes one or two strands of DNA to move up between adjacent thymines. Dimers (TT) are formed, thereby interfering with DNA replication, which can lead to mutations in mild cases and death in severe cases. Ultraviolet sterilization is strong and stable, but its penetration is poor. Even thin glass can filter out most of it. Therefore, ultraviolet rays are only suitable for disinfecting indoor air and object surfaces.

Drying and low-temperature antibacterial method:

The propagules of some bacteria will die quickly when dried, but the spores are resistant to desiccation. For example, the spores of Bacillus anthracis can resist desiccation for more than 20 years. Drying is often used to preserve food. Low temperature can slow down bacterial metabolism.

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"Microorganisms Everywhere" PPT:

Hunan Education Edition fifth grade science volume 2, microorganisms are everywhere PPT, the first part content: deterioration phenomenon Food will be ( ) if left for a period of time. Food deterioration is a common phenomenon in our lives. Add the cooled rice to three disposable cups, which one will spoil first:..