What conditions do bacteria and fungi need to survive?

Both bacteria and fungi are harmful to human health. They grow very quickly and have strong reproduction abilities. Generally, they need to survive in humid or wet places, especially indoors or on clothing. You need to pay attention to your own cleanliness and keep the indoor environment dry.

What conditions do bacteria and fungi need to survive?

Bacteria and fungi require water, carbon source, nitrogen source and inorganic salts to survive. The specific carbon and nitrogen sources of bacteria vary depending on whether they are autotrophic or heterotrophic. Autotrophic bacteria can usually convert inorganic carbon into organic carbon, which usually requires exogenous energy, such as light energy or chemical energy (photoautotrophy, chemoautotrophy); heterotrophic bacteria absorb energy from organic carbon sources, such as carbohydrates, ethanol, acetic acid, etc., and may or may not use inorganic nitrogen sources; heterotrophic bacteria can also be divided into aerobic, facultative aerobic or anaerobic, depending on whether the organic carbon source is oxidized through oxygen oxidation or other oxidation pathways when converting energy. Fungi are basically heterotrophic, and autotrophic eukaryotic single-cell organisms are commonly single-cell algae; the carbon source required for growth is usually carbohydrates, and the nitrogen source is usually amino acids or proteins; some fungi can perform anaerobic fermentation, but most are aerobic or facultative aerobic types; many fungi grow slower than bacteria, but fungi are more resistant to high salt than bacteria and are more suitable for growing in a wider temperature range, which is why pickled foods or foods in the refrigerator are not easy to spoil but can still mold over time.

Conditions for bacterial growth and reproduction

The growth and reproduction of bacteria requires suitable environmental conditions. Different types of bacteria have different growth and reproduction conditions, and some types require special environmental conditions. But its basic conditions include nutrition, pH, temperature, gas and other aspects.

1. Nutrients: When bacteria are artificially cultured outside the body, their nutritional needs must be met according to the tropism of the bacteria.

2. Acidity and alkalinity: The most suitable acidity and alkalinity for most pathogens is pH 7.2~7.6. At this pH, the bacterial enzyme activity is strong and the growth and reproduction are vigorous. Some bacteria, such as Vibrio cholerae, grow best under alkaline conditions of pH 8.4-9.2, and Mycobacterium tuberculosis grows best under pH 6.5-6.8. During bacterial metabolism, sugars are broken down to produce acid, which lowers the pH and is not conducive to bacterial growth.

3. Temperature: Different types of bacteria have different temperature requirements. The optimum growth temperature for most pathogens is 37°C, so a 37°C constant temperature incubator is often used in laboratories to culture bacteria. Some bacteria, such as Yersinia pestis, grow best at 28-30°C. Thermophiles can grow at 50~60℃, while marine bacteria are cryophiles and can grow at 0~30℃.

4. Gas: The gases needed for bacteria to grow and reproduce are oxygen and carbon dioxide.

According to the bacteria's need for oxygen, they can be divided into three categories: ① Obligate aerobic bacteria: bacteria that have a complete respiratory enzyme system, require molecular oxygen as a hydrogen acceptor to complete aerobic respiration, and must grow in an aerobic environment, such as Mycobacterium tuberculosis. Some bacteria grow well under low oxygen pressure (5%~6%), and high oxygen pressure (10%) has an inhibitory effect on them, which are called microaerobic bacteria, such as Campylobacter jejuni. ② Obligate anaerobes: lack a complete respiratory enzyme system, use substances other than oxygen as hydrogen acceptors, and can only ferment in an anaerobic environment. When free oxygen exists, they cannot use molecular oxygen, and because of the lack of decomposition of toxic oxygen radicals, they cannot use oxygen.

The enzyme is also affected by the H2O produced in the aerobic environment.