Eventually, the population is large enough to have an impact we can detect, such as formation of a physical structure. You might notice this as plaque on your teeth. It takes over a million bacteria to form a visible structure, but this can occur in only about eight hours when conditions are optimal for E.
Some microbes produce new cells asymmetrically. In this situation, one parent cell produces a single daughter cell by a process called budding. During budding the parent cell develops a small protrusion known as the bud.
The materials necessary to support a new cell are sent into the bud, which eventually splits from the parent cell to form a new daughter cell. The parent cell continues to make buds, but the budded daughter cells do not divide. Buds can remain connected in a chain or separate into individual cells Figure 4. Saccharomyces cerevisiae, a yeast used to make bread, is a budding yeast.
There are also multicellular microbes , like algae and the fungi that form molds. For these microbes, multiple cells work together to keep the organism alive. Each cell might perform slightly different functions for the organism. When a parent cell divides, each daughter cell begins to perform specific functions based on its surroundings. The entire organism grows as new cells form and take on new functions. This is similar to the way larger organisms, like animals, grow.
All types of microbial growth are heavily impacted by environmental conditions. One of the most critical factors for microbial growth is the availability of nutrients and energy. Microbes need carbohydrates, fats, proteins, metals, and vitamins to survive, just like animals. The process of using nutrients and converting them into cellular material requires energy. Every microbe has unique nutritional requirements depending on the types of molecules it is capable of making for itself.
Most microbes are fairly robust, meaning they can find a way to grow in a variety of nutritional conditions. Nonetheless, microbes grow more slowly when nutrients are limited. Temperature also impacts microbial growth. Most microbes grow optimally within a certain temperature range dictated by the ability of proteins within the cell to function.
In general, at low temperatures, microbes grow slower. At higher temperatures, microbes grow more quickly.
For instance, pathogens often grow best at normal body temperature, but slowly at cooler temperatures outside the body or when body temperature increases during a fever. Extremely high temperatures usually denature the components required for the cells to survive and are lethal for many microbes.
Nonetheless, a few exceptional microbes actually prefer to grow at very high temperatures or very low temperatures. These microbes, known as extremophiles , can grow near hydrothermal vents where the temperature is above boiling or surrounded by solid ice. Even when nutrients are available and the temperature is right, many other environmental factors can influence the growth of microbes. These include acidity, availability of water, and atmospheric pressure.
Each microbe prefers a range of properties for multiple features of the environment. Overall, microbes typically grow best at a specific set of conditions and less well at other conditions Figure 5.
Specific preferences for growth are as diverse as the types of microbes. Decades of research have developed the current understanding of microbial growth to establish the principles outlined above. Establishing common principles allows us to target broad groups of microbes, while unique requirements for growth allows us to target specific microbes. This knowledge enables the control of microbial growth that facilitates many of our interactions with microbes today.
Many methods of control seek to eliminate harmful microbes from foods or equipment. For example, high temperature is often used to kill microbes during cooking or through processes like pasteurization.
In this way, potentially harmful microbes are broadly eliminated from the food product making it safe to consume and store. Similarly, chemicals in disinfectants can damage or kill microbes broadly on surfaces. Alcohols like ethanol and isopropanol damage the cell membranes.
This is why they grow on foods with high moisture content such as chicken. Foods that are dehydrated or freeze-dried can be stored for much longer as the moisture has been removed. Food — Food provides energy and nutrients for bacteria to grow. High risk foods particularly protein foods such as chicken and dairy products are rich in nutrients and moisture and so promote bacterial growth.
Time — If provided with the optimum conditions for growth, bacteria can multiply to millions over a small period of time via binary fission. Set your location: Set Cancel. My Location: Loading Font Size:. By Topic. What conditions encourage bacteria to grow? Need more information?
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