Life processes of microbes

The structure of bacteria

Bacterial life – reproduction

Bacterial life - feeding

Toxins

C Bacteria

Although microbes are very different from the plants and animals you are familiar with, most still have the characteristics of living things:

ovement espirationensitivityrowtheproductionxcretionutrition

Life processes of microbes

M R S G R E N

By understanding how different microbes carry out their life processes, and the conditions that suit them best, we can encourage the growth of desirable microbes or prevent the growth of undesirable ones.

Life processes

Living microbes carry out the life processes of all living things: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition.

The structure of bacteria

nuclear regioncontains the genetic code

flagellaallow the cell to move

cell membranecontrols the movement of substances into or out of the cell

cell wallgives shape and protects the membrane

gelatinous sheathprotects from viruses

cytoplasmwhere life functions are carried out

Click on the name to see which part is which.

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The structure of bacteria

Controls entry and exit of dissolved substances.

Sticky layer that protects cell from viruses.

Where the chromosomes are located.

Provides shape and protection.

Where life functions take place.

Allow the particle to move.

cell wall

nuclear region

flagella

cytoplasm

cell membrane

gelatinous sheath

Label the diagram and complete the table.

6C 1 The structure of bacteria

cell membrane

cytoplasm

flagella

nuclear regioncell wall

gelatinous sheath

Bacterial life

Reproduction

Bacteria reproduce by binary fission.

First the cell gets longer and the chromosome is copied.

One chromosome goes to each end, then the cell wall and membrane begin to pinch in.

Finally two identical daughter cells separate.

Under ideal conditions some bacteria can double their number in only 20 minutes.

When the food supply or space runs out, or toxins (poisons produced by the bacteria) build up, bacterial numbers will first start to level off, and then to decrease.

Feeding

Bacteria feed by extra-cellular digestion.

Digestion is the process of breaking down large food molecules (such as starch) into tiny molecules (such as glucose) that can pass through the cell membrane.

Extra-cellular means outside the cell.

First the bacterium secretes enzymes into the food.

e.g. ‘Ex-it’ = go out

These enzymes break down the food into tiny molecules.

Finally the digested food is able to pass through the cell membrane and into the bacterium itself.

Bacterial life

Bacteria reproduce by binary fission. First the cell gets larger and the chromosome is copied, then two chromosomes move to opposite ends of the cell and the walls pinch in, until two identical cells are formed.

Bacteria feed by extra-cellular digestion.

First enzymes are secreted into the food, then the large food molecules are broken down, and finally small food molecules are absorbed into the cell.

Toxins

A toxin is something poisonous. Most pathogenic bacteria produce toxins, and it is the toxin that causes the illness, rather than the bacteria itself.

Many bacteria secrete toxins into their surrounding environment, similar to the way they secrete enzymes to digest food. In other bacteria, the toxin is contained in the cell wall and released when the bacteria is destroyed by the host’s immune system.

The toxin produced by the cholera bacteria causes diarrhoea, the tetanus toxin prevents muscles from relaxing, while the botulism toxin (from which botox is made) causes paralysis.

Because it is the toxins produced by bacteria that make us sick, it is possible to become ill from food containing those toxins, even after all the bacteria that produced those toxins have been killed by thorough cooking.

Toxins

Most pathogenic bacteria make us sick because of the toxins (poisons) they produce. These toxins may cause illness even after all the bacteria which produced them have been killed.

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