How bacteria spreads

A single bacterium can divide and become two bacteria for every 20 minutes if it thrives well. This means that a single bacterium can become quite a million bacteria – 1,000,000 – of approximately 6 ½ hours!
When a bacteria divides, there will be created a wall down through the bacterium. Eventually, when the wall is done, share it out and turn into two. In each of the two new bacteria will be there so created a new wall, and they divide, so there are four bacteria. And the four bacteria divides, there are eight ...And how can it continue.

How long can food keep?
How long food can stay, depends on how quickly the bacteria in food grows. Bacteria grows by sharing. And the more times they divide, the more they grow. How quickly bacteria grows depends on how they thrive. It is dependent on:
humidity
oxygen
temperature
Humidity
Humidity plays an important role, because the bacteria cannot share it without water. So if we are talking about completely dry food such as flour, bread, or oatmeal, bacteria have a harder time to grow. The same is true for other kinds of food, as it dries. E.g. grapes and plums, which will turn into raisins and prunes. They can like flour, oatmeal and other dry foods stick for a long time.
Oxygen
Some bacteria need oxygen to survive. Others can survive without oxygen. Oxygen is in the air. Therefore, we must ensure that foods with bacteria that need oxygen to survive, don't get any air. It does, for example, by wrapping them up close in and afterwards sucking all the air out of the wrapping. It's called vacuum packed foods.
Temperature
Most bacteria cannot grow at a temperature of 5 degrees or less. On the other hand, grows rapidly when the temperature is above 5 degrees. But only until it becomes over 75 degrees. When the temperature is 75 degrees or above, so the door most bacteria!
Microwave
You can also heat food by giving the rays. It is what one does when one is warming something in a microwave oven. When it warms the large portions and food with many different ingredients in micro-wave oven, it is not certain that the food will be just hot all over the place. Therefore one must always brand according to whether the food is cooked thoroughly.
Salt and sugar
Bacteria thrive in bad food, with much salt or sugar. Therefore, they have it not well in foods like jams and salami.