A spoonful of  curd is added to a cup of milk and left for a week, after which small white worms were noticed in the curd. How did the worms enter the closed container ?

Worms in closed container

During the process of adding curd to milk in a closed container, we aren’t just adding curd — we are also adding hundreds of living organisms!(which is the origin for the worms in closed container) This spoonful of curd is full of microorganisms that are so small that it is impossible to see with our naked eyes.

Lactic acid bacteria (Lactobacillus sp.) are the major bacteria present in curd. They feed on sugar (lactose) in milk, producing lactic acid as a byproduct.

As the bacteria reproduce using lactose as a source of carbon, it produces lactic acid as waste.

This lactic acid makes the milk taste sour. It also causes the milk proteins to become denatured and coagulated because of its acidic nature.

When this process is allowed for single day, we get a cup of curd. If it is prolonged for a week, the curd will get spoilt because of microorganisms.

Eggs of maggots are always present in the air if it is not filtered, so that when you had added the spoonful of curd to the milk, the eggs present the air might have fallen in the milk.

The fly life cycle is composed of four stages: egg, larva (commonly known as a maggot, which is the worm), pupa, adult.

The eggs are laid in decaying flesh, animal dung, manure, or pools of stagnant water — whatever has ample food for the larva, generally in a moist area.

It can easily suspend in the air like fungal spores, and as a result even the presence of air can result in the growth of maggots or worms. After 8-20 hours, the egg hatches and the fly enters the maggot stage.

The maggot gorges itself on food until it is ready to enter the pupal stage, and adult worm develops.

And this is reason for finding worms in the closed container.

The `original’ experiment refuting `spontaneous generation‘ was done using common houseflies and maggots.

When raw meat at room temperature was covered with a cloth tent so that the flies could not land on the meat, no maggots hatched. The uncovered meat produced maggots because the flies were able to lay their eggs in the meat hence producing the maggots (Francesco Redi, 1668).

In 1768 Lazzaro Spallanzani proved that microbes came from the air, and could be killed by boiling.

Yet it was not until 1862 that Louis Pasteur performed a series of careful experiments, which conclusively proved that a truly sterile medium would remain sterile.