In the viable plate count method, a measured volume of a culture is evenly spread across an agar surface and incubated. Each represents one from the original sample.

In the viable plate count method, a measured volume of a culture is evenly spread across an agar surface and incubated. Each colony represents one cell from the original sample.

Explanation:

A viable count is the number of colony forming units (cfu) of microbes per gram or per milliliter of the sample, or cfu/gm or cfu/ml.  

In order to find whether the cells counted is viable or not, methods like plate-count method, membrane-filter methods are used. These tests allow the visible cells to grow and multiply to check the viability.

The plate count method is done by growing the microorganisms like bacteria on a plate in a nutrient medium or substrate like the agar surface. The bacteria will grow into colonies and will be visible to the naked eye.

Each colony unit is counted and each unit in a colony represents a single cell of the bacteria or any microorganism cultured and counted.

The counting is done by various methods like hemocytometers, streak plate etc.  

lysosome is this part of the cell is surrounded by a very thick outer membrane to protect the rest of the cell from its strong enzymes.