Question

what is a colony and and how does it relate to a bacterial cell?

why is it important to study single colonies of bacteria?

what are the advantages of growing bacteria on a plate vs broth?

how can you tell whether the colonies on your plate are from the original culture and not contaminants?

Answer 1

A) A colony may be defined as the group of multiple microorganisms that have similar genetic identity and are originated from single cell ( mother cell ).

A colony relates to bacterial cell in a way that bacterial cell consist of several bacterial colonies means bacterial colony consist of millions of bacterial cells.

The colonies are useful in a way that colonies give an idea of required conditions to produce the bacteria in a particular environment. Hence, it makes easier to create more bacterial cells.

B) It is important to study single colonies of bacteria because we want to study single genera of bacteria and not of multiple bacteria. Also to study the special characters of that bacteria, single colonies are studied.

Also, we want a pure colony and that can be obtained only by studying single colony, not a multiple colony.

Hence, it is important to study single colonies of bacteria.

C) Plate ( generally Agar plate ) is advantageous over broth.

Agar is a mixture of Agarabiose and Agaropectin. It melts at about 80 to 85 °C and solidifies at 40 °C. It can be easily mixed with broth. As it has a higher melting point, it is better than gelatin. Also, porosity and viscosity can also be adjusted.

Hence, due to all these advantageous features, agar plates are preferred.

D) Contamination usually occurs during inoculation or pouring agar plates. Bacterial and fungal growth can make plates unusable.

If the plates are having any filamentous, fuzzy, hair like growth ( which occurs due to fungal growth ), then the plates are contaminated. If this kind of growth is not seen, then the plate is original culture.

Fungal contamination mainly occurs at the edges of agar plates. If some morphological different colonies from the bacteria used to inoculate platea are displayed on plate, this means the plates are contaminated and if no different morphological different colonies are found, then the plates are fresh and free from contamination.

We can also place the plate at 37°C incubator and then can identify minute difference in morphology of bacterial colonies using magnifying glass.