Question

1. what is selective stains in detail?

2. what is phylogenetic group?

3. What major assumption is made in relating plate count results to cell number?

Answer 1

1. Selective stains: These are stains which will enhance the colour contrast of specific/desired cells or tissues. Selective stains allow us to distinguish cells/tissues from other cell/tissues which are not interested

Eg. Trypan blue- is a stain used to chitin. Trypan blue selectively colour dead cells. This is used as a selective stain to distinguish dead cells from live cells

Cotton blue- is a selective stain used to identift fungal cells. Cotton blue will selectively stain chitin. Therefore fungal cells can be easily identified (Fungal cells are made of chitin)

2. Phylogenetic group: Phylogenetic group is a group of related organisms having a common ancestor. John Hutchinson introduced Phylogenetic classification of organisms. A phylogenetic tree is used for the represent the evolution of a group of descendent organisms from the ancestor organism. Eg. Mammals- a Phylogenetic group of animals characterized by the presence of mammary glands.

3. The major major assumption that can be made in relating plate count results to cell number is the number of live cells in the culture. Plant count or colony count in the plate is a representation of live cells present in the culture. This method can be used for a rough estimation the viability of the cells present in the culture. When we use colorimetric method, it gives the density/turbidity of the culture medium