The cytoplasm of Gram positive bacteria are said to be more acidic
than those of Gram negative ones.
Hence the dye is said to bind with more affinity to Gram positive cells.
An organized system of meticulously constructed narrow trenches, which are partially filled with washed gravel or crushed stone, into which a pipe is placed. Discharges from septic tanks are passed through these trenches.
Primary stain: Strong Carbol Fuchsin (contain Basic fuchsin and Phenol)
Decolourizer 20% sulphuric acid
Counterstain LoelTler's Methylene blue or 1% Malachite green, Picric acid for color-blind workers
Beaded appearance is used to describe the appearance of Mycobacterla when the cell doesn't stain uniformly. showing stained and unstained regions. These forms are common in Mycobacterium tuberculosis while Mycobacterium bovis stains uniformly. Most saprophytic Mycobacteria stain uniformly.
Sputum smears for Mycobacterla can be stained by fluorescent dyes such as Auramine and Rhodamlne as they have affinity for mycolic acid In their cell walIs The fluorescent microscopy is useful in screening large number of specimens. Large area of smear can be quickly observed that too under high power dry objective.
The process of kdling all hying forms including spores is called sterilization and the process of killing of only the vegetative form of pathogenic bacteria as well as other microbes is disinfection
It is the cytoplasm (especially the nucleic acid) that gets stained and not the cell wall. Presence of an intact cell wall is important for retaining Gram positivity. Cell wall deficient forms such as Mycoplasma and L forms are Gram negative.
A compound of magnesium ribonucleate and basic protein concentrated at the cell membrane helps Gram positive bacteria retain the primary dye. Gram negative bacteria do not possess this substance.
Alkylation (hydrogen atom is replaced with an alkyl group) of protein. DNA. and RNA afFects bacterial metabolism and replication. EQ gas (8.5%) is often mixed with stabilizers such as CO2 (91 5%) or hydrochlorofluorocarbons (HCFC). This requires high humidity (40-80%) and long exposure times (1-6 hrs).
Decolourization is the most important step as this step differentiates between Gram positive and Gram negative bacteria. Over-decolourization can result in Gram positive bacteria appearing Gram negative and under-decolourization can result in Gram negative bacteria appearing Gram positive.