Gram Reaction and Morphology of Some Common Bacterial Genera

Staining Methods in Microbiology
Part 2
Staining Methods in Microbiology Introduction
Simple Stains
Simple Staining Method for Bacteria in Milk (Method of Breed)
Demonstration of Anthrax Bacilli by Simple Staining
Staining of Selection
Negative Stains
Differential Stains
Staining Method of Hucker and Conn
Staining Method of Preston and Morrell
Rapid Method for Gram Stain
Acid Fast Stains
Gram Reaction and Morphology of Some of the Common Bacterial Genera
Ziehl Neelsen Method
Modifications of Zeihl Neelsen Method
Staining Method of Gross
Staining Method of Truant et al
Cytological Stains
Endospore Stains
Staining Method of Scahaeffer and Fusion Modified by Ashby

Gram Reaction and Morphology of Some Common Bacterial Genera

Gram reaction and morphology of some of the common bacterial genera.

Gram Reaction^a	Morphological Character	Genera
Positive	Rods in chain, non-sporulating.	Lactobacillus
	Rods either in chain or single sporulating	Bacillus
	As above, but spores bigger than the cell.	Clostridium.
	Bigger rods, often forming obstuse angle or small bundle of parallel cells	Mycobacteria^b.
	Cocci in bunch	Staphylococcus
	Cocci in chain	Streptococcus
	Cocci, ovoid or lanceolate occurring in pair.	Diplococcus.
	Cocci, sporulating.	Sporasarcina
Negative	Rods either in single or short chain	Corynebacterium, Salmonella, shigella, Proteus, Pseudomonas, Escherichia, Sarratia, Azotobacter, Rhizobium etc.
	Rods, Ovoid	Yersinia, Pasteurella, Francusella
	Rods, curved	Vibrio
	Cocci in pair.	Neisseria.
	Cocci in single	Veillonella, Acidoaminococcus, Megaspaera.
	spiralc	Treponema, Borrelia, Spirillum, Lactospira

a. Gram reactions listed for various genera are based on the results of the test
with 24 hours old cultures.
b. The Gram reaction is debatable.
c. The staining of these organisms require special staining technique.

them, even with acid and alcohol. Acid-fast cells retain the primary stain and non acid-fast bacteria lose the same. In order to show structures and cells those have been decolourized and to form a contrast with the red stained bacilli, in this preparation the use of malachite green or methylene blue as a counterstain is recommended.

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