Dictionary » G » Gram staining

Gram staining

Definition

noun

A staining method performed to determine whether a bacterial species is gram-positive (i.e. violet stain) or gram-negative (i.e. pink stain)


Supplement

Gram staining is derived from its inventor, Hans Christian Gram, a Danish bacteriologist. It was his method of staining bacteria that gained him international reputation in the field of bacteriology. His purpose of developing such method is to help in viewing bacteria under a microscope by staining them with dyes, i.e. crystal violet and safranin (or fuchsine).

Later on, gram staining became an essential method in classifying bacteria as either gram-positive or gram-negative. Gram-positive bacteria are those that retain the primary stain, i.e. crystal violet dye. Gram-negative bacteria are those that take the counterstain dye, i.e. safranin (pink colour).

Gram staining is done by preparing a heat-fixed smear of bacteria from slant of broth cultures onto a slide. The smear is stained first with the primary dye (crystal violet) for about a minute, and washed with tap water to remove excess dye. The slide is next flooded with Gram's iodine that act as a mordant. After one minute, the slide is washed with tap water, and then with 95% alcohol (about 30 seconds). To stop the decolorization, the slide is washed with tap water (for another 30 seconds). The slide is then flooded with the counterstain (safranin or fuchsine) for half a minute. After which, the slide is washed, drained, and blotted to be examined under the microscope.


Synonym(s):

See also:


Please contribute to this project, if you have more information about this term feel free to edit this page



Results from our forum


URGENT HELP IDENTIFYING UNKNOWN BACTERIA!!!

... be very appreciative if anybody can help me identify it. thanks so much GRAM NEGATIVE- clustered in chains, splotches, and red/pink. Blue Vegetative cells. SPORE REACTION (-) ACID FAST STAINING (-) NUTRIENT BROTH CULTURE- Quite turbid, slightly cloudy, no skin NUTRIENT ...

See entire post
by microbiologyhelp
Wed Nov 20, 2013 6:09 pm
 
Forum: Microbiology
Topic: URGENT HELP IDENTIFYING UNKNOWN BACTERIA!!!
Replies: 7
Views: 8752

Bacterial Taxonomy

... make more such charts. I would particularly like a chart that relates Gram-staining to taxonomy, one that makes note of all the common exceptions. Maybe there is already ...

See entire post
by wildfunguy
Sat Oct 19, 2013 6:12 pm
 
Forum: Microbiology
Topic: Bacterial Taxonomy
Replies: 3
Views: 5484

Using oxidizing agents in gram stain

... happen if I replaced iodine with another oxidizing agent during the gram staining process ? So far I know that the purpose of the iodine is to form a complex with the ...

See entire post
by ccBiologist
Sun Sep 22, 2013 2:44 pm
 
Forum: Microbiology
Topic: Using oxidizing agents in gram stain
Replies: 1
Views: 1820

Help with my unknow??

... on my unknown in Microbiology and I'm actually stuck now. I've done gram staining and have determined that my bacteria is gram neg, med rods. However, the tests I've ...

See entire post
by student2012
Sun Nov 25, 2012 3:15 am
 
Forum: Microbiology
Topic: Help with my unknow??
Replies: 2
Views: 2055

How to create a science project about acne?

If you don't have the ability to do staining and culturing, it would be really hard to test acne the way you are thinking. ... them dichotomous keys, to determine what kind of bacteria you are looking at. Gram stain is the first step, but then cell shape, cluster patterns, etc all indicate ...

See entire post
by tmbirkhead
Sun Sep 23, 2012 5:25 am
 
Forum: Human Biology
Topic: How to create a science project about acne?
Replies: 2
Views: 4712
View all matching forum results

This page was last modified 00:46, 30 November 2014. This page has been accessed 164 times. 
What links here | Related changes | Permanent link