Gram staining

[lara]

Hi

Can some1 tell me y do some gram+ve appear gram-ve & vice versa?
Bacillus,acetobacter etc.do.No,don't tell me it is contamination.Gimme some solid answer.

[Mjhavok]

Clean the pipette before you use it.

[Mjhavok]

The Deinococcus-Thermus are a small group of bacteria comprised of cocci highly resistant to environmental hazards. There are two main groups. The Deinococcales include a single genus, Deinococcus, with several species that are resistant to radiation; they have become famous for their ability to eat nuclear waste and other toxic materials, survive in the vacuum of space and survive extremes of heat and cold. The Thermales include several genera resistant to heat. Thermus aquaticus was important in the development of the polymerase chain reaction where repeated cycles of heating DNA to near boiling make it advantageous to use a thermo-stable DNA polymerase enzyme. These bacteria have thick cell walls that give them gram-positive stains, but they include a second membrane and so are closer in structure to those of gram-negative bacteria.

From "www.wikipedia.com"

[lara]

thanx 4 the reply. keepin' aside the contaminated pipette,it has been recorded that the OLDER cultures of bacteria give the wrong results.can ther b any structural changes, mutations or shock proteins involved?
thermales was newz 2 me,but how can it xplain the phenomenon in common bacteria like bacillus?

[mothorc]

we just see in bacteria, Gram + change to Gram- like baccilus when the cell become old. The first step in Gram stain colorized the peptidoglycan (Gram -), phospholipid membrane (Gram +) or peptidoglycan if phospholipid membrane is lost.Then when we wash them by ethanol, The violet color (bold color)in phospholipid membrane will be solubed. After wash step, Gram + and Gram - which lost phospholipid membrane absorb will lose its color and we can see the nest stain (colorless).
So when baccilus cell become old, its phospholipid membrane eroded by outermembrane lipase.
You can try Ryu's test for confidence result
edit: sorry, I was terribly wrong but I will find more information
Mothorc