germ
In medicine, a (usually disease-causing) microorganism or pathogen.
G
Gram staining
Developed by the Danish bacteriologist Hans Christian Gram, Gram staining is a method for rendering bacteria more visible under the microscope with the aid of a special dye. Depending on differences in their cell-wall structures, bacteria can basically be divided into two groups: Gram-positive and Gram-negative bacteria.
Gram-negative bacteria
Gram-negative bacteria have a thin cell wall with a single-layered murein. They therefore absorb no dye during Gram staining, and appear reddish under the microscope. Gram-negative bacteria are primarily rod bacteria and are endotoxic. Well-known members of this family are Legionella, the pseudomonads, and Borrelia.
Gram-positive bacteria
Gram-positive bacteria stain dark-blue during Gram staining. The reason for this is a thick cell wall and a multi-layered murein which may account for up to 50% of the dry matter of the membrane. Gram-positive bacteria are primarily Cocci and are exotoxic. Examples are Listeria, Clostridia, Streptococci and Staphylococci.
guanine
Guanine (C5H5N5O) is one of the four coding nucleobases of DNA and RNA. Guanine always base-pairs with the complementary cytosine, forming three hydrogen bonds with the latter.