A diplococcus is a round bacterium that typically occurs in the form of two joined cells.
Neutrophils infected with Neisseria gonorrhoeae, with characteristic small gram-negative diplococci.
Diplococcus formation of S. pneumoniae bacteria
A representation of diplococcus formation in Enterococcus.
Gram-negative bacteria are bacteria that unlike gram-positive bacteria do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is their cell envelope, which consists of a thin peptidoglycan cell wall sandwiched between an inner (cytoplasmic) membrane and an outer membrane. These bacteria are found in all environments that support life on Earth.
Microscopic image of gram-negative Pseudomonas aeruginosa bacteria (pink-red rods)