These bacteria are round, flattened cells adjacent to each other. They can be found in different arrangements, namely, diplococci (in pairs), tetrads (arrangement of groups of four), streptococci (in pairs), and staphylococci (in clusters).
Diplococci Bacteria : These bacteria are usually found in pairs as two joined cells. The name originates from the word diplo , meaning double, and coccus , meaning berry. One example of a diplococci strain is Neisseria gonorrhea . A typically gram-negative bacterium causes a sexually transmitted infection called gonorrhea . Another example of diplococcus strain is Moraxella catarrhalis that is a gram-negative bacterium that causes infections of the respiratory system
Tetrad Bacteria : They are formed when the bacterium divides into two planes to form a square of four bacteria called a tetrad . Examples of tetrad-forming bacteria are Aerococcus , a urinary tract pathogen, Pediococcus , and Tetragenococcus , both of which ferment foods. Aerococcus urinae is an emerging cause of urinary tract infections, which was previously thought to be non-pathogenic (i.e., harmless) and a clinically insignificant urinary contaminant.
Staphylococci Bacteria : The term staphylococcus comes from the word Staphylo meaning grape-like clusters and coccus, meaning berry. The arrangement of staphylococci resembles cells aggregating in a grape-like structure. These are universally present on mucous membranes and the skin, usually as gram-positive facultative aerobes . An important example is that of Staphylococcus aureus, which is frequently implicated in food poisoning Staphylococcus epidermis , which is normally found on the skin and is a part of the normal skin flora. It is known to be non-pathogenic but can be rendered pathogenic (i.e., harmful) in immunosuppressed individuals.
Streptococci Bacteria : The term streptococcus originates from the words “strepto ” meaning chains and coccus, meaning berry. The arrangement of streptococcus resembles cells in chains attached. This species causes a variety of conditions in humans. An example of streptococci bacteria is Streptococcus pyogenes , known to cause rheumatic fever, tonsillitis, strep throat, and other respiratory infections. Another example of this bacteria is Streptococcus bovis, which causes urinary tract infections.
Sarcinae Bacteria : These bacteria are usually non-motile, with sizes between 1.8 and 3.0 µm in diameter. This arrangement is formed when bacteria divide into three perpendicular planes forming packets of 8 or more cells. It is pathogenic and is usually implicated in gastrointestinal disorders such as gastroparesis or gastric ulcers.
