Cocci (singular -<unk> , from the Latin coccinus (scarlet) and derived from the Greek kokkos (berry) ) are any microorganism (usually bacteria) whose overall shape is spherical or nearly spherical.
Aggregations of coccoid bacteria often occur and these forms have specific names as well; listed here are the basic forms as well as representative bacterial genera:
pairs, or diplococci (Neisseria)
groups of four or eight known as tetrads or sarcina (Micrococci)
bead-like chains, or streptococci (Streptococcus)
grapelike clusters, or staphylococci (Staphylococcus)
Important human pathogens caused by coccoid bacteria include staphylococci infections, some types of food poisoning, 
some urinary tract infections, toxic shock syndrome, gonorrhea, as well as some forms of meningitis, throat infections, pneumonias, and sinusitis.
Coccus
Proteus
Bacteroides
Bacillus
Streptococcus
Lactobacillus
Pseudomonas
Arcobacter