Nitrosococcus
noun
Ni·tro·so·coc·cus nī-ˌtrō-sō-ˈkä-kəs 
: a genus of large, spherical to ellipsoidal, nitrifying bacteria (family Chromatiaceae) that live in saline environments (such as oceans and salt lakes) and obtain energy for growth by oxidizing ammonia to nitrites
Word History
Etymology
New Latin, from nitrosus nitrous + -o- + -coccus