Genera of bacteria and algae.
[Latin diminutive ending -ella.]
This forms the genus and informal names of a variety of bacteria and algae. Examples include Chlorella (Greek khlōros, green), a single-celled green alga; Legionella (first identified following an outbreak at a meeting of the American Legion), the bacterium which causes legionnaires' disease; Salmonella (Daniel E Salmon, 1850–1914, an American veterinary surgeon), a bacterium that causes food poisoning; Shigella (Kiyoshi Shiga, 1870–1957, Japanese bacteriologist), a bacterium, some kinds of which cause dysentery.
Many other words in -ella occur in English. Some are Latin diminutives: rubella, the medical term for German measles (Latin rubellus, reddish); lamella, a thin layer (Latin lamina, thin plate). Others are plurals of Latin words in -ellum: flagella, cerebella. Another group are Italian diminutives adopted into English: umbrella (Latin umbra, shade; at first it kept off the sun rather than rain); mortadella, a type of sausage (Latin murtatum, seasoned with myrtle berries); villanella, an Italian rustic-style part-song (villano, peasant).