From the Greek for "small" & "life" comes this 7-letter word for a germ or a disease-causing bacterium
Some 
bacteria are used to supply products that improve human life, others cause 
disease,... [DOC] [TLE] infection facts, information, pictures | Encyclopedia.com articles ... [PAR] Ironically, these life-forms, including bacteria and viruses, are so small that they ... 
of another organism, causing contamination and disease in the host organism.