A microorganism or microbe could be a microscopic organism, which can exist in its single-celled form or during a colony of cells. The possible existence of unseen microbial life was suspected from the earlier periods, like in Jain scriptures from 6th century BC India and therefore the 1st century BC book On Agriculture by Marcus Terentius Varro. The scientific study of microorganisms began with their observation under the microscope within the 1670s by Antonie van Leeuwenhoek. within the 1850s, Pasteur found that microorganisms caused food spoilage, debunking the speculation of autogeny. within the 1880s, bacteriologists discovered that microorganisms caused the disease of tuberculosis, cholera, and anthrax.