Why was it impossible to know about bacteria 5,000
years ago

Im assuming because microscopes hadnt been invented. Also the idea of communicable diseases wasnt around so people assumed it was things like god that caused illness

A true understanding of the physiology of these bacteria and their roles in ecology, host health, and natural product production requires their cultivation in the laboratory. Recent advances in growing these species include coculture with other bacteria, recreating the environment in the laboratory, and combining these approaches with microcultivation technology to increase throughput and access rare species. These studies are unraveling the molecular mechanisms of unculturability and are identifying growth factors that promote the growth of previously unculturable organisms. This minireview summarizes the recent discoveries in this area and discusses the potential future of the field.

Explanation:

a and c are the answeres