Answer : 1. "ए.वी. लीउवेनहाँक"
Explanation :

The discovery of bacteria is attributed to Antonie van Leeuwenhoek, a Dutch scientist, who observed bacteria using a simple microscope that he designed and built. In the 1670s, Leeuwenhoek made detailed observations of microorganisms, including bacteria, in samples from various sources. His pioneering work laid the foundation for the understanding of the microbial world.