Final answer:
Escherichia coli (E. coli) played a pivotal role in molecular biology as a model organism for understanding fundamental genetic processes, which are consistent across various life forms.
Step-by-step explanation:
The bacterial species that had a central role in advancing the field of molecular biology is Escherichia coli (E. coli). E. coli has been a primary model organism for studying molecular mechanisms such as gene regulation, expression, and DNA replication. The insights gleaned from E. coli have been applied across different domains of life because of the fundamental biochemical unity among all organisms, a concept encapsulated by Jacques Monod's statement, "What is true for E. coli is also true for the elephant." This unity makes studies in E. coli relevant to understanding genetics in both prokaryotes and eukaryotes.