The vital force or vitalism mentioned for Wöhler meant, at that time, also that living organisms can arise spontaneously from nonliving matter (e.g. flies on putrid meat and microorganisms in broth), i.e. theory of spontaneous generation. Noted chemists like Wöhler did not know the role of microorganisms during the change of sugar to alcohol, i.e. fermentation, but rather saw it as a mere chemical change that my require oxygen to activate some vital force. It took several decades to definitely discredit the theory of spontaneous generation in the 19th century by the work of Louis Pasteur after the pioneering study to research this theory by Lazzarro Spallanzani in 1768.
Although microorganisms could be seen by the aid of microscope in the 17th century by Antonie van Leeuwenhoek, it was not until the 19th century that microbiology began to develop as a truly scientific discipline. Pasteur established that living microorganisms are responsible for the chemical changes that occur during fermentation and meanwhile discovered that some microorganisms carry out anaerobic metabolism, i.e. in absence of air, or more specifically in absence of molecular oxygen.
During the same period of Pasteur’s studies, Robert Koch was developing methods for growing individual types of microorganisms in the laboratory. These pure culture methods permitted him to establish the relationship between a microorganism and an infectious disease like anthrax, tuberculosis and cholera, i.e. the germ theory of disease, which was previously proposed by Koch’s mentor, Jacob Henle, at the University of Göttingen.
– Ronald M. Atlas, Principles of Microbiology, 1. edition, 1995, Mosby-Year Book, Inc.
– Online Wikipedia.