Microbiology was believed by many microbiologists to experience its second golden age, prior to that is the first golden age which initiated by Pasteur’s Germ theory of disease. The second golden age of microbiology introduced another field of general biology which is molecular genetics. It uses microorganisms as a model in conducting researches. It started in the year 1940’s, when Salvador Luria and Max Dulbrück worked on the genetics of a bacterium, Escherichia coli or E. coli. They studied the gene expression and mutation of E. coli and found out that bacterial cells could develop spontaneous mutations and these mutations could give rise to resistance of bacterial cells to viral infection.
In 1941, another experiment was conducted by George Beadle and Edward Tatum using the fungus named Neurospora. They demonstrated that each gene is responsible for producing a single enzyme, also known as one gene, one enzyme hypothesis. In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty, used the bacteria Streptococcus pneumonia to suggest that deoxyribonucleic acid (DNA) is the genetic material in cells. It was supported by Alfred Hershey and Martha Chase in 1953, when they performed an experiment using a virus that infects bacterial cells called bacteriophage to provide sufficient evidence that DNA is the genetic material of bacteria.
With the advent of electron microscope, the two types of cellular organization are realized. Bacterial cells were shown to be cellular in nature similar to plant and animal cell although some differences were found. The main difference was that in animal cells, plant cells, fungi, and protest, the genetic material is enclosed within a nucleus and is surrounded by a nuclear membrane. That’s the reason why these cells are called eukaryotes. On the other hand, bacteria and archaea cells lacked nucleus therefore the DNA which is part of the physical chromosome is not surrounded by a membrane. These cells are known as prokaryotes. Viruses lack cellular organization and therefore they are not considered as cells.
With the used of the knowledge in Paul Erlich “salvarsan” and Alexander Fleming “penicillin”, Howard Florey and Ernest Chain do a mass production of antibiotics to cure infectious diseases in World War II. Soon after, the antibiotics actinomycin and streptomycin were discovered in samples of soil and were instrumental in treating tuberculosis. These discoveries were followed by many many more and numerous diseases were treated. However, overuse of antibiotics has led to antibiotic-resistant strains of bacteria which is a problem we are still facing today.
The second golden age of microbiology is the rise of what we are now studying molecular genetics. Microbial science was once again, recognized as a fundamental scientific discipline.