The second golden age of microbiology. The years between 1943 and 1970 constitute the second golden age of microbiology. The 1940s introduced the field of molecular genetics to general biology. Before 1940s, biologists used to think that protein was the hereditary material of bacteria. After several scientists studied genes and their functions in the 1940s in 1953, sufficient evidence existed to state that DNA is the hereditary material of bacteria. With the advent of the electron microscope during this second Golden Age, two cell types, eukaryotic and prokaryotic cell types were identified as well.

Also, after the discovery of penicillin by Fleming and of other antibiotics by other scientists, there was a mass production of antibiotics needed for those wounded during World War Two. Let's look at each one of these events in detail. In 1943, Italian microbiologist Salvador Luria and German physicist max del bruck worked on the genetics of the bacteria, E. coli. They wanted to know if mutations occur spontaneously, or if the environment induces them. A mutation is a change in the DNA sequence or trait, which can be transmitted to subsequent generations. They concluded from their experiments that bacterial cells could develop spontaneous mutations.

And that those mutations could give rise to resistance of bacterial cells to viral infections. The use of eco lie by these scientists to study microbial genetics open the way for the use of microorganisms as modern systems for study many principles of biology. In 1941, Americans George Beadle and Edward Tata use the fungus named notice for to demonstrate that each gene is responsible for producing a single enzyme. This is also known as the one gene one enzyme hypothesis. In 1944, Oswald Avery, Colleen McLeod and Mark Glen McCarty use the bacteria streptococcus pneumoniae, such to suggest that deoxyribonucleic acid or DNA is the genetic material in cells. Then, in 1953, American biochemist Alfred Hershey and geneticist Martha chase used a virus that infects bacteria known as a bacterial farge.

To provide irrefutable evidence that DNA is in fact the genetic material. Although the first electron microscope was invented in 1931, it was further developed in the 1940s. The electron microscope can amplify objects and cells thousands of times more than the light microscope With the help of the electron microscope, bacterial cells were shown to be cellular in nature, similar to plant and animal cells, although some differences were found. The main difference was that in animal cells, plant cells, fungi and protista, the genetic material is enclosed within a nucleus and is surrounded by a nuclear membrane. For this reason, these cells are known as eukaryotic you meaning crew and carry on meaning nucleus. On the other hand, bacteria and archaea cells lacked a nucleus.

Therefore, the DNA which is part of the physical chromosome, is not surrounded by a membrane. These cells are known as prokaryotes, pro meaning before and carry On, meaning nucleus. In other words, evolutionarily, these cells existed before the eukaryotic cells. Now, viruses, on the other hand, lack a cellular organization and therefore, they are not considered ourselves. We should study viruses in more detail at a later point in time. As you may recall from our study of disease treatment, Paul Ehrlich in 1910 discovered silver sun and arsenic based compound to treat syphilis.

The agent of chemotherapy, the age I'm sorry, of chemotherapy had begun. In 1929, Alexander Fleming, a Scottish scientist, notice that a particular type of mold, a species of the genus Penicillium, known as Penicillium, not autumn had grown over his culture of bacteria as shown over here. This bacteria that he used was staphylococcus. If it were not for the fact that there was no bacterial growth in the area surrounding the mold over here, he concluded that the mole destroyed the bacterial cells. But his discovery of the antibiotic would have gone unnoticed. So because there was no growth around the mold, he concluded that the mold destroy the bacterial cells he named The anti microbial penicillin and developed an essay for its production.

However, it was only in the 1940s during World War Two that there was a need for mass production of antibiotics. Howard Florrie and Ernest chain, were able to purify penicillin and carry out clinical trials to show that the antimicrobial agent had its potency as a drug. I didn't mind antibiotics were discovered as well. protocell was discovered but by Gerhard dogmatic and was shown to be effective against bacterial species such as streptococcus and staphylococcus Suleman Waxman discovered the antibiotics act minimized sin and streptomycin, which are soil bacteria. By definition, antibiotics are antimicrobial substances produced naturally by mold or bacterial species that either inhibit growth or kill other microorganisms. By 1950s, antibiotics were well established in medical practices.

So much so that the medical and layperson both began to wonder. Could this be the end of the age of infectious diseases? In the 1960s, interest in the study of microbes was fading away. At the same time, there was an increasing evidence showing that certain bacterial species were becoming resistant to antibiotics.