Para entender a situação e as tendências em Microbiologia, é importante conhecer as pessoas e eventos que fizeram parte da sua história. Nesta retrospectiva irei mencionar algumas pessoas que foram importantes que não foram necessariamente microbiologistas, mas colaboraram para as bases de todos os ramos das ciências.

A "Era de Ouro" da Microbiologia foi de 1850 a 1920. Durante este período a pesquisa estabeleceu que certos microrganismos poderiam causar doenças em humanos, animais e plantas. Ficou claro também que osmicrorganismos podem causar alterações químicas no ambiente, incluindo o solo e a água. Quando esta época acabou a microbiologia havia se estabelecido como uma disciplina científica com identidade própria. 

Após os progressos alcançados pela "Era de Ouro", a imunologia e a virologia se tornaram as principais áreas de estudo, assim como as doenças infecciosas e a microbiologia ambiental (ecologia microbiana). Além disso a biologia molecular e a genética de microrganismos também se desenvolveram bastante, a medida que novas metodologias foram sendo desenvolvidas para estudo da estrutura e atividade das proteínas e ácidos nucleicos. Alguns dos principais marcos são descritos abaixo.

Francis Bacon, René Descartes and Isaac Newton were not microbiologists, but influenced all science branches by establishing the basis of scientific method of investigation. Bacon and Descartes ideas were very different in many aspects, but Newton unified them by introducing an appropriate combination, using mathematic and physics as the only way to describe our world. According to them the universe was like a perfect machine, and to understand it It was necessary to decompose it in parts (atomistic and mechanicist). The scientists main goal were to extract from nature, under torture, all its secrets. They believed that the universe is fixed, without any significant changes since its creation. 

Charles Robert Darwin, 1809 - 1882

When Darwin published "Origin of Species" (1859), he introduced a fundamental change in all sciences. The universe is in constant evolution. It was the begining of questioning the Cartesian vision of the world as a great and perfect machine created by God's hands.

Important discoveries and achievements relating microorganisms with human diseases were made by persons like Robert Koch, Louis Pasteur, Joseph Lister, Ilya Metchnikoff and Paul Ehrlich. They established the basis of Microbiology Science, intimately related with health science. 

Martinus Beijerinck

In 1888 Martinus Beijerinck initiated a new approach toward microorganisms. He used enrichment culture minus nitrogenous compounds to obtain a pure culture of the root nodule bacterium Rhizobium demonstrating that enrichment culture creates the conditions for optimal growth of a desired bacterium, but most important, he studied a microrganism withouth being related with humans, but plants, starting the Environmental Microbiology. In the next year (1889) Sergei Winogradsky studid Beggiatoa bacteria and determines that it can use inorganic H2S as an energy source and CO2 as a carbon source. He establishes the concept of autotrophy and its relationship to natural cycles. 

Angus Smith in 1882 initiates some preliminary research in "blowing air" into sewage tanks to avoid undesirable, malodorous anaerobic results. 

David Bergey et al. in the early's 1900 published the first edition of Bergey's Manual of Determinative Bacteriology an important reference that is constantly revised to identifying bacterial species until today. 

Ardern and Lockett (1914 Salford, England) Using fill-and-draw cycling had provided the premier demonstration and pronouncement of activated sludge treatment 

Frederick Twort in 1915 discovered the bacteriophage, and . Two years later, Felix d'Herrelle independently describes bacterial viruses and coins the name "bacteriophage." 

Frederick Griffith in 1928 discovers transformation in bacteria and establishes the foundation of molecular genetics. He shows that infecting mice with a mixture of live, avirulent, rough Streptococcus pneumoniae Type I and heat-killed, virulent smooth S. pneumoniae Type II leads to death of the mice. Live, virulent, smooth S. pneumoniae Type II are isolated from the dead mice. 

Alexander Fleming (1929) discovered the penicillin, effectively launching the "Antibiotics Era," a major revolution in public health and medicine. 

Selman Waksman -(born 1888) began a systematic screening program for antimicrobial compounds produced by soil microorganisms. From several antibiotics discovered and characterized, streptomycin was the one proved to be one of the only antibiotics that could be used to successfully treat tuberculosis. Waksman's work showed that many actinomycetes (and especially members of the genus Streptomyces) were antibiotic producers, and that many but not all of these compounds could be used in clinical medicine. Waksman also coined and defined the word "antibiotic". 

Joshua Lederberg et al in a series of papers starting in 1946 publish the first paper on conjugation in bacteria, and the transfer of genetic information by viruses. 

Francis Crick and Maurice Wilkins, together with James Watson (1953), describe the double-helix structure of DNA. This achievement made possible to initiate a new understanding of molecular genetics of microorganisms. The next major steps in our century in microbiology are all related with new findings and methodologies that amplify the knowledge of bacterial genes.