The year 2015 marks the 100th anniversary of a publication by William Twort, in which he first described lysis of bacterial cultures by a filterable, self-replicating agent. In 1917, Félix d’Herelle, coined the name “bacteriophage” for the proposed agent. Two Belgian teams of microbiologists were among the few to critically examine the nature of the bacteriophage at that time. Although their experimental results agreed, their interpretations did not. Richard Bruynoghe interpreted them as supportive of d’Herelle’s notion of an ultramicroscopic microorganism. (...) Jules Bordet found the proposal of a complex organism unnecessary and saw the bacteriophage as a simple endogenous bacterial enzyme endowed with capacity to induce its own secretion as well as ability to cause lysis of the bacteria. Two decades would elapse before bacteriophages were visualized and confirmed to be organized particles. However, by that time, Bruynoghe’s work, that had only been published in short notes in society proceedings, was virtually forgotten. The present paper revives his original observations and arguments, while also recognizing that Bordet’s alternative hypothesis had scientific merit. (shrink)

The 1940s and 1950s were marked by intense debates over the origin of drug resistance in microbes. Bacteriologists had traditionally invoked the notions of ‘training’ and ‘adaptation’ to account for the ability of microbes to acquire new traits. As the field of bacterial genetics emerged, however, its participants rejected ‘Lamarckian’ views of microbial heredity, and offered statistical evidence that drug resistance resulted from the selection of random resistant mutants. Antibiotic resistance became a key issue among those disputing physiological vs. genetic (...) explanations of variation in bacteria. Postwar developments connected with the Lysenko affair gave this debate a new political valence.Proponents of the neo-Darwinian synthesis weighed in with support for the genetic theory. However, certain features of drug resistance seemed inexplicable by mutation and selection, particularly the phenomenon of ‘multiple resistance’—the emergence of resistance in a single strain against several unrelated antibiotics. In the late 1950s, Tsutomu Watanabe and his collaborators solved this puzzle by determining that resistance could be conferred by cytoplasmic resistance factors rather than chromosomal mutation. These R factors could carry resistance to many antibiotics and seemed able to promote their own dissemination in bacterial populations. In the end, the vindication of the genetic view of drug resistance was accompanied by a recasting of the ‘gene’ to include extrachromosomal hereditary units carried on viruses and plasmids. (shrink)

Frederick Griffith was an English bacteriologist at the Pathological Laboratory of the Ministry of Health in London who believed that progress in the epidemiology and control of infectious diseases would come only with more precise knowledge of the identity of the causative microorganisms. Over the years, Griffith developed and expanded a serological technique for identifying pathogenic microorganisms, which allowed the tracing of the sources of infectious disease outbreaks: slide agglutination. Yet Griffith is not remembered for his contributions to the biology (...) and epidemiology of infectious diseases so much as for discovering the phenomenon known as ‘transformation’. Griffith’s discovery, for many, was a pure case of serendipity whose biological relevance had also largely escaped him. In this paper, I argue that the key to understanding the significance of bacterial transformation – and the scientific legacy of Fred Griffith – rests not only on it initiating a cascade of events leading to molecular genetics but also on its implications for epidemiology based on the biology of host–parasite interactions. Looking at Griffith’s entire career, instead of focusing only on the transformation study, we can better appreciate the place of the latter within Griffith’s overall contributions. Presented in this way, Griffith’s experiment on bacterial transformation also ceases to appear as an anomaly, which in turn leads us to rethink some of the most prevalent historical conceptions about his work. (shrink)