Around the turn of the twentieth century, microbiologists in Western Europe and North America began to organize centralized collections of microbial cultures. Collectors published lists of the strains they cultured, offering to send duplicates to colleagues near and far. This essay explores the history of microbial culture collections through two cases: Johanna Westerdijk’s collection of phytopathogenic fungi in the Netherlands and Ernst Georg Pringsheim’s collection of single-celled algae at the German University in Prague. Historians of science have tended to look (...) at twentieth-century biological specimen collections as either repositories of communal research materials or storehouses of economically important biological variation. An examination of Westerdijk’s and Pringsheim’s collections illustrates how collectors, researchers, and patrons ascribed different kinds of value to collections featuring distinctive microbial life forms. This essay argues that characteristics of cultivated microorganisms, such as a fungus’s propensity to infect crops or an alga’s amenability to experimentation, shaped the trajectories of Westerdijk’s and Pringsheim’s collections as these collectors developed relationships with colleagues and patrons. Letters between Westerdijk and Pringsheim open a window onto divergences in their approaches to collecting cultures, while also shedding light on the aspirational internationality of the collections that resulted. (shrink)

. Early microbiome research found numerous associations between microbial community patterns and host physiological states. These findings hinted at community-level explanations. “Top-down” experiments, working with whole communities, strengthened these explanatory expectations. Now, “bottom-up” mechanism-seeking approaches are dissecting communities to focus on specific microbes carrying out particular biochemical activities. To understand the interplay between methodological and explanatory scales, we examine claims of “dysbiosis,” when host illness is proposed as the consequence of a community state. Our analysis concludes with general observations about (...) how methodologies relate to explanations, and the implications for microbiome research. (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)

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)

Prompted by recent recognitions of the omnipresence of horizontal gene transfer among microbial species and the associated emphasis on exchange, rather than isolation, as the driving force of evolution, this essay will reflect on hybridization as one of the central concerns of nineteenth-century biology. I will argue that an emphasis on horizontal exchange was already endorsed by ‘biology’ when it came into being around 1800 and was brought to full fruition with the emergence of genetics in 1900. The true revolution (...) in nineteenth-century life sciences, I maintain, consisted in a fundamental shift in ontology, which eroded the boundaries between individual and species, and allowed biologists to move up and down the scale of organic complexity. Life became a property extending both ‘downwards’, to the parts that organisms were composed of, as well as ‘upwards’, to the collective entities constituted by the relations of exchange and interaction that organisms engage in to reproduce. This mode of thinking was crystallized by Gregor Mendel and consolidated in the late nineteenth-century conjunction of biochemistry, microbiology and breeding in agro-industrial settings. This conjunction and its implications are especially exemplified by Wilhelm Johannsen’s and Martinus Beijerinck’s work on pure lines and cultures. An understanding of the subsequent constraints imposed by the evolutionary synthesis of the twentieth century on models of genetic systems may require us to rethink the history of biology and displace Darwin’s theory of natural selection from that history’s centre. (shrink)

Microbial diversity has become a leitmotiv of contemporary microbiology, as epitomized in the concept of the microbiome, with significant consequences for the classification of microbes. In this paper, I contrast microbiology’s current diversity ideal with its influential predecessor in the twentieth century, that of purity, as epitomized in Robert Koch’s bacteriological culture methods. Purity and diversity, the two polar opposites with regard to making sense of the microbial world, have been operationalized in microbiological practice by tools such as the “clean” (...) Petri dish versus the “dirty” Winogradsky column, the latter a container that mimics, in the laboratory, the natural environment that teems with diverse microbial life. By tracing the impact of the practices and concepts of purity and diversity on microbial classification through a history of techniques, tools, and manuals, I show the shifts in these concepts over the last century. Juxtaposing the dominant purity ideal with the more restricted, but continuously articulated, diversity ideal in microbial ecology not only provides a fresh perspective on microbial classification that goes beyond its intellectual history, but also contextualizes the present focus on diversity. By covering the period of a century, this paper outlines a revised longue durée historiography that takes its inspiration from artifacts, such as Petri dish and the Winogradsky column, and thereby simple, but influential technologies that often remain invisible. This enables the problem of historical continuity in modern science to be addressed and the accelerationist narratives of its development to be countered. (shrink)

Microbial diversity has become a leitmotiv of contemporary microbiology, as epitomized in the concept of the microbiome, with significant consequences for the classification of microbes. In this paper, I contrast microbiology’s current diversity ideal with its influential predecessor in the twentieth century, that of purity, as epitomized in Robert Koch’s bacteriological culture methods. Purity and diversity, the two polar opposites with regard to making sense of the microbial world, have been operationalized in microbiological practice by tools such as the “clean” (...) Petri dish versus the “dirty” Winogradsky column, the latter a container that mimics, in the laboratory, the natural environment that teems with diverse microbial life. By tracing the impact of the practices and concepts of purity and diversity on microbial classification through a history of techniques, tools, and manuals, I show the shifts in these concepts over the last century. Juxtaposing the dominant purity ideal with the more restricted, but continuously articulated, diversity ideal in microbial ecology not only provides a fresh perspective on microbial classification that goes beyond its intellectual history, but also contextualizes the present focus on diversity. By covering the period of a century, this paper outlines a revised longue durée historiography that takes its inspiration from artifacts, such as Petri dish and the Winogradsky column, and thereby simple, but influential technologies that often remain invisible. This enables the problem of historical continuity in modern science to be addressed and the accelerationist narratives of its development to be countered. (shrink)

This paper attempts to bring new insights to a long-standing historical debate over medical specialization by analyzing the formation of medical mycology, a somewhat marginal biomedical discipline that emerged in the mid-twentieth century around studies of fungal disease in humans. The study of fungi predates that of bacteria and viruses, but from the 1880s it became eclipsed by bacteriology. However, in the postwar period, there were moves to establish medical mycology as an independent speciality. I trace the processes that led (...) to the launch of professional societies in the United States, Britain and Japan, three major players in medical mycology, and more broadly in biomedicine. The analysis of the three different national contexts illustrates how geographical, medico-technological, epidemiological, political and social conditions gave the specialty a distinctive character in each country; this was further complicated by the different and changing medical fields in which fungal diseases were studied and treated. The three case studies show medical specialization as a process that is not simply cumulative but responds to specific historical events and developments. (shrink)