Microbes before microbiology: Christian Gottfried Ehrenberg and Berlin's infusoria.

Naturalist Christian Gottfried Ehrenberg pioneered research on living and fossil infusoria (including protists and bacteria) since the 1830s by collecting samples from all over the world, thus describing numerous microbes and discussing their effects for the planet and for humankind. This article introduces Ehrenberg as a natural historian of microbes and situates his work in the nineteenth century life sciences with respect to debates about cell theory, evolution, and concepts of disease. I argue that in spite of occurring before these major conceptual innovations of the life sciences, Ehrenberg's work on the diversity of microbes found in earth or air is more exciting than historiography has made it appear so far, especially in light of today's ecological microbiology.

Cycles and circulation: a theme in the history of biology and medicine.

We invite systematic consideration of the metaphors of cycles and circulation as a long-term theme in the history of the life and environmental sciences and medicine. Ubiquitous in ancient religious and philosophical traditions, especially in representing the seasons and the motions of celestial bodies, circles once symbolized perfection. Over the centuries cyclic images in western medicine, natural philosophy, natural history and eventually biology gained independence from cosmology and theology and came to depend less on strictly circular forms.

The molecular vista: current perspectives on molecules and life in the twentieth century.

This essay considers how scholarly approaches to the development of molecular biology have too often narrowed the historical aperture to genes, overlooking the ways in which other objects and processes contributed to the molecularization of life. From structural and dynamic studies of biomolecules to cellular membranes and organelles to metabolism and nutrition, new work by historians, philosophers, and STS scholars of the life sciences has revitalized older issues, such as the relationship of life to matter, or of physicochemical inquiries to biology. This scholarship points to a novel molecular vista that opens up a pluralist view of molecularizations in the twentieth century and considers their relevance to current science.

Petri dish versus Winogradsky column: a longue durée perspective on purity and diversity in microbiology, 1880s-1980s.

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.

Conference report "Stoffwechsel. Histories of metabolism", workshop organized by Mathias Grote at Technische Universität Berlin, November 28-29th, 2014.

Historical analyses of what metabolism has been conceived of, how concepts of metabolism were related to disciplines such as nineteenth-century nutritional physiology or twentieth-century biochemistry, and how their genealogies relate to the current developments may be helpful to understand the various, at times polemic, ways in which the boundaries between metabolism and heredity have been re-drawn. Against this background, a small number of scholars gathered in Berlin for a workshop that equally aimed at bringing new stories to the fore, and at considering seemingly known ones in a new light. Some aspects of the discussions are summarized in this paper.

Of ion pumps, sensors and channels - perspectives on microbial rhodopsins between science and history.

We present a historical overview of research on microbial rhodopsins ranging from the 1960s to the present date. Bacteriorhodopsin (BR), the first identified microbial rhodopsin, was discovered in the context of cell and membrane biology and shown to be an outward directed proton transporter. In the 1970s, BR had a big impact on membrane structural research and bioenergetics, that made it to a model for membrane proteins and established it as a probe for the introduction of various biophysical techniques that are widely used today.

Purple matter, membranes and 'molecular pumps' in rhodopsin research (1960s-1980s).

In the context of 1960s research on biological membranes, scientists stumbled upon a curiously coloured material substance, which became called the "purple membrane." Interactions with the material as well as chemical analyses led to the conclusion that the microbial membrane contained a photoactive molecule similar to rhodopsin, the light receptor of animals' retinae. Until 1975, the find led to the formation of novel objects in science, and subsequently to the development of a field in the molecular life sciences that comprised biophysics, bioenergetics as well as membrane and structural biology.

Jeewanu, or the 'particles of life'. The approach of Krishna Bahadur in 20th century origin of life research.

Starting in the 1960s, the Indian chemist Krishna Bahadur, from the University of Allahabad, published on organic and inorganic particles that he had synthesized and baptized 'Jeewanu', or 'particle of life'. Bahadur conceived of the Jeewanu as a simple form of the living. These studies are presented in a historical perspective and positioned within mid-20th century research on the origin of life, notably the so-called 'coacervate theory' of the Soviet biochemist Aleksandr I Oparin.

Enlightening the life sciences: the history of halobacterial and microbial rhodopsin research.

The history of research on microbial rhodopsins offers a novel perspective on the history of the molecular life sciences. Events in this history play important roles in the development of fields such as general microbiology, membrane research, bioenergetics, metagenomics and, very recently, neurobiology. New concepts, techniques, methods and fields have arisen as a result of microbial rhodopsin investigations.

Surfaces of action: cells and membranes in electrochemistry and the life sciences.

The term 'cell', in addition to designating fundamental units of life, has also been applied since the nineteenth century to technical apparatuses such as fuel and galvanic cells. This paper shows that such technologies, based on the electrical effects of chemical reactions taking place in containers, had a far-reaching impact on the concept of the biological cell. My argument revolves around the controversy over oxidative phosphorylation in bioenergetics between 1961 and 1977.

The maltose ATP-binding cassette transporter in the 21st century--towards a structural dynamic perspective on its mode of action.

The maltose/maltodextrin transport system of Escherichia coli/Salmonella, composed of periplasmic maltose-binding protein, MalE, the pore-forming subunits MalF and MalG, and a homodimer of the nucleotide-binding subunit, MalK, serves as a model for canonical ATP-binding cassette importers in general. The wealth of knowledge accumulated on the maltose transporter in more than three decades by genetic, molecular genetic and biochemical means was complemented more recently by crystal structures of the isolated MalK dimer and of two conformational states of the full transporter. Here, we summarize insights into the transport mechanism provided by these structures and draw the reader's attention to experimental tools by which the dynamics of the transporter can be studied during substrate translocation.

Canonical and ECF-type ATP-binding cassette importers in prokaryotes: diversity in modular organization and cellular functions.

Since their discovery in the 1960s as 'osmotic shock-sensitive' transporters, a plethora of so-called binding protein-dependent (canonical) ATP-binding cassette (ABC) importers has been identified in bacteria and archaea. Their cellular functions go far beyond the uptake of nutrients. Canonical ABC importers play important roles in the maintenance of cell integrity, responses to environmental stresses, cell-to-cell communication and cell differentiation and in pathogenicity.

NMR assignments of the periplasmic loop P2 of the MalF subunit of the maltose ATP binding cassette transporter.

We have assigned the (1)H, (15)N, (13)C backbone resonances of the second periplasmic loop P2 of the MalF subunit of the maltose ATP binding cassette transporter of Escherichia coli/Salmonella which is important for the recognition of the maltose binding protein MalE.

Transmembrane signaling in the maltose ABC transporter MalFGK2-E: periplasmic MalF-P2 loop communicates substrate availability to the ATP-bound MalK dimer.

ABC transporters are ubiquitous membrane proteins that translocate solutes across biological membranes at the expense of ATP. In prokaryotic ABC importers, the extracytoplasmic anchoring of the substrate-binding protein (receptor) is emerging as a key determinant for the structural rearrangements in the cytoplasmically exposed ATP-binding cassette domains and in the transmembrane gates during the nucleotide cycle. Here the molecular mechanism of such signaling events was addressed by electron paramagnetic resonance spectroscopy of spin-labeled ATP-binding cassette maltose transporter variants (MalFGK2-E).

Periplasmic loop P2 of the MalF subunit of the maltose ATP binding cassette transporter is sufficient to bind the maltose binding protein MalE.

The Escherichia coli maltose transporter belongs to the ATP binding cassette (ABC) transporter superfamily. Recently, the crystal structure of the full transporter MalFGK2 in complex with the maltose binding protein (MBP) was determined [Oldham, M. L.

The MalF P2 loop of the ATP-binding cassette transporter MalFGK2 from Escherichia coli and Salmonella enterica serovar typhimurium interacts with maltose binding protein (MalE) throughout the catalytic cycle.

We have investigated the interaction of the uncommonly large periplasmic P2 loop of the MalF subunit of the maltose ATP-binding cassette transporter (MalFGK(2)) from Escherichia coli and Salmonella enterica serovar Typhimurium with maltose binding protein (MalE) by site-specific chemical cross-linking in the assembled transport complex. We focused on possible distance changes between two pairs of residues of the P2 loop and MalE during the transport cycle. The distance between MalF(S205C) and MalE(T80C) ( approximately 5 A) remained unchanged under all conditions tested.