Antonie van Leeuwenhoek (1632-1723): Master of Fleas and Father of Microbiology.

The Dutch scientist and entrepreneur Antonie van Leeuwenhoek (1632-1723) was the first to discover and describe microorganisms (protists, bacteria), living beings he characterized as "animalcules" (little animals) [...].

Mendel-200: Pea as a model system to analyze hormone-mediated stem elongation.

In a recent Review Article on Gregor Mendel's (1822-1884) work with pea (Pisum sativum)-plants, it was proposed that this crop species should be re-vitalized as a model organism for the study of cell- and organ growth. Here, we describe the effect of exogenous gibberellic acid (GA3) on the growth of the second internode in 4-day-old light-grown pea seedlings (Pisum sativum, large var. "Senator"). lnjection of glucose into the internode caused a growth-promoting effect similar to that of the hormone GA3. Imbibition of dry pea seeds in GA3, or water as control, resulted in a drastic enhancement in organ development in this tall variety. Similar results were reported for dwarf peas. These "classical" experimental protocols are suitable to study the elusive effect of gibberellins (which act in coordination with auxin) on the regulation of plant development at the biochemical and molecular levels.

Forever young: stem cell and plant regeneration one century after Haberlandt 1921.

Plants are characterized by a post-embryonic mode of organ development, which results in a need for these photoautotrophic organisms to regenerate lost parts in the course of their life cycle. This capacity depends on the presence of "pluripotent stem cells," which are part of the meristems within the plant body. One hundred years ago, the botanist Gottlieb Haberlandt (1854-1945) published experiments showing wounding-induced callus formation, which led ultimately to plant regeneration in tissue culture and thence to the techniques of "plant biotechnology," with practical applications for mankind. Here, we recount Haberlandt's discovery within the context of his long research life and his most influential book Physiologische Pflanzenanatomie. In the second part, we describe and analyze a plant tissue-culture regeneration system using sterile, dark-grown sunflower (Helianthus annuus) seedlings as experimental material. We document that excised hook segments, which contain a "stem cell niche," can regenerate entire miniature H. annuus-plantlets that, raised in a light/dark regime, develop flowers. Finally, we discuss molecular data relevant to plant regeneration with reference to phytohormones and conclude that, one century after Haberlandt, 1921, the exact biochemical/genetic mechanisms responsible for the capability of stem cells to remain "forever young" are, although already complex, really just beginning to become known.

On the historical roots of creationism and intelligent design: German Allmacht and Darwinian evolution in context.

As detailed in a Letter published in Science in 2017, the adherents of creationism and intelligent design are still active in promoting their biblical-literalist views of the origin and evolution of life on Earth. In this contribution, we take a look at this ideological phenomenon in the USA and analyze the philosophical roots of this ongoing movement. Specifically, we discuss Vernon Kellogg's book entitled Headquarters Nights (1917) with reference to the German 'Allmacht' (English-omnipotence) and Darwinian evolution to demonstrate how this publication bolstered the development of active anti-evolutionism in the USA among American fundamentalist Christians, inclusive of the Intelligent Design (ID)-agenda. The current activities of creationist associations in the USA and Germany are summarized, with reference to a new pro-ID-group established in Austria in 2019 that is sponsored by the Discovery Institute in Seattle, Washington (USA).

The Warburg-effects: basic metabolic processes with reference to cancer development and global photosynthesis.

One century ago (1920), Otto Warburg (1883-1970) discovered that in liquid cultures of unicellular green algae (Chlorella sp.) molecular oxygen (O2) exerts an inhibitory effect on photosynthesis. Decades later, O2 dependent suppression of photosynthetic carbon dioxide (CO2) assimilation (the "green" Warbur geffect) was confirmed on the leaves of seed plants. Here, we summarize the history of this discovery and elucidate the consequences of the photorespiratory pathway in land plants with reference to unpublished CO2 exchange data measured on the leaves of sunflower (Helianthus annuus) plants. In addition, we discuss the inefficiency of the key enzyme Rubisco and analyze data concerning the productivity of C3 vs. C4 crop species (sunflower vs. maize, Zea mays). Warburg's discovery inaugurated a research agenda in the biochemistry of photosynthetic CO2 assimilation that continues to the present. In addition, we briefly discuss Warburg's model of metabolic processes in cancer, net primary production (global photosynthesis) with respect to climate change, trees and other land plants as CO2 removers, and potential climate mitigators in the Anthropocene.

Auxin action in developing maize coleoptiles: challenges and open questions.

The year 2020 marks the 150th anniversary of the elucidation of the process of plant organ growth at the cellular level by Julius Sachs (1870). In this Addendum to a Review Article in Molecular Plant, we describe this fundamental discovery and argue that the etiolated grass coleoptile still represents the system of choice for the experimental analysis of auxin (indole-3-acetic acid, IAA)-action. With reference to the phenomenon of 'tissue tension', we discuss the acid-growth hypotheses of IAA-induced wall loosening and the process of vacuolar expansion, respectively. IAA-mediated elongation appears to be independent of wall acidification, and may be regulated via the secretion of glycoproteins into the outer epidermal wall, whereby turgor (and tissue) pressure provides the 'driving force' for growth. As predicted by the "acid growth-hypothesis", the fungal phytotoxin Fusicoccin (Fc) induces organ elongation via the rapid secretion of protons. We conclude that "cell elongation" can only be understood at the level of the entire organ that displays biomechanical features not established by single cells. This systems-level approach can be traced back to the work of Sachs (1870).

Ernst Haeckel, ancient forests, and the Anthropocene.

In this Addendum to an article in  Nature commemorating the 100th anniversary of Ernst Haeckel's death (9 August 1919), we recall the largely forgotten fact that Haeckel (1868) was an early proponent of the concept of an "Anthropozoic Age", a 19th-century anticipation of the "Anthropocene". Haeckel in particular highlighted man's extensive remodeling of the planet in ancient forests. Earlier influences on Haeckel included Alexander von Humboldt (1769-1859) and dozens of similar writers in the 19th century Romantic era, including the Italian geologist and priest Antonio Stoppani (1824-1891), and the American diplomat and environmentalist George P. Marsh (1801-1882). Starting in the 1840s, Marsh described in extraordinary detail the destructive influence of mankind on natural ecosystems, again with particular emphasis on the destruction of forests. Marsh, like Haeckel after him, was a pioneer in describing the far-reaching human re-modeling of the planet that they and their colleagues presciently labeled the "Anthropozoic Age".

Correct spelling of a recently described species of Helobdella (Annelida: Clitellata: Hirudinea).

In a recently published article (Saglam et al. 2018) the name of a new species of Hirudinea (Annelida, Clitellata) was simultaneously published in three different ways, as Helobdella serendipitious (Saglam et al. 2018: 61, 70, 71, 73), Helobdella serendipitous (ibid.: 63, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74), and as Helobdella serendipidous (ibid.: 75). Acting as first reviser according to Article 24 of the International Code of Zoological Nomenclature (ICZN 1999) here we determine serendipitous as the correct spelling of the species epitheton.

Light and plant development: the discovery of phototropins by Winslow R. Briggs (1928-2019).

The American biologist Winslow Russel Briggs (1928-2019) was a global leader in plant physiology, genetics and photobiology. In this contribution, we try to share our knowledge of the remarkable career of this outstanding scientist. After earning his PhD at Harvard (Cambridge, Massachusetts), he started his independent research program at Stanford University (California). Among many major contributions was his elegant experiment that conclusively demonstrated the role of auxin transport in the phototropic bending response of grass coleoptiles. During subsequent years as Professor of biology at Harvard University, Briggs focused on phytochrome and photomorphogenesis. In 1973, he re-located to Stanford to become Director of the Department of Plant Biology, Carnegie Institution for Science, and faculty member in the Biology Department at Stanford University. After his retirement (1993), he continued his research on "light and plant development" as an emeritus at Carnegie until the day of his death on February 11, 2019. Through his long research career, Briggs stayed at the cutting edge by re-inventing himself from a plant physiologist, to biochemist, geneticist, and molecular biologist. He made numerous discoveries, including the LOV-domain photoreceptor phototropin. Winslow Briggs, who was also a naturalist and gifted pianist, inspired and promoted the work of generations of young scientists - as mentor, colleague and friend.

Ernst Haeckel (1834-1919): The German Darwin and his impact on modern biology.

The year 2019 marks the 100th anniversary of the death of Ernst Haeckel, a German zoologist, artist, and philosopher of science, who defended and supplemented Charles Darwin's system of theories regarding the mechanisms of biological evolution. We briefly recapitulate Haeckel's remarkable career and reproduce the Laudatio read by the President of the Linnean Society of London (1 July 1908), when Haeckel was awarded the Darwin-Wallace Medal. Finally, we summarize the importance of Haeckel's original concepts, insights, and theories with reference to our current knowledge in the areas of evolutionary biology, molecular phylogenetics, systematic zoology, and philosophical issues today.

Plasmodial slime molds and the evolution of microbial husbandry.

Detailed analyses into the life cycle of the soil-dwelling microbe Dictyostelium discoideum led to the conclusion that this "social amoeba" practices some form of "non-monoculture farming" via the transfer of bacteria to novel environments. Herein, we show that in myxomycetes (plasmodial slime molds or myxogastrids) a similar "farming symbiosis" has evolved. Based on laboratory studies of two representative species in the genera Fuligo and Didymium, the sexual life cycle of these enigmatic microbes that feed on bacteria was reconstructed, with reference to plasmo- and karyogamy. We document that the spores carry and transfer bacteria and hence may inoculate new habitats. The significance of this finding with respect to Ernst Haeckel's work on myxomycetes and his concept of ecology are addressed.

Julius von Sachs' forgotten 1897-article: sexuality and gender in plants vs. humans.

One hundred and fifty years ago, Julius von Sachs' (1832-1897) monumental Lehrbuch der Botanik (Textbook of Botany) was published, which signified the origin of physiological botany and its integration with evolutionary biology. Sachs regarded the physiology of photoautotrophic organisms as a sub-discipline of botany, and introduced a Darwinian perspective into the emerging plant sciences. Here, we summarize Sachs' achievements and his description of sexuality with respect to the cellular basis of plant and animal biparental reproduction. We reproduce and analyze a forgotten paper (Gutachten) of Sachs dealing with Die Akademische Frau (The Academic Woman), published during the year of his death on the question concerning gender equality in humans. Finally, we summarize his endorsement of woman's rights to pursue academic studies in the natural sciences at the University level, and conclude that Sachs was a humanist as well as a great scientist.

Systems biology of eukaryotic superorganisms and the holobiont concept.

The founders of modern biology (Jean Lamarck, Charles Darwin, August Weismann etc.) were organismic life scientists who attempted to understand the morphology and evolution of living beings as a whole (i.e., the phenotype). However, with the emergence of the study of animal and plant physiology in the nineteenth century, this "holistic view" of the living world changed and was ultimately replaced by a reductionistic perspective. Here, I summarize the history of systems biology, i.e., the modern approach to understand living beings as integrative organisms, from genotype to phenotype. It is documented that the physiologists Claude Bernard and Julius Sachs, who studied humans and plants, respectively, were early pioneers of this discipline, which was formally founded 50 years ago. In 1968, two influential monographs, authored by Ludwig von Bertalanffy and Mihajlo D. Mesarovic, were published, wherein a "systems theory of biology" was outlined. Definitions of systems biology are presented with reference to metabolic or cell signaling networks, analyzed via genomics, proteomics, and other methods, combined with computer simulations/mathematical modeling. Then, key insights of this discipline with respect to epiphytic microbes (Methylobacterium sp.) and simple bacteria (Mycoplasma sp.) are described. The principles of homeostasis, molecular systems energetics, gnotobiology, and holobionts (i.e., complexities of host-microbiota interactions) are outlined, and the significance of systems biology for evolutionary theories is addressed. Based on the microbe-Homo sapiens-symbiosis, it is concluded that human biology and health should be interpreted in light of a view of the biomedical sciences that is based on the holobiont concept.

Julius Sachs (1868): The father of plant physiology.

The year 2018 marks the 150th anniversary of the first publication of Julius von Sachs' (1832-1897) Lehrbuch der Botanik (Textbook of Botany), which provided a comprehensive summary of what was then known about the plant sciences. Three years earlier, in 1865, Sachs produced the equally impressive Handbuch der Experimental-Physiologie der Pflanzen (Handbook of Experimental Plant Physiology), which summarized the state of knowledge in all aspects of the discipline known today as plant physiology. Both of these books provided numerous insights based on Sachs' seminal experiments. By virtue of a reliance on detailed empirical observation and the rigorous application of chemical and physical principles, it is fair to say that the publication of these two monumental works marked the beginning of what can be called "modern-day" plant science. Moreover, Sachs' Lehrbuch der Botanik prefigured the ascendance of plant molecular biology and the systems biology of photoautotrophic organisms. Regrettably, many of the insights of this great scientist have been forgotten by the generations who followed. It is only fitting, therefore, that the anniversary of the publication of the Lehrbuch der Botanik and the career of "the father of plant physiology" should be honored and reviewed, particularly because Sachs established the physiology of green organisms as an integral branch of botany and incorporated a Darwinian perspective into plant biology. Here we highlight key insights, with particular emphasis on Sachs' detailed discussion of sexual reproduction at the cellular level and his endorsement of Darwinian evolution.

Phylogenetic and morphological resolution of the Helobdella stagnalis species-complex (Annelida: Clitellata: Hirudinea).

The glossiphoniid freshwater leech, Helobdella stagnalis, was described by Linnaeus 1758 based on common European specimens. The presence of a brown, chitinous scute on the dorsal-anterior surface, as observed on leeches elsewhere in the world, has generally led to the classification of all scute-bearing members of the genus as H. stagnalis. Here we describe the morphology and behavior of the type species from Europe, and analyze H. stagnalis-like specimens collected worldwide. We present evidence for at least four distinct scute-bearing Helobdella species that can be morphologically resolved. Maximum Parsimony (MP) and Bayesian Inference (BI) analyses at the mitochondrial cytochrome c oxidase subunit I (COI) locus further supported this notion, with divergence values suggesting a mid-Miocene ancestor of this successful group of cosmopolitan hirudineans. New species, Helobdella echoensis nov. sp., Helobdella eriensis nov. sp., and Helobdella serendipitious nov. sp., are described, based on morphological, anatomical and molecular data. Current distribution patterns of Helobdella spp. suggest a robust, global dispersal mechanism, as well as local pockets of endemism.

Russia's new Lysenkoism.

During the late 1940s and 1950s, a pseudo-scientific concept based on Marxist-Leninist ideology became internationally known as 'Lysenkoism'. Lysenkoism was a neo-Lamarckian idea, claiming that in crop plants, such as wheat, environmental influences are heritable via all cells of the organism. Lysenkoism was applied to agriculture during the Stalin era with disastrous consequences. Despite the triumphs of modern genetics, and the disproval of Lysenkoism, recent years have seen a 're-thinking' of this doctrine in Russia. This disturbing pro-Lysenko movement, which is accompanied by a growing sympathy for Stalin, claims to have its scientific roots in modern epigenetics, specifically the heritability of variation by mechanisms other than changes in DNA sequence. Based on recent research on the model plant Arabidopsis thaliana, its is clear that Lysenkoism has nothing to do with heritable 'epigenetic' modifications. Biologists should defend science against ideological and political interferences.

Boron and the evolutionary development of roots.

Experimental work has shown that Boron (i.e., Boric acid, B) is an essential and multifunctional microelement for vascular plant development. In addition to its other functions, which include xylem development and lignin biosynthesis, we now know that B is involved in phytohormone-signaling and influences the mechanical properties of intercellular pectins. From these data, we conclude that B played an important role during the evolutionary development of lignified tissues, and that it may have been involved in the evolution of vascular plant roots, as hypothesized by D. H. Lewis in 1980. Herein, we review the data pertaining to Lewis' hypothesis, present experimental results on the role of B in root (vs. rhizoid) formation in sunflower vs. a liverwort, and describe the appearance of roots in the fossil record. Open questions are addressed, notably the lack of our knowledge concerning soil microbes and their interactive roles with the micronutrient B during root formation.