Julia A. Vorholt | |
|---|---|
 2016 | |
| Born | September 15, 1969 |
| Scientific career | |
| Thesis | Formylmethanofuran-Dehydrogenasen aus methanogenen Archaea Rolle von Eisen-Schwefel-Zentren, von Molybdän und Wolfram und von Selen (1997) |
| Doctoral advisor | Rudolf K. Thauer |
Julia A. Vorholt (born September 15, 1969 [1] ) is a full professor of microbiology at ETH Zurich and an elected member of the German Academy of Sciences Leopoldina. [1]
She earned her PhD in 1997 under professor Rudolf K. Thauer at the Max Planck Institute for Terrestrial Microbiology, for which she was awarded the Otto Hahn Medal, and is a German national residing in Switzerland. [1] Following her Ph.D., she was a postdoctoral researcher with Mary Lidstrom at the University of Washington. [2]
She is a member of the European Academy of Microbiology (EAM). [3]
Current projects of the Vorholt lab at ETH Zurich include: [4]
In addition, work from her lab was significant in refuting previous claims by NASA scientists that the arsenic-tolerant bacteria GFAJ-1 could utilize arsenic instead of phosphorus in DNA and other essential biomolecules. [5] [6]
As of 2013 she had 90 publications, [1] and as of 2015 her work has been cited approximately 4100 times. [7]
Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but only the grey form, which has a metallic appearance, is important to industry.
An extremophile is an organism that is able to live in extreme environments, i.e. environments with conditions approaching or expanding the limits of what known life can adapt to, such as extreme temperature, radiation, salinity, or pH level.
Bacterial growth is proliferation of bacterium into two daughter cells, in a process called binary fission. Providing no event occurs, the resulting daughter cells are genetically identical to the original cell. Hence, bacterial growth occurs. Both daughter cells from the division do not necessarily survive. However, if the surviving number exceeds unity on average, the bacterial population undergoes exponential growth. The measurement of an exponential bacterial growth curve in batch culture was traditionally a part of the training of all microbiologists; the basic means requires bacterial enumeration by direct and individual, direct and bulk (biomass), indirect and individual, or indirect and bulk methods. Models reconcile theory with the measurements.
A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPSs). The cells within the biofilm produce the EPS components, which are typically a polymeric conglomeration of extracellular polysaccharides, proteins, lipids and DNA. Because they have three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as "cities for microbes".
Paul Charles William Davies is an English physicist, writer and broadcaster, a professor in Arizona State University and director of BEYOND: Center for Fundamental Concepts in Science. He is affiliated with the Institute for Quantum Studies in Chapman University in California. He previously held academic appointments in the University of Cambridge, University College London, University of Newcastle upon Tyne, University of Adelaide and Macquarie University. His research interests are in the fields of cosmology, quantum field theory, and astrobiology.
The arsenate is an ion with the chemical formula AsO3−4. Bonding in arsenate consists of a central arsenic atom, with oxidation state +5, double bonded to one oxygen atom and single bonded to a further three oxygen atoms. The four oxygen atoms orient around the arsenic atom in a tetrahedral geometry. Resonance disperses the ion's −3 charge across all four oxygen atoms.
In microbiology, the phyllosphere is the total above-ground surface of a plant when viewed as a habitat for microorganisms. The phyllosphere can be further subdivided into the caulosphere (stems), phylloplane (leaves), anthosphere (flowers), and carposphere (fruits). The below-ground microbial habitats are referred to as the rhizosphere and laimosphere. Most plants host diverse communities of microorganisms including bacteria, fungi, archaea, and protists. Some are beneficial to the plant, others function as plant pathogens and may damage the host plant or even kill it.
Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota. It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically important groups of bacteria belong to this class. It is composed by all Gram-negative microbes and is the most phylogenetically and physiologically diverse class of Proteobacteria.
Methylorubrum extorquens is a Gram-negative bacterium. Methylorubrum species often appear pink, and are classified as pink-pigmented facultative methylotrophs, or PPFMs. The wild type has been known to use both methane and multiple carbon compounds as energy sources. Specifically, M. extorquens has been observed to use primarily methanol and C1 compounds as substrates in their energy cycles. It has been also observed that use lanthanides as a cofactor to increase its methanol dehydrogenase activity
For the American folk-rock singer-songwriter, see Nancy Moran.
Felisa Wolfe-Simon is an American microbial geobiologist and biogeochemist. In 2010, Wolfe-Simon led a team that discovered GFAJ-1, an extremophile bacterium that they claimed was capable of substituting arsenic for a small percentage of its phosphorus to sustain its growth, thus advancing the remarkable possibility of non-RNA/DNA-based genetics. However, these conclusions were immediately debated and criticized in correspondence to the original journal of publication, and have since come to be widely disbelieved. In 2012, two reports refuting the most significant aspects of the original results were published in the same journal in which the original findings had been previously published.
Arsenic biochemistry refers to biochemical processes that can use arsenic or its compounds, such as arsenate. Arsenic is a moderately abundant element in Earth's crust, and although many arsenic compounds are often considered highly toxic to most life, a wide variety of organoarsenic compounds are produced biologically and various organic and inorganic arsenic compounds are metabolized by numerous organisms. This pattern is general for other related elements, including selenium, which can exhibit both beneficial and deleterious effects. Arsenic biochemistry has become topical since many toxic arsenic compounds are found in some aquifers, potentially affecting many millions of people via biochemical processes.
GFAJ-1 is a strain of rod-shaped bacteria in the family Halomonadaceae. It is an extremophile that was isolated from the hypersaline and alkaline Mono Lake in eastern California by geobiologist Felisa Wolfe-Simon, a NASA research fellow in residence at the US Geological Survey. In a 2010 Science journal publication, the authors claimed that the microbe, when starved of phosphorus, is capable of substituting arsenic for a small percentage of its phosphorus to sustain its growth. Immediately after publication, other microbiologists and biochemists expressed doubt about this claim, which was robustly criticized in the scientific community. Subsequent independent studies published in 2012 found no detectable arsenate in the DNA of GFAJ-1, refuted the claim, and demonstrated that GFAJ-1 is simply an arsenate-resistant, phosphate-dependent organism.
Arsenate-reducing bacteria are bacteria which reduce arsenates. Arsenate-reducing bacteria are ubiquitous in arsenic-contaminated groundwater (aqueous environment). Arsenates are salts or esters of arsenic acid (H3AsO4), consisting of the ion AsO43−. They are moderate oxidizers that can be reduced to arsenites and to arsine. Arsenate can serve as a respiratory electron acceptor for oxidation of organic substrates and H2S or H2. Arsenates occur naturally in minerals such as adamite, alarsite, legrandite, and erythrite, and as hydrated or anhydrous arsenates. Arsenates are similar to phosphates since arsenic (As) and phosphorus (P) occur in group 15 (or VA) of the periodic table. Unlike phosphates, arsenates are not readily lost from minerals due to weathering. They are the predominant form of inorganic arsenic in aqueous aerobic environments. On the other hand, arsenite is more common in anaerobic environments, more mobile, and more toxic than arsenate. Arsenite is 25–60 times more toxic and more mobile than arsenate under most environmental conditions. Arsenate can lead to poisoning, since it can replace inorganic phosphate in the glyceraldehyde-3-phosphate --> 1,3-biphosphoglycerate step of glycolysis, producing 1-arseno-3-phosphoglycerate instead. Although glycolysis continues, 1 ATP molecule is lost. Thus, arsenate is toxic due to its ability to uncouple glycolysis. Arsenate can also inhibit pyruvate conversion into acetyl-CoA, thereby blocking the TCA cycle, resulting in additional loss of ATP.
Rosemary Jeanne Redfield is a microbiologist associated with the University of British Columbia where she worked as a faculty member in the Department of Zoology from 1993 until retiring in 2021.
Mark Alexander Lever is a microbial ecologist who studies the role of microorganisms in the global carbon cycle. He is a professor of environmental microbiology in the Department of Environmental Systems Science in the Institute of Biogeochemical and Pollutant Dynamics at ETH Zurich.
Mary E. Lidstrom is a Professor of Microbiology at the University of Washington. She also holds the Frank Jungers Chair of Engineering, in the Department of Chemical Engineering. She currently is a fellow of the American Academy of Microbiology, a member of the National Academy of Sciences and serves on the editorial boards of the Journal of Bacteriology and FEMS Microbial Ecology.
Abigail A. Salyers was a microbiologist who pioneered the field of human microbiome research. Her work on the bacterial phylum Bacteroidetes and its ecology led to a better understanding of antibiotic resistance and mobile genetic elements. At a time where the prevailing paradigm was focused on E. coli as a model organism, Salyers emphasized the importance of investigating the breadth of microbial diversity. She was one of the first to conceptualize the human body as a microbial ecosystem. Over the course of her 40-year career, she was presented with numerous awards for teaching and research and an honorary degree from ETH Zurich, and served as president of the American Society for Microbiology.
The plant microbiome, also known as the phytomicrobiome, plays roles in plant health and productivity and has received significant attention in recent years. The microbiome has been defined as "a characteristic microbial community occupying a reasonably well-defined habitat which has distinct physio-chemical properties. The term thus not only refers to the microorganisms involved but also encompasses their theatre of activity".
Some microorganisms, such as endophytes, penetrate and occupy the plant internal tissues, forming the endospheric microbiome. The arbuscular mycorrhizal and other endophytic fungi are the dominant colonizers of the endosphere. Bacteria, and to some degree archaea, are important members of endosphere communities. Some of these endophytic microbes interact with their host and provide obvious benefits to plants. Unlike the rhizosphere and the rhizoplane, the endospheres harbor highly specific microbial communities. The root endophytic community can be very distinct from that of the adjacent soil community. In general, diversity of the endophytic community is lower than the diversity of the microbial community outside the plant. The identity and diversity of the endophytic microbiome of above-and below-ground tissues may also differ within the plant.
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