SMALL IS POWERFUL: Recollections of a Microbiologist and Oceanographer

Jannasch, Holger W.

doi:10.1146/annurev.micro.51.1.1

Cited by 14 publications

(4 citation statements)

References 119 publications

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“…The intellectual challenge embodied in Darwin's words quoted above still represents the main driving force for many of us trying to understand more of the natural world, but increasingly this is perceived as too unrealistic for the modern world, where scientific research is in danger of being absorbed into society's paid beaurocracy as a service industry. One of my favorite sages, the late Holger Jannasch (1997), commenting on the waste caused by funding pressures, wrote: "The effect is worse on younger scientists, who are not rewarded for tackling a problem with perseverance, but for hopping from one promising or prioritized subject to another; funding, not science, being the ultimate goal". I hope young scientists are wise enough to balance these destructive pressures with the basic joy of science which Holger stated later in the same article: "My critical remarks notwithstanding, I am, as most of my colleagues are, well aware of the privilege of being paid for work that often feels like the pursuit of a hobby".…”

mentioning

confidence: 99%

The sedimentary record of dinoflagellate cysts: looking back into the future of phytoplankton blooms

Dale¹

2001

Sci. Mar.

104

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confidence: 99%

The sedimentary record of dinoflagellate cysts: looking back into the future of phytoplankton blooms

Dale¹

2001

Sci. Mar.

104

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“…Most notably the assumed temperature of 25°C, while the effects of the pressure between one bar and in situ were negligible ( Helgeson, 1969 ). But effects of pressure and temperature on thermodynamic calculations are much less severe than the effects on kinetics ( Jannasch, 1997 ), and even the temperature effect does not influence the conclusions drawn here: The standard Gibbs energy of sulfate reduction per mole acetate, for example, only change from −48.1 to −44.5 kJ (mol acetate) −1 between reference temperature and pressure (25°C, 1 bar) and in situ conditions (2°C, 50 bar) at the Greenlandic sites. Thus, the coarse calculations still allow us to conclude that ΔG r from mineralization of organic carbon to CO 2 was shared between the guilds of fermenters and terminal oxidizers in a ratio of roughly 1:1 regardless of site and sediment age.…”

Section: Discussionmentioning

confidence: 99%

Cell-specific rates of sulfate reduction and fermentation in the sub-seafloor biosphere

Jaussi,

Jørgensen,

Kjeldsen

et al. 2023

Front. Microbiol.

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Microorganisms in subsurface sediments live from recalcitrant organic matter deposited thousands or millions of years ago. Their catabolic activities are low, but the deep biosphere is of global importance due to its volume. The stability of deeply buried sediments provides a natural laboratory where prokaryotic communities that live in steady state with their environments can be studied over long time scales. We tested if a balance is established between the flow of energy, the microbial community size, and the basal power requirement needed to maintain cells in sediments buried meters below the sea floor. We measured rates of carbon oxidation by sulfate reduction and counted the microbial cells throughout ten carefully selected sediment cores with ages from years to millions of years. The rates of carbon oxidation were converted to power (J s−1 i.e., Watt) using the Gibbs free energy of the anaerobic oxidation of complex organic carbon. We separated energy dissipation by fermentation from sulfate reduction. Similarly, we separated the community into sulfate reducers and non-sulfate reducers based on the dsrB gene, so that sulfate reduction could be related to sulfate reducers. We found that the per-cell sulfate reduction rate was stable near 10−2 fmol C cell−1 day−1 right below the zone of bioturbation and did not decrease with increasing depth and sediment age. The corresponding power dissipation rate was 10−17 W sulfate-reducing cell−1. The cell-specific power dissipation of sulfate reducers in old sediments was similar to the slowest growing anaerobic cultures. The energy from mineralization of organic matter that was not dissipated by sulfate reduction was distributed evenly to all cells that did not possess the dsrB gene, i.e., cells operationally defined as fermenting. In contrast to sulfate reducers, the fermenting cells had decreasing catabolism as the sediment aged. A vast difference in power requirement between fermenters and sulfate reducers caused the microbial community in old sediments to consist of a minute fraction of sulfate reducers and a vast majority of fermenters.

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“…It is not easy to explain that science is an adventure and not a career (87). I am still as excited about new results as I was 50 years ago.…”

Section: Swan Song (2014)mentioning

confidence: 98%

My Lifelong Passion for Biochemistry and Anaerobic Microorganisms

Thauer

2015

Annu. Rev. Microbiol.

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Early parental influence led me first to medical school, but after developing a passion for biochemistry and sensing the need for a deeper foundation, I changed to chemistry. During breaks between semesters, I worked in various biochemistry labs to acquire a feeling for the different areas of investigation. The scientific puzzle that fascinated me most was the metabolism of the anaerobic bacterium Clostridium kluyveri, which I took on in 1965 in Karl Decker's lab in Freiburg, Germany. I quickly realized that little was known about the biochemistry of strict anaerobes such as clostridia, methanogens, acetogens, and sulfate-reducing bacteria and that these were ideal model organisms to study fundamental questions of energy conservation, CO 2 fixation, and the evolution of metabolic pathways. My passion for anaerobes was born then and is unabated even after 50 years of study.

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SMALL IS POWERFUL: Recollections of a Microbiologist and Oceanographer

Cited by 14 publications

References 119 publications

The sedimentary record of dinoflagellate cysts: looking back into the future of phytoplankton blooms

The sedimentary record of dinoflagellate cysts: looking back into the future of phytoplankton blooms

Cell-specific rates of sulfate reduction and fermentation in the sub-seafloor biosphere

My Lifelong Passion for Biochemistry and Anaerobic Microorganisms

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