idw – Informationsdienst Wissenschaft

Nachrichten, Termine, Experten

Grafik: idw-Logo
Grafik: idw-Logo

idw - Informationsdienst
Wissenschaft

Science Video Project
idw-Abo

idw-News App:

AppStore

Google Play Store



Instance:
Share on: 
10/04/2024 11:00

Microbes attacked with poison gas in battle for iron in the Earth’s early oceans

Christfried Dornis Hochschulkommunikation
Eberhard Karls Universität Tübingen

    Team from the Universities of Tübingen and Bristol hypothesizes the contribution of different bacteria to form today’s deposits of banded iron ores

    Early in the Earth’s development, the atmosphere contained no oxygen. Yet the iron dissolved in the oceans was oxidized in gigantic quantities and deposited as rock. It can be seen today, for example, as banded iron ore in South Africa. A new study investigates how various bacteria excrete insoluble iron as part of their metabolic processes. Some – the phototrophic iron oxidizers – gain energy by oxidizing the iron with the help of sunlight, and others by reacting the iron with nitrate as an oxidizing agent. An international research team including Dr. Casey Bryce from the University of Bristol and Dr. Verena Nikeleit and Professor Andreas Kappler, geomicrobiologists at the University of Tübingen, examined these processes and asked: Which microbes had the upper hand in the competition for the iron? The rival bacteria also used nitrogen monoxide, a toxic gas. The study has been published in the journal Nature Geoscience.

    Two to three billion years ago, the composition of the Earth's atmosphere was completely different. “The oceans at that time contained vast quantities of iron in its reduced form. Under today’s conditions, it would have been quickly oxidized by the oxygen in the atmosphere to form rusty iron minerals,” explains Andreas Kappler. Although there was no oxygen during this early phase on Earth, huge rock deposits of iron show that microbes were oxidizing it effectively even then.

    Experiments in the lab

    “Before there was oxygen on Earth, phototrophic iron oxidizers formed the huge iron oxide deposits known today as banded iron ores,” says Dr Casey Bryce, head of the project. Formerly of the University of Tübingen, Bryce is now a Senior Lecturer at the University of Bristol School of Earth Sciences. “We wanted to know whether these bacteria were in competition with other iron oxidizers that used nitrate,” she adds. This led to the questions of whether these competing microbes could actually coexist, and if so, which of them were primarily responsible for iron oxidation.

    “In order to better understand the situation on early Earth, we conducted laboratory experiments,” says Verena Nikeleit, who since the study has moved to the Norwegian research center NORCE. The research team used one bacterial strain of each of the different iron oxidizers and allowed them to grow under the conditions that prevailed two to three billion years ago, in the light and with the same concentrations of iron, nitrate and carbon dioxide. “To our surprise, the nitrate was quickly used up and the iron was oxidized. But we could not detect any iron oxidation by the phototrophic iron oxidizers,” says Nikeleit. The analyses showed that the nitrate-consuming iron oxidizers formed nitrogen monoxide as a toxic by-product. “This brought the activity of the phototrophic iron oxidizers to a complete standstill. In other words, these microbes killed the phototrophic iron oxidizers by producing a poisonous gas.”

    A complex network of interactions

    “One hypothesis is that the phototrophic iron oxidizers probably contributed very little to the formation of banded iron ores in later phases of the Earth's history,” says Andreas Kappler. This is because the activity of other microbes caused the Earth's atmosphere to contain increasingly more oxygen - a kind of early major environmental pollution event. “This may also have reached some areas of the oceans where nitrate could then be formed as a result. Our results provide the first experimental evidence for the hypothesis that phototrophic iron oxidizers in areas of high productivity may have been exposed to toxic nitrogen monoxide during this time. They must have moved further away from the nutrient-rich areas and were therefore not able to deposit as much iron.”

    According to Casey Bryce, by the research team's calculations iron oxidation by nitrate-reducing bacteria may have initially compensated for the reduced contribution of phototrophic iron oxidizers. “So the initial competition between the different bacteria would not immediately stop the formation of the banded iron formations,” she says. Further measurements and investigations are needed to get a more precise picture of the processes. “Our study provides an insight into how the oxygen enrichment of the Earth's atmosphere could have affected other nutrient cycles in the oceans. This illustrates the complex network of biogeochemical interactions that controlled life in the Earth's early oceans,” Bryce says.


    Contact for scientific information:

    Professor Dr. Andreas Kappler
    University of Tübingen
    Faculty of Science
    Geomicrobiology
    Phone +49 7071 29-74992
    andreas.kappler[at]uni-tuebingen.de


    Original publication:

    Verena Nikeleit, Adrian Mellage, Giorgio Bianchini, Lea Sauter, Steffen Buessecker, Stefanie Gotterbarm, Manuel Schad, Kurt Konhauser, Aubrey L. Zerkle, Patricia Sanchez-Baracaldo, Andreas Kappler, Casey Bryce: Inhibition of phototrophic iron oxidation by nitric oxide in ferruginous environments. Nature Geoscience, https://doi.org/10.1038/s41561-024-01560-9


    Images

    Precambrian banded iron deposits (Banded Iron Formation) in South Africa.
    Precambrian banded iron deposits (Banded Iron Formation) in South Africa.
    Andreas Kappler
    Andreas Kappler

    Microscopic images of a culture of phototrophic iron oxidizers (Rhodobacter ferrooxidans SW2). The living bacteria (stained green) can be seen on, around and in the iron minerals formed.
    Microscopic images of a culture of phototrophic iron oxidizers (Rhodobacter ferrooxidans SW2). The l ...
    Verena Nikeleit
    Verena Nikeleit


    Criteria of this press release:
    Journalists, Scientists and scholars
    Biology, Geosciences, Oceanology / climate
    transregional, national
    Research results, Scientific Publications
    English


     

    Help

    Search / advanced search of the idw archives
    Combination of search terms

    You can combine search terms with and, or and/or not, e.g. Philo not logy.

    Brackets

    You can use brackets to separate combinations from each other, e.g. (Philo not logy) or (Psycho and logy).

    Phrases

    Coherent groups of words will be located as complete phrases if you put them into quotation marks, e.g. “Federal Republic of Germany”.

    Selection criteria

    You can also use the advanced search without entering search terms. It will then follow the criteria you have selected (e.g. country or subject area).

    If you have not selected any criteria in a given category, the entire category will be searched (e.g. all subject areas or all countries).