Anammox bacteria generate energy from wastewater while taking a breath

June 29, 2020

A type of anaerobic bacteria responsible for more than 50 percent of nitrogen loss from marine environments has been shown to use solid-state matter present outside their cells for respiration. The finding by KAUST researchers adds to knowledge of the global nitrogen cycle and has important energy-saving potential for wastewater treatment.

Living organisms use oxidation/reduction reactions to harvest the energy they need for survival. This involves the transfer of electrons from an electron donor to an electron acceptor with energy generation. In humans, electrons are released from the food we digest and accepted by soluble oxygen inside our cells. But in many bacteria, other strategies are used for oxidation/reduction, with different types of electron donors and acceptors.

Anammox are anaerobic bacteria found in oxygen-lacking marine and freshwater environments, such as sediments. They derive energy by using ammonium as their electron donor and intracellular soluble nitrite as the acceptor, with the release of nitrogen gas--or so scientists thought.

"We found that freshwater and marine anammox bacteria can also transfer electrons from ammonium to extracellular electron acceptors, like graphene oxide or electrodes in microbial electrolysis cells," says Ph.D. student, Dario Shaw. This novel extracellular electron transfer by anammox bacteria had been conjectured by scientists for more than a decade, but had not been properly explored.

Environmental biotechnologist Pascal Saikaly led a team that found, by looking into the anammox genome, that these bacteria had iron-containing proteins called cytochromes that are also present in types of bacteria known for their ability to transport electrons outside their cells. "We wanted to know if anammox bacteria could also perform extracellular electron transfer," says Saikaly.

They found that electrons were transferred from ammonium inside the bacteria to solid-state matter outside the cell. For this to happen, the electrons crossed three different barriers, starting from inside an anammox cellular organelle called the anammoxosome. "This means that we have demonstrated for the first time a type of bacteria that can transfer electrons through three different membranes," says Saikaly. "This finding challenges our perceptions of cell biology."

"Our findings are a breakthrough in the fields of microbial ecology, bioelectrochemistry and sustainable wastewater treatment," adds Shaw. Anammox bacteria are already used to make wastewater reusable by removing ammonium. They save energy compared to the conventional use of aerobic bacteria, which require oxygen as the electron acceptor for ammonium oxidation. Providing oxygen through an aeration system requires a lot of energy. Anammox bacteria used for wastewater treatment do not need oxygen, but they do currently need nitrite as the electron acceptor. This is provided by another type of bacteria that needs oxygen, and thus energy, to produce it.

The new finding suggests that anammox alone could be used for ammonium removal, while also producing energy in the form of an electric current or energy-rich hydrogen gas in microbial electrolysis cells.
-end-


King Abdullah University of Science & Technology (KAUST)

Related Bacteria Articles from Brightsurf:

Siblings can also differ from one another in bacteria
A research team from the University of Tübingen and the German Center for Infection Research (DZIF) is investigating how pathogens influence the immune response of their host with genetic variation.

How bacteria fertilize soya
Soya and clover have their very own fertiliser factories in their roots, where bacteria manufacture ammonium, which is crucial for plant growth.

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.

Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.

Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.

Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.

Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.

How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.

The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?

Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.

Read More: Bacteria News and Bacteria Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.