BioTechniques News
Tristan Free
Halloween may have been and gone, but spooky science is going nowhere. In this latest horror movie-esque development, scientists have uncovered ‘zombie’ bacteria that continue to produce extracellular DNA after death.
In an unnerving twist for microbial research, bacteria, or more specifically the dormant viruses they harbor, have been found to synthesize extracellular DNA (eDNA)… after they have died. The discovery comes from researchers at Aarhus University (Denmark), who have also managed to hijack the process to yield specific DNA structures, which they hope could eventually lead to the development of new biological materials.
Bacteria rely on eDNA to provide structural support when building the microbial communities they live in, known as biofilms. These biofilms contain bacteriophages – some of which lie dormant in bacterial genomes as prophages – which facilitate the release of eDNA from cells into the extracellular matrix. Despite being vital to biofilm formation and function, we still know very little about the role of these viruses in controlling eDNA synthesis, structure and activity.
In an attempt to change that, the Aarhus team turned to two bacterial species, Shewanella oneidensis and Bacillus subtilis – strains that are routinely harnessed for environmental applications including bioremediation and microbial fuel cells. Crucially, however, they also produce biofilms that are poor in eDNA.
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First, the researchers added a circular DNA template to bacterial cultures, which would produce a detectable product if replicated by phage machinery. Then, they deprived the bacteria of nutrients, which resulted in prophage activation followed by cell lysis. Even with the cells burst open, eDNA production was reported in the biofilm: real-time monitoring using fluorescent reporter strains revealed that DNA synthesis occurred predominantly after bacterial lysis, coinciding with prophage replication.
“In a way, life goes on after the bacterium has died,” mused the study’s first author Gabriel Antonio Minero.
DNA superstructures were detected in both species of bacteria using fluorescent probes – in S. oneidensis, these resembled a flower, whereas in B. subtilis they had a wire-like shape. When they used a bacterial strain that lacked prophages, none of this DNA was produced, highlighting the importance of the viruses in posthumous eDNA synthesis.
Moreover, the team demonstrated that they were able to manipulate this process, producing secondary DNA structures called G-quadruplexes that folded into superstructures with remarkable morphological diversity. These structures are able to bind other molecules and act like enzymes, accelerating certain chemical reactions.
As such, this work establishes a novel platform for engineering functional DNA materials using bacteria, with potential applications in environmental biotechnology such as wastewater treatment, CO2 capture and bioenergy production. Now that’s a zombie that we can get behind.
The post Back from the dead: ‘zombie’ bacteria produce DNA from beyond the grave appeared first on BioTechniques.
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