Finding in title is quoted from the abstract in the research paper, https://doi.org/10.7554/eLife.80808:

>In their natural environment, most bacteria preferentially live as complex surface-attached multicellular colonies called biofilms. Biofilms begin with a few cells adhering to a surface, where they multiply to form a mature colony.

>In Caulobacter crescentus biofilms, extracellular DNA (eDNA) is released upon cell death and prevents newborn cells from joining the established biofilm.

>Thus, eDNA promotes the dispersal of newborn cells and the subsequent colonization of new environments.

>Thus, a programmed cell death mechanism using an O2-regulated TAS stimulates dispersal away from areas of a biofilm with decreased O2 availability and favors colonization of a new, more hospitable environment.

... and from the linked summary released by Université de Montréal:

>”We showed that Caulobacter uses a programmed cell death mechanism that causes some cells to sacrifice themselves when the conditions inside the biofilm deteriorate,” said team member Cécile Berne, the lead author of the study.

>“Known as a toxin-antitoxin system, this mechanism uses a toxin that targets a vital function and its associated antidote, the antitoxin,” she said. “The toxin is more stable than the antitoxin and when programmed cell death is initiated, the amount of antitoxin is reduced, resulting in cell death.’’

>“Using a combination of genetics and microscopy, we showed that the toxin-antitoxin system is activated when oxygen becomes sparse as the biofilm becomes larger and cells compete for the available oxygen,’’ Berne added.

>The resulting death of a subset of cells releases DNA, which promotes the dispersal of their live siblings to potentially more hospitable environments, thereby preventing overcrowding that would further reduce environmental quality in the biofilm.

>“The downside is that the biofilm lifestyle is also a strategy used by pathogenic bacteria to become more resistant to antibiotics,” said Brun.