Zombie bites and airborne transmission are some of the fictional and
all-too-real methods that pathogens like bacteria and viruses use to infect
new hosts. Biologists from San Diego State University have identified a new
way that one type of bacteria invades multiple cells within a living
organism.
The study, published this week in Nature Communications, describes how a new
species of bacteria, Bordetella atropi, which the researchers named for the
Greek fate Atropos responsible for cutting the threads of life, invades its
roundworm host.
And it is aptly named because the bacteria changes its shape into a long
thread, growing up to 100 times the usual size of one bacterium in the span
of 30 hours without dividing.
By altering the genes of Bordetella atropi, the research team discovered
that this invasive threading relies on the same genes and molecules that
other bacteria use when they are in a nutrient-rich environment. However,
these other bacteria only use this pathway to make subtly larger cells,
whereas the B. atropi bacteria grows continuously.
Other bacteria often transform into threads, called filamentation, in
response to dangerous environments or damage to their DNA. This lets them
continue to grow in size, but delay dividing into new bacterial cells until
they fix the damage caused by the stress.
Here, however, the researchers were the first to observe filamentation as a
way of spreading from cell to cell in a living organism for a purpose other
than the stress response. They believe that instead the new species is
invading the host cells, detecting this rich environment and triggering
filamentation in order to quickly infect more cells and access additional
nutrients for their growth.
"We went from finding the worm in the ground, finding the bacteria, and
carrying it all the way to the molecular mechanism of how the bacteria
infects the worm," said Robert Luallen, biology professor and principal
investigator of the study. "We're seeing things that no one's ever seen
before."
Although neither the bacteria nor the roundworm that Luallen studies infects
humans, it is possible that the spreading mechanism may also be used by
human pathogens. Separately, the nutrient-induced filamentation process
might be used by other bacteria to form biofilms, which can coat the tubing
of catheters and lead to complications for patients.
Reference:
Tuan D. Tran et al, Bacterial filamentation as a mechanism for cell-to-cell
spread within an animal host, Nature Communications (2022).
DOI: 10.1038/s41467-022-28297-6