Bacteria that suck out the innards of fellow microbes could someday be used to treat the growing number of antibiotic-resistant infections. That is one implication of a fascinating new study into the bacterium Micavibrio aeruginosavorus.
The news is timely, as a pressure group last week called on the government to do more to deliver new antibiotics. The Antibiotics Action petition delivered to 10 Downing Street, signed by over 4,500 clinicians and scientists, signified the growing attention being paid to antibiotic resistance in public discussion.
If ministers hear the plea, they might do well to look down the microscope at M. aeruginosavorus. This bacterium is one of few known species to prey on other bacteria in a vampire-like fashion, by attaching to the cell wall and sucking out the cell’s insides. Many of its prey are bacteria that cause human illness—and some, like Pseudomonas aeruginosa (which often invades the lungs of cystic fibrosis patients) and Klebsiella pneumoniae (which can cause a type of pneumonia), represent a growing number of hospital-acquired infections.
M. aeruginosavorus is a promising candidate for combating bugs that are resistant to traditional antibiotics. The analysis of its genome, published in BMC Genomics, is an important early step in studying the bacterium’s biology. Until now, even that step has been difficult. Since the vampire bacterium can’t survive outside the presence of its prey, it can’t be isolated for study.
However, using modern sequencing technology, Martin Wu at the University of Virginia was able to genetically sequence the community of bacteria and tease out M. aeruginosavorus’s individual genome afterward.
Meeting resistance
Antibiotic resistance is a large and growing problem. More than 70 per cent of the bacteria that cause hospital-acquired infections (pdf) are resistant to at least one of the antibiotics used to treat them. This has contributed to longer hospital stays and more deaths from infection. One of the commonly resistant bacteria is Pseudomonas aeruginosa.
“We’re losing the war,” says Daniel Kadouri, a collaborator of Dr Wu’s, and a researcher at the University of Medicine and Dentistry of New Jersey. “We have bacteria now that are resistant to everything. There are clinical wards that basically are closed because they have P. aeruginosa infection there. There are wounds that we can’t treat, that the only thing we can do is amputate. We’re looking back at 19th century medicine now.”
P. aeruginosa is a common pathogen in hospital-acquired infections, and is also a deadly invader in the lungs of many cystic fibrosis patients. The bacterium is nearly impossible to treat with antibiotics since it forms a ‘biofilm’, a thin coating of bacteria that is highly resistant to attack. In a wound, the biofilm spreads across the surface and provokes constant inflammation as the immune system unsuccessfully battles the infection. Moreover, the bacterium is now commonly resistant to the sole oral antibiotic with which it was generally treated.
Engineered for eating
P. aeruginosa is, however, one of the favourite meals of vampire bacterium M. aeruginosavorus. (‘Aeruginosavorus’ in Latin literally means ‘aeruginosa-eater’.) This has led researchers to ponder whether the predator bacteria could be used to battle infections when traditional antibiotics fail.
These Dracula bugs could work in various ways, which are in the very early stages of investigation. One line of thought is that M. aeruginosavorus could serve as a “living antibiotic”. For instance, an infected wound could be coated with the predator bacteria to devour the infection but leave human cells untouched. It appears that the bacterium has no interest in attacking non-bacterial cells, which would mean that as soon as the infection was killed the vampire bacteria would die as well.
Even antibiotic-resistant bacteria would be susceptible, and it appears that they are unable to develop resistance to this mode of attack. The recent genetic sequencing of M. aeruginosavorus may allow it to be genetically modified so that it is a more ruthless killer, or more specific to one type of prey.
A second possibility is using the vampire bacterium to treat internal infections, such as in the lungs. This is a more complicated issue, since many helpful bacteria that reside in the body would also potentially be preyed upon. However, the genetic sequencing of M. aeruginosavorus will help researchers to identify the proteins it uses to attack prey, which may inspire new antibiotics for resistant forms of the infection.
Vampire bacteria are unlikely, however, to make much of a near-term dent in the problem of antibiotic resistance—a problem that is also, sadly, all too undead.
(Image credit: University of Virginia)
Wang, Z., Kadouri, D., & Wu, M. (2011). Genomic insights into an obligate epibiotic bacterial predator: Micavibrio aeruginosavorus ARL-13 BMC Genomics, 12 (1) DOI: 10.1186/1471-2164-12-453