Subpopulations of Pseudomonas aeruginosa inflict distinct tissue damage during infection

Scientists have discovered that Pseudomonas aeruginosa, a common opportunistic pathogen, can store excess carbon in structures called carbonosomes. These carbonosomes are made up of (R)-3-hydroxy fatty acids, which bacteria can use during periods of nutrient imbalance. While carbonosomes were initially thought to simply store surplus carbon, recent research suggests they may also play a role in helping bacteria cope with stress.

Researchers used flow cytometry and fluorescence microscopy to study carbonosomes in P. aeruginosa that had been starved of nitrogen but given extra carbon. They found that carbonosomes significantly affected the bacteria's energy production, protein synthesis, flagellar movement, and antioxidant levels. This impact on cellular processes gave growth-arrested P. aeruginosa a competitive advantage when nutrients fluctuated.

Furthermore, carbonosome production seemed to be a consistent trait across various laboratory and clinical strains of P. aeruginosa, although the levels varied. The Liverpool epidemic strain LESB58, for instance, had minimal BODIPY staining indicating low carbonosome production, while a closely related strain LESB65 showed high levels of staining.

Interestingly, when P. aeruginosa cells without the ability to produce new carbonosomes were exposed to the antibiotic tobramycin, they began to break down and depolymerize their existing carbonosomes. This depolymerization significantly increased the bacteria's susceptibility to the antibiotic. The researchers concluded that carbonosomes have a substantial impact on the physiology, metabolism, and antibiotic resistance of P. aeruginosa.