UNIST team links prey surface structure to attack strength of predatory bacteria
In short
UNIST said on 22 October that a team led by Prof. Robert Mitchell found that the structure of lipopolysaccharide (LPS) on the E. coli outer membrane affects how efficiently the predatory bacterium Bdellovibrio bacteriovorus attacks. Shortened inner cores delayed the attack in all four strains tested, while a long O-antigen chain lowered efficiency in two of the four. The outlets say the work could help develop 'living antibacterial' agents.
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Ulsan National Institute of Science and Technology (UNIST) said on 22 October that a team led by Prof. Robert Mitchell of its Department of Life Sciences found that the structure of lipopolysaccharide (LPS) in the E. coli outer membrane affects how efficiently the predatory bacterium Bdellovibrio bacteriovorus attacks. Newsis described the LPS structure as a major factor in that efficiency. [ 1 , 2 , 3 ]
According to Seoul Economic Daily and Newsis, Bdellovibrio invades other bacteria, breaks down components of the host's cytoplasm, multiplies and then destroys the host. Seoul Economic Daily wrote that it can remove resistant bacteria that existing antibiotics do not affect, and that it also breaks down the host's genetic material, which can prevent resistance genes from spreading. Seoul Economic Daily said it had not been clear which surface structures are involved when the bacterium recognises and enters a host. [ 1 , 2 ]
The team focused on the LPS chains extending from the outer membrane of Gram-negative bacteria. Seoul Economic Daily reported that they removed E. coli's LPS synthesis genes one at a time and compared the attack of four Bdellovibrio strains. The shorter the 'inner core', the sugar chain closest to the outer membrane, the more the initial attack was delayed in all four strains. More E. coli survived as the chain was cut, and the share of hosts rounding into 'bdelloplasts' fell. When the removed genes were restored, E. coli again became vulnerable to predation. [ 1 , 2 ]
Adding a long sugar chain called O-antigen to the chain ends lowered attack efficiency in two of the four strains, while the other two were not greatly affected, Seoul Economic Daily and Newsis reported. Seoul Economic Daily said the long chain covered surface structures the predator needs to attach and enter. Both outlets said the strains differ in their ability to recognise the host surface or overcome barriers. The team proposed a 'Goldilocks LPS structure' model, in which the inner core is kept and the outer long chains do not block access too much, according to Seoul Economic Daily. [ 1 , 2 , 3 ]
The team also found a way to raise attack strength. When the predatory bacteria were incubated for one hour in a solution containing E. coli LPS and then mixed with E. coli, they killed the E. coli faster than without pre-treatment. How this pre-exposure raises attack activity is not known, and Newsis said the team added that follow-up research is needed. [ 1 , 2 , 3 ]
Mitchell said that to use predatory bacteria as an antibacterial tool, one must know how well they attack a target pathogen and what governs the effect. He said the study would be a basis for selecting bacteria matched to a pathogen's surface structure and finding conditions that raise attack activity. The results were published online in The ISME Journal on 14 September, per Seoul Economic Daily and Newsis. The work was supported by the National Institute of Health under the Ministry of Health and Welfare, the National Research Foundation of Korea under the Ministry of Science and ICT, and the US Air Force Office of Scientific Research. [ 1 , 2 , 3 ]
Why it matters
The outlets report that the findings could help choose predatory bacteria suited to a given pathogen's surface and find conditions that raise their attack activity. They frame this as a basis for new antibacterial approaches against antibiotic-resistant bacteria. The work is basic research, and the documents report no clinical use.
Key facts
- UNIST said on 22 October that Prof. Robert Mitchell's team in the Department of Life Sciences found that the structure of LPS in the E. coli outer membrane affects the attack efficiency of Bdellovibrio bacteriovorus. [ 1 , 2 , 3 ]
- When the inner core of LPS was shortened, the initial attack was delayed in all four Bdellovibrio strains tested. [ 1 , 2 ]
- Adding a long O-antigen to the outside of LPS lowered attack efficiency in two of the four strains; the other two showed no major change. [ 1 , 2 ]
- Pre-incubating the predatory bacteria for one hour in an LPS solution made them kill E. coli faster than without pre-exposure. [ 1 , 2 , 3 ]
- The results were published online in The ISME Journal on 14 September. [ 1 , 2 ]
- The research was supported by the National Institute of Health under the Ministry of Health and Welfare, the National Research Foundation of Korea under the Ministry of Science and ICT, and the US Air Force Office of Scientific Research. [ 1 , 2 ]
Confirmed by several sources
- UNIST announced that LPS structure on E. coli affects the attack efficiency of the predatory bacterium Bdellovibrio bacteriovorus. [ 1 , 2 , 3 ]
- A shorter inner core delayed the initial attack, and a long O-antigen reduced attack efficiency in some strains. [ 1 , 2 , 3 ]
- One hour of pre-exposure to an LPS solution made the predatory bacteria kill E. coli faster. [ 1 , 2 , 3 ]
Still unclear
- Why pre-exposure to LPS raises the predatory bacteria's attack efficiency is not known. Newsis said the mechanism has not been established and the team said follow-up research is needed; Seoul Economic Daily said the team plans further research.
- Whether the findings will lead to a usable 'living antibacterial' treatment. The outlets only say the work is expected to be a basis for such development, and give no timeline or clinical data.