Certain bacteria when facing starvation deploy a microscopic needle-like machine to stab neighbouring bacteria and feed on them, an international research team led by an Indian scientist has discovered, unveiling a predatory strategy previously unknown to science.

In their laboratory, the scientists filmed individual cells for up to 40 hours and observed bacteria under starvation conditions unleash a multi-protein machine, known as Type-6 Secretion System (T6SS), to kill their neighbours and harvest their cellular insides.

“When times get tough, the bacteria kill their neighbours and eat them — this is a foraging strategy never before directly observed,” Glen D’Souza, an assistant professor at the school of molecular sciences at the Arizona State University who led the study, told The Telegraph.

Researchers at the Harvard Medical School had discovered the T6SS machinery in 2006 and studies had since then shown that bacteria use this spear-like gun to inject toxins into other bacteria while competing for nutrients or territory. The bacteria themselves produce the toxins and load them into the T6SS spikes.

D’Souza and his colleagues have now shown that the common bacteria known as Vibrio tailor the T6SS firings to their environmental circumstances — a response to what D’Souza calls “either feast-driven competition or famine-triggered foraging”.

“When nutrients are plentiful, the bacteria use T6SS to clear competitors — essentially killing indiscriminately to secure territory,” D’Souza said.

“But as resources dwindle, the firing shifts purpose: the bacteria appear to delay attacks until prey can serve as a nutrient source, then unleash the T6SS to harvest their neighbours’ insides at a controlled pace. This is a switch from competition to calculated predation.”

The toxins injected into the neighbouring cells cause the cells to break apart and release their insides, which are consumed by the predator bacteria.

The researchers believe that such fundamental insights into bacterial survival strategies might open the door to novel medical applications.

“Our findings add a new layer to the role of T6SS,” Astrid Stubbusch, a postdoctoral researcher at Monash University in Australia and first author of the study, published in the US journal Science on Thursday, told this newspaper. The other collaborators were from France, South Korea, Switzerland and the US.

Stubbusch said T6SS might help researchers come up with new strategies to fight infections.

“The toxins deliveredby T6SS and their specifictargets could inspire the development of new antibioticsand novel drug targets,” she said.

Genome sequencing data show that thousands of bacterial species are equipped with T6SS to stab neighbours for nutrition.

The findings are “remarkable”, said Amitesh Anand, a scientist at the Tata Institute of Fundamental Research, Mumbai, who was not associated with the study.

“Prevailing wisdom was that the killing is meant to conserve resources — but this study shows that the killed cells themselves become part of the resource,” said Anand, who leads research to understand community behaviour among bacteria.

D’Souza, who studied in Mumbai and Baroda and pursued research in Germany and Switzerland before joining the Arizona State University, said the insights into T6SS could lead to new therapeutic avenues.

One possibility, he said, would be engineering gut-friendly bacteria to use T6SS to target harmful bacteria while sparing beneficial microbes.