The insecticidal potential of Bacillus cereus group strains from insect-dense regions of the United Kingdom

Farmers have long relied on a natural ally to protect their crops: a soil-dwelling bacterium that produces proteins toxic to insects but harmless to humans. This microscopic warrior, known as Bacillus thuringiensis, has been sprayed on fields and engineered into seeds for decades, serving as the world's most important biological pesticide. However, just as insects evolve to survive chemical sprays, they are now learning to resist these natural defenses. As the pests adapt, the old tools are becoming less effective, creating an urgent need to find new sources of insect-killing power. Scientists are turning back to nature, searching for fresh strains of bacteria in the wild that might hold the keys to the next generation of crop protection.

In a recent study, researchers set out to explore this potential by looking in places where insects live in great numbers. They traveled to three specific locations across the United Kingdom, including a forest with heavy infestations of beetles, an agricultural research station, and coastal heathlands teeming with moth caterpillars. From the soil, leaves, and even the bodies of dead insects found at these sites, the team collected thirteen new strains of the Bacillus cereus group, the family of bacteria that includes the famous pest-fighter. Using advanced genetic sequencing, they mapped the entire DNA code of each strain to see what weapons they carried. The goal was to determine if these wild bacteria possessed the same insect-killing genes as the commercial varieties, or if they held something entirely new.

The investigation revealed a rich diversity of bacteria, far more varied than a single type of pest-fighter. The thirteen strains belonged to different genetic families and carried distinct sets of instructions. Five of these strains were found to possess the specific genes that produce crystal proteins, the very toxins that make Bacillus thuringiensis effective against insects. These genes were not random; they appeared to match the local insect populations. For instance, the strains found in the coastal areas, where winter moths are abundant, carried genes known to target moth-like insects. The strains from the forest, where beetles were common, carried a broader mix of toxins, including those effective against beetles. This suggests that the bacteria are naturally tuned to the specific pests in their immediate environment, evolving to fight the local threats.

Beyond the known toxins, the researchers looked for something more elusive: the genetic blueprints for secondary metabolites. These are complex chemical compounds that bacteria produce to help them survive and compete, often acting as antibiotics or additional poisons. The team scanned the genomes for clusters of genes responsible for making these substances. They found a total of 274 such gene clusters across the thirteen strains. What was most striking was that the vast majority of these clusters—more than 60 percent—did not match any known chemical factory in the scientific database. They were entirely new. This indicates that these wild bacteria are capable of producing a wide array of unique chemicals that scientists have never seen before, offering a vast, untapped reservoir of potential new insecticides.

One of the most intriguing findings came from a strain isolated from a dead caterpillar. Unlike the others, this bacterium did not carry the standard crystal protein genes. Instead, it was packed with the novel gene clusters mentioned earlier. This raises a fascinating possibility: the insect may not have been killed by the familiar crystal proteins, but by one of these unknown chemical weapons. If true, it means that the "cheaters" of the bacterial world—strains that do not produce the common toxins but perhaps rely on other, more potent chemical attacks—could be just as dangerous to pests as the well-known killers.

The study also compared these new wild strains to the commercial bacteria currently used by farmers. Several of the new strains were genetically almost identical to the commercial varieties, suggesting that the powerful insect-killing lineages found in nature are the same ones that have been cultivated for agriculture. However, the discovery of the unique gene clusters in the other strains suggests that nature still holds secrets that commercial farming has not yet tapped. While the researchers caution that more work is needed to confirm exactly what these new chemicals do and whether they can be safely used, the findings offer a clear path forward. By looking in the right places—specifically in environments where insects are thriving—scientists can find bacteria that are not only fighting the same battles as our crops but are also armed with weapons we have yet to discover.