Symbiotic bacteria in planthoppers break record for smallest non-organelle genome ever found
Phys.org
February 20, 2026
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Scientists have discovered that symbiotic bacteria living inside planthoppers have achieved a remarkable feat: they possess the smallest non-organelle genome ever recorded. This groundbreaking finding, published in *Nature Communications*, reveals how these bacteria, which provide essential nutrients to their insect hosts, undergo significant genomic reduction over time. Some of them have lost so many genes that their genomes are nearly indistinguishable from organelles like mitochondria or chloroplasts.
The study highlights the unique relationship between planthoppers and their bacterial symbionts. These bacteria, known as primary endosymbionts, live within specialized cells of the insects and play a critical role in their survival by supplying nutrients that the plant-based diet of planthoppers cannot provide. Over evolutionary time, these bacteria have undergone massive gene loss, resulting in genomes as small as 139 kilobases—far smaller than any previously known free-living bacterium.
The shrinking genomes of these symbionts raise intriguing questions about the boundaries between organelles and bacteria. While mitochondria and chloroplasts are remnants of endosymbiotic bacteria, they have lost most of their genes over millions of years, relying on host cells for survival. The planthopper bacteria, however, retain enough genetic material to remain functional yet exhibit a level of genome reduction that challenges traditional definitions.
This discovery not only advances our understanding of symbiosis and genome evolution but also has broader implications for science. It provides insights into how mutualistic relationships between organisms evolve and how genomes adapt to specific ecological niches. Such research could inform efforts to manipulate insect-microbe interactions, potentially offering new strategies for pest control or improving agricultural practices.
Ultimately, the study underscores the importance of exploring these tiny genomes to unravel the complexities of life's interdependencies. By understanding how bacteria and insects co-evolve, scientists can gain deeper insights into the mechanisms that drive genetic change and the role of symbiosis in shaping biodiversity. This knowledge could open doors to innovative solutions in fields ranging from medicine to biotechnology.
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Originally published on Phys.org on 2/20/2026