Scientists of the Insect Symbiosis Research Group at the Max Planck Institute for Chemical Ecology set out to address this question and elucidate the possible role of symbiotic bacteria in the nutrition of firebugs and cotton stainers. By using high-throughput sequencing technologies and deciphering almost 300,000 copies of bacterial 16S rRNA genes, they discovered that the bugs cultivate a characteristic community of three to six bacterial symbionts in a specific mid-gut region. "The symbionts are transferred to the eggs by female bugs, and the hatchlings later take them up by probing the egg surface," explains Sailendharan Sudakaran, PhD student in the Insect Symbiosis Group. "This guarantees that the bugs maintain the symbionts throughout their entire life and pass them on to the next generation." Bugs from different localities and even across different species showed very similar microbial communities, indicating that the bugs have been associated with their symbionts over millions of years.
To find out whether the bacterial symbionts help the bugs to survive on the plant seeds as their sole food source, the researchers performed a simple yet elegant experiment: They dipped bug eggs into bleach and ethanol and thereby killed the microbial community on the surface without harming the developing egg itself. Some of the eggs were then re-infected with a mixture of bacteria from an adult bug's gut, while others remained symbiont-free. Interestingly, the symbiont-free individuals showed markedly higher mortality, needed longer to develop into adults, and produced much fewer offspring than bugs with their native symbionts. "Symbiont-free bugs showed clear signs of malnutrition, although they were fed on the same plant seeds as their symbiont-bearing counterparts. This can only be explained by an important contribution of the bacteria towards host nutrition", says Hassan Salem, another PhD student in the group.
|Contact: Martin Kaltenpoth|
Max Planck Institute for Chemical Ecology