Insects are successful in part because they are able to exploit resources that other organisms cannot utilize. Some foods offer incomplete nutrition that must be supplemented in some way. One way that insects supplement their diet is by hosting symbiotic bacteria. The bacteria symbionts produce excess amounts of important vitamins and other nutrients that are available to the insect. Some symbionts produce enzymes that aid in digestion. Others produce substances that kill or control pathogens that could harm or kill the insect. The bacteria get a protected and relatively stable environment, a steady food supply and can reproduce as the insect reproduces. These bacteria contributions to digestion and nutrition benefit the host insect directly and the bacteria symbiont indirectly.
In some instances, bacterial symbionts are hosted in special cells or organs of the insect. The digestive system of many insects contains blind pouches called “gastric caeca” that extend from the insect midgut. The gastric caeca may be sites of nutrient absorption, but also have other functions. A recent study of the gastric caeca of Hemiptera (true bugs) found over 30 species of unique Actinobacteria. Many species of Actinobacteria are symbionts of insects; However, the relationship between the Actinobacteria and the Hemiptera in the study is not yet determined.
Why might studies of these symbionts be important? Many insects are reliant on their symbionts for survival. Strategies that impair or eliminate the symbionts could be used to control pest insects. Actinobacteria are known to produce important anti-biotics. Insect symbiotic bacteria are an untapped source for discovery of new antibiotics of potential medical importance.