Looking in some bacterial 16S sequences obtained by some ants I found some bacteria already known in plants. This is not unusual for members of the insect order Hemiptera since they are small plant feeders with mouthparts adapted for sucking plant sap. During feeding, their stylets penetrate the plant tissue and withdraw plant fluids making hemipteran insects effective vectors of plant pathogens, especially viruses, but also bacteria. But ants?
While working on several hemipteran–symbiont systems, Caspi-Flugera and Zchori-Feina found high similarities between bacterial genes associated with hemipterans and bacterial genes associated with plants, some of the latter referred to as plant pathogens. Therefore, they assume that some bacteria may be shared by hemipterans and plants, first evolving a symbiont of one and later, via feeding, becoming adapted to the other.
According to Caspi-Flugera and Zchori-Feina: “One possible explanation for the identity in gene sequences of symbionts and endophytes is that the bacterium was first established as an endophyte, later acquired the capacity to be vectored by a hemipteran and, with time, developed the ability to be vertically transmitted (and thus sustained) in the new host. The process of becoming a symbiont demands mutual changes and matching for both the symbiont and the host such that each of the partners will benefit. Such a process can be envisioned because many pathogenic bacteria depend on insect vectors for their horizontal transfer. In return, they may change the plant in ways that make it more attractive for the insect vectors (Weintraub and Beanland, 2006) and eventually, such plant-pathogenic bacteria could become essential for the insect”.
I’m still a bit confuse about what could happen in ants, but the ability of symbiotic bacteria to be transmitted among very diverse species, survive, and develop an array of different lifestyles, is realy amazing having vast implications on virtually all living organisms.
Caspi-Fluger, A., & Zchori-Fein, E. (2010) Do plants and insects share the same symbionts? Israel Journal of Plant Sciences, 58, 113-119 DOI: 10.1560/IJPS.58.2.113