Search for: All records

An endosymbiotic bacterium of the genusSodalis, designated as strain HZ^T, was cultured from the parasitoid waspSpalangia cameroni, which develops on the pupae of various host flies. The bacterium was detected inS. cameronideveloped on houseflies,Musca domestica, in a poultry facility in Hazon, northern Israel. After culturing, this bacterium displayed no surface motility on Luria–Bertani agar and was rod-shaped and irregular in size, ~10–30 nm in diameter and 5–20 µm in length. Phylogenetic analyses revealed that strain HZ^Tis closely related toSodalis praecaptivusstrain HS^T, a free-living species of the genusSodalisthat includes many insect endosymbionts. Although these bacteria maintain >98% sequence identity in shared genes, genomic characterization revealed that strain HZ^Thas undergone substantial reductive evolution, such that it lacks many gene functions that are maintained inS. praecaptivusstrain HS^T. Based on the results of phylogenetic, genomic and chemotaxonomic analyses, we propose that this endosymbiont should be classified in a new subspecies asS. praecaptivussubsp. spalangiaesubsp. nov. The type strain for this new subspecies is HZ^T(=ATCC TSD-398^T=NCIMB 15482^T). The subspeciesSodalis praecaptivussubsp.praecaptivusstrain HS^Tis created automatically with the type strain ATCC BAA-2554^T(=DSMZ 27494^T). 

Abstract Evolution results from the interaction of stochastic and deterministic processes that create a web of historical contingency, shaping gene content and organismal function. To understand the scope of this interaction, we examine the relative contributions of stochasticity, determinism, and contingency in shaping gene inactivation in 34 lineages of endosymbiotic bacteria,Sodalis, found in parasitic lice,Columbicola, that are independently undergoing genome degeneration. Here we show that the process of genome degeneration in this system is largely deterministic: genes involved in amino acid biosynthesis are lost while those involved in providing B-vitamins to the host are retained. In contrast, many genes encoding redundant functions, including components of the respiratory chain and DNA repair pathways, are subject to stochastic loss, yielding historical contingencies that constrain subsequent losses. Thus, while selection results in functional convergence between symbiont lineages, stochastic mutations initiate distinct evolutionary trajectories, generating diverse gene inventories that lack the functional redundancy typically found in free-living relatives.