“They acquired it very anciently by taking in a respiring bacterium as an endosymbiont.”

“Genes have recently been discovered in the nuclear genomes of these that appear to have been introduced by an ancestral endosymbiont.”

“Nutritional upgrading for omnivorous carpenter ants by the endosymbiont Blochmannia.”

“The two became one organism, an arrangement called endosymbiosis, and swapped some genetic material to create a new hybrid genome.”

“There is no doubt that secondary endosymbiosis involves a complicated series of events.”

“Potential explanations for these patterns are suggested by the biology of this endosymbiosis.”

“Several species of asexual endosymbionts have experienced accelerated rates of molecular evolution relative to their free-living relatives.”

“In that species, algal endosymbionts occur in both the mantle and gills.”

“For example, bacterial endosymbionts as found in the giant vent Pogonophora are also present in many meiofaunal oligochaetes, nematodes and flatworms.”