Within the short accessory branch clade, species with specialized cleaning behaviors form a monophyletic clade, however, the integrity of the clade was sensitive to alignment criteria.
Interestingly, the majority of accessory genes of species L. monocytogenes were either scattered along the chromosomes (46%) or found inside hyper variable regions (20% when excluding MGE) and thus likely originated from a wide range of diversifying forces.
More than half of the species accessory genes (1161) furthermore displayed homologues in only one or two strains implying relatively recent insertions that are rarely fixed in the population.
Depending on the bacterial species, accessory genes may encode virulence factors, antibiotic resistance determinants, or other loci that contribute to the adaptation of the bacterium to its environment [ 24].
And if accessories are a species of idleness, then free of sloth.
Another mechanism for competitive binding can be influential binding meaning that one species of accessory proteins alters the binding or unbinding characteristics of another species.
In summary, nearly one third of the accessory genes of the species have been introduced by identifiable MGEs, representing a large proportion of gene-scale diversity [ 64].
In C. chilata, displaying a similar swim bladder-saccule-bone relationship, auditory sensitivities and hearing bandwidth were comparable to species lacking accessory auditory structures [ 24, 29].
Loliginids have a streamlined, muscular body morphology and internal shell similar to many pelagic squids, while bearing corneas reminiscent of benthic squids, bacteriogenic photophores (in some species), and accessory reproductive structures found largely in benthic species.
An extensive amount of variation can often be found within the accessory genome of a species and it is important to investigate this source of variation to understand the adaptive potential of a given species [ 48, 53].
