The association of TTX with consumed, infecting, or symbiotic bacterial populations within the metazoan species from which it is isolated is relatively clear; presence of TTX-producing bacteria within a metazoan's microbiome is determined by culture methods, the presence of the toxin by chemical analysis, and the association of the bacteria with TTX production by toxicity assay of media in which suspected bacteria are grown. As Lago et al. note, "there is good evidence that uptake of bacteria producing TTX is an important element of TTX toxicity in marine metazoans that present this toxin." TTX-producing bacteria include "Actinomyces", "Aeromonas", "Alteromonas", "Bacillus", "Pseudomonas", and "Vibrio" species; in the following animals, specific bacterial species have been implicated: