Humic acid interferes with species recognition in zebrafish (Danio rerio)

Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Journal of Chemical Ecology 33 (2007): 2090-2096, doi:10.1007/s10886-007-9377-z.Few studies have addressed how chemosensation may be impaired by chemical alterations of the environment and anthropogenic disturbance. Humic acid (HA) is a pervasive, naturally occurring organic derivative found in aquatic and terrestrial environments; human activity, however, can lead to elevated levels of HA. Recent studies suggest that environments that contain high levels of HA may hinder chemical communication. We tested the ability of adult zebrafish (Danio rerio) to discriminate between conspecific and heterospecific urinary chemical cues found in the presence and absence of HA. We show that high humic acid levels (200 mg/l) can impair the ability to differentiate conspecifics from heterospecifics. We also found that zebrafish prefer untreated water over HA-treated water. These findings suggest that, in addition to human-produced synthetic compounds, changes in the abundance of naturally occurring substances may also negatively impact natural behaviors in aquatic species by disturbing the sensory environment

Intestinal colonization of genotoxic Escherichia coli strains encoding colibactin and cytotoxic necrotizing factor in small mammal pets

© 2019 Elsevier B.V. Escherichia coli encoding colibactin (clb), cytolethal distending toxin (cdt), and hemolysin-associated cytotoxic necrotizing factor (cnf) are associated with various intestinal and extra-intestinal diseases in humans and animals. Small mammal pets are not evaluated for genotoxin-encoding E. coli. Thus, the prevalence of such strains is unknown. The objective of this study was to isolate and characterize genotoxin-encoding E. coli from healthy and ill small mammal pets examined at a veterinary clinic and at two animal adoption centers. E. coli isolates were cultured from fecal samples and biochemically characterized. A total of 65 animals, including mice, rats, rabbits, guinea pigs, and hedgehogs, were screened. Twenty-six E. coli isolates were obtained from 24 animals. Twelve of the 26 isolates (46.2 %) were PCR-positive for the pks genes clbA and clbQ. Two isolates (7.7 %) were PCR-positive for cnf. All isolates were PCR-negative for cdt. All genotoxin-encoding isolates belonged to the pathogen-associated phylogenetic group B2. Representative genotoxin-encoding isolates had serotypes previously associated with clinical disease in humans and animals. Isolates encoding pks or cnf induced megalocytosis and cytotoxicity to HeLa cells in vitro. Although most isolates were obtained from healthy pets, two guinea pigs with diarrhea had pks-positive isolates cultured from their feces. Whole genome sequencing on four representative isolates confirmed the presence of pks and cnf genes and identified other virulence factors associated with pathogenicity in animals and humans. Our results suggest that small mammalian pets may serve as a reservoir for potentially pathogenic E. coli and implicate a zoonotic risk