Characterization of a virulence related hypothetical protein in Edwardsiella ictaluri

Although the biochemical characterization of E. ictaluri, the subsequent disease progression of enteric septicemia of catfish (ESC), and the associated pathologic lesions are well characterized, the mechanism of invasion of E. ictaluri into a susceptible host is poorly understood. Identification and confirmation of virulence factors and associated genes of E. ictaluri is crucial to elucidating the pathogenesis of this important disease. A signature tagged mutagenesis (STM) study conducted by Thune et al. (2006) identified 50 E. ictaluri clones with transposon insertions in genes potentially involved in pathogenesis. A specific STM mutant, 233PR, carrying a transposon insertion in a gene encoding a hypothetical adhesin protein, was selected for further characterization. In addition, an isogenic mutant was created by inserting a kanamycin resistance cassette 222 bp downstream from the site of the transposon insertion in 233PR in order to examine the effects of differential protein truncation on function. Bioinformatic analysis of the E. ictaluri genome revealed a pathogenicity island encoding genes with similarity to a gene cluster encoding putative adhesin/hemolysin genes in E. coli CL3 (Shen et al. 2004). In vivo results demonstrated the importance of the putative adhesin’s role in E. ictaluri pathogenesis and that protein length correlated to the level of attenuation. In vitro data did not support a role in adhesion, invasion, or intracellular replication in cell culture. The E. ictaluri PAI genes were designated eacA-H for Edwardsiella attenuation complex Results demonstrate that EacF, the putative adhesin, is a virulence factor, but further investigation is required to determine its specific role in E. ictaluri pathogenesis

Pacific Ocean–wide profile of CYP1A1 expression, stable carbon and nitrogen isotope ratios, and organic contaminant burden in sperm whale skin biopsies

This paper is not subject to U.S. copyright. The definitive version was published in Environmental Health Perspectives 119 (2011): 337-343, doi:10.1289/ehp.0901809.Background: Ocean pollution affects marine organisms and ecosystems as well as humans. The International Oceanographic Commission recommends ocean health monitoring programs to investigate the presence of marine contaminants and the health of threatened species and the use of multiple and early-warning biomarker approaches. Objective: We explored the hypothesis that biomarker and contaminant analyses in skin biopsies of the threatened sperm whale (Physeter macrocephalus) could reveal geographical trends in exposure on an oceanwide scale. Methods: We analyzed cytochrome P450 1A1 (CYP1A1) expression (by immunohistochemistry), stable nitrogen and carbon isotope ratios (as general indicators of trophic position and latitude, respectively), and contaminant burdens in skin biopsies to explore regional trends in the Pacific Ocean. Results: Biomarker analyses revealed significant regional differences within the Pacific Ocean. CYP1A1 expression was highest in whales from the Galapagos, a United Nations Educational, Scientific, and Cultural Organization World Heritage marine reserve, and was lowest in the sampling sites farthest away from continents. We examined the possible influence of the whales’ sex, diet, or range and other parameters on regional variation in CYP1A1 expression, but data were inconclusive. In general, CYP1A1 expression was not significantly correlated with contaminant burdens in blubber. However, small sample sizes precluded detailed chemical analyses, and power to detect significant associations was limited. Conclusions: Our large-scale monitoring study was successful at identifying regional differences in CYP1A1 expression, providing a baseline for this known biomarker of exposure to aryl hydrocarbon receptor agonists. However, we could not identify factors that explained this variation. Future oceanwide CYP1A1 expression profiles in cetacean skin biopsies are warranted and could reveal whether globally distributed chemicals occur at biochemically relevant concentrations on a global basis, which may provide a measure of ocean integrity.Funding was provided by National Institute of Environmental Health Sciences grant P42-ES-0469, Superfund Basic Research Program grant P42ES007381, NOAA Sea Grant NA86RG0075 R/B-162, and the Ocean Alliance