Edwardsiella tarda is a broad host-range pathogen infecting both animals and humans. E. tarda isolates from red sea bream Pagrus major are non-motile, whereas isolates from Japanese eel Anguilla japonica and Japanese flounder Paralichthys olivaceus are motile with peritrichous flagella. We compared the fliC gene coding for flagellin (FliC) in motile and non-motile E. tarda strains isolated from diseased fish. Twenty-two amino acid residues differed in the predicted FliC amino acid sequences between non-motile and motile strains. There were no significant differences either in the upstream sequences regulating transcription of the fliC gene or in the fliC transcript levels between motile and non-motile strains. The predicted secondary structure of FliC in non-motile E. tarda differed from that of motile strains, and the modeled data suggested that the secondary structure may be the important factor responsible for non-flagellation in the non-motile strains.KEY WORDS: Edwardsiella tarda · fliC gene sequence · Base changes · Flagellation · Motility · Red sea bream · Japanese flounder Resale or republication not permitted without written consent of the publisherDis Aquat Org 76: [113][114][115][116][117][118][119][120][121] 2007 while the atypical strain exhibits high virulence only in red sea bream.Bacterial flagella are important structures for pathogenic bacteria because they provide motility and increase adhesion to mucosal surfaces (Ramos et al. 2004). The flagellar filament is composed of approximately 20 000 subunits of the protein known as flagellin (FliC). Expression of flagella can be controlled by various genes in response to environmental changes. McIntosh & Austin (1991) showed that another fish pathogen, Aeromonas salmonicida, expresses flagella only at supra-optimal environmental temperatures (from 30 to 37°C). In Edwardsiella tarda, the fliC gene coding for the FliC protein was previously cloned and sequenced from strain PPD130/91, a motile strain (Tan et al. 2002). The other conditions and genes related to the expression of flagella are unknown in E. tarda.In this study we determined the mechanism of motility expression and flagellation in typical and atypical strains of Edwardsiella tarda. We show that non-motile strains do not form flagella in vitro in response to changing environmental temperatures. The data suggests that an alteration of the fliC gene sequence in non-motile strains is likely to be responsible for the deficiency in flagella formation in atypical strains. MATERIALS AND METHODSBacterial strains and media. Thirteen Edwardsiella tarda strains isolated from diseased Japanese flounder or diseased red sea bream were used (Table 1). The E. tarda strains were grown in Triptic-Soy broth (TSB, Eiken) or on Tryptic-Soy agar (TSA, Nissui) at 30°C unless otherwise indicated. Motility tests.The motility of the test strain was examined using a wet mount method with a light microscope (the direct method), and sulfide indole motility (SIM) media (Eiken) (the indirect method) at a vari...
DiŠerences in the taste of the meat of hard-shelled, ovigerous and soft-shelled female swimming crabs Portunus trituberculatus were investigated. To quantify taste, hot-water extracts were prepared and then a sensory test and a taste-sensor analysis were performed. Sensory testing revealed that the ovigerous and soft-shelled crabs were inferior in umami and overall taste as compared with the hard-shelled crabs, and this result corresponded well to theˆndings using the taste-sensor. Additionally, to examine the factors determining diŠerences in umami and sweetness, we analyzed the proximate composition, free amino acids and nucleic-acid-related compounds in the crab meat. The amounts of free amino acids and inosinic acid in the meat of crabs of the diŠerent shell types were judged to cause the signiˆcant diŠerences detected in those tastes, with larger amounts resulting in a better taste.
IntroductionEels are animals commonly used in zoological research, as these species have a unique catadromous life history and belong to a phylogenetically ancient group of Teleostei. However, eel reproduction is difficult to investigate, since mature samples are not easily obtainable in the wild. In this study, we tested daggertooth pike conger (Muraenesox cinereus), an Anguilliformes species, as a potential model for the investigation of the reproductive biology of eels. Seventy individuals were caught between June and October, which is supposed to be their spawning season, from inshore of the Seto Inland Sea.ResultsThe lengths and ages of samples ranged from 510 to 1239 mm and three to nine years, respectively, and the sex ratio was skewed towards females (96 % of the total sample). The gonado-somatic index of the females peaked in July. Histological observation revealed that these ovaries were similar to those of other eel species and contained matured oocytes (migratory-nucleus stage), suggesting that pike conger spawn inshore in July. The plasma concentrations of sex steroid hormones (estradiol-17β and 11-keto-testosterone) in females gradually increased during maturation and decreased after spawning, indicating the involvement of these hormones in oogenesis of pike conger.ConclusionsThe present study is the first to report on characteristics of natural oogenesis in pike conger. Because naturally maturing samples can easily be captured, daggertooth pike conger may represent an excellent model for the study of reproduction in Anguilliformes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.