L. Verdonck

Vibrios associated with Penaeus chinensis (Crustacea: Decapoda) larvae in Chinese shrimp hatcheries

Bacteriological surveys were performed in 1995 and 1996 in three shrimp hatcheries located in the north of the Peoples Republic of China. Samples were taken from routine productions of healthy Penaeus chinensis larvae, their environment and from diseased larvae. A total of 186 isolates from the dominant bacterial flora was characterized by Biolog metabolic fingerprinting and identified by comparison to a database of 850 Vibrio type- and reference strains. Representative Vibrio harveyi strains were further genotypically analyzed by AFLP fingerprinting of whole-genomes. An overwhelming predominance of V. alginolyticus and V. harveyi was observed in the larval developmental stages from zoea stage on. The flora associated with larvae is not very stable and is influenced by the bacterial flora of the administered food and by the environment. In the 1995 survey, the bacterial flora of successful P. chinensis larvae productions was mainly dominated by V. alginolyticus and unidentified Gram negative strains, while V. harveyi was absent. The bacterial numbers gradually increased from nauplii stage to post-larval stage, but few vibrios were isolated from nauplii stage. High V. harveyi numbers (up to 105 CFU/larva) in the larvae are correlated with weak larvae and mass mortalities. Between V. harveyi strains, isolated from healthy and diseased larvae, no phenotypic or genotypic differences were found. The presence of V. alginolyticus might influence the pathogenicity of V. harveyi or might have an impact on the resistance of larvae to bacterial pathogens.

Dominant intestinal microflora of sea bream and sea bass larvae, from two hatcheries, during larval development.

Copyright (c) 1997 Elsevier Science B.V. All rights reserved. The intestinal microflora of larval sea bream (Dicentrarchus labrax) and sea bass (Sparus aurata) from two marine hatcheries (Greece and Spain) was studied. Samples for bacteriological analysis were taken during feeding regimes of the larvae with rotifers and Artemia. A total of five production cycles was examined: three involved sea bream and two involved sea bass. When the larvae were fed with rotifers, the incidence of Vibrio anguillarum, Vibrio tubiashii and non-vibrio groups was high. During feeding with Artemia, Vibrio alginolyticus, Vibrio proteolyticus, Vibrio harveyi and Vibrio natriegens were mainly isolated. During larval development, no dominant and persistent colonisation of the intestine by any given bacterial species was observed. Fluctuations in the composition of the dominant microflora appeared to reflect the bacterial composition of the ingested live feed. Selection towards the genus Vibrio was not observed until the larvae reached the end of the larval life stage. Two additional samples were taken during massive mortality outbreaks in bream larvae. In both samples, V. anguillarum was dominant as associated with the feeding with rotifers. The results suggest that disease outbreaks can occur when V. anguillarum dominates in the larval intestine.

Characterization of Vibrio viscosus and Vibrio wodanis isolated at different geographical locations: a proposal for reclassification of Vibrio viscosus as Moritella viscosa comb. nov.

Vibrio viscosus and Vibrio wodanis are recently described species of psychrotropic bacteria that have been found associated with a disease called winter ulcer, affecting salmonid fish reared in saline water in Norway, Iceland and recently in Scotland. V. viscosus and V. wodanis strains initially isolated from fish in Iceland and Norway were subjected to characterization using biochemical tests, SDS-PAGE of whole-cell proteins and a novel DNA fingerprinting method, amplified fragment length polymorphism (AFLP). The V. viscosus strains isolated from diseased fish grouped into homogeneous subgroups according to geographical origin and challenge experiments revealed that representatives of these groups are virulent. The results revealed that the V. wodanis strains are heterogeneous genotypically and phenotypically. Sequencing of almost complete 16S rRNA genes of V. viscosus and V. wodanis revealed that V. viscosus showed a 99.1% sequence similarity to Moritella marina and V. wodanis showed a 98.8% sequence similarity to Vibrio logei CIP 103204. A reclassification of Vibrio viscosus as Moritella viscosa comb. nov. is proposed.

Normal coordinate analysis of α-FeOOH - a molecular approach

Abstract The infrared spectra of α-FeOOH and the deuteratad analogue have been interpreted by a normal coordinate analysis. The assumption was made of partial covalent bond formation between the oxy and hydroxy oxygen and iron. Frequencies and force constants involving the motion of the hydrogen atom and the Fe-OH bond are evaluated in a distorted Fe3OH tetrahedron. The Fe-O parameters are separately derived in a quasi planar trigonal Fe3O geometry.

Vibrios associated with routine productions of Brachionus plicatilis

Abstract Surveys for bacteriological analysis were carried out in 1990–1991 in two different marine fish hatcheries located in Greece and northern Spain. Samples were taken from 12 different routine productions of Brachionus plicatilis before and during enrichment. Isolates were characterized by whole cell fatty acid methyl ester analysis and by BIOLOG metabolic fingerprinting. Vibrio anguillarum and/or Vibrio alginolyticus were dominant Vibrio species in the rotifer samples taken after enrichment and rinsing, before being delivered to the fish larvae. None of the Vibrio anguillarum strains belonged to the pathogenic serotypes for juvenile and adult fish.

Liquid chromatography of organotin compounds in cyanopropyl silica gel

Abstract Several stationary phases were evaluated for the liquid chromatography of organotin compounds. Cyanopropyl-derivatized silica gels are the most versatile phases for this type of analysis. In order to reduce stationary phase activity, an iodine chloride “on-column” pretreatment was developed. This leads to very fast quantitative and qualitative separations, as was demonstrated by the analysis of organotin standards, orgnotin-containing tungsten carbonyl complexes and organotin halides for reaction kinetic studies.

Diversity of Vibrio anguillarum Isolates from Different Geographical and Biological Habitats, Determined by the Use of a Combination of eight Different Typing Methods

Summary In the present investigation we have studied 260 presumed Vibrio anguillarum isolates from a wide range of habitats, ,using a combination of eight different typing methods. The aims of the study were to investigate the diversity of V. anguillarum, as indicated by the use of combined typing, and to determine if strains with identical or similar characteristics were present in certain geographical locations, or in certain fish species. We also present a simple numerical method to analyse data obtained from combined typing. Two hundred and sixty isolates named as V. anguillarum from various fish species, rotifers, Artemia, water and sediment were subjected to the following eight assays: Species identification using ribotyping and the BIOLOG GN plates, subtyping using determination of outer membrane profiles, plasmid typing, serotyping, determination of lipopolysaccharide profiles and biotyping with API 20E, and biochemical fingerprinting with the PhenePlate system. The diversity among all isolates, calculated as Simpsons diversity index (Di), varied between 0.19 (ribotyping), i.e. most isolates belonged to the same type, and 0.98 (PhP), i.e. most isolates different. Upon combination of all methods, where a difference between two strains in at least two methods was regarded as significant, a diversity of 0.92 was obtained. Isolates collected from fish showed lower diversity (Di = 0.89) than those collected from other sources (environment, rotifers, Artemia) (Di = 0.98). The lowest diversities were found among isolates collected from rainbow trout (Oncorhynchus mykiss), salmon (Salmo salar) and turbot (Scophthalmus maximus). Isolates from close geographical locations were also less diverse than isolates obtained from more distant locations. We conclude that the diversity of V. anguillarum is high, as shown by the combined typing methods. However, it seems that strains with specific characteristics are associated with certain geographic areas, and also with certain fish species. This could only be detected by applying a combination of several typing methods. Our results emphasise the need to use several different typing methods for studies of bacterial diversity.

Preparation and characterization of a titanium(IV) silsesquioxane epoxidation catalyst anchored into mesoporous MCM-41.

Abstract This paper describes the synthesis and spectroscopic study of a titanium(IV) silsesquioxane complex, which is heterogenised in the pores of an MCM-41 host material. Its immobilization is performed via chemical bonding, not by means of physical adsorption. As a linking molecule between the MCM-41 carrier and the silsesquioxane, (3-glycidyloxypropyl)trimethoxysilane is used. Characterization is performed by using nitrogen adsorption techniques, TGA, diffuse reflectance infrared spectroscopy (DRIFT) and ICP-MS. Also its catalytic activity towards the epoxidation of alkenes shows interesting results.

Low-generation carbosilane dendrimers as core for starpolymers using a Ru-ROMP catalyst

Abstract Synthesis of new metathesis initiators by coupling Ru-complexes to low generation carbosilane dendrimers (G0–Ru, G1–Ru). These initiators show a very high activity for the ROMP of NBE. Using these dendrimer complexes, multi-arm starpolymers can be developed in a controlled manner.

The proton magnetic resonance spectra of benzyltin derivatives

Abstract The PMR spectra of a series of benzyltin compounds (C 6 H 5 CH 2 ) n SnX 4-n ( I ⪡ n ⪡4, X=H, Cl, Br, I, OCOCH 3 ) have been studied. Evidence is presented that substituents X equally influence all the ring protons chemical shifts and this is ascribed to changes in the π-electron system of the ring. The methylene group shifts are the result of ring current, inductive effect and diamagnetic anisotropy contributions. The coupling constants J (Sn-C-H) cannot be interpreted by changes in s electron density around the tin atom only.