Characterization of Micrococcus luteus and Bacillus marisflavi Recovered from Common Dentex (Dentex dentex) Larviculture System

In this manuscript, thirty yellow-pigmented Gram-positive bacteria were isolated from natural intestine microflora and from sea water around the marine cage of a rearing tank of common dentex (Dentex dentex), in the Aegean Sea on the Turkish coast and were characterized. Eighteen isolates were assigned to the species Micrococcus luteus, the other twelve to the species Bacillus marisflavi. Eight representative strains, six from B. marisflavi and two from M. luteus, were chosen for further 16S rDNA analyses. A pathogenicity assay for the isolated bacterial strains was carried out in rainbow trout and it evidenced absence of pathogenicity in the tested strains. The isolated strains were tested for in vitro antagonistic activity against Listonella anguillarum, a pathogen bacterium diffused in Mediterranean aquaculture and affecting various fish species. The isolated bacterial strains showed antagonistic activity against the pathogenic bacterium, suggesting a possible role of isolates as probiotics. In this study, for the first time, bacterial strains of the species B. marisflavi, known as an environmental species, were recovered in the gut microbiota of a healthy fish. The use of the isolates characterized in this study, mainly the yellow-pigmented bacterium, is suggested as possible probiotics to improve fish health, along with alternative methods of maintaining a healthy environment

A Study on Probiotic Bacteria Isolated from Common Dentex (Dentex dentex) Larvae and their antagonistic effect on Photobacterium damselae subsp. Damselae

Bacterial species that can be considered as probiotic are gradually gaining attention and contributing to the success of aquaculture. The aim of this study was to determine the indigenous dominant probiotic bacterial species of common dentex (Dentex dentex) larvae and their effectivness against the putative fish pathogen Photobacterium damselae subsp. damselae at different feeding stages. In 2009-2010 samples of larvae and tank water were collected at 5 different occasions. After inoculations of samples, bacterial isolates were identified with standard biochemical methods. The antagonistic effects of the identified probiotic bacteria against P. damselae subsp. damselae isolated from different mariculture fishes were determined by using disc diffusion method. Bacillus cereus, B. macquariensis, and other Bacillus sp., Micrococcus luteus, Flavobacterium flevense and Flavobacterium sp. were identified as candidate probiotic species and their antagonistic effect against different P. damselae isolates was identified. The results of this study showed that B. cereus and M. luteus are more effective against Photobacterium damselae subsp. damselae. As a result, the identification of the candidate probiotic species and the widespread use of probiotics may improve the success of common dentex culture in the future

Identification and Genotyping of Vibrio ordalii: A Comparison of Different Methods

The phenotypical, serological, and molecular identification of Vibrio ordalii isolates recovered from diseased gilthead sea bream (Sparus aurata) in the Mediterranean area were investigated. Most isolates had similar phenotypic characteristics, but some showed small differentiation in biochemical analysis. Both slide agglutination and enzyme linked immunosorbent assay (ELISA) showed that the isolates were antigenically homogeneous and no different serotypes were detected. SDS-PAGE analysis showed that the structure of lipopolysaccharide (LPS) was heterogeneous, that outer membrane proteins (OMP) display homogeneous grouping protein banding patterns, and that the LPS profile of the isolates had different banding patterns. However, random amplified polymorphic DNA (RAPD) analysis revealed genetic variation (up to 90.4%) among isolates of the same species

Formation of Pinocytic Activity in Cultured Common Dentex (Dentex dentex) Larvae Intestine

Larval fish have a relatively poorly developed immune system and hence they primarily rely on non-specific immune responses produced in the skin and gut. This study aims to illustrate the fine structure of gut development in common dentex (Dentex dentex) larvae and determine the initiation of pinocytic activity, which is an important early non-specific immune response in fish intestines, during various live-food feeding stages (yeast enriched rotifer, Artemia nauplii and metanauplii) from hatching (D0) to 25 days after hatching (D25) by using transmission electron microscopy (TEM). A total of 54 larvae were sampled and examined with electron microscopy. The results show that hind-gut intestine enterocytes have morphological features which suggest they play a role in absorption and intracellular digestion of nutrients in fish. The presence of vigorous pinocytic activity in the Artemia feeding stage between 17-25 days after hatching is evidence for the development of a non-specific immune system. In the present study, the ultrastructural gut development of cultured common dentex was investigated for the first time and the data reported in this study may provide additional fundamental knowledge for improving larval rearing success in common dentex culture

A Study on Probiotic Bacteria Isolated from Common Dentex (Dentex dentex) Larvae and their antagonistic effect on Photobacterium damselae subsp damselae

Bacterial species that can be considered as probiotic are gradually gaining attention and contributing to the success of aquaculture. The aim of this study was to determine the indigenous dominant probiotic bacterial species of common dentex (Dentex dentex) larvae and their effectiveness against the putative fish pathogen Photobacterium damselae subsp. damselae at different feeding stages. In 2009-2010 samples of larvae and tank water were collected at 5 different occasions. After inoculations of samples, bacterial isolates were identified with standard biochemical methods. The antagonistic effects of the identified probiotic bacteria against P. damselae subsp. damselae isolated from different mariculture fishes were determined by using disc diffusion method. Bacillus cereus, B. macquariensis, and other Bacillus sp., Micrococcus luteus, Flavobacterium flevense and Flavobacterium sp. were identified as candidate probiotic species and their antagonistic effect against different P. damselae isolates was identified. The results of this study showed that B. cereus and M. luteus are more effective against Photobacterium damselae subsp. damselae. As a result, the identification of the candidate probiotic species and the widespread use of probiotics may improve the success of common dentex culture in the future

Characterization of Vibrio alginolyticus Isolates from Diseased Cultured Gilthead Sea Bream, Sparus aurata

Biochemical, pathogenical, antigenical, and molecular characteristics of Vibrio alginolyticus iso- lates from diseased cultured gilthead sea bream juveniles (4 and 20 g) were determined by lab- oratory challenge experiments. Intraperitonal challenge resulted in development of the disease but immersion did not. Electrophoresis of outer membrane protein (OMP) and lipopolysaccha- rides (LPS) was performed using sodium dodecyl sulphate poly-acrylamide gel electrophoresis (SDS-PAGE). Molecular typing of Vibrio isolates was conducted using random amplification of polymorphic DNA (RAPD). According to SDS-PAGE of surface antigens of the isolates, profiles of both OMP and LPS were heterogeneous. According to RAPD, isolated bacteria varied genet- ically. The findings reveal differences among V. alginolyticus isolates from diseased cultured gilt- head sea bream in Turkey

The first observation of viral erythrocytic infection associated with pathogenic bacteria and some ectoparasites in cultured Mediterranean sea bass (Dicentrarchus labrax L.) in Turkey

This paper describes the first occurrence of viral erythrocytic infection associated with pathogenic bacteria and some ectoparasites in cultured Mediterranean sea bass (Dicentrarchus labrax) in Turkey. Generally, fish infected by the organisms were anaemic, and experienced moderate or high levels of mortality during disease outbreaks. While Photobacterium damselae subsp damselae, Aeromonas salmonicida subsp. salmonicida, Aeromonas sobria, Listonella (Vibrio) anguillarum, and Staphylococcus epidermidis were isolated from diseased fish, haematological and electron microscopical examination also indicated the presence of viral erythrocytic infection in diseased sea bass. Erythrocytes of affected sea bass had. single, double or multiple intracytoplasmic inclusions ranging in size from 0.3 to 1.6 mu m. Some of these erythrocytes had single or multiple, small or large vacuoles which were usually associated with inclusion bodies. Confirmation of viral erythrocytic infection is based on the observation of polyhedral virions 85-157 nm in diameter in the cytoplasm of the affected erythrocytes using electron microscopy. Clinically infected sea bass had low haematocrit values (Ht) ranging from 2% to 29% and low RBC counts ranging from 14,200 to 3,760,000 per ml

Reproductive biology of little tunny, Euthynnus alletteratus (Rafinesque), from the north-eastern Mediterranean Sea

The study aimed at identifying spawning season and potential year classes reaching maturity in the north-eastern Mediterranean, an area where little information on tuna spawning is available. Gonads (60 ovaries and 36 testis) were obtained from little tunny, Euthynnus alletteratus. The fish were caught between November 2002 and May 2005 in the north-eastern Mediterranean Sea. The ovaries were histologically examined to determine the reproductive conditions and developmental stages of oocytes. Seven females sampled in May, July, and August were sexually mature (stage III or IV). The gonado-somatic index (GSI) indicated that spawning generally occurred between May and September. The most intensive spawning period was observed between July and August. The sex ratio was calculated as 1 : 1.7 M/F (total n = 96). The length and weight relationship was calculated with W = 0.038 L(2.77), ages from year I to IV being included in the analysis

First observation of rickettsia-like organisms in cultured sea bass (Dicentrarchus labrax) in Turkey

This paper describes the first observation of rickettsia-like organisms (RLOs) in cultured European sea bass (Dicentrarchus labrax) in Turkey. Generally, fish infected by the organism were anorexic, lethargic and experienced high levels of mortality during disease outbreaks. Internally, most of the affected fish exhibited grey to yellow coloured multifocal nodules in their kidneys and spleens. Although Listonella (Vibrio) anguillarum and Photobacterium damselae subsp. piscicida were isolated from diseased fish, clinical and pathological examination also indicated the presence of RLOs in diseased sea bass. Histopathologically, multifocal necrosis of parenchyma cells of the spleen, liver, kidney skeletal and heart muscle was observed, associated with an inflammatory reaction. Diseased fish also contained what appeared to be RLOs within the cytoplasmic vacuoles of their blood monocytes. The presence of RLOs in tissues of diseased fish was confirmed by immunohistochemistry (IHC)