Isolation and characterization of bacteria with antibacterial properties from Nile tilapia (Oreochromis niloticus).

One hundred and twenty bacterial isolates were obtained from the intestinal mucus of Nile tilapia (Oreochromis niloticus) and screened for antagonistic activity and adherence abilities. Based on in vitro antagonism against two pathogens (Streptococcus iniae and Edwardsiella piscicida), five isolates were selected and identified by 16S rRNA gene sequence analysis. All antagonistic isolates were affiliated to the genus Bacillus, which showed inhibitory activity against S. iniae. Only the isolate B191 (closely related to Bacillus mojavensis) inhibited the growth of both pathogens. Moreover, isolate B191 adhered significantly better to fish intestinal mucus than other antagonistic isolates. According to our results, these bacterial isolates, particularly isolate B191, should be further studied to explore their probiotic effects under in vivo conditions.

Bacterial community structure in the intestinal ecosystem of rainbow trout (Oncorhynchus mykiss) as revealed by pyrosequencing-based analysis of 16S rRNA genes.

In this study, we determined the diversity and composition of bacterial communities within the intestinal ecosystem of farmed rainbow trout (Oncorhynchus mykiss). Healthy rainbow trout, weighing between 520 and 750 g, were fed a commercial diet. Subsequently, genomic DNA was isolated from the intestinal mucus (n = 16 fish samples) and combined into groups of four fish samples each for pyrosequencing analysis of bacterial 16S rRNA genes. The results revealed that the most abundant operational taxonomic units (OTUs) were affiliated to the genera Acinetobacter, Cetobacterium, Pseudomonas, and Psychrobacter, and to a lesser extent, the genera Aeromonas, Clostridium, Deefgea, Flavobacterium, Neptuniibacter, and Mycoplasma. These findings could be used as a baseline for further studies about the role of bacterial communities in normal and altered host physiological states.

Parasitic copepods of the common sole, Solea solea (L.), from the Eastern Mediterranean coast of Turkey.

There is increasing interest in the common sole, Solea solea (Linnaeus), as an alternative fish species in aquaculture in the Mediterranean region, and parasitic copepods are a potential hazard for farmed finfish. This paper provides taxonomic information on two species of sea lice (family Caligidae) collected from S. solea in eastern Mediterranean waters off the Turkish coast. Caligus brevicaudatus A. Scott, 1901 and Caligus apodus (Brian, 1924) were both found and this is the first report of C. brevicaudatus in Turkish waters. The discovery of C. apodus on S. solea is a new host record. Key diagnostic characters of both species are reported, supported by light and scanning electron microscopy observations. During a 12-month survey a prevalence of 28% was recorded for C. brevicaudatus, whereas for C. apodus peak prevalence was much lower (3%).

Comparative seasonal sterol profiles in edible parts of Mediterranean fish and shellfish species.

The effect of different seasons on sterol content of seafoods was investigated. There were four sterols (cholesterol, sitosterol, desmosterol and stigmasterol) identified, with cholesterol being the predominant sterol. Stigmasterol was a minor component in fish muscle, whilst sitosterol was one of the main phytosterols found in fish muscle. Cholesterol content of fish consisted of 38-100% of total sterols in fish and 54-80% of total sterols in shellfish. The highest cholesterol content of fish muscle was found in summer and the lowest in autumn, whereas season did not have any effect on cholesterol level of green tiger prawn and speckled shrimp. Total sterol content of fish muscle ranged from 49 to 110 mg/100 g, although the range of total sterols in shrimp muscle was between 62 and 91 mg/100 g. The result of the study showed that total sterols in fish were generally found at lower levels in winter compared with other seasons.