فصلنامه فیزیولوژی و بیوتکنولوژی آبزیان
سال سوم شماره 3 (پاییز 1394)

Effcts of Beta-plus as probiotic on growth properties, survival, hematological factors and intestinal bacterial density of brown trout were investigated. Numbers of 585 juveniles during 3 months have studied with 105±5 in weight, 15 basins with a density of 39 fish per 1,500 liters. Different level of Beta-plus were used ranged as 0, 0.5, 1, 1.5 and 2Kg per ton of food) with 3 repeats in a completely randomized design. The results showed according to adding the probiotics in feed, growth properties such as PBWI, BWf, FCR and SGR were improved (P0.05), while the probiotic reduced amounts of RBC, Hb and HTC (P

Histopathological changes as biomarkers in risk assessment of fish health are used in both laboratory and field environments. In this study, the histopathological lesions induced by sub-lethal concentrations of chromium was investigated in gill and liver of Epinephelus stoliczkae under laboratory conditions. For this purpose 200 number of Epinephelus stoliczkae with an average weight of 389.5±92.4g and the average total length of 29.6±2.2cm were exposed to three concentrations of 3.6, 7.31 and 14.6ppm of chromium for 21 days in the laboratory fixed conditions, and samples of gill and liver tissues were extracted in during 0.5, 1, 7, 14 and 21 days after start the experiment. Results of histopathological studies by light microscopy in the gill tissue were clubbing, hyperplasia, hyperemia and epithelial lifting of the lamellae, and in the liver tissue were necrosis, vacuolation, Irregular of hepatocytes, melanomacrophage centers and dilatation of liver sinusoids. Results of histopathological studies showed special relationship between chromium concentration and severity of lesion. The most severe lesion was observed at higher concentrations of chromium and longer duration of exposure, in the fish tissues.

The impact of different levels of dietary nucleotides (Optimon diet, as a growth promoter containing nucleotide) on some serum biochemical indices of juvenile common carp, Cyprinus carpio (4.74 ±0.2 g), was assesses during an 8-week period. The experimental fish were kept in 70 L tanks with a storage density of 20 fish per tank. Dietary nucleotides in 4 levels of 0 (control), 0.5, 1.0 and 1.5 percent were added to the diet (triplicate). After 8 weeks, serum biochemical parameters including glucose, total protein, cortisol, C3 and C4 in fish fed diets with nucleotides showed significant differences compared to the control group (P>0.05). The highest amount of serum biochemical parameters were observed at 1% dietary nucleotide. The results indicated that dietary nucleotides can change hematological and serum biochemical parameters in juvenile common carp.

Application of prebiotics is a promising way in aquaculture, as non-digestible food ingredients that improve host health by stimulating or limiting the growth of bacteria in the host gut. Aim of this study was to investigate the protective effect of dietary commercial prebiotic, Immunogen®, on liver histopathology lesions exposured to Aeromonas hydrophila infection in rainbow trout (Oncorhynchus mykiss). This study was performed on 180 healthy sub-adult rainbow trout (81.65±1.49g) under experimental condition in three groups. In the first group (control) and second group, fish were fed the basal diet and in the third group, the prebiotic Immunogen was added to basal diet (one control group and two trial treatments with three replicates). After 6 weeks feeding, two last groups were injected by Aeromonas hydrophila (untreated-infected and treated-infected groups). Histophatological results revealed that lesions such as necrotic hepatocyte, cytoplasmic vacuolation, nucleus degeneration and entera cellular edema within the untreated-infected group were more than treated-infected group administrated by Immunogen®. These findings suggested improved resistance of rainbow trout liver administrated by Immunogen® during bacterial infection.

Biomacromolecules of thermophilic organisms are often thermostable. Apart from high temperature they are also known to withstand denaturants of extremely acidic and alkaline conditions. Thermostable enzymes have capable potentioal in the food and paper industries, detergents, drugs, toxic wastes removal and oil drilling. The enzymes can be produced from the thermophiles through either optimized fermentation of the microorganisms or cloning of fast-growing mesophiles by recombinant DNA technology. Metalloproteases are metal ion dependent protease. Metalloproteases that used in this study was a zinc-dependent endopeptidase. Metalloprotease gene was cloned from Anoxybacillus flavithermus. For the amplification of the gene, PCR was performed. A pair of primers designed with a cleavage site for enzymes XhoI and NheI and vector pET21a() clone was transformed into BL21 host. The results of the cloned gene sequence analysis showed similarity to the protease gene different variants of the species Anoxybacillus flavithermus.

Heterocyst-forming cyanobacteria are a group of N2-fixing microorganisms which normally grow in the damp soil of rice farms and fresh water wetlands. Cyanobacteria are important source of secondary metabolites. They have been shown to produce a variety of antibacterial, antifungal, antilarval, antiprotozoan, antialgal, and generally, cytotoxic secondary metabolites. Considering the extensive industrial and pharmaceutical uses of blue-green algae, antimicrobial activity of the native Anabaena sp. from Guilan wetlands studied. Studied Bacteria included Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli and Micrococcus luteus and fungi included Fusarium fujikuroi, Rhizoctonia solani, Colletotrichum sp. 62 and Saccharomyces cerevisiae. Antimicrobial effects were detected by Disk Agar Diffusion method. Tetracycline was used as a positive control for bacteria and mancozeb was used for fungi. The inhibition zone diameter was measured. The results showed that the extracts from Anabaena sp. were not effective against studied bacteria and fungi.