جستجوی مقالات مرتبط با کلیدواژه « bacterial flora » در نشریات گروه « محیط زیست »

Bacterial infectious diseases are one of the important causes of losses in silver carp aquaculture, due to its detritivorous method, that occur due to temperature changes, manipulation and low quality of farmed water. Four fish breeding farms in Sangar area of ​​Rasht, which had silver carp (Hypophthalmichthys molitrix) brood stocks (5.76± 0.99 Kg}, were considered as sampling sites. In order to isolate and identify the bacterial flora of the gastrointestinal tract of silver carp brood stocks fish with apparently healthy appearance, 30 in equal proportions of male and female were selected and samples were prepared individually for culture. The bacterial flora went to culture. After autopsy, the gastrointestinal tract of the fish was removed and preliminary and differential microbial culture was performed from the intestinal contents. The grown samples were purified after replanting and based on the table of chemical tests; their properties were studied and identified as species. There were observed No significant differences in the study of physicochemical variables of sampled farm water and bacterial count of water in sampling sites (p>0.05). After isolation and determination of morphological and biochemical traits, samples of isolated bacteria of 8 genera from the gastrointestinal tract of silver carp brood stocks were identified, the most common of which were Bacillus, Aeromonas and Pseudomonas, although samples opportunistic and general gram-positives such as Micrococcus sp. And Staphylococcus sp. were also observed. Based on the results of this study, there were no significant differences in bacteria count between gram-negative and gram-positive bacteria isolated from the samples (p>0.05). Although many of the bacteria isolated in this study are known to be pathogenic, they are not primary pathogens and are found in and around aquatic bodies and in seawater, estuaries and environments. Fresh water is considered as a part of the natural microflora of the aquatic body and may become pathogenic in conditions of stress and degradation of the aquatic immune system.

This study was conducted to screen 7 species of the broodstocks silver carp (Hypophthalmichthys molitrix) digestive tracts bacterial flora including Bacillus subtilis, Enterobacteriaceae, Corynebacterium jijicum, Staphylococcus, Pseudomonas, Micrococcus luteus, Aeromonas, and Unidentified. Antibacterial activities of these candidates bacterial flora were conducted under disc diffusion, well diffusion, and cross streak methods. The tree probiotics candidates (Bacillus, Corynebacterium, and Micrococcus) were shown antibacterial activity against pathogenic bacteria. Candidate Bacillus showed a significant inhibition zone (20 ml) against the pathogen in the disk diffusion method. On the other hand, the addition of 10 ml of Bacillus supernatant to Aeromonas pathogenic species leads to killing them completely at 12 hours. The pH 8 and temperature 30 o was found optimum to grow candidates bacteria and produce antibacterial bio-components. There are significant differences between 8 treatments under different dosages of candidates bacteria and control (without bacteria of beaker included silver carp larva) in fish survival (P<0.05). From this, we can conclude that the candidate Bacillus subtilis maybe can be probiotics for silver carp culture.

The Karoun 4 dam lake with 2/5 billion m3 is one of the important reservoirs in Iran. This can be considered in aquaculture. In this study, the effects of cage culture in bacterial load were investigated. Sampling of lake water was carried in 2013 for 6 months from April to September. The water samples were provided in several distances from cages. According to the results the presence of some bacteria include Escherichia coli, Staphylococcus and Streptococcus in samples were 47%, 70% and 23% respectively. The variance analysis showed a significant difference between the number of coliform and staphylococcus bacteria (P<0.01) but no significant difference was observed between total bacteria, E. cloi and Staphylococcus (P>0.01).Also the results showed the highest number of bacteria in near cages distances but just the number of coliform and streptococcus have a significant difference (P<0.01).