育肥饲料中虾青素含量对雄性中华绒螯蟹肠道和鳃部可培养优势细菌数量和组成的影响

在育肥饲料中添加虾青素会影响中华绒螫蟹肠道及鳃内的可培养优势菌群以及机体的免疫力,本实验旨在探讨饲料中虾青素含量及养殖水体对其肠道和鳃部菌群的影响。采用不同虾青素含量的饲料(0.00、26.60、41.62、81.37和75.35 mg/kg,分别对应饲料1#~5#)对雄性中华绒螫蟹进行育肥70 d后,利用基础培养基和选择性培养基对其肠道、鳃及养殖水体中的细菌进行传统分离和纯化,所得菌株进行16S rRNA测序,再进行同源性分析后做系统进化树。结果发现,在分离获得的106株细菌(登录号:KU570293~KU570368,KU570370,KU570372~KU570383,KU601302~KU6013 16,KU720553)中,92株为优势菌株,其中,肠道、鳃部和水体各29、32和31株。肠道中的可培养优势细菌属于柠檬酸杆菌属、假单胞菌属和气单胞菌属;而鳃中可培养优势细菌属于柠檬酸杆菌属、芽孢杆菌属、假单胞菌属和气单胞菌属;养殖水体中可培养优势细菌属于芽孢杆菌属、气单胞菌属、柠檬酸杆菌属、假单胞菌属和黄杆菌属。饲料2#组肠道中可培养细菌总数最高(1.06×10~8cfu/g);饲料5#肠道中的潜在致病菌数量最低,但其可培养细菌总数显著高于其他饲料组;饲料3#组肠道和鳃中潜在致病菌数量相对较高。研究表明,饲料中添加不同含量的虾青素能够显著影响雄性中华绒螫蟹肠道和鳃中的菌群构成,但对水体中可培养细菌数量无显著影响。本研究首次对投喂不同含量虾青素饲料的育肥期雄性中华绒螫蟹肠道、鳃及养殖水体可培养的优势细菌数量和组成进行分析,探究了饲料中虾青素含量以及养殖水体与蟹肠道内可培养细菌之间的联系,为中华绒螫蟹营养免疫和菌群调控提供了理论基础。     

Environmental conditions at sea-cages, and ectoparasites on farmed European sea-bass, Dicentrarchus labrax (L.), and gilt-head sea-bream, Sparus aurata L., at two farms in Greece

Water quality in sea-cages, and metazoan ectoparasites on bass, Dicentrarchus labrax (L.), and bream, Sparus aurata L., were sampled at two fish farms in south-west Greece over 2 years. The seabed and marine life around the cages of one farm was surveyed using scuba. The most frequent and abundant parasites were the monogeans Sparicotyle chrysophrii and Furnestinia echeneis on the gills of bream, and Diplectanum aequans on the gills of bass. The copepod Caligus minimus occasionally occurred in the buccal cavity of bass, but only in low numbers. Prevalence and abundance of parasites increased with bass size but F echeneis levels decreased with bream size. There were no other clear relationships between water quality, parasite levels and fish size. Ammonia varied seasonally with sea temperature, and with oxygen levels below 6 mg 1^-1 on many occasions, it is possible that fish suffered stress from a combination of high ammonia and low oxygen conditions. There was no accumulation of waste food or faeces below the cages at the one farm surveyed, but there were thousands of wild fish, including mullet (Mugilidae), Spicara sp. and Diplodus spp., present around the cages. Water quality may be improved by changes in farm management, such as reducing stocking densities below the present 16 kg nr^-3. Oxygen should be monitored at the cages on site daily. How comparable environmental conditions and impacts, and parasitization are at other bass and bream sea cage farms is unknown.     

Quantitative and qualitative studies on bacterial flora of hybrid tilapia (Oreochromis niloticus × O. aureus) cultured in earthen ponds in Saudi Arabia

The bacterial flora of the rearing pond water and sediment as well as the gills and intestine of healthy hybrid tilapia cultured in Saudi Arabia was estimated quantitatively and qualitatively, the isolates being identified at genus or species level. Total viable counts of bacteria (measured as colony‐forming units, cfu) were in the range 5.6 ± 0.8 × 10³ to 2.4 ± 1.2 × 10⁴ cfu mL^?1 in pond water; 9.3 ± 1.1 × 10⁶ to 1.9 ± 1.5 × 10⁸ cfu g^?1 in sediment; 7.1 ± 0.7 × 10⁵ to 8.7 ± 1.1 × 10⁶ cfu g^?1 in the gills of tilapia; and 3.4 ± 1.8 × 10⁶ to 5.8 ± 0.4 × 10⁷ cfu g^?1 in the intestine of tilapia. In total, 15 bacterial genera and 18 species were identified. Pond water and sediment bacteria reflected the bacterial composition in the gills and intestine of tilapia. In contrast to gill bacteria, more diversification was observed in intestinal bacteria. Corynebacterium urealyticum, Shewanella putrefaciens and Aeromonas hydrophila predominated in all samples. In pond water, C. urealyticurn, S. putrefaciens, A. hydrophila, Flavobacterium sp. and Pseudomonas sp. were the most predominant bacterial species (prevalence > 10%), whereas A. hydrophila, C. urealyticum, S. putrefaciens and Escherichia coli were predominant in pond sediment, and C. urealyticum, S. putrefaciens and A. hydrophila were predominant in both the gills and intestine of tilapia.     

Effect of Chitosan and Garlic Essential Oil on Microbiological and Biochemical Changes that Affect Quality in Grass Carp (Ctenopharyngodon idellus) Fillets During Storage at 4°C

Solutions of chitosan (2%, w/v), garlic essential oil (5%, v/v), and their combination (2%, w/v chitosan +5%, v/v garlic essential oil) were applied to the surface of grass carp fillets. Subsequently, sensory, microbiological analyses (total viable count (TVC), Pseudomonas spp., Aeromonas spp., and H₂S-producing bacteria), and physicochemical changes (total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), and centrifugation loss) of grass carp fillets were evaluated over a 16-day storage at 4 ± 1°C. The treated samples resulted in significantly (p < 0.05) higher overall acceptance scores than the control from day 8. The TVC of grass carp fillets was reduced from the initial level (4.0 log CFU/g) to 2–3 log CFU/g when the fillets were treated with either garlic essential oil or chitosan solution. After 4 days of storage, the Pseudomonas spp. counts in the chitosan-treated samples were significantly lower (p < 0.05) than the counts in control and samples treated with garlic essential oil. A lag phase of 6 days for the counts of H₂S-producing bacteria of fish fillets that were treated with chitosan or the combination solution was observed. The combination of chitosan with garlic essential oil did not show synergistic effects, although it displayed a higher degree of antimicrobial efficacy with respect to the spoiled bacteria. However, the combination of chitosan with garlic essential oil was the most effective at inhibiting the formation of TVB-N. Samples that were treated with garlic essential oil displayed the highest TBARS levels on days 4 and 6 (p < 0.05).     

Intestinal microflora of salmonids: a review

Microflora isolated from fish intestines have been described for a limited number of salmonid fish species. The size of the microbial population of salmonids appears to vary within different regions of the gastrointestinal tract. The genera present in the gastrointestinal tract seem to be those which can survive and multiply in the intestinal tract. The predominant bacteria isolated from the salmonid gut are aerobes or facultative anaerobes. Few investigations have evaluated obligate anaerobes in the digestive tract of salmonids, and these studies have suggested that the population levels of obligate anaerobes are lower than those of facultative anaerobes. The bacterial genera isolated from fish intestines vary with salinity, antibiotics, chromic oxide, diet and dietary components such as linoleic acid, and display day-to-day fluctuations. Acinelobacter spp., Enterobacter spp. and Pseu-domonas spp. are regarded as autochthonous in Oncorhynchus species, while Aeromonas spp., Flavobacterium spp., Pseudomonas spp. and Lactobacillus spp. are suggested as autochthonous in Arctic charr, Salvelinus alpinus(L.).     

Autochthonous probiotic as growth promoter and immunomodulator for Astyanax bimaculatus cultured in water recirculation system

This work aimed to evaluate the probiotic Lactobacillus spp. in the microbiota of Astyanax bimaculatus reared in a water recirculation system. The experiment was randomized, using 800 postlarvae distributed into eight polyethylene containers, separated into two treatments, in quadruplicate: supplementation with Lactobacillus spp. (Probiotic) and no supplementation (Control). After 90 days of culture, 13 fish per container were anaesthetized. Three of these underwent microbiological evaluation, and haematological analyses were carried out on five. Immunological assessment was performed on another five fish. Zootechnical parameters were evaluated for all animals. In the microbiological evaluation, the probiotic group presented higher counts of lactic acid bacteria, but lower counts of Vibrio spp., Pseudomonas spp., and Staphylococcus spp., when compared with control. After haematological analysis, the supplemented group presented low haematimetric indices of Mean Corpuscular Haemoglobin Concentration and Mean Corpuscular Haemoglobin (MCHC and MCH, respectively) and higher amounts of total leucocytes, thrombocytes and circulating monocytes when compared with control. The immunological profile did not differ between treatments. In the zootechnical performance, probiotic group presented higher productivity, survival and apparent food efficiency when compared with control. Therefore, when Lactobacillus spp. was supplemented in the diet of A. bimaculatus, immunocompetence and the zootechnical performance of animals increased.     

Bacterial Flora in Turbot Scophthalmus maximus Cultured in Deepwell Seawater of Liaodong Peninsula

The microbial flora in turbot (Scophthalmus maximus) cultured in deepwell seawater from Liaodong Peninsula, China was studied for the first time. The total amount of aerobic meso- and psychrophilic microflora from the culturing water, gills, and skin were 3.46–3.82, 3.19–4.28, and 1.70–1.95 log cfu/g, respectively. Out of 204 strains isolated from fresh turbot meat with skin, Gram-positive bacteria accounted for 19.2% of the total aerobic meso- and psychrophilic microflora, and 72.1% were Gram-negative bacteria. Phylogenetic analysis was performed using 16S rDNA sequences of microbial flora isolated from turbot. The predominant bacteria in fresh turbot were Micrococcus, Serratia liquefaciens, and Enterobacteriaceae. Meanwhile, the bacterial flora of refrigerated turbot fish were investigated, and the results indicated that Shewanella putrefaciens was the predominant spoilage bacteria.     

Identification of the adherent microbiota on the gills and skin of poly‐cultured gibel carp (Carassius auratus gibelio) and bluntnose black bream (Megalobrama amblycephala Yih)

PCR‐denaturing gradient gel electrophoresis (DGGE) was applied to analyse the microbial community attached to the gills and skin of poly‐cultured gibel carp (Carassius auratus gibelio) and bluntnose black bream (Megalobrama amblycephala Yih) and compare these results with those detected in the rearing water. The microbiota discussed included bacteria, fungi and a specific bacterial taxa of actinomycetes was also analysed. Proteobacteria, Firmicutes, Actinobacteria, Cyanobacteria, Ascomycota, Basidiomycota and some unclassified microbiota were identified. Based on our results, we concluded that: (1) the adherent bacterial/fungal communities on the gills and skin were different from those in the rearing water, (2) the bacterial/fungal diversities on fish gills were lower than that on fish skin, (3) the adherent bacterial/fungal communities on gill and skin of gibel carp were different from that of bluntnose black bream and (4) the adherent actinomycetal community showed certain similarity between the skin of different hosts. Based on our conclusions, we suggested that the topic investigated in the present study merits further investigations.     

Aerobic Bacterial Flora of Common Carp (Cyprinus carpio L.) Cultured in Earthen Ponds in Saudi Arabia

ABSTRACT

Quantitative and qualitative estimation of bacterial flora present in pond water, sediments, gills, and intestine of healthy common carp Cyprinus carpio cultured in Saudi Arabia were performed and identified to species level where possible. Mean total viable bacterial counts in pond water ranged from 1.2?±?2.9?×?10⁴ to 2.5?±?3.5?×?10⁵ cfu/mL; in sediments, 9.3?±?2.1?×?10⁷ to 2.7?±?3.5?×?10⁹ cfu/g; in gills filaments, 4.3?±?2.9?×?10⁶ to 1.6?±?3.9?×?10⁷ cfu/g; and in intestine, 8.7?±?4.1?×?10⁹ to 5.4?±?3.2?×?10¹⁰ cfu/g. Gram-negative rod-shaped bacteria dominated (76%) the populations. In total, 12 bacterial genera and 15 species were identified. Pond water and sediment bacteria had the reflection on bacterial composition of gills and intestine of carp. Intestinal bacteria showed more diversification in contrast to gill bacteria. Aeromonas hydrophila, Shewanella putrefaciens, Vibrio cholerae, Corynebacterium urealyticum, Vibrio vulnificus, Vibrio sp., and Staphylococcus sp. were the common bacteria in all the populations. In pond water and carp intestine, A. hydrophila, S. putrefaciens, V. cholerae, and C. urealyticum were the most dominant bacteria (prevalence ≥ 10%) where pond sediments and the carp gills experienced with more one dominant bacterium V. vulnificus. Only the A. hydrophila covered one fourth (25%) of the total bacterial populations.     

Intestinal bacterial flora of Mediterranean gilthead sea bream (Sparus aurata Linnaeus) as a novel source of natural surface active compounds

Microbial communities play different functions in the digestive tract of fish and represent a source of bioactive compounds. This study was aimed to detect the presence of biosurfactant (BS)‐producing bacteria in the intestine of gilthead sea bream (Sparus aurata L.) to select strains candidate for biotechnological applications in aquaculture. A total of 100 bacterial strains were isolated from the guts of three groups of fish and analysed by different qualitative screening tests and the tensiometric analysis. BSs were extracted, characterized by thin‐layer chromatography (TLC) and their antibacterial activity against bacterial pathogens of interest in aquaculture was determined. A total of 17 out of 100 strains, affiliated to the genera Pseudomonas (11 isolates), Acinetobacter (1 isolate), Sphingomonas (4 isolates) and Aeromonas (1 isolate), displayed a stable emulsion production with the E₂₄ index from 0% to 44%, a surface tension reduction from 8.3 to 30 mN/m and 11 of them exhibited antibacterial activity against fish pathogens. The TLC analysis indicated that the intestinal BSs consisted of compounds ascribed to the class of glycolipids–rhamnolipids. This is the first study reporting on the isolation and selection of BS‐producing bacteria from fish gut, a natural novel source of surface active compounds with potential biotechnological applications in aquaculture.     

Diagnostic methods for identifying different Aeromonas species and examining their pathogenicity factors,their correlation to cytotoxicity and adherence to fish mucus

Aeromonas spp. are ubiquitous in the aquatic environment, acting as facultative or obligate pathogens for fish. Identifying Aeromonas spp. is important for pathogenesis and prognosis in diagnostic cases but can be difficult because of their close relationship. Forty‐four already characterized isolates of Aeromonas spp. were analysed by 16S rRNA gene sequencing, by gyrase B sequencing, by analysing their fatty acid profiles, by biochemical reactions and by MALDI‐TOF MS. To determine their pathogenicity, cytotoxicity, adhesion to mucus and the expression of 12 virulence factors were tested. The susceptibility of the isolates towards 13 different antibiotics was determined. MALDI‐TOF MS was found to be an acceptable identification method for Aeromonas spp. Although the method does not detect all species correctly, it is time‐effective and entails relatively low costs and no other methods achieved better results. A high prevalence of virulence‐related gene fragments was detected in almost all examined Aeromonas spp., especially in A. hydrophila and A. salmonicida, and most isolates exhibited a cytotoxic effect. Single isolates of A. hydrophila and A. salmonicida showed multiple resistance to antibiotics. These results might indicate the potentially pathogenic capacity of Aeromonas spp., suggesting a risk for aquatic animals and even humans, given their ubiquitous nature.     

基于16SrDNA分析的浒苔外生细菌多样性研究

为研究浙江近海浒苔Ulva spp.(Enteromorpha spp.)外生细菌多样性,采用传统的形态学和16S rDNA测序分析的方法,从舟山朱家尖、宁海国华电厂和奉化南沙3个地区分离到可培养的浒苔外生细菌及其周围海水细菌65株。根据细菌菌落特征和革兰氏染色结果等将分离到的细菌分为26种表型。16S rDNA序列测序比对发现:菌株与不动杆菌属(Acinetobacter)、交替单胞菌属(Alteromonas)、弧菌属(Vibrio)、假交替单胞菌属(Pseudoalteromonas)、微小杆菌属(Exiguobacterium)、芽孢杆菌属(Bacillus)、赤细菌属(Erythrobacter)、微球菌属(Micrococcus)、假单胞菌属(Pseudomonas)、深海杆菌属(Idiomarina)、Phaeobacter、Roseivirgaj和Silicibacter等23个属相应菌株具有较高同源性。对不同地区浒苔外生细菌进行了Shannon-Wiener多样性指数分析。研究表明:(1)宁海国华电厂的浒苔外生细菌多样性最丰富,多样性指数为93.98%;(2)浒苔外生细菌与其生活地区密切相关,其群落组成具有地域差异,其优势类群也不尽相同,但均归属于变形菌门。     

Phenotypical and genotypical characterization of Shewanella putrefaciens strains isolated from diseased freshwater fish

Between 2007 and 2012, a variety of disease outbreaks most often characterized by skin disorders were observed among different species of freshwater fish in Poland. In most cases, the clinical signs included focally necrotized gills, necrotic skin lesions or ulcers. Internally, haemorrhages, oedematous kidney and abnormal spleen enlargement were generally noted. The disorders were accompanied by increased mortality. Most of the problems concerned cultured common carp Cyprinus carpio L. and rainbow trout Oncorhynchus mykiss (Walbaum). Fish have been examined from a number of these farms, and additionally, the wild and ornamental fish with similar clinical signs of diseases were also tested. Bacteria were isolated consistently from lesions and internal organs. They had characteristic orange-pigmented colonies which grew in pure culture or constituted 55–95% of total bacterial flora. One hundred and eighteen isolates were collected and biochemically identified as Shewanella putrefaciens group, and this was confirmed by sequencing. Challenge tests confirmed the pathogenicity of these bacteria. This is the first report characterizing and describing S. putrefaciens as a pathogen of different species of freshwater fish in Europe.     

Winter kill in intensively stocked channel catfish (Ictalurus punctatus): Coinfection with Aeromonas veronii,Streptococcus parauberis and Shewanella putrefaciens

Unusual persistent natural mortality occurred in a floating in‐pond raceway system intensively stocked with channel and hybrid catfish beginning in early November 2016 up until March 2017. The temperature during the period of outbreak ranged from 7.2 to 23.7°C. Gross examination of freshly dead and moribund fish revealed pale gills, slight abdominal distension and swollen inflamed vents. Comprehensive necropsy of 20 fish demonstrated vast amounts of bloody ascitic fluid in the coelomic cavity, visceral congestion, splenomegaly and pale friable livers but macroscopically normal kidneys, suggesting systemic bacterial infection. Bacterial cultures were initiated from skin, gills and major internal organs. Following incubation, a mixture of three bacterial colony phenotypes was observed on agar plates. Presumptive biochemical characterization of the isolates followed by 16S‐rRNA sequence analysis resulted in the identification of Aeromonas veronii, Streptococcus parauberis and Shewanella putrefaciens. Channel catfish juveniles were experimentally infected with the recovered isolates to fulfil Koch's postulates. Moreover, an antibiogram was used to evaluate the susceptibility of the isolates to antimicrobial drugs approved for use in aquaculture. Aquaflor was used successfully for treatment. Here, we report bacterial coinfection lead by A. veronii and the first identification of S. parauberis and S. putrefaciens from cultured catfish in North America.     

Microbiological Quality of Farmed Tropical Freshwater Prawn (Macrobrachium rosenbergii de Man)

ABSTRACT

The objective of this study was to determine the microbiological quality of farmed giant freshwater prawn (Macrobrachium rosenbergii) collected from four freshwater farms located in Kerala (India). Microbiological counts on whole, deheaded, and deheaded and deveined prawn as well as on head and intestine were determined. Average counts (log₁₀ cfu g^?1) on whole prawn were 6.9 (total mesophilic counts (TPC) at 37°C) and 4.1 (psychrotrophic count at 7°C). The results indicated that the aerobic counts were within the acceptable limit. The levels of enterococci and faecal coliforms in farmed M. rosenbergii were high. There was an increase in the numbers of enterococci and Staphylococcus aureus after deheading. The major groups of bacteria comprising the flora of M. rosenbergii were Aeromonadaceae, Enterobacteriaceae and Pseudomonas. Farmed M. rosenbergii carried pathogenic bacteria such as Enterococcus spp., S. aureus, Aeromonas hydrophila, A. veronii biovar sobria and Clostridium perfringens. The results of the study suggest adoption of good farming and post harvest practices to improve the microbiological quality of farmed freshwater prawn.     

Bacterial microflora associated with farmed freshwater prawn Macrobrachium rosenbergii (de Man) and the aquaculture environment

The initial counts of bacteria associated with farmed giant freshwater prawn (Macrobrachium rosenbergii de Man) as well as with the water and sediment from two farms located at Kottayam district in Kerala (India) were determined. A total of 367 randomly selected isolates were characterized and identified. Prawn samples yielded mean microbiological counts of 4.92 log CFU g^?1 of shell with muscle and 7.78 log CFU g^?1 of intestine at 30°C. Bacterial numbers in the intestine of prawn were much higher than those in the pond water. Motile and non‐motile aerobic Gram‐negative bacteria together with Enterobacteriaceae accounted for 60–70% of the mesophiles isolated from water and prawn. However, the microorganisms isolated in significant numbers from shell with muscle and intestine of prawn were not recovered from the growing waters. Among Gram‐positive bacteria, Micrococcus, Bacillus, coryneforms, and Arthrobacter were found. Faecal coliforms and enterococci were found in significant numbers in M. rosenbergii. The rearing practices such as feeding and pond fertilization could have influenced the microflora in prawn. The commensal microflora of freshwater prawn included opportunistic pathogens such as Aeromonas spp. and Streptococcus spp. Storage of prawn at elevated temperatures can permit their survival and growth leading to quality loss. Care should be exercised during handling and processing to prevent contamination of edible meat.     

An outbreak of Shewanella putrefaciens group in wild eels Anguilla anguilla L. favoured by hypoxic aquatic environments

Microbiological analyses were conducted on wild eels from the L′Albufera Lake (Spain). A total of 174 individuals were collected in two surveys (i.e. year 2008 and autumn–winter 2014) among those caught by local fishermen into the lagoon. The prevalence of Shewanella putrefaciens group was 1.7% in 2008 and rose above 32% in 2014. It was due to an outbreak of shewanellosis that presented a morbidity rate of 64%. S. putrefaciens group strains were isolated as pure cultures from the sick eels that showed white ulcers surrounded by a reddish inflammation, damage of the mouth, extensive skin discoloration, exophthalmia, ascites and bad odour. The S. putrefaciens group was recovered from freshwater samples taken at the L′Albufera system, along autumn–winter 2015. Its counts significantly increased in freshwater parallel to hypoxia and temperature rising. Shewanellae strains were identified as S. putrefaciens and S. xiamenensis by 16S rRNA gene sequencing. These isolates recovered from sick eels or freshwater were virulent for European eel by IP challenge (LD₅₀ 10⁶ CFU g^?1 body weight). They also caused 30–38% cumulative mortality, in European eels challenged by a 2‐h bath (10⁷ CFU mL^?1). These results suggest that shewanellosis could be transmitted through water highlighting the fact that hypoxic conditions increase this bacterium levels in water.     

Effect of CO2 on Chemical and Microbial Changes of Pacific White Shrimp During Modified Atmosphere Packaging

ABSTRACT

This study monitored the physical, chemical, and sensory quality of raw Pacific white shrimp (Litopenaeus vannamei) and the evolution of microbial flora under modified atmosphere packaging (MAP) with varying concentrations of CO₂ (95% CO₂/5% O₂; 80% CO₂/15% N₂/5% O₂; 65% CO₂/30% N₂/5% O₂) at 4°C during 10-day storage. Plate counts on selective agars indicated that MAP had a strong inhibitory effect on psychrotrophic bacteria, mesophilic bacteria, Enterobacteriaceae, and H₂S-producing bacteria. Analyses with molecular techniques (denaturing gradient gel electrophoresis, DGGE) by extracting bacterial DNA from shrimp samples showed that Vibrio spp. and Aeromonas spp. were predominant in fresh MAP samples. Shewanella putrefaciens, which dominated in samples stored in air, were found sporadically in MAP samples. Interestingly, lactic acid bacteria were not predominant in MAP samples, whose pH values were high (6.66 to 8.14) during storage. The content of total volatile basic nitrogen in MAP samples was about 10 mg N/g lower than the control at the end of storage. Higher lightness values and sensory scores were also observed in samples under MAP. However, MAP with CO₂ concentrations higher than 80% did not enhance the inhibitory effect on bacterial growth but induced more severe reddening and sensory quality loss.     

Phylogenetic analysis of intestinal bacteria of freshwater salmon Salmo salar and sea trout Salmo trutta trutta and diet

The microbial diversity of culturable intestinal microflora of wild freshwater salmonid fishes salmon Salmo salar and sea trout Salmo trutta trutta juveniles (0+ years old) from the same environmental conditions were investigated by means of molecular identification techniques and analysis of diet. Significant differences in the intestinal microbial diversity were observed in different fish species. The predominant group in the intestinal tract of the salmon comprised representatives of the Enterobacteriaceae family (23%), Plesiomonas (19.2%) and Carnobacterium (15.3%). Predominant microbiota in sea trout intestinal tract were Enterobacteriaceae (52%), Aeromonas (22%) and Pseudomonas (14%). The results show that Enterobacteriaceae were predominant in the intestinal tract of the salmon and the sea trout juveniles raised on diets of different compositions. However, molecular identification of the intestinal microbiota at the species or genus level revealed differences in these fish species. Bacteria in the hindgut of salmon included Pragia and Serratia. However, bacteria in the gut contents of sea trout from the Enterobacteriaceae family were Buttiauxella, Enterobacter, Moellerella, Pantoea, Rahnella and Tiedjeia arctica. A novel phylotype of T. arctica is harbored in the intestinal tract of wild salmon, and may correspond to a previously undescribed species.     

A drop in ambient temperature results in a transient reduction of interrenal ACTH responsiveness in the gilthead sea bream (Sparus aurata, L.)

This study investigated the effects of a drop in water temperature (18 °C to 9 °C in 24 h) on the pituitary and interrenal hormones of the gilthead sea bream Sparus aurata. The in vitro sensitivity of the interrenal tissue to ACTH, plasma levels of cortisol, ACTH, -MSH, GH, glucose, lactate and ions were determined. In vitro ACTH, stimulated the release of cortisol from isolated interrenal glands from control gilthead sea bream in a concentration dependent fashion. However, the interrenal cells were less sensitive to ACTH as soon as 24 h following the onset of the temperature drop. At this time, plasma cortisol and ACTH levels were raised, and plasma GH concentrations were decreased, whereas no significant changes were found in plasma -MSH. After 96 h plasma ACTH levels had recovered whereas plasma cortisol levels were still higher than controls after 8 days of the beginning of the experiment. Interrenal sensitivity had recovered after 8 days. The results may help to clarify the relationship between the stress response and the aetiology of the winter syndrome in sea bream.