Microbial ecology of the intestinal tract of gilthead sea bream (<i>Sparus aurata</i> Linneus, 1758)

The study of fish gut microflora is important because it reflects the bacterial composition of the rearing environment and the dietary regimen of ingested food; moreover these microbiota play a role in the health and the quality of adult fish. The aim of this research was to study the microbial ecology of the gut of two groups of gilthead sea bream (Sparus aurata L.) reared in off-shore floating cages and in lagoon, located in Sardinian coast, in order to quantify the heterotrophic bacteria and to identify at genus and species level the dominant bacterial communities of the intestinal tract by means of the ARDRA technique and sequencing of the 16S rRNA gene. This study aimed to test the microbiological quality of fish and intestinal microbial biodiversity in order to detect a possible link with the rearing system. The results showed a significantly higher bacterial load in the gilthead sea bream farmed in the lagoon than in the fish from the off-shore cages and highlighted a different bacterial qualitative composition of the gut microflora in the two groups of fish, although the presence of the Pseudomonas spp. was observed in all the fish studied. A greater microbial diversity at species level was observed in the sea bream reared in the lagoon

Biosurfactants from Marine Microorganisms

The marine biosphere represents a yet underexploited natural source of bioactive compounds, mainly of microbial origin. Among them, biosurfactants (BSs) are functional molecules, which are attracting a great interest due to their biocompatibility, versatility, and applications in several biotechnological fields. BSs are surface active amphipathic compounds, containing both a hydrophilic and a hydrophobic moiety, which are grouped in low (glycolipids and lipopeptides) or high molecular weight (polymeric complexes) compounds. A number of environmental factors such as pH, salinity, temperature, and nutrient availability can affect microbial BS production. Marine microorganisms with different phylogenetic affiliations and isolated from several marine habitats (e.g., seawater, sediments, and higher organisms) worldwide (spanning from the Mediterranean Sea to Antarctica) have been reported as surfactant producers. However, most of the marine microbial world remains still unexplored. The present chapter aims at giving a general overview on the recent advances about BSs of marine origin, in order to enhance the knowledge inherent their production, chemical characterization and identification, interesting biological properties, and potential biotechnological applications

Bacterial flora associated with the digestive tract of gilthead seabreams reared in floating cages in the Alghero Bay (North western Sardinia, Italy): preliminary results

The intestinal microflora of fish is highly variable and can depend on many factors such as species, developmental stage, environmental conditions, trophic habits and, in the case of farmed fish, on rearing conditions (i.e., fish density, quality of rearing water, dietary regimen, etc.). Different studies showed that Gram-negative bacteria such as Enterobacteriaceae and the Vibrio-Aeromonas group dominate the fish intestine. However, since few studies have been carried out on the bacterial flora of intensively reared marine teleosts, the aim of the present study was to investigate the microflora associated with the digestive tract of Sparus aurata specimens reared in floating cages. A total of 30 gilthead seabreams (mean weight 324.9±61.4 g) starved for 48 hours was sampled in autumn 2008 from a fish farming facility located in the Alghero Bay (North western Sardinia, Italy: Lat 40°33’43.9’’N, Long 8°16’09.0’’E). The intestine between the pyloric caeca and the anus of each specimen was removed and analysed by means of conventional bacteriological techniques using five culture media: Plate Count Agar (PCA), Nutrient Agar (NA), Violet Red Bile Glucose Agar (VRBGA), Violet Red Bile Agar Mug (VRBA-MUG), and de Man-Rogosa-Sharpe (MRS) agar. Total viable counts on PCA and NA were quite similar, showing mean values of 126.7±109.0 colony forming units (cfu) per gram intestinal tissue (between 10.0 and 495.0 cfu/g) and 108.0±101.6 cfu/g (from nil to 350.0 cfu/g), respectively. The mean number of Enterobacteriaceae determined on VRBGA proved to be 46.3±42.8 cfu/g (from nil to 150 cfu/ g) and the VRBA-MUG mean count were 30.4±29.3 cfu/g (from nil to 95.0 cfu/g). No bacterial colonies were instead detected using the MRS medium. These results, although preliminary, evidenced a relative low number of bacteria associated with the digestive tract of the fish examined, thus indicating good hygienic conditions inside the cages as well as a suitable rearing density and a balanced diet for the seabreams

Survey of the genetic variability of populations of <i>Ruditapes philippinarum</i> from tre Gulf of Olbia (N-E Sardinia) by microsatellites = Indagine sulla variabilità genetica di popolazioni di <i>Ruditapes philippinarum</i> provenienti dal golfo di Olbia (N-E Sardegna)

Genetic variability was investigated at six microsatellite loci of the Manila clam Ruditapes philippinarum (Adams &amp; Reeve, 1850) (Bivalvia) from the Gulf of Olbia (N-E Sardinia) and Sacca di Goro (N Adriatic Sea). We found no significant differentiation among Sardinian samples and between those and the Adriatic one, which suggests the absence of a founder effect in Sardinian population

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

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Fishery Wastes as a Yet Undiscovered Treasure from the Sea: Biomolecules Sources, Extraction Methods and Valorization

The search for new biological sources of commercial value is a major goal for the sustainable management of natural resources. The huge amount of fishery by-catch or processing by-products continuously produced needs to be managed to avoid environmental problems and keep resource sustainability. Fishery by-products can represent an interesting source of high added value bioactive compounds, such as proteins, carbohydrates, collagen, polyunsaturated fatty acids, chitin, polyphenolic constituents, carotenoids, vitamins, alkaloids, tocopherols, tocotrienols, toxins; nevertheless, their biotechnological potential is still largely underutilized. Depending on their structural and functional characteristics, marine-derived biomolecules can find several applications in food industry, agriculture, biotechnological (chemical, industrial or environmental) fields. Fish internal organs are a rich and underexplored source of bioactive compounds; the fish gut microbiota biosynthesizes essential or short-chain fatty acids, vitamins, minerals or enzymes and is also a source of probiotic candidates, in turn producing bioactive compounds with antibiotic and biosurfactant/bioemulsifier activities. Chemical, enzymatic and/or microbial processing of fishery by-catch or processing by-products allows the production of different valuable bioactive compounds; to date, however, the lack of cost-effective extraction strategies so far has prevented their exploitation on a large scale. Standardization and optimization of extraction procedures are urgently required, as processing conditions can affect the qualitative and quantitative properties of these biomolecules. Valorization routes for such raw materials can provide a great additional value for companies involved in the field of bioprospecting. The present review aims at collecting current knowledge on fishery by-catch or by-products, exploring the valorization of their active biomolecules, in application of the circular economy paradigm applied to the fishery field. It will address specific issues from a biorefinery perspective: (i) fish tissues and organs as potential sources of metabolites, antibiotics and probiotics; (ii) screening for bioactive compounds; (iii) extraction processes and innovative technologies for purification and chemical characterization; (iv) energy production technologies for the exhausted biomass. We provide a general perspective on the techno-economic feasibility and the environmental footprint of the production process, as well as on the definition of legal constraints for the new products production and commercial use

Intestinal Microbial Ecology and Fillet Metal Chemistry of Wild Grey Mullets Reflect the Variability of the Aquatic Environment in a Western Mediterranean Coastal Lagoon (Santa Giusta, Sardinia, Italy)

Fish populations play an active role in the maintenance of aquatic ecosystems biodiversity. Their intestinal microbiota and fillet chemistry depend on abiotic and biotic factors of the water environments that they inhabit. The present study investigated the grey mullets’ gut microbiota from a transitional aquatic ecosystem (Santa Giusta Lagoon, Sardinia, Italy) by a multidisciplinary approach which refers the results of (1) gut cultivable microbiota analyses (MA), (2) the trace metal assessment of fish muscle (TM), (3) the physico-chemical water monitoring (PC). MA detected the greatest number of total aerobic heterotrophic bacteria, Enterobacteriaceae and coliforms in Autumn (mean values 1.3 × 105, 2.4 × 104, 1.1 × 104 cfu g−1, respectively) when the accumulated rain and mean values of nutrients (reactive phosphorous and silica) were the highest. Marine bacteria were more numerous in Summer (mean value 7.4 × 105 cfu g−1) when the highest mean values of water temperature and salinity were registered. The gut bacteria were identified as Pseudomonas spp. (64%), Aeromonas spp. (17%), Ochrobactrum pseudogrignonense (10%), Providencia spp. (5%), Enterobacter ludwigii (2%) and Kocuria tytonicola (2%). TM showed that Ca, Na, B and Ni increased their concentrations in Winter while maxima of P, Zn, Cu and Fe were found in muscles of fish sampled in Summer. This study highlighted that the fish intestinal microbiota and metal composition of the fillet reflected the seasonal aquatic environmental variability

Chemometric treatment of simple physical and chemical data for the discrimination of unifloral honeys

: In this work, nonspecific physico-chemical parameters were determined in 160 honey samples belonging to the four main botanical categories present in Sardinia Island, Italy (strawberry tree, thistle, asphodel and eucalyptus) in order to develop a discriminant method for determining the botanical origin of honey. All the possible combinations of the seven physico-chemical parameters (pH, free acidity, electrical conductivity, color, total phenolic compounds, FRAP activity, and DPPH activity) measured in the honey samples were evaluated by Linear Discriminant Analysis (LDA). LDA models led to the prediction of each botanical origin with a very low level of misclassification (typically less than 5%). Since very high levels of correct prediction in cross validation (98.3%) and external validation (100%) were obtained considering only four parameters (i.e. pH, acidity, conductivity and DPPH), these results might allow a fast and easy control of the botanical origin of honeys

HLA-DQB1*0305 and −DQB1*0304 alleles among Sardinians: evolutionary and practical implications for oligotyping

This study, performed in individuals of Sardiaian descent, reports an epidemiologic and molecular analysis of the recently identified DQB1*0304 and DQB1*0305 alleles*. These two alleles having a gene frequency of 0.017 and 0.005, respectively, are not uncommon in Sardinia and are distributed fairly uniformly on the island. The analysis of DQB1 second and third exons of the two alleles revealed that although they have always been found included within the same DRB1*0403-DQA1*03 haplotype, they had a different origin. The sequence pattern of DQB1*0305 confirmed that it originated from the DQB1*0302 “recipient” gene by the insertion of a DQB1*0402 nucleotide stretch, within its β-sheet region, while that of DQB1*0304 suggested that it originated from the DQB1*0301 gene, either by a single point mutation at codon 57 (GCC instead of GAC) or, alternatively, by a segmental transfer of a DQB1*0302 motif, including codon 57, within its α-helic region. Independently from the mechanism of generation, the fact that DQB1*0304 originated from DQB1*0301 allele was intriguing considering that, in over 1500 HLA class II Sardinian haplotypes examined, neither the putative parental DRB1*0403-DQA1*03-DQB1*0301 nor any DRB1*04-DQA1*03-DQB1*0301 haplotypes were found. Finally, since the assignment of DQB1*0305 may be inaccurate with the traditional panel of probes commonly used for DQB1 oligotyping, the use of an additional oligonucleotide probe is recommended

Isolation and Identification of Bacteria with Surface and Antibacterial Activity from the Gut of Mediterranean Grey Mullets

Fish gut represents a peculiar ecological niche where bacteria can transit and reside to play vital roles by producing bio-compounds with nutritional, immunomodulatory and other functions. This complex microbial ecosystem reflects several factors (environment, feeding regimen, fish species, etc.). The objective of the present study was the identification of intestinal microbial strains able to produce molecules called biosurfactants (BSs), which were tested for surface and antibacterial activity in order to select a group of probiotic bacteria for aquaculture use. Forty-two bacterial isolates from the digestive tracts of twenty Mediterranean grey mullets were screened for testing emulsifying (E-24), surface and antibiotic activities. Fifty percent of bacteria, ascribed to Pseudomonas aeruginosa, Pseudomonas sp., P. putida and P. anguilliseptica, P. stutzeri, P. protegens and Enterobacter ludwigii were found to be surfactant producers. Of the tested strains, 26.6% exhibited an antibacterial activity against Staphylococcus aureus (10.0 &plusmn; 0.0&ndash;14.5 &plusmn; 0.7 mm inhibition zone), and among them, 23.3% of isolates also showed inhibitory activity vs. Proteus mirabilis (10.0 &plusmn; 0.0&ndash;18.5 &plusmn; 0.7 mm inhibition zone) and 6.6% vs. Klebsiella pneumoniae (11.5 &plusmn; 0.7&ndash;17.5 &plusmn; 0.7 mm inhibition zone). According to preliminary chemical analysis, the bioactive compounds are suggested to be ascribed to the class of glycolipids. This works indicated that fish gut is a source of bioactive compounds which deserves to be explored