Abstract: The greater amberjack, Seriola dumerilii (Risso 1810) is a semi-pelagic fish and a worldwide species; it is considered a promising candidate for the diversification of Mediterranean aquaculture. In this paper an experimental injection with Listonella (Vibrio) anguillarum was performed to study the immune response of S. dumerilii. Antibody titres to L. anguillarum O1 were determined with indirect-ELISA at different times over a period of 42 days. Results showed that the antibody levels against L. anguillarum were significantly higher in the challenged fish compared to the control. They started developing since the 5th day reaching the highest peak on day 20 after injection, indicating a fast response of the immune system. The observed antibody titre was very high versus L. anguillarum if compared to other fish species.
Abstract: This study evaluates the effectiveness of three different molecular techniques, repetitive extragenic palindromic PCR (REP-PCR), enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) and the random amplified polymorphic DNA (RAPD-PCR) for rapid typing of Photobacterium damselae ssp. piscicida strains isolated from different species of marine fish and geographic areas. The results obtained by the three methods showed that RAPD and ERIC-PCR were more discriminative for suitable rapid typing of Ph. damselae ssp. piscicida than REP-PCR. The analysis of DNA banding patterns generated by both molecular methods (RAPD and ERIC-PCR) clearly separated the strains into two main groups that strongly correlated with their geographic origin. Moreover, the REP-PCR analysis was less reproducible than the RAPD and ERIC-PCR methods and does not allow the establishment of genetic groups. RAPD and ERIC-PCR constitute valuable tools for molecular typing of Ph. damselae ssp. piscicida strains, which can be used in epidemiological studies of photobacteriosis infections.
Abstract: A seasonal study of the quantitative and qualitative distribution of heterotrophic bacterial community was carried out in the Adriatic Sea between April 1995 and January 1996, in order to evaluate its spatial and temporal variability and metabolic potential in the degradation processes of organic matter. The culturable bacteria (CFU) ranged between 0.1 and 22% of total bacterioplankton with a maximum percentage in surface samples of coastal zones. Their distribution was generally affected by the prevailing hydrological conditions. At the coastal stations about 44-75% of CFU variance could be explained by river runoff. The changes in the composition of heterotrophic bacterial community showed a seasonal succession of main bacterial groups, with a prevalence of Gram negative, non fermenting bacteria in the cold period (April-January) and an increase of Vibrionaccae and pigmented bacteria in summer. The seasonal variations were more important at the stations influenced by rivers than offshore. The bacterial community showed a greater versatility for organic polymers hydrolysis in the offshore station than in the coastal areas. Over 60% of all isolated heterotrophic bacteria expressed peptidase, lipase and phosphatase ectoenzymes activities, in all seasons and showed an increasing trend in warm period (in July October). The alpha- and beta-glucosidase potentials of bacteria were lower (20% on average) and showed different pattern during the year. These results suggest different role of the bacterial community in the decomposition of organic matter in the Adriatic Sea. Since only 20% of bacterial strains expressed glucosidase activity, carbohydrate-rich polymers such as mucilage might accumulate.
Abstract: A year's monitoring of faecal pollution of marine coastal waters surrounding Messina was carried out in 1996/97. The distribution of faecal coliforms was evaluated in 15 stations located along the Sicilian coastline, sampled monthly in coincidence of the two opposing current phases ("montante" and "scendente" currents) which characterise the Straits of Messina. The data obtained provided a complete picture of hygienic-sanitary conditions of the area and highlighted the presence of heavily polluted sites in correspondence with river outflows. Higher bacterial counts were associated with lower salinity values and higher ammonia concentrations; over an annual study, they occurred during the coldest months, showing the negative impact of continental water inputs on the bacteriological quality of coastal waters.
Abstract: AIM: Leucine aminopeptidase (LAP), an enzyme involved in the decomposition of natural peptides, was measured in different marine and brackish ecosystems, together with some environmental and microbiological parameters. METHODS AND RESULTS: The fluorogenic compound L-leucine-7-amido-4-methyl coumarin was specifically used for the determination of this in situ activity. The enzyme data obtained from this comparative study highlighted the strong spatial and temporal variability of the distribution of LAP in aquatic ecosystems, which was sometimes related to the course of environmental variables such as salinity and organic carbon content. CONCLUSIONS: LAP assay has proved to be a rapid method providing useful information on the microbial metabolic processes involved in the mineralization of organic matter. SIGNIFICANCE AND IMPACT OF THE STUDY: The determination of the potential rates of extracellular enzyme activity is of great ecological importance to extend knowledge on the role played by bacteria in aquatic biogeochemical cycles.
Abstract: The determination of Escherichia coli in marine waters through a rapid method, the microscopic indirect immunofluorescent technique, is evaluated in comparison with the conventional count on m-FC agar medium. The data obtained in seawater samples, collected monthly along the Messina coastline, show good sensitivity of the analysis and agreement between the microscopic and culture technique, with a detection limit of 10(2) cells 100 ml(-1) for immunofluorescence.
Abstract: During the last oceanographic cruise carried out in the Straits of Magellan (April 1995), a serological approach was used in order to determine the distribution and composition of the picophytoplankton community with respect to two cyanobacteria species, Synechococcus sp. and bacillaris, characterized respectively by phycoerythrin and phycocyanin as the main accessory photosynthetic pigment. In the period examined, the Straits were characterized by generally low concentrations of total picophytoplankton (10(5)-10(6) cells/l). The qualitative composition of the community showed the prevalence of the species Synechococcus sp. in the Pacific basin, whereas S. bacillaris appears to be predominant in the central area. The immunofluorescence method proved to be effective in the study of the diversity of these microorganisms in aquatic environments.
Abstract: A three year investigation into the microbiological conditions of the waters of the Gulf of Castellammare (TP) was carried out in order to evaluate the possible utilization of this area as an aquaculture site. Analysis of a total of 168 samples was aimed at estimating the quantitative distribution of total and fecal coliforms, enterococci and halophilic vibrios. The qualitative distribution of Vibrio species was also studied with particular reference to potentially pathogenic species. Coliforms showed the highest densities (10(2)-10(3) CFU/100 ml) in November 1993 at the coastal stations and mostly negative values during the subsequent samplings; in contrast, halophilic vibrios prevailed in the warm months. V. alginolyticus and V. fluvialis prevailed respectively among the Vibrio population grown at 35 and 24 degrees C, grouped in 13 and in 4 clusters at similarity levels of 81-96%. Quantitative data demonstrate the presence of low levels of microbial contamination, which suggests the general suitability of the area for fish farming.
Abstract: The autotrophic ammonium-oxidizing bacterium Nitrosococcus oceanus was studied in the brackish lake of Ganzirri by cultural and immunofluorescent methods. The preparation of the specific antiserum in rabbits is reported. The polyclonal antiserum for Nitrosococcus oceanus cross-reacted with other ammonia oxidizing strains, but not with other marine bacteria. Temporal changes were determined by taking monthly water samples from a station 6 m deep and the distribution in sediments was investigated in four stations. Isolation of a strain of Nitrosococcus sp. was obtained from a sediment sample collected in December. The abundance of Nitrosococcus spp. bacteria correlated positively with particulate organic carbon (POC), particulate organic nitrogen (PON), temperature and total bacteria, whereas there was a negative relationship with oxygen tension. No correlation was found between immunofluorescent and MPN counts of Nitrosococcus spp. bacteria.
Abstract: The results of a study carried out by numerical analysis on Vibrio strains isolated from the waters of the Straits of Messina are reported. The quantitative data showed the presence of low bacterial densities (ranging from 9 to 99 CFU/100 ml of water) due to the intense currents which characterize this area; also the highest bacterial counts were generally found during the "montante" current. With regard to the qualitative results, there was a predominance of vibrios belonging to V. mediterranei, V. splendidus II and V. pelagius II species, which represented respectively 25%, 19% and 13% of the total bacterial population. The species distribution did not seem related to sampling stations or depth. The taxonomic structure, obtained using the simple matching coefficient and unweighted average linkage clustering, revealed the presence of 7 main clusters (S = 80-95%), which included strains of various origin because of the particular turbulence of the waters of the Straits.
