Seasonal changes on microbial metabolism and biomass in the euphotic layer of Sicilian Channel.

As a part of a wider project on fisheries ecology, several biological and environmental parameters were monitored during two oceanographic cruises (BANSIC 2012 and NOVESAR 2013) in the Sicily Channel, which connects the Western and Eastern Mediterranean basins. The prokaryotic abundances and biomass as well as hydrolysis rates on organic matter were investigated in the euphotic layer of a retention area for fish larval stages including anchovy (Engraulis encrasicolus, Linnaeus, 1758) with the aim to investigate the different biogeochemical signatures in two seasonal conditions. The environmental parameters, particulate organic carbon and nitrogen together with heterotrophic production were also measured. Results showed significant increases for most of the studied parameters with increasing temperature during summer. This had effects on the Carbon cycle and recycling of nutrients; in fact total prokaryotic abundance and biomass, as well as carbon hydrolyzed by two enzymes (Leucine aminopeptidase and ß-glucosidase), increased significantly during summer. Conversely Alkaline phosphatase activity, Chlorophyll concentration and Oxygen increased during winter. The same environmental parameters affected also the presence of fish eggs. Moreover high percentages of free enzymes (i.e., enzymes not associated with cells) were measured, accounting for percentages variable from 12 to 95 % of the total enzymatic activity, with values generally higher in summer than in winter. In this oligotrophic environment, the prokaryotic biomass was supported by the C hydrolyzed by enzymatic activities. The ratio between the hydrolyzed C and prokaryotic biomass was higher in winter than in summer, indicating that alkaline phosphatase activity contribute to an efficient incorporation of C into biomass in winter.

Role of prokaryotic biomasses and activities in carbon and phosphorus cycles at a coastal, thermohaline front and in offshore waters (Gulf of Manfredonia, Southern Adriatic Sea).

The Western areas of the Adriatic Sea are subjected to inputs of inorganic nutrients and organic matter that can modify the trophic status of the waters and consequently, the microbiological processes involved in the carbon and phosphorus biogeochemical cycles, particularly in shallow coastal environments. To explore this topic, a survey was carried out during the spring of 2003 in a particular hydrodynamic area of the Gulf of Manfredonia, where the potential (P) and real (R) rates of four different microbial exoenzymatic activities (EEA) (α [αG] and ß glucosidases [ßG], leucine aminopeptidase [LAP], and alkaline phosphatase [AP]) as well as the P and R rates of prokaryotic heterotrophic production (PHP), AP as well as the P and R rates of PHP, primary production (PPnet), the prokaryotic and phototrophic stocks and basic hydrological parameters were examined. Three different water masses were found, with a thermohaline front (THF) being detected between the warmer and less saline coastal waters and colder and saltier offshore Adriatic waters. Under the general oligotrophic conditions of the entire Gulf, a decreasing gradient from the coastal toward the offshore areas was detected, with PHP, PPnet, stocks and EEA (αG, ßG, AP) being directly correlated with the temperature and inversely correlated with the salinity, whereas opposite relationships were observed for LAP activity. No enhancement of microbiological activities or stocks was observed at the THF. The use of P or R rates of microbiological activities, which decrease particularly for EEA, could result in discrepancies in interpreting the efficiency of several metabolic processes.

Seasonal dynamics of prokaryotic abundance and activities in relation to environmental parameters in a transitional aquatic ecosystem (Cape Peloro, Italy).

This study examines the effects of temporal changes on microbial parameters in a brackish aquatic ecosystem. To this aim, the abundances of prokaryotes and vibrios together with the rates of enzymatic hydrolysis of proteins by leucine aminopeptidase (LAP), polysaccharides by ß-glucosidase (GLU) and organic phosphates by alkaline phosphatase (AP), heterotrophic prokaryotic production (HPP), respiration (R), were seasonally investigated, during a 2-year period in the coastal area of Cape Peloro (Messina, Italy), constituted by two brackish lakes (Faro and Ganzirri). In addition, physical and chemical parameters (temperature, salinity, nutrients) and particulate organic carbon and nitrogen (POC, PN) were measured. The influence of multiple factors on prokaryotic abundances and activities was analysed. The results showed that Cape Peloro area is characterised by high seasonal variability of the microbial parameters that is higher than the spatial one. Combined changes in particulate matter and temperature (T), could explain the variability in vibrios abundance, GLU and R activities in both lakes, indicating a direct stimulation of the warm season on the heterotrophic prokaryotic metabolism. Positive correlations between T (from 13.3 to 29.6 °C) and HPP, LAP, AP, POC, PN are also observed in Ganzirri Lake. Moreover, the trophic status index and most of the microbial parameters show significant seasonal differences. This study demonstrates that vibrios abundance and microbial activities are responsive to the spatial and seasonal changes of examined area. The combined effects of temperature and trophic conditions on the microbial parameters lead us to suggest their use as potential indicators of the prokaryotic response to climate changes in temperate brackish areas.

Assessment of the ecological status of transitional waters in Sicily (Italy): first characterisation and classification according to a multiparametric approach.

A 1-year cycle of observations was performed in four Sicilian transitional water systems (Oliveri-Tindari, Cape Peloro, Vendicari and Marsala) to characterise their ecological status. A panel of variables among which trophic and microbial (enzyme activities, abundance of hetetrophic bacteria and of bacterial pollution indicators) parameters, were selected. Particulate organic carbon (POC) and nitrogen (PON) and chlorophyll-a (Chl-a) contents defined the trophic state, while microbial hydrolysis rates and abundance gave insights on microbial community efficiency in organic matter transformation and on allochthonous inputs. To classify the trophic state of examined waters, the synthetic trophic state index (TRIX) was calculated. Microbial hydrolysis rates correlated positively with POC and Chl-a, which increased along the eutrophication gradient. The significant relationships among TRIX, trophic and microbial parameters suggested the use of leucine aminopeptidase, alkaline phosphatase and POC as suitable parameters to implement the Water Framework Directive when assessing the ecological status of transitional water systems.

Development of a fluorescent antibody method for the detection of Enterococcus faecium and its potential for coastal aquatic environment monitoring.

A direct, microscopic fluorescent antibody method was developed to detect the occurrence of Enterococcus faecium in coastal aquatic environments and was compared with the conventional membrane filtering method. The "in situ" application of the antibody-based protocol in the analysis of water samples collected from coastal polyhaline habitats demonstrated good sensitivity and ease of implementation. Data obtained with the microscopic technique were in agreement with those obtained from culture counts. The fluorescent antibody method proved to be a rapid and reliable technique for the detection of E. faecium. The advantages and limitations intrinsic to the method are discussed, highlighting the potential of this new technique for monitoring coastal aquatic environments.

Microbial community dynamics during assays of harbour oil spill bioremediation: a microscale simulation study.

AIMS: Microcosm experiments simulating an oil spill event were performed to evaluate the response of the natural microbial community structure of Messina harbour seawater following the accidental load of petroleum. METHODS AND RESULTS: An experimental harbour seawater microcosm, supplemented with nutrients and crude oil, was monitored above 15 days in comparison with unpolluted ones (control microcosms). Bacterial cells were counted with a Live/Dead BacLight viability kit; leucine aminopeptidase, beta-glucosidase, alkaline phosphatase, lipase and esterase enzymes were measured using fluorogenic substrates. The microbial community dynamic was monitored by isolation of total RNA, RT-PCR amplification of 16S rRNA, cloning and sequencing. Oil addition stimulated an increase of the total bacterial abundance, leucine aminopeptidase and phosphatase activity rates, as well as a change in the community structure. This suggested a prompt response of micro-organisms to the load of petroleum hydrocarbons. CONCLUSIONS: The present study on the viability, specific composition and metabolic characteristics of the microbial community allows a more precise assessment of oil pollution. Both structural and functional parameters offer interesting perspectives as indicators to monitor changes caused by petroleum hydrocarbons. SIGNIFICANCE AND IMPACT OF THE STUDY: A better knowledge of microbial structural successions at oil-polluted sites is essential for environmental bioremediation. Data obtained in microcosm studies improve our understanding of natural processes occurring during oil spills.

First data on the distribution and ecology of Vibrio spp. of the Straits of Magellan (South America).

During the austral summer of 1991 a study was carried out on the presence and distribution of the genus Vibrio in the Straits of Magellan. Vibrios strains were isolated using membrane filters and Marine Agar 2216 in anaerobiosis. Variations of the populations of total heterotrophic bacteria and vibrios were observed both on the surface and along the column of water. All vibrios are psychrotrophic and were grouped in 4 cluster among which cluster 1, identified as presumed V. anguillarum, seems the most important including 73% of strains. A certain habitat segregation of clusters was noted. Cluster 4 was found only in a deep and permanently colder water mass. The relations between 20 environmental parameters and the bacterial population were also studied. Significant positive correlations were observed between the vibrios population and various fractions of suspended particulate matter.

[Isolation of V. cholerae no-01 and V. metschnikovii from sewage of the city of Mar del Plata]. / Aislamiento de V. cholerae no-01 y V. metschnikovii en efluentes cloacales de la ciudad de Mar del Plata.

A total of 42 vibrio strains isolated from sewage, together with 7 culture collection strains were studied by numerical taxonomy. A simplified clustering is shown in Fig. 1. Two important phena were determined. Phenon 1, identified as V. cholerae non-01, formed at 0.90% S, contains 32 sewage strains and 2 reference strains. Phenon 2, identified as V. metschnikovii, formed at 0.85% S, contains 5 sewage strains. No typical marine vibrio species were isolated. The phenotypic characteristics of 2 phena are shown in Table 2. All V. cholerae non-01 were haemolytic, proteolytic and lipolytic. They also showed some phenotypic characteristics (degradation of esculin, 81.2%; utilization of: D-glucuronate, 88.2%; cellobiose, 47.0% and lactose, 47.0%), and growth in NaCl 6%, 91.1%. According to literature references, the survival of V. cholerae non-01 in Mar del Plata marine environment is possible.

Aislamiento de V. cholerae no-01 y V. metschnikovii en efluentes cloacales de la ciudad de Mar del Plata / [Isolation of V. cholerae no-01 and V. metschnikovii from sewage of the city of Mar del Plata]

A total of 42 vibrio strains isolated from sewage, together with 7 culture collection strains were studied by numerical taxonomy. A simplified clustering is shown in Fig. 1. Two important phena were determined. Phenon 1, identified as V. cholerae non-01, formed at 0.90

S, contains 32 sewage strains and 2 reference strains. Phenon 2, identified as V. metschnikovii, formed at 0.85

S, contains 5 sewage strains. No typical marine vibrio species were isolated. The phenotypic characteristics of 2 phena are shown in Table 2. All V. cholerae non-01 were haemolytic, proteolytic and lipolytic. They also showed some phenotypic characteristics (degradation of esculin, 81.2

), and growth in NaCl 6

. According to literature references, the survival of V. cholerae non-01 in Mar del Plata marine environment is possible.

[Isolation and quantification of Salmonella in the waters of the Río de la Plata destined for recreation]. / Aislamiento y cuantificación de Salmonella en aguas del Río de la Plata destinadas a recreación.

Thirty three samples from recreational waters from different areas of Río de la Plata were tested for Salmonella (Fig. 1). A 200 ml sample filtered through a diatom bed as well as 2 and 20 ml samples without filtering were studied using a simple and economical technique. The isolation probability was directly dependent on the water volume analyzed. Best results were obtained when tetrathionate broth with novobiocin and Salmonella shigella agar were used (Table 3). Salmonella was isolated from 36% of the samples studied and 12 serotypes were identified (Table 5). The relation between the NPM of each bacteriological indicator used and the NPM of Salmonella are shown in Table 4. Correlation values were calculated by relating mean point logarithms of the classes in Table 4 with the isolation percentages of Salmonella for each class. These values were low, except for fecal Streptococcus (R2 = 0.94). The high density of fecal coliforms found in Bagliardi and Pescadores Beaches (rarely less than 10.000 bacteria/100 ml) and the incidence of Salmonella, lead us to conclude that these waters are unsafe for bathing and swimming, specially for children, according with the international recommendation on the quality of recreational waters. Waters with the characteristics described here should be periodically analyzed for Salmonella concentration. The lack of correlation values between the MPN of total and fecal coliforms and the MPN of Salmonella, also supports this advise.