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The prokaryotic abundance and diversity in three cold, oligotrophic Patagonian lakes (Témpanos, Las Torres and Mercedes) in the northern region Aysén (Chile) were compared in winter and summer using 16S rRNA fluorescence in situ hybridization and PCR-denaturing gradient gel electrophoresis technique. Prokaryotic abundances, numerically dominated by Bacteria, were quite similar in the three lakes, but higher in sediments than in waters, and they were also higher in summer than in winter. The relative contribution of Archaea was greater in waters than in sediments, and in winter rather than in summer. Despite the phylogenetic analysis indicated that most sequences were affiliated to a few taxonomic groups, mainly referred to Proteobacteria (consisting of Beta-, Alpha- and Gammaproteobacteria) and Euryarchaeota (mainly related to uncultured methanogens), their relative abundances differed in each sample, resulting in different bacterial and archaeal assemblages. In winter, the abundance of the dominant bacterial phylotypes were mainly regulated by the increasing levels of total organic carbon in waters. Archaeal abundance and richness appeared mostly influenced by pH in winter and total nitrogen content in summer. The prokaryotic community composition at Témpanos lake, located most northerly and closer to a glacier, greatly differed in respect to the other two lakes. In this lake was detected the highest bacterial diversity, being Betaproteobacteria the most abundant group, whereas Alphaproteobacteria were distinctive of Mercedes. Archaeal community associated with sediments was mainly represent by members related to the order of Methanosarcinales at Mercedes and Las Torres lakes, and by Crenarchaeota at Témpanos lake. Our results indicate that the proximity to the glacier and the seasonality shape the composition of the prokaryotic communities in these remote lakes. These results may be used as baseline information to follow the microbial community responses to potential global changes and to anthropogenic impacts.

The variations in vertical distribution and composition of bacteria in the meromictic Lake Faro (Messina, Italy) were analysed by culture-independent methods in two different mixing conditions. Water samples were collected from a central station from the surface to the bottom (30 m depth) on two different sampling dates--the first characterised by a well-mixed water mass and the second by a marked stratification. A 'red-water' layer, caused by a dense growth of photosynthetic sulphur bacteria, was present at a depth of 25 m in December 2005 and at 15 m in August 2006, defining two different zones in terms of their physicochemical properties. The vertical distribution of bacterioplankton showed that the interface zones were more densely populated than others. In both sampling periods, the highest numbers of live cells were observed within 'red water' layers. The dominant phylotypes of the bacterial community were determined by sequencing the Denaturing Gradient Gel Electrophoresis (DGGE) bands resulting from PCR amplification of 16S rRNA gene fragments. The number of DGGE bands, considered indicative of the total species richness, did not vary predictably across the two different sampling periods. Proteobacteria (α-, γ-, δ- and ε subclass members), Cytophaga-Flavobacterium-Bacteroides, green sulphur bacteria and Cyanobacteria were retrieved from Lake Faro. Most of the bands showed DNA sequences that did not match with other previously described organisms, suggesting the presence of new indigenous bacterial phylotypes.

The aim of this study was to investigate the microbial community thriving at two shallow hydrothermal vents off Panarea Island (Italy). Physico-chemical characteristics of thermal waters were examined in order to establish the effect of the vents on biodiversity of both Bacteria and Archaea. Water and adjacent sediment samples were collected at different times from two vents, characterised by different depth and temperature, and analysed to evaluate total microbial abundances, sulphur-oxidising and thermophilic aerobic bacteria. Total microbial abundances were on average of the order of 10(5) cells ml(-1), expressed as picoplanktonic size fraction. Picophytoplanktonic cells accounted for 0.77-3.83% of the total picoplanktonic cells. The contribution of bacterial and archaeal taxa to prokaryotic community diversity was investigated by PCR-DGGE fingerprinting method. The number of bands derived from bacterial DNA was highest in the DGGE profiles of water sample from the warmest and deepest site (site 2). In contrast, archaeal richness was highest in the water of the coldest and shallowest site (site 1). Sulphur-oxidising bacteria were detected by both culture-dependent and -independent methods. The primary production at the shallow hydrothermal system of Panarea is supported by a complex microbial community composed by phototrophs and chemolithotrophs.

Aims: The occurrence of Helicobacter pylori in the coastal zone of the Straits of Messina (Italy) as free-living and associated with plankton was studied., Methods and Results: Monthly sampling of seawater and plankton was carried out from April 2002 to March, 2003. All environmental samples analysed by cultural method, did not show the presence of H. pylori. The DNA extracted from all environmental samples was tested by PCR by using primers for H. pylori 16S rRNA, ureA and cagA. 16S rRNA PCR yielded amplified products of 522-bp in 15 of 36 (41.7%) of the environmental samples. By using the ureA primers to amplify the urea signal sequences, the predicted PCR products of 491-bp were obtained from eight (22.2%) of 36 environmental samples. PCR with cagA primers yielded amplified products of 349-bp in DNA extracted of seven of 36 (19.4%) of the environmental samples. When 16S rRNA, ureA and cagA amplified gene sequences were aligned with H. pylori 26695 and J99 genome sequences, we obtained a percentage of alignment over 90%., Conclusions: The detection of H. pylori genes in marine samples allows us to consider the marine environment a possible reservoir for this pathogenic bacterium., Significance and Impact of the Study: The direct detection of H. pylori genes may be relevant in order to consider the marine environment as significant reservoir for this bacterium.

Aims: To determine the abundance of faecal and nonfaecal bacteria related to human and animal health, as free living or associated with small (>64 microm) and large (>200 microm) plankton, samples were collected monthly from the coastal zone at Messina (Italy)., Methods and Results: Different enrichment and selective cultural methods were used to determine the abundance of bacteria in sea water and plankton. The bacteria were more frequently isolated from water and large plankton than from small plankton. Vibrio and Aeromonas spp. showed different distribution patterns in water and plankton. Faecal indicators were always present in water and the large size class plankton samples. Enterococci associated with large plankton were more abundant than E. coli in the winter. Vibrio species distributions were different in water and plankton samples. Among arcobacters only A. butzleri was isolated from water and plankton samples. Campylobacter spp. was always absent in small plankton and more frequent in large plankton than in water., Conclusions: The colonization of zooplankton by potentially pathogenic bacteria is a widespread phenomenon., Significance and Impact of the Study: The presence of potentially pathogenic bacteria in sea water and associated with plankton can have ecological and epidemiological implications.

Phylogenetic relationships of a thermophilic, halophilic, aerobic spore-forming strain 4-1(T), isolated from the water of a shallow sea hot spring at Vulcano Island (Italy), revealed its relatedness to members of the genus Bacillus. Chemotaxonomic and phenotypic properties of strain 4-1(T) are sufficiently different from related moderately thermophilic species, e.g., B. smithii, B. fumarioli, B. oleronius, B. sporothermodurans and B. infernus to describe strain 4-1(T) as a new Bacillus species, for which the name Bacillus aeolius sp. nov. is proposed. Strain 4-1(T) is characterised by the potential biotechnological important properties such as exopolysaccharide production, surfactant activity, and utilisation of hydrocarbons.

Water and mussel samples were collected from two brackish lakes, used as mussel farms, at different times of the year, for the quantitative analysis of Vibrio spp. and for the isolation of potentially pathogenic species. The isolates underwent cultural and biochemical tests selected for rapid identification. Glucose oxidizing-fermenting and O/129 sensitive strains were distinguished on the basis of the following tests: sucrose and cellobiose utilization, sulphatase activity and polymyxin B resistance performed, respectively, on TCBS, CPC and SPS media. Responses to the presence of beta-galactosidase, salt requirement and growth on triple sugar iron medium were also added. A total of 125 from 152 isolates were referred to the species Vibrio fluvialis (55 strains), V. alginolyticus (40), V. parahaemolyticus (11), V. vulnificus (10) and V. mimicus (9). The remaining 27 isolates were not identified. The isolation of potentially pathogenic vibrios from cultivated mussels is a risk for health of people consuming raw seafood. Therefore, a long-term monitoring programme should also include the search for these bacterial species.

Arcobacter spp. were isolated from water and mussels of two brackish lakes near Messina (Italy). The isolates were phenotypically characterized on the basis of a large battery of cultural and biochemical tests. By comparison with the reference strains Arcobacter butzleri ATCC 49616 and A. cryaerophilus ATCC 43157 they may be considered Arcobacter butzleri-like bacteria. The current isolation suggests that the brackish environment may play an important role in the survival and transmission of Arcobacter spp. also by seafood cultured in the examined waters.

Microbial research on temporal variation of bacterial densities was carried out on seawater samples collected from two field stations at different depths during the Antarctic summer (oceanographic campaign 1989/1990). Bacterial densities evaluated on Marine Agar 2216 (Difco) and on TCBS Agar (Difco) after incubation at +4 degrees C for 21 days respectively ranged from 0 to 7.9 x 10(2) CFU/ml for heterotrophic bacteria and from 0 to 5.7 x 10(2) CFU/100ml for "presumptive vibrios". During the period of observation, Vibrio densities showed a higher variability than those of total heterotrophic bacteria. A high percentage of gelatinolytic and chitinolytic vibrios was observed. The qualitative composition of heterotrophic bacterial communities was studied on 38 morphological and biochemical characteristics of 152 strains isolated from the stations. The data were subsequently used to determine the structure and metabolic potentialities of bacterial communities in the two sites. Almost all the heterotrophic, psychrotrophic isolates were non fermentative Gram-negative rods, belonging to the genera Pseudomonas/Alcaligenes, Flavobacterium/Cytophaga. The bacterial communities in the two coastal habitats investigated were clearly different.