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The Alcantara River estuary was studied to obtain the first data on both water quality and ecological status of the only River Park in Sicily (Italy). Water samples were seasonally collected from three selected stations in the estuarine area and from one station at the mouth of the estuary in the marine coastal zone. Picoplankton and picophytoplankton counts were among the highest observed in estuarine environments and in other coastal waters of the Mediterranean Sea. The contribution of picophytoplankton to total picoplankton showed greater variations in freshwater (from 0.53% to 8.6%) than in coastal waters (from 1.8% to 4.3%). Picophytoplankton abundance increased in Alcantara waters in winter. Vibrio and Aeromonas spp. abundances ranged from x10(2) to x10(3) CFU 100 ml(-1) and from x10(3) to x10(5) CFU 100 ml(-1) respectively. Vibrio and Aeromonas spp. counts were independent from the fecal contamination level. Bacterial identification of the isolates revealed the presence of pathogenic and potentially pathogenic Vibrio and Aeromonas spp. for humans and animals.

Seawater and plankton samples from the Straits of Messina, Italy, were analysed to confirm the occurrence of potentially pathogenic Arcobacter butzleri, A. cryaerophilus and A. skirrowii. Both classical cultural methods and molecular techniques were used as confirmative steps of the growth in enrichment broth to enumerate and differentiate these bacteria. Only A. butzleri was isolated from seawater and plankton samples and was more abundant when associated with plankton than free-living. A. cryaerophilus was occasionally detected by PCR assay from environmental samples. The PCR procedure, used in a combined method, was useful in enumerating Arcobacter spp. in marine environment.

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.

Seawater samples were collected from a fixed, coastal station in the Terra Nova Bay at different depths during the Xth Oceanographic Cruise in the 1994-95 Antarctic summer. Picoplanktonic abundance, estimated by direct counts in epifluorescence microscopy, ranged from 2.2 x 10(7) to 1.6 x 10(8) cells.l-1. The heterotrophic bacterial densities, evaluated on Marine Agar 2216 (Difco) after incubation at +4 degrees C for 21 days, ranged from 2 x 10(3) to 4.5 x 10(6) CFU.l-1. The qualitative composition of the heterotrophic bacterial community was studied on 64 morphological and biochemical characters of the 125 strains isolated. Heterotrophic, psychrotrophic isolates were tentatively identified at genus level as Pseudomonas, Vibrio, Acinetobacter, and Flavobacterium/Cytophaga. In order to compare the characteristics of the isolates with those previously studied during 1989/90, the synthetical indices of the structure and the metabolic potentiality of the heterotrophic bacterial community were processed. Results showed that the bacterial community was metabolically more active and more homogenous than that previously studied.

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.