ABSTRACT:The relationship between the trophic state of 39 reservoirs located in the semi-arid region of north-east Brazil and their planktonic structure was examined by a sampling survey during the 1998 drought (September to November). A total of 30 environmental and biological parameters, with special attention paid to phytoplankton, were studied once at each reservoir to obtain a synoptic view at a state scale (Pernambuco State). The application of the chlorophyll a-total phosphorus standard relationship for grades of eutrophication revealed a classification in which 90% of the sites were eutrophic-hypertrophic. Among the 202 taxa identified in the phytoplankton assemblages, the cyanobacterium Cylindrospermopsis (Wolsz.) Seenayya et Subba Raju represented more than 80% of the total phytoplankton density in 10 reservoirs and more than 50% in 17 reservoirs. The rarity of other phytoplanktonic groups in the case of the Cylindrospermopsis dominance is the most significant biological feature of these reservoirs. Although rotifers were more closely linked to hypereutrophic conditions than copepods or cladocerans, this dominant group did not seem to play an efficient role in cyanobacterial control. A statistical approach based on the analysis of cross tables (co-inertia analysis) allows us to describe species-environment relationships with a special focus on the factors governing the presence of Cylindrospermopsis. As determined by hierarchical analysis, a major group of studied reservoirs (70%) corresponded to deeper, warmer and hypertrophic reservoirs characterized by the combination of (1) low ammonia concentration, high temperature and pH values, and (2) high percentages of Cylindrospermopsis abundances. Lack of water renewal in 1998 linked to the 1997 El Niño consequences seems to be a major determinant for both trophic conditions and Cylindrospermopsis dominance in the reservoirs studied.KEY WORDS: Bacteria · Phytoplankton · Zooplankton · Cylindrospermopsis · El Niño event · Reservoirs · Co-inertia analysis Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 23: [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] 2000 Cyanobacteria are recognized as a critical problem worldwide and their blooms are typical phenomena in eutrophic lakes, often linked to external nutrient enrichment (Paerl 1988). The influence of local climatological factors (e.g. wind, light intensity, temperature) can accelerate these phenomena and modify the phytoplankton structure, as cyanobacteria are strongly driven by physical factors such as local weather conditions (e.g. Tóth & Padisák 1986, Fabbro & Duivenvoorden 1996. Other factors that potentially influence the biomass and composition of phytoplankton include a stable water column with a turbulence limitation defined as a high ratio between the mixing zone and the euphotic zone (Soranno 1997). In addition, cyanobacteria are inedible prey for many zooplankton organisms because of their large colony size, their toxic effects and low...

Molecular typing and virulence markers were used to evaluate the genetic profiles and virulence potential of 106 Yersinia enterocolitica strains. Of these strains, 71 were bio-serotype 4/O : 3, isolated from human and animal clinical material, and 35 were of biotype 1A or 2 and of diverse serotypes, isolated from food in Brazil between 1968 and 2000. Drug resistance was also investigated. All the strains were resistant to three or more drugs. The isolates showed a virulence-related phenotype in the aesculin, pyrazinamidase and salicin tests, except for the food isolates, only two of which were positive for these tests. For the other phenotypic virulence determinants (autoagglutination, Ca ++ dependence and Congo red absorption), the strains showed a diverse behaviour. The inv, ail and ystA genes were detected in all human and animal strains, while all the food isolates were positive for inv, and 3 % of them positive for ail and ystA. The presence of virF was variable in the three groups of strains. The strains were better discriminated by PFGE than by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR). A higher genomic similarity was observed among the 4/O : 3 strains, isolated from human and animal isolates, than among the food strains, with the exception of two food strains possessing the virulence genes and grouped close to the 4/O : 3 strains by ERIC-PCR. Unusually, the results revealed the virulence potential of a bio-serotype 1A/O : 10 strain, suggesting that food contaminated with Y. enterocolitica biotype 1A may cause infection. This also suggests that ERIC-PCR may be used as a tool to reveal clues about the virulence potential of Y. enterocolitica strains. Furthermore, the results also support the hypothesis that animals may act as reservoirs of Y. enterocolitica for human infections in Brazil, an epidemiological aspect that has not been investigated in this country, confirming data from other parts of the world. INTRODUCTIONYersinia enterocolitica is the most prevalent Yersinia species connected to disease in humans (Bottone, 1999; RobinsBrowne, 2001). It has also frequently been isolated from animals, food and the environment (Fredriksson-Ahomaa et al., 1999;Thoerner et al., 2003; Falcão et al., 2004).Y. enterocolitica is responsible for gastroenteritis and other syndromes in humans and animals (Bottone, 1999 biochemical and serological tests that enable the differentiation of the strains into diverse bio-serotypes (Aleksic & Bockemühl, 1999). Also, pathogenic strains are related to some phenotypic characteristics, such as pyrazinamidase production, aesculin hydrolysis, salicin fermentation, calcium dependence, autoagglutination and Congo red absorption (Bottone, 1999). Molecular genetic studies have emphasized the importance of a virulence plasmid (pYV) that encodes various virulence genes, among them virF, which is an important transcriptional regulator of other plasmid genes, as well as the role of chromosomal virulence genes that mediate cell invasion (inv and ail) and produce a therm...

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In the last few decades, molecular typing has become an important tool in taxonomic, phylogenetic and identification studies of numerous groups of bacteria, including the yersiniae. In this study, Enterobacterial Repetitive Intergenic Consensus PCR (ERIC-PCR), Pulsed-Field Gel Electrophoresis (PFGE), 16S rRNA gene sequencing and Multilocus Sequence Analysis (MLSA) were performed to determine the ability of these techniques to be used in taxonomy and identification of Yersinia strains. A total of 60 Yersinia strains were genotyped by ERIC-PCR and PFGE. Moreover, an in silico analysis was carried out for 16S rRNA gene sequencing and MLSA, using 68 and 49 Yersinia strains, respectively. A phylogenetic tree constructed from the ERIC-PCR, 16S rRNA gene sequencing and MLSA data grouped most of the Yersinia species into distinct species-specific clusters. In the PFGE assay these clusters were not observed. On this basis, ERIC-PCR, 16S rRNA gene sequencing and MLSA seem to be valuable techniques for use in taxonomic and identification studies of the genus Yersinia, whereas PFGE does not. Furthermore, ERIC-PCR has the advantage of being a cheaper, easier and faster assay than 16S rRNA gene sequencing or MLSA, and for these reasons can be considerate an alternative tool in taxonomic studies of yersiniae.

The bacterial genus Yersinia belongs to the family Enterobacteriaceae and comprises 15 species. Species of the genus Yersinia are usually identified by their phenotypic characteristics. Thus, it is essential to establish a complete phenotypic classification for all species of the genus Yersinia. The species Yersinia massiliensis was proposed in 2008, based on 16S rRNA, gyrB, hsp60, rpoB and sodA gene sequences and some distinguishing phenotypic characteristics. In this study, four Yersinia strains classified as Y. massiliensis based on the sequencing of the loci mentioned above were subjected to a more detailed phenotypic characterization. This characterization revealed differences in the results of four tests previously reported as diagnostic for Y. massiliensis and the results of 18 additional tests provided new information about the biochemical diversity of this species. In the light of the results of the phenotypic characteristics of the four strains of Y. massiliensis, an emended description of Y. massiliensis is presented.

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