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The Great Salt Plains (GSP) in north-central Oklahoma, USA is an expansive salt flat (∼65 km2) that is part of the federally protected Salt Plains National Wildlife Refuge. The GSP serves as an ideal environment to study the microbial diversity of a terrestrial, hypersaline system that experiences wide fluctuations in freshwater influx and diel temperature. Our study assessed cyanobacterial diversity at the GSP by focusing on the taxonomic and physiological diversity of GSP isolates, and the 16S rRNA phylogenetic diversity of isolates and environmental clones from three sites (north, central, and south). Taxonomic diversity of isolates was limited to a few genera (mostly Phormidium and Geitlerinema), but physiological diversity based on halotolerance ranges was strikingly more diverse, even between strains of the same phylotype. The phylogenetic tree revealed diversity that spanned a number of cyanobacterial lineages, although diversity at each site was dominated by only a few phylotypes. Unlike other hypersaline systems, a number of environmental clones from the GSP were members of the heterocystous lineage. Although a number of cyanobacterial isolates were close matches with prevalent environmental clones, it is not certain if these clones reflect the same halotolerance ranges of their matching isolates. This caveat is based on the notable disparities we found between strains of the same phylotype and their inherent halotolerance. Our findings support the hypothesis that variable or poikilotrophic environments promote diversification, and in particular, select for variation in ecotype more than phylotype. [ABSTRACT FROM AUTHOR]

Pulp and paper secondary waste-treatment systems in Brazil, Canada, New Zealand, and the U.S.A. contained dynamic cyanobacterial communities, some of which exceeded heterotrophic bacterial biomass. No other viable photoautotrophic populations were detected in the ponds. Regardless of geographical location, Oscillatoriales including Phormidium, Geitlerinema, and Pseudanabaena were the dominant taxa. As well, Chroococcus (Chroococcales) was an important genus in Brazil and New Zealand. The possible impact of cyanobacteria on waste-treatment efficiency deserves further study given their large biomass and diverse metabolic characteristics.Key words: cyanobacteria, blue-green algae, heterotrophic bacteria, community structure, pulp and paper secondary waste treatment.On a observé au Brésil, au Canada, en Nouvelle-Zélande et aux États-Unis que les systèmes de traitement secondaire des rejets d'usines de pâtes et papiers contenaient des populations dynamiques de cyanobactéries dont certaines dépassent même les valeurs de la biomasse bactérienne hétérotrophe. Aucune autre population de photoautotrophes n'a été détectée dans les bassins. Indépendamment de la localisation géographique, les taxons dominants appartenaient aux Oscillatoriales incluant Phormidium, Geitlerinema et Pseudanabaena. Au Brésil et en Nouvelle-Zélande Chroococcus (Chroococcales) était aussi un genre important. L'impact potentiel des cyanobactéries sur l'efficacité du traitement des rejets mérite d'être étudié plus à fond, compte tenu de la biomasse élevée et des caractéristiques métaboliques variées de ces bactéries.Mots clés : cyanobactéries, algues bleues-vertes, bactéries hétérotrophes, organisation de la population, traitement secondaire des rejets d'usines de pâtes et papiers.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

The alga Cladophora glomerata can erupt in nuisance blooms throughout the lower Great Lakes. Since bacterial abundance increases with the emergence and decay of Cladophora, we investigated the prevalence of antibiotic resistance (ABR) in Cladophora-associated bacterial communities up-gradient and down-gradient from a large sewage treatment plant (STP) on Lake Ontario. Although STPs are well-known sources of ABR, we also expected detectable ABR from up-gradient wetland communities, since they receive surface run-off from urban and agricultural sources. Statistically significant differences in aquatic bacterial abundance and ABR were found between down-gradient beach samples and up-gradient coastal wetland samples (ANOVA, Holm-Sidak test, p < 0.05). Decaying and free-floating Cladophora sampled near the STP had the highest bacterial densities overall, including on ampicillin- and vancomycintreated plates. However, quantitative polymerase chain reaction analysis of the ABR genes ampC, tetA, tetB, and vanA from environmental communities showed a different pattern. Some of the highest ABR gene levels occurred at the 2 coastal wetland sites (vanA). Overall, bacterial ABR profiles from environmental samples were distinguishable between living and decaying Cladophora, inferring that Cladophora may control bacterial ABR depending on its life-cycle stage. Our results also show how spatially and temporally dynamic ABR is in nearshore aquatic bacteria, which warrants further research. [ABSTRACT FROM AUTHOR]