Spatial and temporal analysis of estuarine bacterioneuston and bacterioplankton using culture-dependent and culture-independent methodologies |
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Authors: | Juliana S N Azevedo Isabel Ramos Susana Araújo Cláudia S Oliveira António Correia Isabel S Henriques |
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Institution: | (1) CESAM and Department of Biology, University of Aveiro, 3810-193 Aveiro, Portugal;(2) Department of Biology, University of Aveiro, 3810-193 Aveiro, Portugal;(3) Department of Microbiology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal; |
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Abstract: | Bacterioneuston may play a key role in water–air exchange of gases and in processing organic matter and pollutants that accumulate
at the sea-surface microlayer (SML). However, the phylogenetic diversity of bacterioneuston has been poorly characterized.
We analyzed 24 samples each from the SML and underlying water (UW) at three sites in the Ria de Aveiro estuary, Portugal. Cultivation and culture-independent techniques were used to compare bacterioneuston and bacterioplankton.
Culturable heterotrophic bacteria were enriched in the SML. The culturable community was dominated by Psychrobacter and Acinetobacter. The presence of high numbers of Psychrobacter was a notable result. Differences were confined to a few genera overrepresented in UW samples (Kocuria, Agrococcus and Vibrio). 16S rDNA DGGE profiles were highly stable in terms of number and position of bands between sampling sites and dates but
cluster analysis revealed a slight tendency for grouping according to sampled layer. SML-specific DGGE bands affiliated with
Actinobacteria, Cyanobacteria, Gammaproteobacteria and Bacteroidetes. Low similarity between nucleotide sequences of DGGE-bands and previously reported sequences suggest the occurrence of SML-specific
populations. Enrichment of SML for Pseudomonas and Aeromonas was questioned and the diversity of both communities was analyzed. Consistent differences between SML and UW aeromonads communities
were not identified. In terms of Pseudomonas, a culturable operational taxonomic unit was consistently overrepresented within SML samples. Taken together, our results
indicate that the similarity between SML and UW communities depends on spatial and temporal factors. |
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