Bacterial community composition over a dry winter in meso- and eutrophic Portuguese water bodies

Abstract

In order to investigate the bacterial diversity in a number of rivers, reservoirs and lakes in northern and central Portugal during the winter of 2004/5 (atypically dry), we applied molecular methodologies, namely denaturing gradient gel electrophoresis with primers targeting fractions of the bacterial 16S rRNA gene. Environmental parameters such as pH, conductivity, inorganic nutrients, total suspended solids and chlorophyll a were determined in order to characterize the trophic status of the studied water bodies. We found water bodies with oligotrophic to hypereutrophic characteristics. Organisms belonging to the Bacteroidetes and Alphaproteobacteria were found at the highest pH environment. Bacteroidetes were also related to high nutrient concentrations. Verrucomicrobia were associated with the most oligotrophic reservoir and low pH values. Actinobacteria were present in all samples from lakes and reservoirs, indicating its preference for lentic water bodies. Cyanobacteria dominance was related to high pH and conductivity levels. In general the conductivity values recorded in winter 2005 were the highest over recent years and chlorophyll a also reached very high levels. The data emphasize an enhanced risk of eutrophication for the studied water bodies, especially in the subsequent months when the temperature rises.

Molecular Fingerprinting of Cyanobacteria from River Biofilms as a Water Quality Monitoring Tool

“…In our study, different phylotypes showed various responses to environmental characteristics such as nutrient concentrations (DIN and SRP), conductivity, discharge, and dissolved oxygen. These results are consistent with those of studies in eutrophic lakes (37,48) and of similar investigations in rivers on bacterial community composition (13,35,49), where the dominance of different genotypes largely related to changes in nutrient concentrations and dissolved oxygen has been noted.…”

“…However, certain limitations, such as comigration of different DNA fragments and the presence of different bands with the same sequence in a single lane, have been noted that can introduce bias into the analysis and, therefore, jeopardize the correct interpretation of the data (39). The present study found no evidence for comigration of different DNA fragments; instead, bands in the community patterns could be unambiguously assigned to a single phylotype, since comigrating bands had identical or almost identical sequences, as previously found in several DGGE/TGGE studies (15,(32)(33)(34)(35)(36)(37). Although we cannot completely exclude the possibility of identical sequences from different bands in the same lane, the small number of such cases suggests that this is not a major concern for our analysis.…”

“…All the bands at the same position had the same nucleotide composition or were nearly identical (99.3% to 100% similarity), as we found in a similar study in another Spanish river (Guadalix River; unpublished data). Consequently, bands with the same electrophoretic position were considered the same phylotype as reported by other authors (15,(32)(33)(34)(35)(36)(37). Only three phylotypes corresponding to Chamaesiphon had different electrophoretic migration profiles with almost the same sequence, although most sequences recovered corresponded to the same position.…”

A Guide to the Natural History of Freshwater Lake Bacteria

“…1 , manuscript in press at Environmental Microbiology (141a) (includes GenBank accession numbers FJ827781 to FJ828505); 2 , GenBank accession numbers for the sequenced clones are HQ386253 to HQ386631; 3 , GenBank accession numbers for the sequenced clones are FJ916807 to FJ916903 and HQ530565 to HQ532908, except HQ530583, HQ531638, and HQ532521. (Based on data from references 2, 3,4,11,20,22,24,27,35,38,41,42,44,45,46,48,49,52,61,63,69,73,74,82,83,84,85,89,93,95,101,105,106,108,116,124,126,127,134,135,139,140,141,147,148,149,15...…”

Global Transcriptional Response of the Alkali-Tolerant CyanobacteriumSynechocystissp. Strain PCC 6803 to a pH 10 Environment

“…Many cyanobacterial strains are alkali tolerant and grow at pHs ranging from neutral to 10 to 11, so that cyanobacteria both generate and thrive in alkaline conditions. There have been numerous reports of habitats where photosynthetic rates are high (such as shallow lakes), pH values exceed pH 10, and cyanobacteria become the major phytoplankton species (7,27). Such populations of cyanobacteria are frequently associated with the production of a range of secondary metabolites, including nuisance and toxic compounds (5).…”