Investigations on cyanobacterial diversity in a shallow estuary (Southern Baltic Sea) including genes relevant to salinity resistance and iron starvation acclimation

Abstract

The cyanobacterial diversity in the pelagic of a shallow estuary at the Southern Baltic Sea has been investigated by a combination of classical morphological data and a polymerase chain reaction (PCR)-based molecular approach. The aim of the study was to investigate possible changes in the composition of the cyanobacterial community along the salinity and nutrient gradients. For this purpose partial gene sequences of cyanobacterial 16S rDNA and of two functional genes (ggpS- salinity tolerance marker, isiA- iron starvation marker) were amplified and compared with total community DNA. Random distribution of ggpS genotypes along the salinity gradient suggests that synthesis of the osmolyte glucosylglycerol is not restricted to higher salinity sampling sites. Most of the isiA sequences formed a new homogenous cluster in a phylogenetic tree, which indicates that the indigenous cyanobacterial community comprises a group of unknown species. Minimum iron concentrations, which can activate isiA transcription in model cyanobacteria, occurred at a few sampling sites with high phytoplankton biomass and moderate salinity. Nevertheless, isiA expression could be detected at all sampling sites, which indicated restricted iron supply to cyanobacterial phytoplankton in summer.

Luminescent Whole-Cell Cyanobacterial Bioreporter for Measuring Fe Availability in Diverse Marine Environments

“…Results obtained with the cyanobacterial bioreporter provide support for previous studies demonstrating Fe deficiency in surface waters of the Baltic (12,28,34,39). Characterization of the Fe bioreporter demonstrated that non-steady-state growth rates were suppressed by 40% and 70% when the bioreporter was grown at a pFe of 20.4 and 21.4, respectively, compared to Fe-sufficient conditions.…”

Phytoplankton diversity and photosynthetic acclimation along a longitudinal transect through a shallow estuary in summer

“…Of the 42 morphotypes found in these samples, 10 probably represented more than 1 species but could not be differentiated quantitatively during counting. Solitary rod-shaped cyanobacteria were the most dominant 'unit', which was also reported as one species of a Synechococcus-like species by molecular methods (Geiß et al 2004). Two abundant colonyforming Chroococcales, Aphanothece clathrata and Gomphosphaeria pusilla, each consisted of 3 to 4 species.…”

“…From this mean cell number, the total cells per species and biomass were calculated. Cell volumes and carbon were estimated as described by Geiß et al (2004). The morphological differentiation of taxonomic units was performed with the highest resolution possible (Anagnostidis & Komárek 1988 for filamentous cyanobacteria; Pankow 1990).…”

“…The number of different 16S rDNA fragments, which were selectively amplified by polymerase chain reaction (PCR) from plankton DNA for cyanobacteria and eukaryotic chloroplasts, was determined from 3 or 4 independent PCR analyses and denaturing gradient gel electrophoresis (DGGE) as described by Geiß et al (2004).…”

Testing of primers for the study of cyanobacterial molecular diversity by DGGE

“…Indeed, they have been used unmodified (e.g. Casamayor et al, 2000;Garcia-Pichel et al, 2001;Abed et al, 2002;Geiß et al, 2004) or slightly adapted (Zwart et al, 2005) for numerous DGGE studies investigating cyanobacterial diversity in environmental samples.…”