Genetic diversity and distribution of periphytic Synechococcus spp. in biofilms and picoplankton of Lake Constance

Abstract

In various water depths of the littoral zone of Lake Constance (Bodensee) cyanobacteria of the Synechococcus-type were isolated from biofilms (periphyton) on three natural substrates and an artificial one (unglazed tiles). From one tile three strains of phycoerythrin (PE)-rich Synechococcus spp. were isolated, the first examples of these organisms in the epibenthos. Phylogenetic inference based on the 16S-23S rRNA intergenic spacer (ITS-1) assigned all periphytic isolates to two clusters of the picophytoplankton clade (evolutionary lineage VI of cyanobacteria). The sequence divergence in the ITS-1 was used to design specific PCR primers to allow direct, culture-independent detection and quantification of isolated Synechococcus strains in natural periphytic and pelagic samples. Denaturing gradient gel electrophoresis (DGGE) analysis revealed depth-related differences of Synechococcus spp. distribution on tiles placed in the littoral zone. Synechococcus genotypes were observed which occurred in both the periphyton (on tiles) and in the pelagic picoplankton. A strain with one of these genotypes, Synechococcus sp. BO 8805, was isolated from the pelagic zone in 1988. Its genotype was found on tiles that had been exposed at different water depths in the littoral zone in spring and autumn of the year 2000. Quantitative analysis with a genotype-specific TaqMan probe and real-time Taq nuclease assays (TNA) confirmed its presence in the pelagic zone, although appearance of this and related genotypes was highly irregular and exhibited strong differences between consecutive years. Our results show that the ability to form significant subpopulations in pelagic and periphytic communities exists in three out of four phylogenetic clusters of Synechococcus spp. in Lake Constance. This versatility may be a key feature in the ubiquity of the evolutionary lineage VI of cyanobacteria.

Genetic Diversity of Picocyanobacteria in Tibetan Lakes: Assessing the Endemic and Universal Distributions

“…Similar low taxa richness of picocyanobacterial (20) and the total bacterial (44) communities in Tibetan lakes was also described. These results contrast with previous observations of diverse picocyanobacterial lineages in other lakes at lower elevations, such as Lake Constance (ϳ400 m above sea level) (17), Lake Mondsee (ϳ500 m) (16), Lake Superior (ϳ180 m) (22), and the Great Mazurian Lakes (ϳ110 m) (21), or in the brackish Baltic Sea (18,19). Evidence also showed that individual water bodies can harbor a diverse range of picocyanobacteria (27).…”

“…Prochlorococcus, the cluster 5 Synechococcus, and Cyanobium form a tightly clustered phylogenetic group (3,13), sometimes called the "Syn/Pro clade" (14), the "PS clade" (13), or "group 6b" (5). However, many nonmarine picocyanobacterial lineages (clusters) found in freshwater or brackish environments fell into this group (5,(15)(16)(17) (Table 1 shows a summary). A few of these clusters were widely found in both freshwater lakes and the brackish Baltic Sea, such as the C. gracile cluster, subalpine cluster I, subalpine cluster II, group I, and the LBP1 cluster (5,15,16,18,19), supporting the high dispersive potential of microbes.…”

Vertical Distribution of Epibenthic Freshwater Cyanobacterial Synechococcus spp. Strains Depends on Their Ability for Photoprotection

“…strains examined in this study were isolated in the year 2000 from two series of tiles (samples were collected from the beginning of March to mid of April and from end of August to mid of October) placed for six weeks at different water depths (7.0, 1.0, and 0.5 m) in the littoral zone of Lake Constance (47° 41′N 09° 07′E, 476 km 2 , maximal depth 254 m), a large oligotrophic prealpine fresh water lake in Germany (details in [22]). As proposed previously [22], we refer to these strains as epibenthic (collected from submerged tiles) in order to distinguish them from pelagic (free-living), epiphytic (collected from macrophytes) or epilithic (collected from stones). Four of these strains were PC-rich (PC1-1, PC2-1, PC3-0.5, and PC4-0.5) and three were PE-rich (PE1-7, PE2-7, and PE3-7).…”

“…The number after the dash indicates the water depth from which the strain was originally collected (Table 1). Since the year 2000, non-axenic cultures (co-culture with heterotrophic bacteria) of these strains were grown on solidified BG 11 medium (with nitrate) and BG 11o , a medium with a low concentration of combined nitrogen due to the omission of nitrate, under controlled laboratory conditions at 19°C and a white light regime of 12 h light/12 h dark at a light intensity of 8 to 10 µmol photons·m −2 ·s −1 as described [22]. For experiments, colonies were picked and transferred to BG 11/N liquid medium [23].…”

“…Here we provide an experimental proof that the light intensity plays an important role in the vertical distribution of seven Synechococcus spp. strains isolated from the littoral zone of Lake Constance in Germany [22]. While three PE-rich strains from 7.0 m water depth cultivated under laboratory conditions and exposed to light stress showed reduced levels of Chl a and photoprotective carotenoids, four PC-rich strains from 1.0 or 0.5 m water depths had either constant or increased levels of these pigments.…”