MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION OF PLANKTONIC CYANOBACTERIA FROM BELGIUM AND LUXEMBOURG¹

Abstract

For the first time in Belgium and Luxembourg, the diversity and taxonomy of 95 cyanobacterial strains isolated from freshwater blooms were assessed by the comparison of phenotypes and partial 16S rRNA gene sequences. The results showed the high diversity of nanoplanktonic, picoplanktonic, and benthic-periphytic cyanobacteria accompanying the main bloom-forming taxa. Indeed, besides 15 morphotypes of bloom-forming taxa, seven nonbloom-forming planktonic morphotypes and 11 morphotypes from benthic-periphytic taxa were isolated in culture from the plankton samples of 35 water bodies. The bloom-forming strains belonged to the genera Microcystis, Woronichinia, Planktothrix, Anabaena, and Aphanizomenon, whereas the other strains isolated from the same samples were assigned to the nanoplanktonic Aphanocapsa, Aphanothece, Snowella, and Pseudanabaena; to the picoplanktonic Cyanobium; and to the benthicperiphytic Geitlerinema, Komvophoron, Leptolyngbya, Lyngbya, Phormidium, Calothrix, Nostoc, and Trichormus. The results supported both the polyphyletism of genera such as Aphanocapsa, Aphanothece, Leptolyngbya, Geitlerinema, Anabaena, and Aphanizomenon as well as the validity of genera such as Microcystis, Planktothrix, and Pseudanabaena with gas vesicles and cells constricted at the cross wall. The results obtained showed the close relationship between Snowella and Woronichinia for which very few sequences exist. The first sequence of Komvophoron appeared poorly related to other available cyanobacterial sequences. Although in a few cases a good agreement existed between phenotypic and genotypic features, there was generally a discrepancy. Strains with identical morphotypes show small differences in the 16S rRNA sequences, which might be related to the different chemical properties of their habitats. The results showed the importance of the polyphasic approach in order to improve the taxonomy of cyanobacteria.

Phenotypic and genetic diversification of Pseudanabaena spp. (cyanobacteria)

“…Moreover, the 23S rRNA gene displayed more polymorphisms than the 16S rRNA gene, which was virtually identical in virtually all isolates. The phylogenetic analysis of the 16S rRNA gene confirmed that all isolates belong to the Pseudanabaena/Limnothrix group with 99% cluster similarity (Zwart et al, 2005;Willame et al, 2006). From BLAST searches against the GenBank database, we observed that 42% of the isolates were 100% identical to Pseudanabaena sp.…”

“…This cluster is commonly referred to as the Pseudanabaena/Limnothrix group (Gkelis et al, 2005;Willame et al, 2006). This group also comprised several environmental sequences as well as other isolates including the type strain Pseudanabaena PCC7408, strains belonging to L. redekei (Van Goor, Meffert) (Limnothrix sp.…”

“…However, often it is not recognized that smaller cyanobacteria exceed the larger species in terms of biomass and activity and therefore play a major role in the ecosystem dynamics. Several reports mentioned the occurrence of the tiny filamentous Pseudanabaena in cyanobacterial blooms in brackish and freshwater ecosystems (Vasconcelos and Pereira, 2001;Stal et al, 2003;Gkelis et al, 2005;Zwart et al, 2005;Kim et al, 2006;Willame et al, 2006). Nevertheless, Pseudanabaena spp.…”

“…Limnothrix is typically found in mesoto eutrophic freshwater ecosystems, whereas Pseudanabaena is more widely distributed and occurs in diverse aquatic as well as in benthic environments (Castenholz et al, 2001;Zwart et al, 2005;Diez et al, 2007). On the basis of the 16S rRNA gene, Pseudanabaena and Limnothrix form a monophyletic cluster within the cyanobacteria (Zwart et al, 2005;Willame et al, 2006). However, the available molecular data of the Pseudanabaena/Limnothrix group is scarce and consists of a limited number of environmental sequences and a few isolates.…”

Phylogenetic analysis of heterocystous cyanobacteria (Subsections IV and V) using highly iterated palindromes as molecular markers

“…In the present study that focused on 12 heterocystous cyanobacterial genera and 41 cyanobacterial strains in total, the HIP primers and their resolution were found to be sufficient for estimating the phylogenetic relationships amongst heterocystous cyanobacteria. The dendrograms constructed using HIP fingerprints (HIP-AT, HIP-CA, HIP-GC, and HIP-TG) showed that the genus Nostoc was most genetically heterogeneous and advanced amongst all the 12 genera (Rajaniemi et al 2005;Svenning et al 2005;Willame et al 2006). One of the interesting features was the differential alignment of the strains Nostoc sp.…”