Symphyonema bifilamentata sp. nov., the Right Fischerella ambigua 108b: Half a Decade of Research on Taxonomy and Bioactive Compounds in New Light

Since 1965 a cyanobacterial strain termed ‘Fischerella ambigua 108b’ was the object of several studies investigating its potential as a resource for new bioactive compounds in several European institutes. Over decades these investigations uncovered several unique small molecules and their respective biosynthetic pathways, including the polychlorinated triphenyls of the ambigol family and the tjipanazoles. However, the true taxonomic character of the producing strain remained concealed until now. Applying a polyphasic approach considering the phylogenetic position based on the 16S rRNA and the protein coding gene rbcLX, secondary structures and morphological features, we present the strain ‘Fischerella ambigua 108b’ as Symphyonema bifilamentata sp. nov. 97.28. Although there is the type species (holotype) S. sinense C.-C. Jao 1944 there is no authentic living strain or material for genetic analyses for the genus Symphyonema available. Thus we suggest and provide an epitypification of S. bifilamentata sp. nov. 97.28 as a valid reference for the genus Symphyonema. Its affiliation to the family Symphyonemataceae sheds not only new light on this rare taxon but also on the classes of bioactive metabolites of these heterocytous and true-branching cyanobacteria which we report here. We show conclusively that the literature on the isolation of bioactive products from this organism provides further support for a clear distinction between the secondary metabolism of Symphyonema bifilamentata sp. nov. 97.28 compared to related and other taxa, pointing to the assignment of this organism into a separate genus.

True branching and phenotypic plasticity in the planktonic cyanobacterium Dolichospermum brachiatum sp. nov. (Nostocales, Aphanizomenonaceae), from south-eastern Australia

Phenotypic plasticity in the cyanobacteria provides adaptive strategies to cope with changes in prevailing environmental conditions. Plasticity may manifest in morphological, physiological, or behavioural responses. Determining if variable phenotypes are truly novel expressions evolved via adaptive genetic change, rather than intrinsic characteristics within the spectrum of intraspecific diversity has rarely been studied. Poorly characterised or unrecognised intraspecific variability is as problematic as cryptic diversity in terms of imposing limitations on the use of morphology-based identifications to recognise algal diversity. We isolated strains from a population of filamentous cyanobacteria from the plankton of a temperate lake in Western Victoria, Australia putatively identified as the cylindrospermopsin producer Chrysosporum ovalisporum which displayed aberrant vegetative and apical cells and akinete morphology, and T-type true branching. In culture, strains grown in phosphorus-free media showed morphology and true branching consistent with the wild types suggesting that these features are a phenotypic response to P-limitation. Results of the phylogenetic analyses of these strains using the 16S-23S rRNA, and the secondary structure of the ITS region of the 16S-23S rRNA operon confirmed that the isolated strains were a novel species, here designated Dolichospermum brachiatum. This is the first record of true branching in the genus Dolichospermum and only the second observation from the Aphanizomenonaceae. These findings support our current understanding that true branching in cyanobacteria is a polyphyletic trait, having arisen several times in the evolution of this Phylum.

Morphology, distribution and ecology of the freshwater red algae Paralemanea (Batrachospermaceae, Batrachospermales, Rhodophyta) in Serbia

This paper describes the morphology, distribution and ecology of 15 populations of Paralemanea collected from 2004 to 2011 in 12 rivers in Serbia. On the basis of morphological and reproductive characteristics, two species were identified: P. annulata (12 populations) and P. catenata (3 populations). Morphological (presence of a stalk, thalli length, nodal diameter (ND), internodal diameter (ID), node and internode diameter ratio (ND:ID) and reproductive (arrangement of spermatangial sori, length and diameter of carpospores, presence of Chantransia stage) features described in the literature are generally confirmed in the populations from Serbia. True branching was observed in six populations of P. annulata in the gametophyte stage. False branching (whorled branching) occurred in five populations of both species observed. In the Pcinja (P2), Ibar (IB5) and Crnovrska rivers (CR10), the number of whorled branching was 6-11 (P. annulata). For P. catenata the number of such branching was 3-5 in the Nisava River (N8) and Sokobanjska Moravica River (SM12). False branching appears at damaged thalli, somewhat repairing it. Algae belonging to the Paralemanea genus were found at altitudes from 160 to 780 m (P. annulata), and from 240 to 400 m (P. catenata), at water temperatures ranging from 11.5 to 29?C (P. annulata) and from 12.6 to 17.4?C (P. catenata), in neutral and weakly alkaline waters, with a high level of oxygen concentration, with conductivity ranging from 70 to 433 ?S/cm for P. annulata, and 260 to 440 ?S /cm for P. catenata. It was also observed that P. annulata and P. catenata often grow in oligotrophic conditions and rarely in eutrophic conditions.

Aetokthonos hydrillicola gen. et sp. nov.: Epiphytic cyanobacteria on invasive aquatic plants implicated in Avian Vacuolar Myelinopathy

Research into the taxonomy of a novel cyanobacterial epiphyte in locations where birds, most notably Bald eagle and American coots, are dying from a neurologic disease (Avian Vacuolar Myelinopathy—AVM) has been ongoing since 2001. Field investigations revealed that all sites where birds were dying had extensive invasive aquatic vegetation with dense colonies of an unknown cyanobacterial species growing on the underside of leaves. Morphological evaluation indicated that this was a true-branching, heterocystous taxon falling within the former order Stigonematales. However, 16S rRNA gene sequence demonstrated that it did not match closely with any described genus or species. More recent sequence analysis of the 16S rRNA gene and associated ITS region from additional true branching species resulted in a unique phylogenetic placement distant from the other clades of true-branching cyanobacteria. Light, epifluorescent, and transmission and scanning electron micrographs confirm the novel characteristics of this species, which is true-branching form with uniseriate basal filaments. It is encased within a firm sheath and has heterocytes both within the filaments and at the tips of the branches. The species is in a new genus of uncertain family assignment, and is herein named Aetokthonos hydrillicola gen. et sp. nov.

Cyanocohniella calida gen. et sp. nov. (Cyanobacteria: Aphanizomenonaceae) a new cyanobacterium from the thermal springs from Karlovy Vary, Czech Republic

The thermal springs of Karlovy Vary (Carlsbad) is the locus classicus of the well-known thermal cyanobacterium Mastigocladus laminosus. In addition to the nominate variety, several other varieties and forms were described based on differences in morphology (true-branching versus non-branching) or ecology (thermal versus non-thermal). The cyanobacterial strain Kaštovský 1996/2, which was provisionally identified as M. laminosus f. nostocoides, was also isolated from this locality and discussed in previous work. Based on both morphological and molecular (SSU) analyses, this strain was found to not belong to Mastigocladus, but rather to an undescribed genus, presumably within the Nostocaceae. This strain was subsequently lost, and absence of type materials prevented the description of the genus. The species was successfully re-isolated in 2012. The new strain is identical in morphology, life cycle, and 16S rRNA sequence to the lost strain 1996/2. It is herein described as Cyanocohniella calida gen. et sp. nov. The genus differs from all other Nostocaceae and Aphanizomenonaceae by the unique combination of these characteristics: 1) thermal-tolerant ecology, 2) life cycle that includes Pseudanabaenaceae-like, Nostoc-like and Chlorogloeopsis-like stages, 3) absence of aerotopes, and 4) phylogenetic placement in the Aphanizomenonaceae. The sister taxa, based on 16S rRNA gene sequence phylogenetic analysis, are Cyanospira and Anabaenopsis, both spiral, planktonic, aerotope-bearing, tropical genera and species clearly distinct from C. calida.

Molecular phylogeny of the heterocystous cyanobacteria (subsections IV and V) based on nifD

The heterocystous cyanobacteria are currently placed in subsections IV and V, which are distinguished by cellular division in one plane (false branching) and in more than one plane (true branching), respectively. Published phylogenies of 16S rRNA gene sequence data support the monophyly of the heterocystous cyanobacteria, with members of subsection V embedded within subsection IV. It has been postulated that members of subsection V arose from within subsection IV. Therefore, phylogenetic analysis of nucleotide sequences of the nitrogen-fixation gene nifD from representatives of subsections IV and V was performed by using maximum-likelihood criteria. The heterocystous cyanobacteria are supported as being monophyletic, with the non-heterocystous cyanobacteria as their closest relative. However, neither subsection IV nor subsection V is monophyletic, with representatives of both subsections intermixed in two sister clades. Analysis of nifD does not support recognition of two distinct subsections.

Polyphyly of true branching cyanobacteria (Stigonematales)

Cyanobacteria with true branching are classified in Subsection V (formerly order Stigonematales) in the phylum Cyanobacteria. They exhibit a high degree of morphological complexity and are known from particular biotopes. Only a few stigonematalean morphotypes have been cultured, and therefore the high variability of morphotypes found in nature is under-represented in culture. Axenic cultures of Chlorogloeopsis and Fischerella sensu Rippka et al. were, to date, the only representatives of this Subsection in phylogenetic studies. The 16S rDNA sequence analysis data in this report confirm that heterocyst-forming cyanobacteria are a monophyletic group. However, unlike previous studies have suggested, these 16S rDNA data on new Stigonematales strains show that the true branching cyanobacteria are polyphyletic and can be separated into at least two major groups defined by their branching type, the first group being characterized by T-branching and the second group by Y-branching. Cyanobacteria with intercalary heterocysts and either no branching or false-branching also formed separate clusters. In consequence, our phylogenetic data do not correlate with the bacteriological and traditional classifications, which distinguish filamentous heterocystous cyanobacteria with or without true branching (Nostocales/Stigonematales).