An Evaluation of Four Phylogenetic Markers in <Emphasis Type="Italic">Nostoc</Emphasis>: Implications for Cyanobacterial Phylogenetic Studies at the Intrageneric Level

The success of some phylogenetic markers in cyanobacteria owes to the design of cyanobacteria-specific primers, but a few studies have directly investigated the evolution “behavior” of the loci. In this study, we performed a case study in Nostoc to evaluate rpoC1, hetR, rbcLX, and 16S rRNA–tRNA^Ile–tRNA^Ala-23S rRNA internal transcribed spacer (ITS) as phylogenetic markers. The results indicated that the gene trees of these loci are not congruent with the phylogeny based on 16S rRNA gene. The mechanisms contributing to the incongruence include randomized variation and recombination. As the results suggested, one should be careful to choose the molecular markers for phylogenetic reconstruction at the intrageneric level in cyanobacteria.     

cpcBA-IGS as an effective marker to characterize Microcystis wesenbergii (Komárek) Komárek in Kondrateva (cyanobacteria)

Microcystis wesenbergii (Komárek) Komárek in Kondrateva, a major bloom forming cyanobacterial species, possesses unique colonial characteristics which can be easily distinguished from other Microcystis species. However, there is still no genetic marker to effectively characterize M. wesenbergii. In this research, thirteen strains of M. wesenbergii, collected from eight locations in Chinese water bodies were examined for molecular characterization of both cpcBA-IGS sequences (phycocyanin intergenic spacer and flanking regions) and ITS sequences (internal transcribed spacer region between 16S and 23S rDNA). The phylogenetic analysis based on cpcBA-IGS sequences showed that the M. wesenbergii strains formed a distinct cluster with high support values, indicating the cpcBA-IGS region could be used to characterize and distinguish M. wesenbergii from other species of Microcystis. These developed primers were verified to be effective in distinguishing M. wesenbergii from other species of Microcystis and from other species in different genera of cyanobacteria.     

Association of Elm Yellows Subgroup 16SrV‐B Phytoplasma with a Disease of Hovenia dulcis

Japanese raisin (Hovenia dulcis) trees with typical phytoplasma‐like symptoms were observed for the first time in South Korea. The disease, named Japanese raisin witches’ broom, is progressively destructive. The cause of the graft‐transmissible disease was confirmed by electron microscopy and molecular studies. The 16S rDNA sequence analysis showed that the phytoplasma was closely related to the elm yellows (EY) group, ribosomal subgroup 16SrV‐B. The 16S‐23S rDNA intergenic spacer region, fragment of rp operon and secY gene sequences had 96–99% similarity with members of EY phytoplasma. Based on the sequence analyses and phylogenetic studies, it was confirmed that the phytoplasma infecting Japanese raisin trees in Korea belongs to the EY group.     

POLYPHASIC STUDY OF ANTARCTIC CYANOBACTERIAL STRAINS1

We isolated 59 strains of cyanobacteria from the benthic microbial mats of 23 Antarctic lakes, from five locations in two regions, in order to characterize their morphological and genotypic diversity. On the basis of their morphology, the cyanobacteria were assigned to 12 species that included four Antarctic endemic taxa. Sequences of the ribosomal RNA gene were determined for 56 strains. In general, the strains closely related at the 16S rRNA gene level belonged to the same morphospecies. Nevertheless, divergences were observed concerning the diversity in terms of species richness, novelty, and geographical distribution. For the 56 strains, 21 operational taxonomic units (OTUs, defined as groups of partial 16S rRNA gene sequences with more than 97.5% similarity) were found, including nine novel and three exclusively Antarctic OTUs. Sequences of Petalonema cf. involvens and Chondrocystis sp. were determined for the first time. The internally transcribed spacer (ITS) between the 16S and the 23S rRNA genes was sequenced for 33 strains, and similar groupings were observed with the 16S rRNA gene and the ITS, even when the strains were derived from different lakes and regions. In addition, 48 strains were screened for antimicrobial and cytotoxic activities, and 17 strains were bioactive against the gram‐positive Staphylococcus aureus, or the fungi Aspergillus fumigatus and Cryptococcus neoformans. The bioactivities were not in coincidence with the phylogenetic relationships, but rather were specific to certain strains.     

Genetic diversity of <Emphasis Type="Italic">Microcystis</Emphasis> blooms (Cyanobacteria) in recently constructed reservoirs in Tigray (Northern Ethiopia) assessed by rDNA ITS

The cyanobacterium Microcystis is notorious for forming extensive and potentially toxic blooms in nutrient-rich freshwater bodies worldwide. However, little is known about the factors underlying the genetic diversity and structure of natural Microcystis populations, despite the fact that this knowledge is essential to understand the build-up of blooms. Microcystis blooms are common and occur year-round in Africa, but are underinvestigated in this continent. We studied the genetic diversity and structure of Microcystis populations in 30 man-made reservoirs in Tigray (Northern Ethiopia) using Denaturing Gradient Gel Electrophoresis of the 16S–23S rDNA internal transcribed spacer (ITS) region and assessed the importance of local environmental conditions and geographic position of the reservoirs for the observed patterns. The analyses showed that both regional and local Microcystis ITS diversity in these recently constructed reservoirs was relatively low, with several dense blooms containing only a single ITS type. Especially one non-toxic ITS type dominated a considerable fraction of Microcystis blooms, but appeared restricted in its geographic distribution. The relationship between Microcystis ITS population structure and abiotic variables (water clarity, pH) and with zooplankton (Daphnia biomass) indicates a (limited) influence of environmental conditions on Microcystis population structure in the reservoirs of Tigray.     

Low Intraspecific Diversity in a Polynucleobacter Subcluster Population Numerically Dominating Bacterioplankton of a Freshwater Pond

Cultivation-dependent and -independent methods were combined to investigate the microdiversity of a Polynucleobacter subcluster population (Betaproteobacteria) numerically dominating the bacterioplankton of a small, humic freshwater pond. Complete coverage of the population by cultivation allowed the analysis of microdiversity beyond the phylogenetic resolution of ribosomal markers. Fluorescent in situ hybridization with two probes specific for the narrow subcluster C (PnecC bacteria) of the Polynucleobacter cluster revealed that this population contributed up to 60% to the total number of bacterioplankton cells. Microdiversity was investigated for a date at which the highest relative numbers of PnecC were observed. A clone library of fragments of the ribosomal operon (16S rRNA genes, complete 16S-23S internal transcribed spacer 1 [ITS1], partial 23S rRNA genes) amplified with universal bacterial primers was constructed. The library was stepwise screened for fragments from PnecC bacteria and for different ITS genotypes of PnecC bacteria. The isolated PnecC strains were characterized by sequencing of the 16S rRNA genes and the ITS1. Both the clone library and the established culture collection contained only the same three ITS genotypes, and one of them contributed 46% to the entire number of clones. Genomic fingerprinting of the isolates with several methods always resulted in the detection of only one fingerprint per ITS genotype. We conclude that a Polynucleobacter population with an extremely low intraspecific diversity and an uneven structure numerically dominated the bacterioplankton community in the investigated habitat. This low intraspecific diversity is in strong contrast to the high intraspecific diversities found in marine bacterial populations.     

GEITLERINEMA SPECIES (OSCILLATORIALES,CYANOBACTERIA) REVEALED BY CELLULAR MORPHOLOGY,ULTRASTRUCTURE, AND DNA SEQUENCING1

Geitlerinema amphibium (C. Agardh ex Gomont) Anagn. and G. unigranulatum (Rama N. Singh) Komárek et M. T. P. Azevedo are morphologically close species with characteristics frequently overlapping. Ten strains of Geitlerinema (six of G. amphibium and four of G. unigranulatum) were analyzed by DNA sequencing and transmission electronic and optical microscopy. Among the investigated strains, the two species were not separated with respect to cellular dimensions, and cellular width was the most varying characteristic. The number and localization of granules, as well as other ultrastructural characteristics, did not provide a means to discriminate between the two species. The two species were not separated either by geography or environment. These results were further corroborated by the analysis of the cpcB‐cpcA intergenic spacer (PC‐IGS) sequences. Given the fact that morphology is very uniform, plus the coexistence of these populations in the same habitat, it would be nearly impossible to distinguish between them in nature. On the other hand, two of the analyzed strains were distinct from all others based on the PC‐IGS sequences, in spite of their morphological similarity. PC‐IGS sequences indicate that these two strains could be a different species of Geitlerinema. Using morphology, cell ultrastructure, and PC‐IGS sequences, it is not possible to distinguish G. amphibium and G. unigranulatum. Therefore, they should be treated as one species, G. unigranulatum as a synonym of G. amphibium.     

Genetic Diversity and Structure of the Invasive Toxic Cyanobacterium <Emphasis Type="Italic">Cylindrospermopsis raciborskii</Emphasis>

Strains of the invasive toxic cyanobacteria Cylindrospermopsis raciborskii were genetically evaluated with four genetic markers encompassing in total 2.9 kb (16S rRNA, ITS longer spacer, ITS shorter spacer and rpoC1) to assess the phylogenetic relationships, genetic variation and population differentiation of the species across all five continents. The phylogenetic analysis showed that the C. raciborskii strains grouped into three well-supported distinct clusters: (I) European (II) African/American, and (III) Asian/Australian. The European group presented a high genetic similarity with the Asian and the Australian isolates than with the African and American isolates. Several Portuguese isolates were analyzed (n = 7) and revealed a low genetic differentiation with little geographical structure. The genetic distance among groups and phylogenetic relationships obtained in this study suggest that the recent invasion of C. raciborskii in Portuguese and other European temperate environments could have had its origin in the Asian and/or Australian continents.     

Genotypic and phenotypic diversity of cyanobacteria assigned to the genus <Emphasis Type="Italic">Phormidium</Emphasis> (Oscillatoriales) from different habitats and geographical sites

In this study, 30 strains of filamentous, non-heterocystous cyanobacteria from different habitats and different geographical regions assigned to diverse oscillatorian genera but here collectively referred to as members of the Phormidium group have been characterized using a polyphasic approach by comparing phenotypic and molecular characteristics. The phenotypic analysis dealt with cell and filament morphology, ultrastructure, phycoerythrin content, and complementary chromatic adaptation. The molecular phylogenetic analyses were based on sequences of the 16S rRNA gene and the adjacent intergenic transcribed spacer (ITS). The sequences were located on multiple branches of the inferred cyanobacterial 16S rRNA tree. For some, but not all, strains with identical 16S rDNA sequences, a higher level of discrimination was achieved by analyses of the less conserved ITS sequences. As shown for other cyanobacteria, no correlation was found between position of the strains in the phylogenetic tree and their geographic origin. Genetically similar strains originated from distant sites while other strains isolated from the same sampling site were in different phylogenetic clusters. Also the presence of phycoerythrin was not correlated with the strains’ position in the phylogenetic trees. In contrast, there was some correlation among inferred phylogenetic relationship, original environmental habitat, and morphology. Closely related strains came from similar ecosystems and shared the same morphological and ultrastructural features. Nevertheless, structural properties are insufficient in themselves for identification at the genus or species level since some phylogenetically distant members also showed similar morphological traits. Our results reconfirm that the Phormidium group is not phylogenetically coherent and requires revision.     

Ribosomal DNA variation within and among individuals ofLisianthius (Gentianaceae) populations

Restriction endonuclease fragment analysis of nuclear ribosomal DNA (rDNA) was completed on 25 individuals each from seven populations of theLisianthius skinneri (Gentianaceae) species complex in Panama. Seven restriction enzymes were used to determine the amount and type of rDNA variation within and among individuals of the populations. No restriction site variation was seen within populations or individuals although site differences were seen among populations. Spacer length variation within and among individuals of populations was mapped to the internal transcribed spacer (ITS) region between the 18S and 5.8S rRNA genes, a region inLisianthius rDNA that previously was shown to exhibit length differences among populations. This is the first reported case of such variation within and among individuals of populations for the ITS region. Presence or absence of ITS spacer length variation is not correlated with levels of isozymic heterozygosity within populations. No detectable length variation within individuals or populations was seen in the larger intergenic spacer (IGS). Although populations varied with respect to IGS length, all individuals of a given population had a single and equivalent IGS length.     

Systematics of the subfamily Haplorchiinae (Trematoda: Heterphyidae), based on nuclear ribosomal DNA genes and ITS2 region

Phylogenetic relationships of 6 species in the trematode subfamily Haplorchiinae were analyzed using small and large subunit of ribosomal DNA genes (18S rDNA and 28S rDNA) and internal transcribed spacer subunit II (ITS2) region as molecular markers. Maximum Likelihood and Bayesian inference analyses of combined rDNAs and ITS2 indicated a close relationship between the genera Haplorchis and Procerovum, while these two genera were distinct from Stellantchasmus falcatus. These phylogenetic relationships were consistent with the number of testes but not with the characters of the modification of the seminal vesicle or of the ventral sucker. Although three Haplorchis spp. were, together with Procerovum, in the same cluster, their mutual topology was incongruent between rDNA and ITS2 trees. Phylogenetic analyses using other molecular markers with more species are necessary to work out solid phylogenetic relationships among the species in this subfamily.     

Phylogenetic analysis of Piscirickettsia salmonis by 16S, internal transcribed spacer (ITS) and 23S ribosomal DNA sequencing

Piscirickettsia salmonis, the etiologic agent of piscirickettsiosis, is a systemic disease of salmonid fish. Variations in virulence and mortality have been observed during epizootics at different geographical regions and in laboratory experiments with isolates from these different locations. This raises the possibility that biogeographical patterns of genetic variation might be a significant factor with this disease. To assess the genetic variability the 16S ribosomal DNA, the internal transcribed spacer (ITS) and the 23S ribosomal DNA of isolates from 3 different hosts and 3 geographic origins were amplified using the polymerase chain reaction (PCR). Results of this analysis confirm that P. salmonis is a member of the gamma subgroup of the Proteobacteria and show that the isolates form a tight monophyletic cluster with 16S rDNA similarities ranging from 99.7 to 98.5%. The ITS regions were 309 base pairs (bp), did not contain tRNA genes, and varied between isolates (95.2 to 99.7% similarity). Two-thirds of the 23S rRNA gene was sequenced from 5 of the isolates, yielding similarities ranging from 97.9 to 99.8%. Phylogenetic trees were constructed based on the 16S rDNA, ITS and 23S rDNA sequence data and compared. The trees were topologically similar, suggesting that the 3 types of molecules provided similar phylogenetic information. Five of the isolates are closely related (> 99.4% 16S rDNA similarity, 99.1% to 99.7% ITS and 99.3 to 99.8% 23S rDNA similarities). The sequence of one Chilean isolate, EM-90, was unique, with 16S rDNA similarities to the other isolates ranging from 98.5 to 98.9%, the ITS from 95.2 to 96.9% and the 23S rDNA from 97.6 to 98.5%.     

Reptodigitus Chapmanii (Nostocales,Hapalosiphonaceae) Gen. Nov.: A Unique Nostocalean (Cyanobacteria) Genus Based on a Polyphasic Approach1

The Nostocales is a monophyletic, heterocytous lineage of cyanobacteria capable of akinete production and division in multiple planes, depending upon family-level clade. While present in a variety of ecosystems, the diversity of the Nostocales has been poorly elucidated. Due to environmentally -induced phenotypic plasticity, morphology alone is often insufficient to determine the true phylogenetic placement of these taxa. In order to bridge this gap, taxonomists now employ the polyphasic approach, combining methods such as morphological analysis, phylogenetic analysis based on DNA sequence and genetic identity based on ribosomal genes, and secondary structure of the 16S-23S ITS and 16S rRNA gene sequences, as well as ecological characterization. Using this combined approach, a new genus and species (Reptodigitus chapmanii gen. et sp. nov.) isolated from the St. Johns River (Jacksonville, Florida, USA) within the Nostocales is herein described. Phylogenetic analyses place this taxon within the Hapalosiphonaceae, sister to the clade containing Fischerella, Hapalosiphon, and Westiellopsis. The 16S-23S ITS secondary folding structure analysis also supports the erection of this new genus.     

Phylogeny and species delineation in the marine diatom Pseudo‐nitzschia (Bacillariophyta) using cox1, LSU,and ITS2 rRNA genes: A perspective in character evolution

Analyses of the mitochondrial cox1, the nuclear‐encoded large subunit (LSU), and the internal transcribed spacer 2 (ITS2) RNA coding region of Pseudo‐nitzschia revealed that the P. pseudodelicatissima complex can be phylogenetically grouped into three distinct clades (Groups I–III), while the P. delicatissima complex forms another distinct clade (Group IV) in both the LSU and ITS2 phylogenetic trees. It was elucidated that comprehensive taxon sampling (sampling of sequences), selection of appropriate target genes and outgroup, and alignment strategies influenced the phylogenetic accuracy. Based on the genetic divergence, ITS2 resulted in the most resolved trees, followed by cox1 and LSU. The morphological characters available for Pseudo‐nitzschia, although limited in number, were overall in agreement with the phylogenies when mapped onto the ITS2 tree. Information on the presence/absence of a central nodule, number of rows of poroids in each stria, and of sectors dividing the poroids mapped onto the ITS2 tree revealed the evolution of the recently diverged species. The morphologically based species complexes showed evolutionary relevance in agreement with molecular phylogeny inferred from ITS2 sequence–structure data. The data set of the hypervariable region of ITS2 improved the phylogenetic inference compared to the cox1 and LSU data sets. The taxonomic status of P. cuspidata and P. pseudodelicatissima requires further elucidation.     

First Report of Aster Yellows Phytoplasma (16SrI‐B) Associated with Witches' Broom Disease of Melia azedarach var. japonica in Korea

Melia azedarach var. japonica trees with leaf yellowing, small leaves and witches' broom were observed for the first time in Korea. A phytoplasma from the symptomatic leaves was identified based on the 16Sr DNA sequence as a member of aster yellows group, ribosomal subgroup 16SrI‐B. Sequence analyses of more variable regions such as 16S–23S intergenic spacer region, secY gene, ribosomal protein (rp) operon and tuf gene showed 99.5?100% nucleotide identity to several GenBank sequences of group 16SrI phytoplasmas. Phylogenetic analysis confirmed that the Melia azedarach witches' broom phytoplasma belongs to aster yellows group.     

Growing coffee: Psilanthus (Rubiaceae) subsumed on the basis of molecular and morphological data; implications for the size,morphology, distribution and evolutionary history of Coffea

Morphological and molecular phylogenetic studies show that there is a close relationship between Coffea and Psilanthus. In this study we reassess species relationships based on improved species sampling for Psilanthus, including P. melanocarpus, a species that shares morpho‐taxonomic characters of both genera. Analyses are performed using parsimony and Bayesian inference, on sequence data from four plastid regions [trnL–F intron, trnL–F IGS, rpl16 intron and accD–psa1 intergenic spacer (IGS)] and the internal transcribed spacer (ITS) region of nuclear ribosomal DNA (ITS 1/5.8S/ITS 2). Several major lineages with geographical coherence, as identified in previous studies based on smaller and larger data sets, are supported. Our results also confirm previous studies showing that the level of sequence divergence between Coffea and Psilanthus species is negligible, particularly given the much longer branch lengths separating other genera of tribe Coffeeae. There are strong indications that neither Psilanthus nor Coffea is monophyletic. Psilanthus melanocarpus is nested with the Coffea–Psilanthus clade, which means that there is only one critical difference between Coffea and Psilanthus; the former has a long‐emergent style and the latter a short, included style. Based on these new data, in addition to other systematically informative evidence from a broad range of studies, and especially morphology, Psilanthus is subsumed into Coffea. This decision increases the number of species in Coffea from 104 to 124, extends the distribution to tropical Asia and Australasia and broadens the morphological characterization of the genus. The implications for understanding the evolutionary history of Coffea are discussed. A group of closely related species is informally named the ‘Coffea liberica alliance’. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 357–377.     

Comparative phylogeography of Amphicarpaea legumes and their root-nodule symbionts in Japan and North America

Aim Relationships of eastern Asian and eastern North American populations of legumes in the genus Amphicarpaea Elliot ex. Nuttall (Phaseoleae–Glycininae) and their root nodule bacteria (Bradyrhizobium Jordan) were analysed to test whether both organisms share an identical biogeographic history. Location Japan and eastern North America (New York and Illinois). Methods Sequences of three plant genes (chloroplast trnL region, nuclear ribosomal ITS, and histone H3‐D) and a segment of the bacterial ribosomal region (partial 16S rRNA and 23S rRNA genes, and the 16S rRNA–23S rRNA ITS) were used to analyse phylogenetic relationships. Results For plants, Japanese populations formed a sister group to a well‐supported clade of all North American genotypes. For nodule bacteria associated with Amphicarpaea, isolates from North America did not form a single clade relative to Asian genotypes. Japanese Bradyrhizobium isolates were closely related to particular sub‐groups of North American bacteria (lineages ‘B’ and ‘C’), with other American bacteria branching earlier. Main conclusions Plants and bacteria showed clear deviations from a pattern of parallel cladogenesis. The most basal Amphicarpaea lineage was associated with a recently‐diverged bacterial group, while one recently‐diverged plant lineage had symbionts that branched in a basal position relative to the other Amphicarpaea bacteria. When analysed with data on symbiotic compatibility from inoculation experiments, the molecular phylogenies suggested that for plants, at least one transition has occurred toward more promiscuous nodulation behaviour. Among bacteria, strains with narrow host range on Amphicarpaea appear to be ancestral to symbiotic generalists.     

Application of ancient DNA to the reconstruction of past microbial assemblages and for the detection of toxic cyanobacteria in subtropical freshwater ecosystems

Ancient DNA (aDNA) analysis of lake sediments is a promising tool for detecting shifts in past microbial assemblages in response to changing environmental conditions. We examined sediment core samples from subtropical, freshwater Laguna Blanca (Uruguay), which has been severely affected by cultural eutrophication since 1960 and where cyanobacterial blooms, particularly those of the saxitoxin‐producer Cylindrospermopsis raciborskii, have been reported since the 1990s. Samples corresponding to ~1846, 1852, 2000 and 2007 AD were selected to perform denaturing gradient gel electrophoresis (DGGE) analysis of the 16S–23S rRNA intergenic transcribed spacer (ribosomal ITS) to compare their prokaryotic assemblage composition. Each stratum showed different ITS patterns, but the composition of 21st century samples was clearly different than those of mid‐19th century. This compositional change was correlated with shifts in sediment organic matter and chlorophyll a content, which were significantly higher in recent samples. The presence of saxitoxin‐producing cyanobacteria was addressed by quantitative real‐time PCR of the sxtU gene involved in toxin biosynthesis. This gene was present only in recent samples, for which clone libraries and ITS sequencing indicated the presence of Cyanobacteria. Phylogenetic analyses identified C. raciborskii only in the 2000 sample, shortly after several years when blooms were recorded in the lake. These data suggest the utility of aDNA for the reconstruction of microbial assemblage shifts in subtropical lakes, at least on centennial scales. The application of aDNA analysis to genes involved in cyanotoxin synthesis extends the applicability of molecular techniques in palaeolimnological studies to include key microbial community characteristics of great scientific and social interest.     

PHYLOGENY AND GENETIC VARIANCE IN TERRESTRIAL MICROCOLEUS (CYANOPHYCEAE) SPECIES BASED ON SEQUENCE ANALYSIS OF THE 16S rRNA GENE AND ASSOCIATED 16S–23S ITS REGION1

Thirty‐one strains of Microcoleus were isolated from desert soils in the United States. Although all these taxa fit the broad definition of Microcoleus vaginatus (Vaucher) Gomont in common usage by soil algal researchers, sequence data for the 16S rRNA gene and 16S–23S internal transcribed spacer (ITS) region indicated that more than one species was represented. Combined sequence and morphological data revealed the presence of two morphologically similar taxa, M. vaginatus and Microcoleus steenstrupii Boye‐Petersen. The rRNA operons of these taxa were sufficiently dissimilar that we suspect the two taxa belong in separate genera. The M. vaginatus clade was most similar to published sequences from Trichodesmium and Arthrospira. When 16S sequences from the isolates we identified as M. steenstrupii were compared with published sequences, our strains grouped with M. chthonoplastes (Mertens) Zanardini ex Gomont and may have closest relatives among several genera in the Phormidiaceae. Organization within the 16S–23S ITS regions was variable between the two taxa. Microcoleus vaginatus had either two tRNA genes (tRNA^Ile and tRNA^Ala) or a fragment of the tRNA^Ile gene in its ITS regions, whereas M. steenstrupii had rRNA operons with either the tRNA^Ile gene or no tRNA genes in its ITS regions. Microcoleus vaginatus showed no subspecific variation within the combined morphological and molecular characterizations, with 16S similarities ranging from 97.1% to 99.9%. Microcoleus steenstrupii showed considerable genetic variability, with 16S similarities ranging from 91.5% to 99.4%. In phylogenetic analyses, we found that this variability was not congruent with geography, and we suspect that our M. steenstrupii strains represent several cryptic species.     

Determination of Cyanobacterial Diversity during Algal Blooms in Daechung Reservoir, Korea, on the Basis of cpcBA Intergenic Spacer Region Analysis

The detection and prevention of cyanobacterial blooms are important issues in water quality management. As such, the diversity and community dynamics of cyanobacteria during cyanobacterial bloom in the Daechung Reservoir, Korea, were studied by analyzing the intergenic spacer (IGS) region between phycocyanin subunit genes cpcB and cpcA (cpcBA IGS). To amplify the cpcBA IGS from environmental samples, new PCR primers that could cover a wider range of cyanobacteria than previously known primers were designed. In the samples taken around the bloom peak (2 September 2003), seven groups of cpcBA IGS sequences were detected, and none of the amplified cpcBA IGSs was closely related to the cpcBA IGS from chloroplasts. Apart from the Microcystis-, Aphanizomenon (Anabaena)-, Pseudanabaena-, and Planktothrix (Oscillatoria)-like groups, the three other groups of cpcBA IGS sequences were only distantly related to previously reported sequences (<85% similarity to their closest relatives). The most prominent changes during the bloom were the gradual decrease and eventual disappearance of the Aphanizomenon (Anabaena)-like group before the bloom peak and the gradual increase and sudden disappearance of Planktothrix (Oscillatoria)-like groups right after the bloom peak. The community succession profile obtained based on the cpcBA IGS analysis was also supported by a PCR-denaturing gradient gel electrophoresis analysis of the 16S rRNA genes.