Morphological, Ecological and Molecular Studies of Vannella simplex Wohlfarth-Bottermann 1960 (Lobosea, Gymnamoebia), with a new Diagnosis of this Species

Vannella simplex (Gymnamoebia, Vannellidae) is one of the most common amoebae species, recorded from a variety of regions. It was originally described as a freshwater species, but has also been reported from shallow-water regions of the Baltic Sea. In the present work, we investigated the morphology and biology of three V. simplex isolates, originating from geographically distant regions. Among them is one brackish water strain, isolated from artificial cyanobacterial mats, which were originally sampled in Nivå Bay (Baltic Sea, The Sound). The strain is cyst-forming and can thrive at salinity ranges from 0–50 ppt. Phylogenetic relationships were investigated by sequencing partial SSU rDNA of the cultured V. simplex isolates. Additional sequences were obtained from four environmental DNA extractions of sediment samples collected from different localities in Switzerland. Analysis of all obtained sequences revealed a monophyletic group. Based on the analysis and comparison of morphological, ecological and molecular data sets we compiled a distribution map of V. simplex and propose an emendation of this species.     

山西省苹果树腐烂病菌的种群结构分析

为明确山西省苹果树腐烂病菌的分布与组成,本研究采集并分离得到来自山西省8个苹果树种植区有代表性的78株腐烂病菌,通过形态特征观察及利用2个DNA片段（ITS和EF1α）构建系统发育树等方法对其遗传结构进行了研究。结果表明山西省苹果树腐烂病由苹果黑腐皮壳菌Valsa mali和梨黑腐皮壳菌Valsa pyri 2个致病种所致,其中V. pyri是优势种,分布于山西省各个苹果树种植区,占菌株总数的58.97%。以山西省8个苹果树种植区腐烂病菌各个种的相对频率进行聚类分析,欧式距离9作为聚类分割点将其种群结构分为3类。第Ⅰ类包括忻州、朔州2个苹果树种植区,V. pyri为该类型苹果树种植区的致病菌、相对频率为100%。第Ⅱ类包括晋城、长治、临汾、太原、运城5个苹果树种植区,V. pyri是这5个种植区的优势种。第Ⅲ类包含晋中1个苹果树种植区,V. mali是该种植区的优势种。     

Viruses of microorganisms in the Baltic Sea: current state of research and perspectives

This paper reviews the current state of research into viruses of microorganisms in the Baltic Sea. Field and experimental studies reveal the great phenotypic and genotypic variety of the Baltic Sea viruses and highlights the importance of phages in the Baltic Sea food-web dynamics. In total, 93 virus isolates from the Baltic Sea have been described, the genome sequence being available for 39 of these. However, these isolates were derived from only eight host species and, therefore, underrepresent the overall viral diversity in the Baltic Sea. The most studied group of viruses is bacteriophages that infect Bacteroidetes, whereas, by contrast, phages of Cyanobacteria, Proteobacteria and Actinobacteria, as well as algal viruses, have been investigated to a lesser extent. No reports on viruses infecting Baltic Sea fungi and archaea isolates have been reported to date. This paper also identifies gaps in our knowledge of the aquatic virology of the Baltic Sea and emphasizes the need for more comprehensive analysis of those viruses that occur in one of the world's largest brackish water ecosystems.     

Integrative taxonomy and phylogeny of leafless Vanilla orchids from the South-West Indian Ocean region reveal two new Malagasy species

The leafless Vanilla species complex from the South-West Indian Ocean (SWIO) region has long been a taxonomic challenge, due to limited patterns of morphological differentiation and an absence of variation within chloroplast sequences. This complex includes seven known morphospecies: V. madagascariensis, V. bosseri, V. decaryana, and V. perrieri endemic to Madagascar, V. humblotii presumed as endemic to the Comoros Archipelago, but also present in Madagascar, V. roscheri from the East African coast, and V. phalaenopsis endemic to Seychelles. A previous population genetic study using microsatellite markers allowed us to distinguish, in addition to the five recognized Malagasy taxa, two other genetic clusters present in the East of the island. An integrative taxonomy approach was therefore conducted by combining microsatellite and morphological data used in the previous study with new data sets, and by adding ITS sequencing data, to validate the taxonomic level of these Malagasy genetic clusters and unravel phylogenetic relationships between SWIO species. As a result, based on phylogenetic, genotypic and morphological evidence, nine species were discriminated in the SWIO region, including seven in Madagascar, with two new eastern species. The leafless Vanilla group originated and diversified in Madagascar, from an ancestor of African descent, with three subsequent independent colonization events from Madagascar to the other territories of SWIO within the two main lineages (white versus yellow flower species). The new Malagasy species, V. allorgeae Andriamihaja & Pailler sp. nov., and V. atsinananensis Andriamihaja & Pailler sp. nov., are described and a new identification key is proposed.     

Is the social parasite Vespa dybowskii using chemical transparency to get her eggs accepted?

Both avian and insect cuckoos must trick their hosts into accepting foreign eggs. In birds this is achieved through egg mimicry. Within the hornets the only known social parasite is the rare Vespa dybowskii. We investigated how the V. dybowskii queen induces tens or hundreds of host workers to accept her eggs and offspring. Since hydrocarbons function as recognition cues in social insects, we investigated these compounds from the surface of eggs and workers of V. dybowskii, both host species (V. simillima and V. crabro) and an additional four non-host species. We found that chemical mimicry of the hosts’ colony odour and their eggs normally associated with wasps was not being employed by V. dybowskii. Chemical insignificance is also unlikely as the amounts of hydrocarbons extracted from parasite, host and non-host eggs were similar. Eggs of V. dybowskii may survive in part due to being chemically transparent, as methyl-branched compounds only represent a tiny proportion (<1%) of the parasites hydrocarbon profile but a large proportion (26–41%) in both host species. However, the functions of various hydrocarbon groups need to be investigated in the hornets before this new acceptance mechanism of parasite eggs and adults is understood.     

Diversity of toxic and nontoxic nodularia isolates (cyanobacteria) and filaments from the Baltic Sea

Cyanobacteria of the genus Nodularia form toxic blooms in brackish waters worldwide. In addition, Nodularia spp. are found in benthic, periphytic, and soil habitats. The majority of the planktic isolates produce a pentapeptide hepatotoxin nodularin. We examined the morphologic, toxicologic, and molecular characters of 18 nodularin-producing and nontoxic Nodularia strains to find appropriate markers for distinguishing the toxic strains from the nontoxic ones in field samples. After classical taxonomy, the examined strains were identified as Nodularia sp., Nodularia spumigena, N. baltica, N. harveyana, and N. sphaerocarpa. Morphologic characters were ambiguous in terms of distinguishing between the toxic and the nontoxic strains. DNA sequences from the short 16S-23S rRNA internally transcribed spacer (ITS1-S) and from the phycocyanin operon intergenic spacer and its flanking regions (PC-IGS) were different for the toxic and the nontoxic strains. Phylogenetic analysis of the ITS1-S and PC-IGS sequences from strains identified as N. spumigena, and N. baltica, and N. litorea indicated that the division of the planktic Nodularia into the three species is not supported by the ITS1-S and PC-IGS sequences. However, the ITS1-S and PC-IGS sequences supported the separation of strains designated N. harveyana and N. sphaerocarpa from one another and the planktic strains. HaeIII digestion of PCR amplified PC-IGS regions of all examined 186 Nodularia filaments collected from the Baltic Sea produced a digestion pattern similar to that found in toxic isolates. Our results suggest that only one planktic Nodularia species is present in the Baltic Sea plankton and that it is nodularin producing.     

Electrophoretic studies on the Anisakis simplex complex (Ascaridida:Anisakidae) from the Mediterranean and North-East Atlantic

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and 1986. Electrophoretic studies on the Anisakis simplex complex (Ascaridida: Anisakidae) from the Mediterranean and North-East Atlantic. International Journal for Parasitology 16: 633–640. The genetic variation of the sibling species Anisakis simplex A and A. simplex B was investigated by electrophoretic analysis of 22 gene-enzyme systems. The two species are reproductively isolated and no gene flow takes place between them. Three loci, Sod, Adk-2 and Lap-1, show distinct alleles in A. simplex A and A. simplex B, allowing their reliable identification both at the larval and adult stages. A fourth locus, Got, appears to be diagnostic at the 95% level. The value of Nei's genetic distance found between A. simplex A and A. simplex B is 0.28. Parameters of genetic variability (He, P, A) are given for both species. The geographic distribution of A. simplex A and A. simplex B appears to be mainly Mediterranean for the former, and mainly North Atlantic for the latter. Several paratenic hosts (fish and squid) and one cetacean definitive host are identified for each of the two species. The names A. pegreffii and A. simplex are tentatively proposed for A. simplex A and A. simplex B respectively.     

The Mitochondrial Genome of Arctica islandica; Phylogeny and Variation

Arctica islandica is known as the longest-lived non-colonial metazoan species on earth and is therefore increasingly being investigated as a new model in aging research. As the mitochondrial genome is associated with the process of aging in many species and bivalves are known to possess a peculiar mechanism of mitochondrial genome inheritance including doubly uniparental inheritance (DUI), we aimed to assess the genomic variability of the A. islandica mitochondrial DNA (mtDNA). We sequenced the complete mitochondrial genomes of A. islandica specimens from three different sites in the Western Palaearctic (Iceland, North Sea, Baltic Sea). We found the A. islandica mtDNA to fall within the normal size range (18 kb) and exhibit similar coding capacity as other animal mtDNAs. The concatenated protein sequences of all currently known Veneroidea mtDNAs were used to robustly place A. islandica in a phylogenetic framework. Analysis of the observed single nucleotide polymorphism (SNP) patterns on further specimen revealed two prevailing haplotypes. Populations in the Baltic and the North Sea are very homogenous, whereas the Icelandic population, from which exceptionally old individuals have been collected, is the most diverse one. Homogeneity in Baltic and North Sea populations point to either stronger environmental constraints or more recent colonization of the habitat. Our analysis lays the foundation for further studies on A. islandica population structures, age research with this organism, and for phylogenetic studies. Accessions for the mitochondrial genome sequences: KC197241 Iceland; KF363951 Baltic Sea; KF363952 North Sea; KF465708 to KF465758 individual amplified regions from different speciemen     

山葡萄种质资源DNA条形码通用序列的筛选

对山葡萄(Vitis amurensis)种质资源样品的ITS、ITS2、psb A-trn H、rbc L和mat K序列进行PCR扩增及测序,优化PCR反应的退火温度,比较各序列的扩增效率、测序成功率、品种间和品种内的差异及barcoding gap图,使用BLAST和NJ树法比较不同序列的鉴定能力,最终从5条DNA片段中筛选出可用于山葡萄种质资源鉴定的DNA条形码通用序列。结果表明,在采集的11份33个山葡萄样品中,psb A-trn H和ITS2序列的扩增与测序成功率较高,其品种间、品种内差异及barcoding gap较ITS、rbc L和mat K序列具有明显的优势,且ITS2序列能够鉴别psb A-trn H序列无法鉴别的品种。实验证明,ITS2和psb A-trn H序列是较适合鉴别山葡萄资源的DNA条形码序列组合。DNA条形码弥补了形态学鉴定的不足,可为山葡萄种质资源的准确鉴定提供科学依据。     

Genetic relatedness of a new Japanese isolates of Alexandrium ostenfeldii bloom population with global isolates

In recent years, blooms of toxic Alexandrium ostenfeldii strains have been reported from around the world. In 2013, the species formed a red tide in a shallow lagoon in western Japan, which was the first report of the species in the area. To investigate the genetic relatedness of Japanese A. ostenfeldii and global isolates, the full-length SSU, ITS and LSU sequences were determined, and phylogenetic analyses were conducted for isolates from western and northern Japan and from the Baltic Sea. Genotyping and microsatellite sequence comparison were performed to estimate the divergence and connectivity between the populations from western Japan and the Baltic Sea. In all phylogenetic analyses, the isolates from western Japan grouped together with global isolates from shallow and low saline areas, such as the Baltic Sea, estuaries on the east coast of U.S.A. and from the Bohai Sea, China. In contrast, the isolates from northern Japan formed a well-supported separate group in the ITS and LSU phylogenies, indicating differentiation between the Japanese populations. This was further supported by the notable differentiation between the sequences of western and northern Japanese isolates, whereas the lowest differentiation was found between the western Japanese and Chinese isolates. Microsatellite genotyping revealed low genetic diversity in the western Japanese population, possibly explained by a recent introduction to the lagoon from where it was detected. The red tide recorded in the shallow lagoon followed notable changes in the salinity of the waterbody and phytoplankton composition, potentially facilitating the bloom of A. ostenfeldii.     

LOCAL ADAPTATION OF CERAMIUM TENUICORNE (CERAMIALES,RHODOPHYTA) WITHIN THE BALTIC SEA1

Ceramium tenuicorne (Kützing) Wærn is a red alga that is widely distributed in the brackish Baltic Sea. We studied the growth response of Ceramium to low salinity and nutrient enrichment, using isolades from two regions of the Baltic Sea where the alga approaches its inner distribution limit. Ecotypic differentiation was observed in that differences in growth response among isolates corresponded to salinity conditions in their regions of origin. Isolates from the Gulf of Bothnia (4 psu) had inherently lower growth rates that were not increased when transferred to higher salinity, but were better adapted to very low salinity levels than isolates from the Baltic Proper (7 psu). Further, the results indicate that Ceramium from different regions of the Baltic Sea vary in their responses to nutrient enrichment. The observed differences may be best described as a quantitative difference in the proportion of isolates with hyposaline adaptation. The results indicate that the wide distribution of Ceramium in the Baltic Sea is better explained by the occurrence of locally adapted genotypes than by a generalist life strategy, and provide example of adaptive differentiation in a marine edge environment.     

The sodium cycle. III. Vibrio alginolyticus resembles Vibrio cholerae and some other vibriones by flagellar motor and ribosomal 5S-RNA structures

An electron microscopic study of the basal bodies of the Vibrio albinolyticus flagellum revealed a four-disc structure. The diameters of the two discs localized closer to the cytoplasmic membrane proved to be about 2-fold shorter than those of the two others. In this respect the basal body of V. alginolyticus resembles very much that of V. cholerae described by Ferris and co-workers. The sequence of the V. alginolyticus ribosomal 5S-RNA showed that it is similar to those of V. cholerae, V. harveyi and some other vibriones. On the basis of the 5S-RNA sequences, a dendrogram of prokaryotes is presented. It confirmed the suggestion that V. alginolyticus is a typical representative of Vibrionaceae rather than a ‘monster’ greatly differing from other vibriones. Possible evolutionary relation of various bacterial species possessing the primary Na⁺ pumps is discussed.     

Culturing Heterotrophic Protists from the Baltic Sea: Mostly the “Usual Suspects” but a Few Novelties as Well

The study of cultured strains has a long tradition in protistological research and has greatly contributed to establishing the morphology, taxonomy, and ecology of many protist species. However, cultivation‐independent techniques, based on 18S rRNA gene sequences, have demonstrated that natural protistan assemblages mainly consist of hitherto uncultured protist lineages. This mismatch impedes the linkage of environmental diversity data with the biological features of cultured strains. Thus, novel taxa need to be obtained in culture to close this knowledge gap. In this study, traditional cultivation techniques were applied to samples from coastal surface waters and from deep oxygen‐depleted waters of the Baltic Sea. Based on 18S rRNA gene sequencing, 126 monoclonal cultures of heterotrophic protists were identified. The majority of the isolated strains were affiliated with already cultured and described taxa, mainly chrysophytes and bodonids. This was likely due to “culturing bias” but also to the eutrophic nature of the Baltic Sea. Nonetheless, ~ 12% of the isolates in our culture collection showed highly divergent 18S rRNA gene sequences compared to those of known organisms and thus may represent novel taxa, either at the species level or at the genus level. Moreover, we also obtained evidence that some of the isolated taxa are ecologically relevant, under certain conditions, in the Baltic Sea.     

Evaluation of an Inoculum Production and Delivery Technique for Valdensinia heterodoxa, a Potential Biological Control Agent for Salal

Inoculum production of Valdensinia heterodoxa Peyr. (isolate PFC 3027), a foliar pathogen of salal (Gaultheria shallon Pursh.), was evaluated on various solid substrates. Incubation on salal leaf pieces resulted in the greatest number of discharged conidia, which is deemed a suitable indicator for sporulation and inoculum dispersal of V. heterodoxa. Subsequently, V. heterodoxa inoculum of two isolates (PFC 2761 and PFC 3027) was produced on salal leaf pieces using four different growth periods (0, 4, 8, or 12 days) and three different cold storage treatments (0, 4, or 8 weeks) following harvest of colonised leaf pieces. Overall, the maximum number of discharged conidia was obtained with a growth period of 4 or 8 days, whereas the effect of a cold storage treatment was inconclusive between the fungal isolates and various growth periods. Conidia discharge from salal leaf piece inoculum of V. heterodoxa (PFC 2761 and PFC 3027) applied on pot soil level resulted in 8-41% leaf damage of intact salal plants. Results from this study indicate the potential of salal plant tissue as both a growth substrate and a suitable delivery technique for V. heterodoxa to control salal.     

Diversity of Aphanizomenonflos-aquae (Cyanobacterium) Populations along a Baltic Sea Salinity Gradient

Colony-forming cyanobacteria of the genus Aphanizomenon form massive blooms in the brackish water of the Baltic Sea during the warmest summer months. There have been recent suggestions claiming that the Baltic Sea Aphanizomenon species may be different from Aphanizomenon flos-aquae found in lakes. In this study, we examined variability in the morphology and 16S-23S rRNA internal transcribed spacer (ITS) sequences of A. flos-aquae populations along a salinity gradient from a string of lakes to a fjord-like extension of the Baltic Sea to the open Baltic Sea. Morphological differences among the populations were negligible. We found that the Baltic Sea was dominated (25 out of 27 sequences) by one ITS1-S (shorter band of ITS 1 [ITS1]) genotype, which also was found in the lakes. The lake populations of A. flos-aquae tended to be genetically more diverse than the Baltic Sea populations. Since the lake ITS1-S genotypes of A. flos-aquae are continuously introduced to the Baltic Sea via inflowing waters, it seems that only one ITS1 genotype is able to persist in the Baltic Sea populations. The results suggest that one of the ITS1-S genotypes found in the lakes is better adapted to the conditions of the Baltic Sea and that natural selection removes most of the lake genotypes from the Baltic Sea A. flos-aquae populations.     

Diversity of Aphanizomenon flos-aquae (cyanobacterium) populations along a Baltic Sea salinity gradient

Colony-forming cyanobacteria of the genus Aphanizomenon form massive blooms in the brackish water of the Baltic Sea during the warmest summer months. There have been recent suggestions claiming that the Baltic Sea Aphanizomenon species may be different from Aphanizomenon flos-aquae found in lakes. In this study, we examined variability in the morphology and 16S-23S rRNA internal transcribed spacer (ITS) sequences of A. flos-aquae populations along a salinity gradient from a string of lakes to a fjord-like extension of the Baltic Sea to the open Baltic Sea. Morphological differences among the populations were negligible. We found that the Baltic Sea was dominated (25 out of 27 sequences) by one ITS1-S (shorter band of ITS 1 [ITS1]) genotype, which also was found in the lakes. The lake populations of A. flos-aquae tended to be genetically more diverse than the Baltic Sea populations. Since the lake ITS1-S genotypes of A. flos-aquae are continuously introduced to the Baltic Sea via inflowing waters, it seems that only one ITS1 genotype is able to persist in the Baltic Sea populations. The results suggest that one of the ITS1-S genotypes found in the lakes is better adapted to the conditions of the Baltic Sea and that natural selection removes most of the lake genotypes from the Baltic Sea A. flos-aquae populations.     

The Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) from Vibrio cholerae enhances insertion of FeS in overproduced NqrF subunit

The Na⁺-translocating NADH:quinone oxidoreductase (Na⁺-NQR) from Vibrio cholerae is a membrane-bound, respiratory Na⁺ pump. Its NqrF subunit contains one FAD and a [2Fe–2S] cluster and catalyzes the initial oxidation of NADH. A soluble variant of NqrF lacking its hydrophobic, N-terminal helix (NqrF′) was produced in V. cholerae wild type and nqr deletion strain. Under identical conditions of growth and induction, the yield of NqrF′ increased by 30% in the presence of the Na⁺-NQR. FAD-containing NqrF′ species with or without the FeS cluster were observed, indicating that assembly of the FeS center, but not insertion of the flavin cofactor, was limited during overproduction in V. cholerae. A comparison of these distinct NqrF′ species with regard to specific NADH dehydrogenase activity, pH dependence of activity and thermal inactivation showed that NqrF′ lacking the [2Fe–2S] cluster was less stable, partially unfolded, and therefore prone to proteolytic degradation in V. cholerae. We conclude that the overall yield of NqrF′ critically depends on the amount of fully assembled, FeS-containing NqrF′ in the V. cholerae host cells. The Na⁺-NQR is proposed to increase the stability of NqrF′ by stimulating the maturation of FeS centers.     

A MOLECULAR AND PHENOTYPIC ANALYSIS OF NODULARIA (CYANOBACTERIA) FROM THE BALTIC SEA

The filamentous diazotrophic cyanobacterium Nodularia forms water blooms each year in the Baltic Sea. Filaments isolated from such water blooms vary in their trichome width, degree of coiling, and properties of their gas vesicles; previously, these characters have been used to classify individuals to species level. To test the validity of such a phenotypic classification, we determined the nucleotide sequences for a region of the phycocyanin locus that includes a noncoding intergenic spacer (PC-IGS), the IGS between two adjacent copies of the gvpA gene (which encodes the main structural gas vesicle protein) and the rDNA internal transcribed spacer (rDNA-ITS), for 13 clonal Nodularia isolates from the Baltic Sea during August 1994. The complete 16S-rDNA sequence was determined for three isolates and was found to be identical in each of them. Molecular sequences for noncoding regions of the genome were used to assign isolates to three groups on the basis of PC-IGS, two groups on the basis of gvpA -IGS, and three groups on the basis of rDNA-ITS. No consistent correlation was found between genotype and any of the phenotypic features examined, and no link was found between any of these features themselves, indicating that these characters are not useful for placing Nodularia isolates into meaningful taxonomic groups. The PC-IGS, gvpA -IGS, and rDNA-ITS genotypic groupings were not congruent. This might indicate that gene flow occurs between individuals in Nodularia populations.     

Isoenzyme diversity and phylogenetic relationships among the American beans of the genus Vigna Savi (Fabaceae)

Electrophoretic variation of 13 isoenzyme systems encoded by 25 gene loci has been studied among the 12 American bean species of the genus Vigna, subgenera Sigmoidotropis and Lasiospron, in comparison with the two pantropical species Vigna luteola and V. vexillata of the subgenera Vigna and Plectrotropis, respectively. Of the 202 electromorphs (putative allozymes) discovered, 106 were phylogenetically informative, i.e. shared by at least two taxa, and 96 were taxon-specific. Parsimony, neighbour-joining and UPGMA analyses of the isozyme data as unordered presence–absence characters revealed the division of the American Vigna species into six clades which mostly correspond to the grouping of species into subgenera and sections in the traditional morphology-based systems, except in the placement of species V. gentryi and V. caracalla. The type species of the section Caracallae, V. caracalla, appears on the cladogram as basally paraphyletic in the subgenus Sigmoidotropis, but apart from the V. linearis group of the same section which forms a separate subclade. Vigna gentryi is not linked to other species of the section Sigmoidotropis, but appears in a distant subclade as a sister species to V. adenantha s. l. of the section Leptospron. The subgenus Lasiospron is sister to the pantropical V. vexillata of the African subgenus Plectrotropis.     

Molecular identification of bacteria associated with filaments of Nodularia spumigena and their effect on the cyanobacterial growth

Colonial and filamentous cyanobacteria frequently have bacteria associated with their extracellular mucus zone or more tightly attached to their cells surface. The toxin-producing cyanobacterium Nodularia spumigena is an important component of the Baltic Sea plankton community, and its filaments are likely to provide a microenvironment suitable for the development of a particular bacteria flora. In the present work, 13 bacterial strains associated with filaments of N. spumigena from the Baltic Sea were isolated and identified by sequencing the 16S rRNA gene. Different bacterial lineages were found associated with the cyanobacterial filaments, including the alpha, beta, and gamma subdivisions of the class Proteobacter and the division Firmicutes (Gram-positive bacteria). Several 16S rRNA gene sequences were not closely related to previously reported sequences of cultured bacteria from the Baltic Sea or to any other reported sequence. Conversely, sequences related to the gamma Proteobacter genus Shewanella, a group previously described in the Baltic Sea, were found among the isolates. The bacterial isolates were grown and added to cultures of exponentially growing N. spumigena. Five isolates, related to the alpha and gamma Proteobacter and Firmicutes, affected negatively the cyanobacterial growth, leading to a lower biomass yield up to 38% relative to controls with no bacteria addition. Five gamma Proteobacter-related strains had no effect on the cyanobacterial growth, while three strains related to Shewanella baltica had a positive effect. Although none of the bacterial isolates showed strong algicidal effect, the observed stimulatory and retarding effects on N. spumigena growth under culture conditions denotes the importance of the associated bacterial community for the dynamics of these cyanobacterial populations in nature. Moreover, several new taxa recovered in this study probably belong to species not yet described.