Article

Unveiling of novel radiations within Trichodesmium cluster by hetR gene sequence analysis.

Department of Botany, Stockholm University, Stockholm, Sweden.
Applied and Environmental Microbiology (Impact Factor: 3.95). 02/2005; 71(1):190-6. DOI: 10.1128/AEM.71.1.190-196.2005
Source: PubMed

ABSTRACT The filamentous nonheterocystous cyanobacterial genus Katagnymene is a common diazotrophic component of tropical and subtropical oceans. To assess the phylogenetic affiliation of this taxon, two partial 16S rRNA gene sequences and 25 partial hetR gene sequences originating from the genera Katagnymene and Trichodesmium collected from open, surface waters of the Atlantic, Indian, and Pacific oceans were compared. Single trichomes or colonies were identified morphologically by using light microscopy and then used directly as templates in hetR PCR analyses. In addition, three cultured strains, identified as Katagnymene pelagica, Katagnymene spiralis, and Trichodesmium sp., were examined. The data show that the genus Katagnymene is in the Trichodesmium cluster and that K. pelagica Lemmermann and K. spiralis Lemmermann are most likely one species, despite their different morphologies. Phylogenetic analyses also unveiled four distinct clusters in the Trichodesmium cluster, including one novel cluster. Our findings emphasize the conclusion that known morphological traits used to differentiate marine nonheterocystous cyanobacteria at the genus and species levels correlate poorly with genetic data, and a revision is therefore suggested.

0 Bookmarks
 · 
91 Views
  • Source
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Biological N2 fixation is an important nitrogen source for surface ocean microbial communities. However, nearly all information on the diversity and gene expression of organisms responsible for oceanic N2 fixation in the environment has come from targeted approaches that assay only a small number of genes and organisms. Using genomes of diazotrophic cyanobacteria to extract reads from extensive meta-genomic and -transcriptomic libraries, we examined diazotroph diversity and gene expression from the Amazon River plume, an area characterized by salinity and nutrient gradients. Diazotroph genome and transcript sequences were most abundant in the transitional waters compared with lower salinity or oceanic water masses. We were able to distinguish two genetically divergent phylotypes within the Hemiaulus-associated Richelia sequences, which were the most abundant diazotroph sequences in the data set. Photosystem (PS)-II transcripts in Richelia populations were much less abundant than those in Trichodesmium, and transcripts from several Richelia PS-II genes were absent, indicating a prominent role for cyclic electron transport in Richelia. In addition, there were several abundant regulatory transcripts, including one that targets a gene involved in PS-I cyclic electron transport in Richelia. High sequence coverage of the Richelia transcripts, as well as those from Trichodesmium populations, allowed us to identify expressed regions of the genomes that had been overlooked by genome annotations. High-coverage genomic and transcription analysis enabled the characterization of distinct phylotypes within diazotrophic populations, revealed a distinction in a core process between dominant populations and provided evidence for a prominent role for noncoding RNAs in microbial communities.The ISME Journal advance online publication, 16 December 2014; doi:10.1038/ismej.2014.240.
    The ISME Journal 12/2014; DOI:10.1038/ismej.2014.240 · 9.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ocean-color sensors have provided the necessary platform for synoptic-scale detection and monitoring of the nitrogen-fixing marine cyanobacterium Trichodesmium spp. Such information is invaluable to global biogeochemical studies which require accurate estimates of atmospherically-fixed nitrogen. This article reviews literature from the past three decades and discusses the development of Trichodesmium-specific remote-sensing methods and how these have been revised with improved knowledge of bio-optical properties and remote-sensing technologies. Overall, the majority of Trichodesmium-specific detection methods have been non-quantitative and developed primarily for mapping the occurrence of dense surface aggregations of the cyanobacteria. The ability to positively discriminate and quantify low background concentrations of Trichodesmium (e.g. < 3200 trichomes L-1) dispersed within the water column still remains an intractable problem. Furthermore, the spectral and spatial resolutions of existing ocean-color sensors are presently a limiting factor for quantitative Trichodesmium remote sensing. It is noted that planned next-generation sensors with higher spectral resolutions, in both low earth and geostationary orbits, are likely to enhance efforts to remotely-sense global Trichodesmium abundance.
    Progress In Oceanography 12/2014; 131. DOI:10.1016/j.pocean.2014.12.013 · 3.99 Impact Factor

Full-text (2 Sources)

Download
3 Downloads
Available from
Nov 4, 2014