Lineage Of Cyanobacteria Research Articles

Characterization of the Halochromic Gloeocapsin Pigment, a Cyanobacterial Biosignature for Paleobiology and Astrobiology

Ultraviolet (UV)-screening compounds represent a substantial asset for the survival of cyanobacteria in extreme environments exposed to high doses of UV radiations on modern and early Earth. Among these molecules, the halochromic pigment gloeocapsin remains poorly characterized and studied. In this study, we identified a gloeocapsin-producing cultivable cyanobacteria: the strain Phormidesmis nigrescens ULC007. We succeeded to extract, to partially purify, and to compare the dark blue pigment from both the ULC007 culture and an environmental Gloeocapsa alpina dominated sample. FT-IR and Raman spectra of G. alpina and P. nigrescens ULC007 pigment extracts strongly suggested a common backbone structure. The high-pressure liquid chromatography-UV-MS/MS analysis of the ULC007 pigment extract allowed to narrow down the molecular formula of gloeocapsin to potentially five candidates within three classes of halochromic molecules: anthraquinone derivatives, coumarin derivatives, and flavonoids. With the discovery of gloeocapsin in P. nigrescens, the production of this pigment is now established for three lineages of cyanobacteria (including G. alpina, P. nigrescens, and Solentia paulocellulare) that belong to three distinct orders (Chroococcales, Pleurocapsales, Synechoccocales), inhabiting very diverse environments. This suggests that gloeocapsin production was a trait of their common ancestor or was acquired by lateral gene transfer. This work represents an important step toward the elucidation of the structure of this enigmatic pigment and its biosynthesis, and it potentially provides a new biosignature for ancient cyanobacteria. It also gives a glimpse on the evolution of UV protection strategies, which are relevant for early phototrophic life on Earth and possibly beyond.

Are Cyanobacteria an Ancestor of Chloroplasts or Just One of the Gene Donors for Plants and Algae?

Chloroplasts of plants and algae are currently believed to originate from a cyanobacterial endosymbiont, mainly based on the shared proteins involved in the oxygenic photosynthesis and gene expression system. The phylogenetic relationship between the chloroplast and cyanobacterial genomes was important evidence for the notion that chloroplasts originated from cyanobacterial endosymbiosis. However, studies in the post-genomic era revealed that various substances (glycolipids, peptidoglycan, etc.) shared by cyanobacteria and chloroplasts are synthesized by different pathways or phylogenetically unrelated enzymes. Membranes and genomes are essential components of a cell (or an organelle), but the origins of these turned out to be different. Besides, phylogenetic trees of chloroplast-encoded genes suggest an alternative possibility that chloroplast genes could be acquired from at least three different lineages of cyanobacteria. We have to seriously examine that the chloroplast genome might be chimeric due to various independent gene flows from cyanobacteria. Chloroplast formation could be more complex than a single event of cyanobacterial endosymbiosis. I present the “host-directed chloroplast formation” hypothesis, in which the eukaryotic host cell that had acquired glycolipid synthesis genes as an adaptation to phosphate limitation facilitated chloroplast formation by providing glycolipid-based membranes (pre-adaptation). The origins of the membranes and the genome could be different, and the origin of the genome could be complex.

Functional Transcripts Indicate Phylogenetically Diverse Active Ammonia-Scavenging Microbiota in Sympatric Sponges.

Symbiotic ammonia scavengers contribute to effective removal of ammonia in sponges. However, the phylogenetic diversity and in situ activity of ammonia-scavenging microbiota between different sponge species are poorly addressed. Here, transcribed ammonia monooxygenase genes (amoA), hydrazine synthase genes (hzsA), and glutamine synthetase genes (glnA) were analyzed to reveal the active ammonia-scavenging microbiota in the sympatric sponges Theonella swinhoei, Plakortis simplex, and Phakellia fusca, and seawater. Archaeal amoA and bacterial glnA transcripts rather than bacterial amoA, hzsA, and archaeal glnA transcripts were detected in the investigated sponges and seawater. The transcribed amoA genes were ascribed to two Thaumarchaeota ecotypes, while the transcribed glnA genes were interspersed among the lineages of Cyanobacteria, Tectomicrobia, Poribacteria, Alpha-, Beta-, Gamma-, and Epsilonproteobacteria. In addition, transcribed abundances of archaeal amoA and bacterial glnA genes in these sponges have been quantified, showing significant variation among the investigated sponges and seawater. The transcriptome-based qualitative and quantitative analyses clarified the different phylogenetic diversity and transcription expression of functional genes related to microbially mediated ammonia scavenging in different sympatric sponges, contributing to the understanding of in situ active ecological functions of sponge microbial symbionts in holobiont nitrogen cycling.

Plants

Plants

A motif-based search in bacterial genomes identifies the ortholog of the small RNA Yfr1 in all lineages of cyanobacteria

BackgroundNon-coding RNAs (ncRNA) are regulators of gene expression in all domains of life. They control growth and differentiation, virulence, motility and various stress responses. The identification of ncRNAs can be a tedious process due to the heterogeneous nature of this molecule class and the missing sequence similarity of orthologs, even among closely related species. The small ncRNA Yfr1 has previously been found in the Prochlorococcus/Synechococcus group of marine cyanobacteria.ResultsHere we show that screening available genome sequences based on an RNA motif and followed by experimental analysis works successfully in detecting this RNA in all lineages of cyanobacteria. Yfr1 is an abundant ncRNA between 54 and 69 nt in size that is ubiquitous for cyanobacteria except for two low light-adapted strains of Prochlorococcus, MIT 9211 and SS120, in which it must have been lost secondarily. Yfr1 consists of two predicted stem-loop elements separated by an unpaired sequence of 16–20 nucleotides containing the ultraconserved undecanucleotide 5'-ACUCCUCACAC-3'.ConclusionStarting with an ncRNA previously found in a narrow group of cyanobacteria only, we show here the highly specific and sensitive identification of its homologs within all lineages of cyanobacteria, whereas it was not detected within the genome sequences of E. coli and of 7 other eubacteria belonging to the alpha-proteobacteria, chlorobiaceae and spirochaete. The integration of RNA motif prediction into computational pipelines for the detection of ncRNAs in bacteria appears as a promising step to improve the quality of such predictions.

Endolithic photosynthetic communities within ancient and recent travertine deposits in Yellowstone National Park

Molecular and culture based methods were used to survey endolithic, photosynthetic communities from hot spring-formed travertine rocks of various ages, ranging from<10 to greater than 300,000 years. Much of this travertine contained a 1-3-mm-thick greenish band composed mainly of cyanobacteria 1-5 mm below the rock surface. The travertine rocks experienced desiccation in summer and freezing in winter. A total of 83 environmental 16S rRNA gene sequences were obtained from clone libraries and denaturing gradient gel electrophoresis. Small subunit rRNA gene sequences and cell morphology were determined for 36 cyanobacterial culture isolates from these samples. Phylogenetic analysis showed that the 16S rRNA gene sequences fell into 15 distinct clusters, including several novel lineages of cyanobacteria.