Project description:Cyanobacteria are highly promising microorganisms in forthcoming biotechnologies. Besides the systematic development of molecular tools for genetic engineering, the design of chassis strains and novel reactor concepts are in focus. The latter includes capillary biofilm reactors (CBR), which offer a high surface area-to-volume ratio and very high cell densities. In this context, Tolypothrix sp. PCC 7712 was found to be highly suited for this reactor system due to maximal surface coverage, extraordinarily strong biofilm attachment, and high biomass formation. Here, we provide the genome sequence of Tolypothrix sp. PCC 7712 to potentially allow targeted strain engineering. Surprisingly, it was almost identical to an available incomplete genome draft of Tolypothrix sp. PCC 7601. Thus, we completely sequenced this strain as well and compared it in detail to strain PCC 7712. Comparative genome analysis revealed 257 and 80 unique protein-coding sequences for strains PCC 7601 and PCC 7712, respectively. Clustering genomes based on average nucleotide identity (ANI) and 16S rRNA homology showed 99.98% similarity and only minor distance, respectively, between the two strains in contrast to 21 other cyanobacterial genomes. Despite these high similarities, both strains differ in the ability to fix atmospheric nitrogen and show specific sequence variations, which are discussed in the paper.
Project description:Here, we report the comparison of transcriptomes of Anabaena sp. PCC7120 and a FurC-overexpressing derivative strain grown under standard conditions (BG11) and after 48 hours of nitrogen step-down (BG110). Anabaena sp PCC7120 is a cyanobacterium that differentiates specialized nitrogen-fixing cells called heterocysts. Our data suggests that FurC directly controls the regulation of heterocyst differentiation and nitrogen fixation in this cyanobacterium. In addition, we found that FurC is also clearly involved in the regulation of several genes belonging to different functional categories, such as iron metabolism, photosynthesis and regulatory functions.
Project description:Transcriptomic analyses using high-throughput methods have revealed abundant antisense transcription in bacteria. Most frequently, antisense transcription is due to the overlap of mRNAs with long 5’ regions or 3’ ends that extend beyond the coding sequence. In addition, antisense RNAs that do not contain any coding sequence are also observed. Nostoc sp. PCC 7120 is a filamentous cyanobacterium that, under nitrogen limitation, behaves as a multicellular organism with division of labor among two different cell types that depend on each other, the vegetative CO2-fixing cells and the nitrogen-fixing heterocysts. Differentiation of heterocysts depends on the global nitrogen regulator NtcA and requires the specific regulator HetR. To identify antisense RNAs potentially involved in heterocyst differentiation we performed an RNA-Seq analysis of cells subjected to nitrogen limitation (either at 9 or 24 hours after nitrogen removal) and analyzed the results in combination with a genome-wide set of nitrogen-regulated transcriptional start sites and a prediction of transcriptional terminators. Our analysis resulted in the definition of a transcriptional map including more than 4,000 transcripts, 65% of them in antisense orientation to other transcripts. In addition to overlapping mRNAs we identified nitrogen-regulated non-coding antisense RNAs transcribed from NtcA-dependent or HetR-dependent promoters.
