Identification and characterization of a direct activator of a gene transfer agent

Gene transfer agents (GTAs) are thought to be ancient bacteriophages that have been co-opted into serving their host and can now transfer any gene between bacteria. Production of GTAs is controlled by several global regulators through unclear mechanisms. In Rhodobacter capsulatus, gene rcc01865 encodes a putative regulatory protein that is essential for GTA production. Here, I show that rcc01865 (hereafter gafA) encodes a transcriptional regulator that binds to the GTA promoter to initiate production of structural and DNA packaging components. Expression of gafA is in turn controlled by the pleiotropic regulator protein CtrA and the quorum-sensing regulator GtaR. GafA and CtrA work together to promote GTA maturation and eventual release through cell lysis. Identification of GafA as a direct GTA regulator allows the first integrated regulatory model to be proposed and paves the way for discovery of GTAs in other species that possess gafA homologues

Absorptive capacity and innovation: When is it better to cooperate?

Cooperation can benefit and hurt firms at the same time. An important question then is: when is it better to cooperate? And, once the decision to cooperate is made, how can an appropriate partner be selected? In this paper we present a model of inter-firm cooperation driven by cognitive distance, appropriability conditions and external knowledge. Absorptive capacity of firms develops as an outcome of the interaction between absorptive R&D and cognitive distance from voluntary and involuntary knowledge spillovers. Thus, we offer a revision of the original model by Cohen and Levinthal (Econ J 99(397):569-596, 1989), accounting for recent empirical findings and explicitly modeling absorptive capacity within the framework of interactive learning. We apply that to the analysis of firms' cooperation and R&D investment preferences. The results show that cognitive distance and appropriability conditions between a firm and its cooperation partner have an ambiguous effect on the profit generated by the firm. Thus, a firm chooses to cooperate and selects a partner conditional on the investments in absorptive capacity it is willing to make to solve the understandability/novelty trade-off. © 2014 Springer-Verlag Berlin Heidelberg

Metagenomic Analysis of the Indian Ocean Picocyanobacterial Community : Structure, Potential Function and Evolution.

Unicellular cyanobacteria are ubiquitous photoautotrophic microbes that contribute substantially to global primary production. Picocyanobacteria such as Synechococcus and Prochlorococcus depend on chlorophyll a-binding protein complexes to capture light energy. In addition, Synechococcus has accessory pigments organized into phycobilisomes, and Prochlorococcus contains chlorophyll b. Across a surface water transect spanning the sparsely studied tropical Indian Ocean, we examined Synechococcus and Prochlorococcus occurrence, taxonomy and habitat preference in an evolutionary context. Shotgun sequencing of size fractionated microbial communities from 0.1 μm to 20 μm and subsequent phylogenetic analysis indicated that cyanobacteria account for up to 15% of annotated reads, with the genera Prochlorococcus and Synechococcus comprising 90% of the cyanobacterial reads, even in the largest size fraction (3.0-20 mm). Phylogenetic analyses of cyanobacterial light-harvesting genes (chl-binding pcb/isiA, allophycocyanin (apcAB), phycocyanin (cpcAB) and phycoerythin (cpeAB)) mostly identified picocyanobacteria clades comprised of overlapping sequences obtained from Indian Ocean, Atlantic and/or Pacific Oceans samples. Habitat reconstructions coupled with phylogenetic analysis of the Indian Ocean samples suggested that large Synechococcus-like ancestors in coastal waters expanded their ecological niche towards open oligotrophic waters in the Indian Ocean through lineage diversification and associated streamlining of genomes (e.g. loss of phycobilisomes and acquisition of Chl b); resulting in contemporary small celled Prochlorococcus. Comparative metagenomic analysis with picocyanobacteria populations in other oceans suggests that this evolutionary scenario may be globally important