The regeneration of bioavailable phosphate from immobilized organophosphorus represents a key process in the global phosphorus cycle and is facilitated by enzymes known as phosphatases. Most bacteria possess at least one of three phosphatases with broad substrate specificity, known as PhoA, PhoX, and PhoD, whose activity is optimal under alkaline conditions. The production and activity of these phosphatases is repressed by phosphate availability. Therefore, they are only fully functional when bacteria experience phosphorus-limiting growth conditions. Here, we reveal a previously overlooked phosphate-insensitive phosphatase, PafA, prevalent in Bacteroidetes, which is highly abundant in nature and represents a major route for the regeneration of environmental phosphate. Using the enzyme from Flavobacterium johnsoniae, we show that PafA is highly active toward phosphomonoesters, is fully functional in the presence of excess phosphate, and is essential for growth on phosphorylated carbohydrates as a sole carbon source. These distinct properties of PafA may expand the metabolic niche of Bacteroidetes by enabling the utilization of abundant organophosphorus substrates as C and P sources, providing a competitive advantage when inhabiting zones of high microbial activity and nutrient demand. PafA, which is constitutively synthesized by soil and marine flavobacteria, rapidly remineralizes phosphomonoesters releasing bioavailable phosphate that can be acquired by neighboring cells. The pafA gene is highly diverse in plant rhizospheres and is abundant in the global ocean, where it is expressed independently of phosphate availability. PafA therefore represents an important enzyme in the context of global biogeochemical cycling and has potential applications in sustainable agriculture.

Summary Bacteriophages infecting Escherichia coli (coliphages) have been used as a proxy for faecal matter and water quality from a variety of environments. However, the diversity of coliphages that is present in seawater remains largely unknown, with previous studies largely focusing on morphological diversity. Here, we isolated and characterized coliphages from three coastal locations in the United Kingdom and Poland. Comparative genomics and phylogenetic analysis of phage isolates facilitated the identification of putative new species within the genera Rb69virus and T5virus and a putative new genus within the subfamily Tunavirinae. Furthermore, genomic and proteomic analysis combined with host range analysis allowed the identification of a putative tail fibre that is likely responsible for the observed differences in host range of phages vB_Eco_mar003J3 and vB_Eco_mar004NP2.

Highlights d Phosphorus (P)-limited diatoms sense P via a Ca 2+dependent signaling pathway d P-Ca 2+ signaling is employed by representative centric and pennate diatom species d Rapid cross-talk with N metabolism mediates diatom recovery responses to P resupply d P-Ca 2+ signaling coordinates diatom recovery responses from P limitation

SummaryMarine phototroph and heterotroph interactions are vital in maintaining the nutrient balance in the oceans as essential nutrients need to be rapidly cycled before sinking to aphotic layers. The aim of this study was to highlight the molecular mechanisms that drive these interactions. For this, we generated a detailed exoproteomic time‐course analysis of a 100‐day co‐culture between the model marine picocyanobacterium Synechococcus sp. WH7803 and the Roseobacter strain Ruegeria pomeroyi DSS‐3, both in nutrient‐enriched and natural oligotrophic seawater. The proteomic data showed a transition between the initial growth phase and stable‐state phase that, in the case of the heterotroph, was caused by a switch in motility attributed to organic matter availability. The phototroph adapted to seawater oligotrophy by reducing its selective leakiness, increasing the acquisition of essential nutrients and secreting conserved proteins of unknown function. We also report a surprisingly high abundance of extracellular superoxide dismutase produced by Synechococcus and a dynamic secretion of potential hydrolytic enzyme candidates used by the heterotroph to cleave organic groups and hydrolase polymeric organic matter produced by the cyanobacterium. The time course dataset we present here will become a reference for understanding the molecular processes underpinning marine phototroph‐heterotroph interactions.