Aminolipids elicit functional trade-offs between competitiveness and bacteriophage attachment in Ruegeria pomeroyi

New insights in bacterial organophosphorus cycling: From human pathogens to environmental bacteria

In terrestrial and aquatic ecosystems, phosphorus (P) availability controls primary production, with consequences for climate regulation and global food security. Understanding the microbial controls on the global P cycle is a prerequisite for minimising our reliance on non-renewable phosphate rock reserves and reducing pollution associated with excessive P fertiliser use. This recognised importance has reinvigorated research into microbial P cycling, which was pioneered over 75 years ago through the study of human pathogenic bacteria-host interactions. Immobilised organic P represents a significant fraction of the total P pool. Hence, microbes have evolved a plethora of mechanisms to transform this fraction into labile inorganic phosphate, the building block for numerous biological molecules. The 'genomics era' has revealed an extraordinary diversity of organic P cycling genes exist in the environment and studies going 'back to the lab' are determining how this diversity relates to function. Through this integrated approach, many hitherto unknown genes and proteins that are involved in microbial P cycling have been discovered. Not only do these fundamental discoveries push the frontier of our knowledge, but several examples also provide exciting opportunities for biotechnology and present possible solutions for improving the sustainability of how we grow our food, both locally and globally. In this review, we provide a comprehensive overview of bacterial organic P cycling, covering studies on human pathogens and how this knowledge is informing new discoveries in environmental microbiology.

Developing a Base Editing System for Marine Roseobacter Clade Bacteria

The Roseobacter clade bacteria are of great significance in marine ecology and biogeochemical cycles, and they are potential microbial chassis for marine synthetic biology due to their versatile metabolic capabilities. Here, we adapted a CRISPR-Cas-based system, base editing, with the combination of nuclease-deactivated Cas9 and deaminase for Roseobacter clade bacteria. Taking the model roseobacter Roseovarius nubinhibens as an example, we achieved precise and efficient genome editing at single-nucleotide resolution without generating double-strand breaks or requesting donor DNAs. Since R. nubinhibens can metabolize aromatic compounds, we interrogated the key genes in the β-ketoadipate pathway with our base editing system via the introduction of premature STOP codons. The essentiality of these genes was demonstrated, and for the first time, we determined PcaQ as a transcription activator experimentally. This is the first report of CRISPR-Cas-based genome editing in the entire clade of Roseobacter bacteria. We believe that our work provides a paradigm for interrogating marine ecology and biogeochemistry with direct genotype-and-phenotype linkages and potentially opens a new avenue for the synthetic biology of marine Roseobacter bacteria.

Membrane lipid composition defines membrane protein spectrum

In addition to glycerophospholipids, bacterial membranes often include amino acid-containing acyloxyacyl lipids. The functional implications of these aminolipids are largely unknown. However, a recent study by Stirrup et al. expands our understanding and shows that they are major determinants for membrane properties and the relative abundance of distinct membrane proteins in bacterial membranes.

Ubiquitous occurrence of a dimethylsulfoniopropionate ABC transporter in abundant marine bacteria

Dimethylsulfoniopropionate (DMSP) is a ubiquitous organosulfur compound in marine environments with important functions in both microorganisms and global biogeochemical carbon and sulfur cycling. The SAR11 clade and marine Roseobacter group (MRG) represent two major groups of heterotrophic bacteria in Earth's surface oceans, which can accumulate DMSP to high millimolar intracellular concentrations. However, few studies have investigated how SAR11 and MRG bacteria import DMSP. Here, through comparative genomics analyses, genetic manipulations, and biochemical analyses, we identified an ABC (ATP-binding cassette)-type DMSP-specific transporter, DmpXWV, in Ruegeria pomeroyi DSS-3, a model strain of the MRG. Mutagenesis suggested that DmpXWV is a key transporter responsible for DMSP uptake in strain DSS-3. DmpX, the substrate binding protein of DmpXWV, had high specificity and binding affinity towards DMSP. Furthermore, the DmpX DMSP-binding mechanism was elucidated from structural analysis. DmpX proteins are prevalent in the numerous cosmopolitan marine bacteria outside the SAR11 clade and the MRG, and dmpX transcription was consistently high across Earth's entire global ocean. Therefore, DmpXWV likely enables pelagic marine bacteria to efficiently import DMSP from seawater. This study offers a new understanding of DMSP transport into marine bacteria and provides novel insights into the environmental adaption of marine bacteria.