Trends in Microbiology最新文献

The evolution of nitrogen fixation undoubtedly altered nearly all corners of the biosphere, given the essential role of nitrogen in the synthesis of biomass. To date, there is no unified view on what planetary conditions gave rise to nitrogen fixation or how these conditions have sustained it evolutionarily. Intriguingly, the concentrations of metals that nitrogenases require to function have changed throughout Earth's history. In this review, we describe the interconnection of the metal and nitrogen cycles with nitrogenase evolution and the importance of ancient ecology in the formation of the modern nitrogen cycle. We argue that exploration of the nitrogen cycle's deep past will provide insights into humanity's immediate environmental challenges centered on nitrogen availability.

The dynamic and complex interactions between plant and microbiomes in the rhizosphere play a major role in the plant's health and productivities. Using interdisciplinary approaches, Behr et al. studied how farming practices can influence the rhizosphere process, offering an exciting direction for microbial manipulation to enhance agricultural productivity.

Biological nitrogen (N₂) fixation is critical in global biogeochemical cycles and in sustaining the productivity of the oceans. There remain many unanswered questions, unresolved hypotheses, and unchallenged paradigms. The fundamental balance of N input and losses has not been fully resolved. One of the major N₂-fixers, Trichodesmium, remains an enigma with intriguing biological and ecological secrets. Cyanobacterial N₂ fixation, once thought to be primarily due to free-living cyanobacteria, now also appears to be dependent on microbial interactions, from microbiomes to unicellular symbioses, which remain poorly characterized. Nitrogenase genes associated with diverse non-cyanobacterial diazotrophs (NCDs) are prevalent, but their significance remains a huge knowledge gap. Answering questions, new and old, such as those discussed here, is needed to understand the ocean's N and C cycles and their responses to environmental change.

Diazotrophs are bacteria and archaea that can reduce atmospheric dinitrogen (N₂) into ammonium. Plant-diazotroph interactions have been explored for over a century as a nitrogen (N) source for crops to improve agricultural productivity and sustainability. This scientific quest has generated much information about the molecular mechanisms underlying the function, assembly, and regulation of nitrogenase, ammonium assimilation, and plant-diazotroph interactions. This review presents various approaches to manipulating N fixation activity, ammonium release by diazotrophs, and plant-diazotroph interactions. We discuss the research avenues explored in this area, propose potential future routes, emphasizing engineering at the metabolic level via biorthogonal signaling, and conclude by highlighting the importance of biocontrol measures and public acceptance.

Salt marshes sit at the terrestrial-aquatic interface of oceans around the world. Unique features of salt marshes that differentiate them from their upland or offshore counterparts include high rates of primary production from vascular plants and saturated saline soils that lead to sharp redox gradients and a diversity of electron acceptors and donors. Moreover, the dynamic nature of root oxygen loss and tidal forcing leads to unique biogeochemical conditions that promote nitrogen cycling. Here, we highlight recent advances in our understanding of key nitrogen cycling processes in salt marshes and discuss areas where additional research is needed to better predict how salt marsh N cycling will respond to future environmental change.

Horizontal exchange of DNA between bacteria and archaea is prevalent and has major potential implications for genome evolution, plasticity, and population fitness. Several transfer mechanisms have been identified, including gene transfer agents (GTAs). GTAs are intricately regulated domesticated viruses that package host DNA into virus-like capsids and transfer this DNA throughout the bacterial community. Several important advances have recently been made in our understanding of these unusual particles. In this review, we highlight some of these findings, primarily for the model GTA produced by Rhodobacter capsulatus but also for newly identified GTA producers. We provide key insights into these important genetic elements, including the differences between GTAs from their ancestral bacteriophages, their regulation and control, and their elusive evolutionary function.

Phages and plasmids are discrete mobile genetic elements (MGEs) with critical roles in gene dissemination across bacteria but limited scope for exchanging DNA between them. By investigating recent gene-sharing events, Pfeifer and Rocha describe how the hybrid elements phage-plasmids (P-Ps) promote gene flow between MGE types and evolve into new ones.