Summary: Bacteria are often thought of as having two dormant phenotypes: the viable but non‐culturable (VBNC) state and the persister state. Here we investigate the relatedness of the two stress‐induced phenotypes at the single‐cell level and examine cell morphology and quantify cell resuscitation. Using the classic starvation conditions to create VBNC cells, we found that the majority of the remaining Escherichia coli population are spherical, have empty cytosol and fail to resuscitate; however, some of the spherical cells resuscitate immediately (most probably those with dense cytosol). Critically, all the culturable cells in this starved population became persister cells within 14 days of starvation. We found that the persister cells initially are rod‐like, have clear but limited membrane damage, can resuscitate immediately and gradually become spherical by aging. After 24 h, only rod‐shaped persister cells survive, and all the spherical cells lyse. Both cell populations formed under the VBNC‐inducing conditions and the persister conditions are metabolically inactive. Therefore, the bacterial population consists of dead cells and persister cells in the VBNC‐inducing conditions; that is, the non‐lysed particles that do not resuscitate are dead, and the dormant cells that resuscitate are persister cells. Hence, ‘VBNC’ and ‘persister’ describe the same dormant phenotype.

It is well known that ammonia is produced through a catalytic reaction at high temperature and pressure from pure nitrogen and hydrogen. This catalytic chemical process is a massive and high-energy-consuming process, but a very important one for nitrogen fixation. Here, we show a non-catalyzed one-step synthesis of ammonia from atmospheric air (nitrogen source) and water (hydrogen source), based on an interfacial reaction between the air plasma gas phase and the water phase, at 25 °C and atmospheric pressure. In the plasma/liquid interfacial reaction (P/L reaction), atomic nitrogen in both air plasma and nitrogen plasma first abstracts hydrogen from the water phase surface at the P/L interface, and then NH is produced without any catalyst. Transiently formed NH is reduced further at the water phase, affording NH₃, which then dissolves in the water phase. The P/L reaction may provide an alternative solution that enables both energy conservation and CO₂ emission reduction.

Summary: Since persister cells survive antibiotic treatments through dormancy and resuscitate to reconstitute infections, it is imperative to determine the rate at which these cells revive. Using two sets of Escherichia coli persister cells, those arising after antibiotic treatment at low levels and those generated at high levels by ceasing transcription via rifampicin pretreatment (shown to be bona fide persisters through eight sets of experiments), we used microscopy of single cells to determine that the resuscitation of dormant persisters is heterogeneous and includes cells that grow immediately. In all, five phenotypes were found during the observation of persister cells when fresh nutrients were added: (i) immediate division, (ii) immediate elongation followed by division, (iii) immediate elongation but no division, (iv) delayed elongation/division and (v) no growth. In addition, once cell division begins, the growth rate is that of exponential cells. Critically, the greater the ribosome content, the faster the persister cells resuscitate.

Cu-Sn alloy electrodes were prepared by simple electrodeposition method for the electrochemical reduction of CO₂ into CO and HCOO⁻. The alloy electrode surfaces provided good selectivity and efficiency in electrochemical CO₂ conversion because they provided appropriate binding energies between the metal and the reactive species obtained through CO₂ reduction. Therefore, product selectivity can be modulated by altering the Cu-Sn crystal structure of the electrode. Using the Cu-Sn alloy electrodes, electrochemical reduction was performed at applied potentials ranging from − 0.69 to − 1.09 V vs. reversible hydrogen electrode (RHE). During electrochemical CO₂ reduction, all the prepared Cu-Sn alloy electrodes showed prominent suppression of hydrogen evolution. In contrast, Cu₈₇Sn₁₃ has high selectivity for CO formation at all the applied potentials, with maximum faradaic efficiency (FE) of 60% for CO at − 0.99 V vs. RHE. On the other hand, Cu₅₅Sn₄₅ obtained a similar selectivity for electrodeposition of Sn, with FE of 90% at − 1.09 V vs. RHE. Surface characterization results showed that the crystal structure of Cu₈₇Sn₁₃ comprised solid solutions that play an important role in increasing the selectivity for CO formation. Additionally, it suggests that the selectivity for HCOO⁻ formation is affected by the surface oxidation state of Sn rather than by crystal structures like intermetallic compounds. The Cu-Sn alloy catalysts prepared by simple electrodeposition can control the selectivity for CO and HCOO⁻ formation by tuning its crystal structure. Surface analyses revealed that solid solutions and the oxidation state of Sn play an important role in the formation of CO and HCOO⁻ upon CO₂ reduction, respectively.

Persistence, the stress-tolerant state, is arguably the most vital phenotype since nearly all cells experience nutrient stress, which causes a sub-population to become dormant. However, how persister cells wake to reconstitute infections is not understood well. Here, using single-cell observations, we determined that Escherichia coli persister cells resuscitate primarily when presented with specific carbon sources, rather than spontaneously. In addition, we found that the mechanism of persister cell waking is through sensing nutrients by chemotaxis and phosphotransferase membrane proteins. Furthermore, nutrient transport reduces the level of secondary messenger cAMP through enzyme IIA; this reduction in cAMP levels leads to ribosome resuscitation and rescue. Resuscitating cells also immediately commence chemotaxis toward nutrients, although flagellar motion is not required for waking. Hence, persister cells wake by perceiving nutrients via membrane receptors that relay the signal to ribosomes via the secondary messenger cAMP, and persisters wake and utilize chemotaxis to acquire nutrients.

An interfacial reaction between the UV irradiated water phase (H˙ provides) and the electron-discharged nitrogen-gas phase (N atom provides) produces ammonia efficiently.