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Conventional CRISPR approaches for precision genome editing rely on the introduction of DNA double-strand breaks (DSB) and activation of homology-directed repair (HDR), which is inherently genotoxic and inefficient in somatic cells. The development of base editing (BE) systems that edit a target base without requiring generation of DSB or HDR offers an alternative. Here, we describe a novel BE system called Pin-point(TM) that recruits a DNA base-modifying enzyme through an RNA aptamer within the gRNA molecule. Pin-point is capable of efficiently modifying base pairs in the human genome with precision and low on-target indel formation. This system can potentially be applied for correcting pathogenic mutations, installing premature stop codons in pathological genes, and introducing other types of genetic changes for basic research and therapeutic development.

Anaerobic ammonium oxidation under iron reducing conditions, also referred to as Feammox, can be carried out by the recently isolated Acidimicrobiaceae sp. A6 (A6). Ammonium is a common water pollutant which is typically removed by nitrification, a process that exerts a high oxygen demand in waste treatment systems. A6 oxidizes ammonium anaerobically using ferric iron [Fe(III)] as an electron acceptor and has also been shown to be an electrode (anode) colonizing bacterium. Results presented here demonstrate that A6, in a pure or enrichment culture, can thrive in microbial electrolysis cells (MECs) by oxidizing ammonium, while using the anode as an electron acceptor. Results also show that current production and ammonium removal increase with the concentration of 9,10-anthraquinone-2,6-disulfonic acid (AQDS), a soluble electron shuttling compound, which is especially noticeable for the pure A6 culture. Electron microscopy of the anode's surface reveals attached cells in the pure culture MEC; however, over the time of operation there is no formation of a biofilm and the majority of cells are in the bulk liquid, explaining the need for AQDS. Maximum coulombic efficiencies of 16.4% and a current density of 4.2 A m−3 were measured. This is a first step towards the development of a Feammox bacteria-based bioelectrochemical system for anaerobic ammonium oxidation while reducing electrodes instead of Fe(III).

Acidimicrobiaceae sp. strain A6 (A6), is an anaerobic autotrophic bacterium capable of oxidizing ammonium (NH

Nitric oxide (NO) removal from a gas stream containing ~500 ppm NO was studied in a hollow fiber membrane (HFM) bioreactor. Compared to other biological NO removal methods the HFM bioreactor achieved NO removal rates that were as good if not better, of up to 92% NO removal, under comparable loadings and reactor size. Results showed that a wastewater stream containing organic carbon can be used as the electron donor to reduce the NO. Hence, combining biological NO treatment with treatment of a wastewater containing organic carbon has may be an effective overall cost-reducing strategy. The effect of different nitrate (NO 3 − ) concentrations on the NO reduction rate was also evaluated, and results showed that NO 3 − does enhance the NO removal rate. The reactor’s performance was studied under six different NO:NO 3 − loading regimes and the NO removal rate as well as the microbial denitrifier community in the reactor was tracked. Specifically, the relevant genes responsible for each denitrification step were tracked during each different NO:NO 3 − loading regime to the reactor. Results showed that the denitrifying microbial community adjust rapidly to changes in the different N loadings, but overall the performance of the reactor is robust and can withstand such variability in terms of NO, NO 3 − and organic carbon removal.

Most studies on electrogenic microorganisms have focused on the most abundant heterotrophs, while other microorganisms also commonly present in electrode microbial communities, such as Actinobacteria strains, have been overlooked. The novel Acidimicrobiaceae sp. strain A6 (Actinobacteria) is an iron-reducing bacterium that can colonize the surface of anodes in sediments and is linked to electrical current production, making it an electrode-reducing bacterium. Furthermore, A6 can carry out anaerobic ammonium oxidation coupled to iron reduction. Therefore, findings from this study open the possibility of using electrodes instead of iron as electron acceptors, as a means to promote A6 to treat NH4+-containing wastewater more efficiently. Altogether, this study expands our knowledge of electrogenic bacteria and opens the possibility of developing Feammox-based technologies coupled to bioelectric systems for the treatment of NH4+ and other contaminants in anoxic systems., Acidimicrobiaceae sp. strain A6 (A6), from the Actinobacteria phylum, was recently identified as a microorganism that can carry out anaerobic ammonium (NH4+) oxidation coupled to iron reduction, a process also known as Feammox. Being an iron-reducing bacterium, A6 was studied as a potential electrode-reducing bacterium that may transfer electrons extracellularly onto electrodes while gaining energy from NH4+ oxidation. Actinobacteria species have been overlooked as electrogenic bacteria, and the importance of lithoautotrophic iron reducers as electrode-reducing bacteria at anodes has not been addressed. By installing electrodes in the soil of a forested riparian wetland where A6 thrives, in soil columns in the laboratory, and in A6-bioaugmented constructed wetland (CW) mesocosms and by operating microbial electrolysis cells (MECs) with pure A6 culture, the characteristics and performances of this organism as an electrode-reducing bacterium candidate were investigated. In this study, we show that Acidimicrobiaceae sp. strain A6, a lithoautotrophic bacterium, is capable of colonizing electrodes under controlled conditions. In addition, A6 appears to be an electrode-reducing bacterium, since current production was boosted shortly after the CWs were seeded with enrichment A6 culture and current production was detected in MECs operated with pure A6, with the anode as the sole electron acceptor and NH4+ as the sole electron donor. IMPORTANCE Most studies on electrogenic microorganisms have focused on the most abundant heterotrophs, while other microorganisms also commonly present in electrode microbial communities, such as Actinobacteria strains, have been overlooked. The novel Acidimicrobiaceae sp. strain A6 (Actinobacteria) is an iron-reducing bacterium that can colonize the surface of anodes in sediments and is linked to electrical current production, making it an electrode-reducing bacterium. Furthermore, A6 can carry out anaerobic ammonium oxidation coupled to iron reduction. Therefore, findings from this study open the possibility of using electrodes instead of iron as electron acceptors, as a means to promote A6 to treat NH4+-containing wastewater more efficiently. Altogether, this study expands our knowledge of electrogenic bacteria and opens the possibility of developing Feammox-based technologies coupled to bioelectric systems for the treatment of NH4+ and other contaminants in anoxic systems.

An Acidimicrobiaceae bacterium A6 (A6), from the Acitnobacteria phylum was recently identified as a microorganism that can carry out anaerobic ammonium oxidation coupled to iron reduction, a process also known as Feammox. Being an iron-reducing bacterium, A6 was studied as a potential electrode-reducing bacterium that may transfer electrons extracellularly onto electrodes while gaining energy from ammonium oxidation. Actinobacteria species have been overlooked as electrogenic bacteria, and the importance of lithoautotrophic iron-reducers as electrode-reducing bacteria at anodes has not been addressed. By installing electrodes in soil of a forested riparian wetland where A6 thrives, as well as in A6 bioaugmented constructed wetland (CW) mesocosms, characteristics and performances of this organism as an electrode-reducing bacterium candidate were investigated. In this study, we show that Acidimicrobiaceae bacterium A6 is a lithoautotrophic bacterium, capable of colonizing electrodes in the field as well as in CW mesocosoms, and that it appears to be an electrode-reducing bacterium since there was a boost in current production shortly after the CWs were seeded with Acidimicrobiaceae bacterium A6.IMPORTANCEMost studies on electrogenic microorganisms have focused on the most abundant heterotrophs, while other microorganisms also commonly present in electrode microbial communities such as Actinobacteria have been overlooked. The novel Acidimicrobiaceae bacterium A6 (Actinobacteria) is an iron-reducing bacterium that can colonize the surface of anodes and is linked to electrical current production, making it an electrode-reducing candidate. Furthermore, A6 can carry out anaerobic ammonium oxidation coupled to iron reduction, therefore, findings from this study open up the possibility of using electrodes instead of iron as electron acceptors as a mean to promote A6 to treat ammonium containing wastewater more efficiently. Altogether, this study expands our knowledge on electrogenic bacteria and opens up the possibility to develop Feammox based technologies coupled to bioelectric systems for the treatment NH4+ and other contaminants in anoxic systems.