The construction of energetically autonomous artificial protocells is one of the most ambitious goals in bottom-up synthetic biology. Here, we show an efficient manner to build adenosine 5′-triphosphate (ATP) synthesizing hybrid multicompartment protocells. Bacterial chromatophores from Rhodobacter sphaeroides accomplish the photophosphorylation of adenosine 5′-diphosphate (ADP) to ATP, functioning as nanosized photosynthetic organellae when encapsulated inside artificial giant phospholipid vesicles (ATP production rate up to ∼100 ATP∙s⁻¹ per ATP synthase). The chromatophore morphology and the orientation of the photophosphorylation proteins were characterized by cryo-electron microscopy (cryo-EM) and time-resolved spectroscopy. The freshly synthesized ATP has been employed for sustaining the transcription of a DNA gene, following the RNA biosynthesis inside individual vesicles by confocal microscopy. The hybrid multicompartment approach here proposed is very promising for the construction of full-fledged artificial protocells because it relies on easy-to-obtain and ready-to-use chromatophores, paving the way for artificial simplified-autotroph protocells (ASAPs). Significance Chromatophores are closed vesicles extracted from photosynthetic bacteria that efficiently perform the photophosphorylation reaction (ADP + Pi → ATP) under illumination. Here we show that, when entrapped inside giant lipid vesicles, they behave as nano-biophotosynthetic organellae, allowing the construction of energetically autonomous artificial protocells. As proof of concept, DNA has been transcribed within an artificial protocell, thanks to the continuous ATP photo-production from chromatophores. Such a hybrid multicompartment approach will speed up the current efforts of constructing cell-like systems of increasing complexity, allowing the implementation of several ATP-dependent processes. Developed at the interface between synthetic biology and systems chemistry, the science of artificial protocells promises unprecedented biotechnological applications, as well as unveiling still unsolved origins-of-life questions.

Interfacing intact and metabolically active photosynthetic bacteria with abiotic electrodes requires both establishing extracellular electron transfer and immobilizing the biocatalyst on electrode surfaces. Artificial approaches for photoinduced electron harvesting through redox polymers reported in literature require the separate synthesis of artificial polymeric matrices and their subsequent combination with bacterial cells, making the development of biophotoanodes complex and less sustainable. Herein, we report a one-pot biocompatible and sustainable approach, inspired by the byssus of mussels, that provides bacterial cells adhesion on multiple surfaces under wet conditions to obtain biohybrid photoanodes with facilitated photoinduced electron harvesting. Purple bacteria were utilized as a model organism, as they are of great interest for the development of photobioelectrochemical systems for H₂ and NH₃ synthesis, biosensing, and bioremediation purposes. The polydopamine matrix preparation strategy allowed the entrapment of active purple bacteria cells by initial oxygenic polymerization followed by electrochemical polymerization. Our results unveil that the deposition of bacterial cells with simultaneous polymerization of polydopamine on the electrode surface enables a 5-fold enhancement in extracellular electron transfer at the biotic/abiotic interface while maintaining the viability of the cells. The presented approach paves the way for a more sustainable development of biohybrid photoelectrodes.

The photosynthetic reaction center is an extraordinarily efficient natural photoconverter, which can be ideally used in combination with conducting or semiconducting interfaces to produce electrical signals in response to absorption of photons. The actual applicability of this protein in bioelectronic devices critically depends on the finding of (a) suitable deposition methods enabling controlled addressing and precise orientation of the protein on electrode interfaces and (b) chemical manipulation protocols able to tune and enhance protein light absorption in specific or broader spectral regions. Literature reports several examples of approaches to fulfill these requirements, which have faced in different ways the fundamental issues of assembling the biological component and non-natural systems, such as electrode surfaces and artificial light harvesting components. Here we present a short overview of the main methods reported to accomplish both the objectives by properly “garnishing” the photosynthetic reaction center (RC) via chemical modifications.

Aminoalkyl substituted heptamethine cyanines show a large Stokes shift, ascribed to the geometry relaxation upon photoexcitation that drives the molecule from a distorted ground state structure to a planar and cyanine-like excited state.