Background Salivary mucin MUC5B seems to promote biodiversity in dental biofilms, and thereby oral health, for example, by inducing synergistic 'mucolytic' activities in a variety of microbial species that need to cooperate for the release of nutrients from the complex glycoprotein. Knowledge of how early colonizers interact with host salivary proteins is integral to better understand the maturation of putatively harmful oral biofilms and could provide key insights into biofilm physiology. Methods The early oral colonizer Streptococcus gordonii DL1 was grown planktonically and in biofilm flow cell systems with uncoated, MUC5B or low-density salivary protein (LDP) coated surfaces. Bacterial cell proteins were extracted and analyzed using a quantitative mass spectrometry-based workflow, and differentially expressed proteins were identified. Results and conclusions Overall, the proteomic profiles of S. gordonii DL1 were similar across conditions. Six novel biofilm cell proteins and three planktonic proteins absent in all biofilm cultures were identified. These differences may provide insights into mechanisms for adaptation to biofilm growth in this species. Salivary MUC5B also elicited specific responses in the biofilm cell proteome. These regulations may represent mechanisms by which this mucin could promote colonization of the commensal S. gordonii in oral biofilms.

BACKGROUND: To respond and adapt to environmental challenges, prokaryotes regulate cellular processes rapidly and reversibly through protein phosphorylation and dephosphorylation. This study investigates the intracellular proteome and Ser/Thr/Tyr phosphoproteome of the oral commensal Streptococcus gordonii. Intracellular proteins from planktonic cells of S. gordonii DL1 were extracted and subjected to 2D-gel electrophoresis. Proteins in general were visualized using Coomassie Brilliant Blue and T-Rex staining. Phosphorylated proteins were visualized with Pro-Q Diamond Phosphoprotein Gel Stain. Proteins were identified by LC-MS/MS and sequence analysis.

RESULTS: In total, sixty-one intracellular proteins were identified in S. gordonii DL1, many of which occurred at multiple isoelectric points. Nineteen of these proteins were present as one or more Ser/Thr/Tyr phosphorylated form. The identified phosphoproteins turned out to be involved in a variety of cellular processes.

CONCLUSION: Nineteen phosphoproteins involved in various cellular functions were identified in S. gordonii. This is the first time the global intracellular Ser/Thr/Tyr phosphorylation profile has been analysed in an oral streptococcus. Comparison with phosphoproteomes of other species from previous studies showed many similarities. Proteins that are consistently found in a phosphorylated state across several species and growth conditions may represent a core phosphoproteome profile shared by many bacteria.

Here we report an enzymic fuel cell in a vein replica that generates sustained electricity, enough to power an e-​ink display, in an authentic human blood stream. We also detail a simple and safe approach for fuel cell evaluation under homeostatic conditions. Our results demonstrate proof-​of-​principle operation of a biocompatible and safe biodevice that could be implanted in superficial human veins, which we anticipate to be a starting point for more sophisticated investigations of personal sources of electricity.

A review. Being inspired by a very recent review entitled: "Electrocatalysis and bioelectrocatalysis - Distinction without a difference" and following the general approach employed by Prof. Dr. Schuhmann, in the current work we point to the similarities and differences between oxygen electroredn. and bioelectroredn. processes. To addnl. distinguish our paper from the recent review we touch on different bioelements, such as redox proteins and living cells, but we still keep a special emphasis on oxidoreductases, biocatalysts par excellence. Moreover, we also exclusively focus on oxygen electroredn. based on direct electron transfer reactions. On the one hand, we corroborate the previously made conclusion regarding intrinsically high activity of the active sites of biol. catalysts, esp. redox enzymes, which results in mass transfer and heterogeneous electron transfer limited currents from oxygen reducing bioelectrodes. On the other hand, we disagree with the statements regarding the exceptionality of precious metal catalysts, and the notion of a huge trade-​off between high activity and stability of non-​precious metal catalysts and bioelements. We show that the activity and stability of noble metal based cathodes is very far from perfect, esp. when these electrodes operate in complex electrolytes, such as physiol. fluids, e.g. human blood.

A review. This work provides an overview of the recent advances in the field of tear-​based wearable electrochem. biodevices, including non-​invasive biosensors, biol. fuel cells and biosupercapacitors. Contact lenses are attractive platforms for fabricating non-​invasive self-​contained gadgets for different applications, starting from devices with casual or mundane purposes only, like personalized smart lenses with direct (invisible for others) displays, and ending with biomedical devices for continuous fitness status and​/or health care monitoring. Key requirements and challenges that confront researchers in this exciting area are discussed.

Here the authors detail an optimized transparent capacitive glucose oxidizing bioanode, capable of supplying current densities of 10 μA cm-​2 at applied potentials of 0.1 V-​0.2 V vs. SCE, when continuously performing in a simple phosphate buffer, pH 7.4 and artificial human tears, both with a glucose concn. of 0.05 mM only. When operating in pulse mode, the bioanode was able to deliver current densities ≤21 μA cm-​2 at the beginning of the pulse with 571 μC cm-​2 total charges stored. The biogenic part of the enzymic device was a recombinant glucose oxidase mutant from Penicillium amagasakiense with high catalytic efficiency towards glucose, up to 14.5x104 M-​1 s-​1. The nonbiogenic part of the anodic system was based on a poly(3,​4-​ethylenedioxythiophene)​-​graphene nanocomposite, as a highly capacitive component with a capacitance d. in the 1 mF cm-​2 range, multi-​walled carbon nanotubes, as an addnl. nanostructuring element, and a conductive org. complex, as an electron shuttle between the redox enzyme and the electrode surface. The bioanode could potentially serve as a prototype of a double-​function enzymic anode for hybrid elec. power biodevices, energizing smart contact lenses.

We herein report on an entirely new kind of electric power device. In the hybrid device, chemical energy is directly converted into electric energy, which is capacitively stored within a singular contrivance. The device is built based on dual-function electrodes, viz. discrete electrodes manifesting simultaneous electrocatalytic and charge-storage features.

Hybrid electric power biodevices, a new type of electric power-producing device, are a combination of an electrochemical capacitor and a biofuel cell. In this Minireview, we summarise existing knowledge on double-function bioelectrodes, that is, single electrodes concurrently manifesting bio-electrocatalytic and charge-storage features, and describe important historical aspects and achievements in this area. We also discuss a recently proposed method for concomitant electric power generation and storage, which is exemplified by fabricated and characterised self-charging bio-supercapacitors, also termed charge-storing biofuel cells. The electric power in these hybrid devices is uninterruptedly generated by direct transformation of chemical energy into electric energy, as occurs in biofuel cells. The power is simultaneously and directly stored within a single device, relying on different types of capacitance based on reversible charge-transfer reactions (pseudocapacitance) and/or electric double-layer capacitance, as in electrochemical capacitors. We also present some unpublished results on both dual-feature electrodes and hybrid biodevices and briefly highlight the prospects for their application.

The recent media hoopla regarding ‘smart’, ‘bionic’, or more appropriately, electronically augmented contact lenses is analyzed in terms of real achievements coupled to the critically important issue of power management. Not depending on the availability, currently or in the near future, of to-the-purpose discrete or integrated electronic devices, power management, including delivery/supply and temporal sustainability, will be an outstanding issue if present-day technology should remain the only option. Radically different approaches have been taken to deliver electric power to electronically augmented contact lenses, that is, ranging from quite simplistic wire-based delivery assemblies, grossly inappropriate for end users, to various elaborate wireless designs drawing on over-the-air power delivery, as well as solar and electrochemical cells. Nonetheless, given the complex restrictions offered by a contact lens, conventional, even state-of-the-art, power management technology is at an impasse, and to ensure a bright future for smart lenses, radical technological measures need to be taken. Bridging the conceptual gap between fuel cells and supercapacitors, an ingenious novel approach to on-lens power management is presented: a charge-storing fuel cell, or alternatively, a self-charging capacitor, that is, a hybrid electric power device.

Two-in-one: A biological supercapacitor—a combination of an electrochemical capacitor and an enzymatic fuel cell—is presented. Both the capacitor and the biofuel cell are built from nanomaterials, namely, polyaniline/carbon nanotube composites and redox enzyme/gold nanoparticle assemblies. The biosupercapacitor is self-charging, membrane- and mediator-less

Miniature, self-contained biodevices powered by biofuel cells may enable a new generation of implantable, wireless, minimally invasive neural interfaces for neurophysiological in vivo studies and for clinical applications. Here we report on the fabrication of a direct electron transfer based glucose/oxygen enzymatic fuel cell (EFC) from genuinely three-dimensional (3D) nanostructured microscale gold electrodes, modified with suitable biocatalysts. We show that the process underlying the simple fabrication method of 3D nanostructured electrodes is based on an electrochemically driven transformation of physically deposited gold nanoparticles. We experimentally demonstrate that mediator-, cofactor-, and membrane-less EFCs do operate in cerebrospinal fluid and in the brain of a rat, producing amounts of electrical power sufficient to drive a self-contained biodevice, viz. 7 μW cm−2 in vitro and 2 μW cm−2 in vivo at an operating voltage of 0.4 V. Last but not least, we also demonstrate an inductive coupling between 3D nanobioelectrodes and living neurons.

Here we present unequivocal exptl. proof that microscale cofactor- and membrane-less, direct electron transfer based enzymic fuel cells do produce significant amts. of elec. energy in human lachrymal liq. (tears). 100 μm diam. gold wires, covered with 17 nm gold nanoparticles, were used to fashion three-dimensional nanostructured microelectrodes, which were biomodified with Corynascus thermophilus cellobiose dehydrogenase and Myrothecium verrucaria bilirubin oxidase as anodic and cathodic bioelements, resp. The following characteristics of miniature glucose/oxygen biodevices operating in human tears were registered: 0.57 V open-circuit voltage, about 1 μW cm-2 max. power d. at a cell voltage of 0.5 V, and more than 20 h operational half-life. Theor. calcns. regarding the max. recoverable elec. energy can be extd. from the biofuel and the biooxidant, glucose and mol. oxygen, each readily available in human lachrymal liq., fully support our belief that biofuel cells can be used as elec. power sources for so called smart contact lenses.

Recent direct and indirect evidence have pointed to both biological reactivity and toxicity of micro- and nano-particles. Particle size appears to be a decisive factor and particles can enter cells in two ways; either through endocytosis, were particles enter the cell in an endosome; or by otherwise passing the cell membrane directly into the cytoplasm. Endocytosis covers sampling of small volumes of fluids and soluble molecules from the milieu surrounding the cell, as well as internalization of large particulate matter such as whole cells or cell fragments from the immediate vicinity of the cells. With respect to toxicity, it is important to identify the size and the chemical composition at which biological systems no longer regard the extraneous matter as particles and hence the material enters the cells directly, through other mechanisms than endocytosis.

A review of some historical developments made in the field of enzymic fuel cells, discussing important design considerations taken when constructing mediator-, cofactor-, and membrane-less biol. fuel cells. Since the topic is rather extensive, only biol. fuel cells utilizing direct electron transfer reactions on both the anodic and cathodic sides are considered. Moreover, the performance of mostly glucose/oxygen biodevices is analyzed and compared. We also present some unpublished results on mediator-, cofactor-, and membrane-less glucose/oxygen biol. fuel cells recently designed in our group and tested in different human physiol. fluids, such as blood, plasma, saliva, and tears. Finally, further perspectives for biol. fuel cell applications are highlighted.