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The mighty power of purple bacteria

Dopamine is an efficient building block to produce a versatile coating polymer able to adhere on a vast repertoire of material surfaces. Polydopamine, a dark-bioinspired polymer, is produced by the self-assembly of the dopamine under aerobic conditions in an alkaline environment. The presence of oxygen is crucial for self-polymerization of dopamine in aqueous solution. In this manuscript we show that is possible to drive the polymerization in absence of oxygen exploiting the metabolism of anaerobic photosynthetic purple bacteria. Graphical Abstract

The effect of the exposure of the photosynthetic reaction center from the purple bacterium Rhodobacter sphaeroides to ethylenediamine (EDA) was investigated by transient absorption spectroscopy and UV-Visible-Near Infrared absorption spectroscopy. It was demonstrated that EDA is not detrimental to the photoactivity of the protein even at pH close to 12. EDA instead appears to inhibit the secondary quinone binding site with an apparent binding constant of 19.05 mM-1.

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 H

Hypersaline wastewaters require the continuous development of new and inexpensive alternatives for bioremediation. Halotolerant bacteria, which tolerate and are able to survive in moderate to high salinity environments, have been explored with promising results for wastewater treatment. Purple photosynthetic bacteria, a wide class of phototrophs, possess extraordinary metabolic versatility and include extremophiles that thrive in habitats having extreme pH, salinity, and light. The ability to grow under extreme environmental conditions of Rhodobacter (R.)sphaeroides, a purple non-sulfur proteobacteria that typically inhabits freshwater was evaluated. To investigate the response of R. sphaeroides to increased medium osmolarity under anerobic growth conditions, media with elevated osmotic strengths were attained by adding NaCl into the growing media at the desired concentrations in the range 0-2.5 M NaCl. Moreover, the pH effect on anaerobic growth was evaluated.

Photosynthetic microorganisms and their Reaction Center (RC) photoenzymes can be used as active materials for bio-optoelectronic applications. Here we report approaches to interface RC molecules extracted from Rhodobacter sphaeroides with electrodes aiming to integrate the RC in electronic and electrochemical devices. Covalent binding with molecular semiconductors or supramolecular organization based on selective interactions have been explored. Alternatively, entrapment of the RC in biocompatible polymers is a convenient approach. These soft structures include polydopamine-based films or polydopamine/ethylenediamine nanoparticles capable of confining and protecting the RC, while improving RC-electrode charge transfer. We also describe the use of these polymers to address living photosynthetic bacterial cells on electrodes.

Photosynthetic purple non-sulfur bacteria (PNB) have been widely utilized as model organisms to study bacterial photosynthesis. More recently, the remarkable resistance of these microorganisms to several metals ions called particular interest. As a result, several research efforts were directed toward clarifying the interactions of metal ions with PNB. The mechanisms of metal ions active uptake and bioabsorption have been studied in detail, unveiling that PNB enable harvesting and removing various toxic ions, thus fostering applications in environmental remediation. Herein, we present the most important achievements in the understanding of intact cell-metal ions interactions and the approaches utilized to study such processes. Following, the application of PNB-metal ions interactions toward metal removal from contaminated environments is presented. Finally, the possible coupling of PNB with abiotic electrodes to obtain biohybrid electrochemical systems is proposed as a sustainable pathway to tune and enhance metal removal and monitoring. Graphic abstract

RNA interference (RNAi) is a sequence identity-dependent RNA degradation mechanism conserved in eukaryotic organisms. One of the roles of RNAi is as a defense system against viral infections, which has been demonstrated in filamentous fungi but not in oomycetes. We investigated the virus-RNAi interplay in the oomycete Phytophthora infestans using a crucifer-infecting strain of the plant virus tobacco mosaic virus (TMVcr) and its derivative TMVcr-Δ122 that is mutated in the sequence of the p122 replicase subunit and thus inhibited in RNA suppression activity. In this study we provide evidence that replication of TMVcr-Δ122 but not of TMVcr was impaired in P. infestans as well as in tobacco plants used as positive control. The interference was associated with induction of high transcription of dicer-like genes Pidcl2 and NtDCL2 and of RNA-dependent-RNA-polymerase Pirdr1 and NtRDR1 in P. infestans and tobacco, respectively. These high transcription levels suggest an RNAi-based response that TMVcr-Δ122 mutant was not able to suppress. Taken altogether, results of this study demonstrated that an antiviral silencing activity operates also in P. infestans and that a plant virus could be a simple and feasible tool for functional studies also in oomycetes.

The following report presents an overview of photochemical realm of photosynthesis with special attention to the simple purple non-sulphur bacteria. Some basic information of the properties of the reaction center, the enzyme responsible for the solar energy transduction are also presented. The second part of the chapter is focussed on the chemical strategy to enhance the photosynthetic activity of the enzyme and to the application of the enhanced reaction center in synthetic biology.

Xylella fastidiosa is a bacterial pathogen affecting many plant species worldwide. Recently, the subspecies pauca (Xfp) has been reported as the causal agent of a devastating disease on olive trees in the Salento area (Apulia region, southeastern Italy), where centenarian and millenarian plants constitute a great agronomic, economic, and landscape trait, as well as an important cultural heritage. It is, therefore, important to develop diagnostic tools able to detect the disease early, even when infected plants are still asymptomatic, to reduce the infection risk for the surrounding plants. The reference analysis is the quantitative real time-Polymerase-Chain-Reaction (qPCR) of the bacterial DNA. The aim of this work was to assess whether the analysis of hyperspectral data, using different statistical methods, was able to select with sufficient accuracy, which plants to analyze with PCR, to save time and economic resources. The study area was selected in the Municipality of Oria (Brindisi). Partial Least Square Regression (PLSR) and Canonical Discriminant Analysis (CDA) indicated that the most important bands were those related to the chlorophyll function, water, lignin content, as can also be seen from the wilting symptoms in Xfp-infected plants. The confusion matrix of CDA showed an overall accuracy of 0.67, but with a better capability to discriminate the infected plants. Finally, an unsupervised classification, using only spectral data, was able to discriminate the infected plants at a very early stage of infection. Then, in phase of testing qPCR should be performed only on the plants predicted as infected from hyperspectral data, thus, saving time and financial resources.

Viruses are common in fungi and oomycetes and some of these viruses share sequence identities with plant viruses belonging to different families and genera. Replication of the plant virus tobacco mosaic virus has been demonstrated in the phytopathogenic fungi Colletotrichum acutatum, C. clavatum and C. theobromicola and more recently, infection of cucumber mosaic virus has been reported in Rhizoctonia solani isolated from potato plants in the field. Here we show that artichoke mottled crinkle virus, potato virus X, potato virus Y and cucumber mosaic virus plus its satellite RNA can replicate and persist in C. acutatum at least through the first subculture and that artichoke Italian latent virus, artichoke mottled crinkle virus, potato virus X, potato virus Y, tobacco mosaic virus and cucumber mosaic virus plus its satellite RNA can replicate and persist in Phytophthora infestans at least through the first subculture. These observations suggest that, unlike in plants, there may be a different basis for host-virus specificity in plant virus infection in filamentous fungi and oomycetes.

Olive anthracnose, a fungal disease caused by species of the genus Colletotrichum, is responsible for severe yield losses and poor oil quality. Typical symptoms appear in autumn or early winter, when the drupes begin to ripen. Under favorable conditions, symptoms on branches and leaves can also occur, leading to chlorosis, severe defoliation, and death of woody organs. Symptomless infection of flowers and blights have also been reported. Latent fruit infections could play an important role as the inoculum source for the autumn-winter epidemics. Application of systemic fungicides has proved effective in field trials, and pre-flowering sprays contribute to reduce latent infection and the inoculum density for autumn infection. However, public concerns about potential risks on the environment and human health promoted the search for alternative and sustainable means. Therefore, the activity of a new sulfur-based product and biocontrol agents (Bacillus subtilis, and endophytic isolates of Aureobasidium pullulans) in reducing the incidence of olive anthracnose was evaluated under field conditions. The sulfur-based product and B. subtilis applied at the pre-flowering stage were as effective as the chemical fungicides in reducing the incidence of latent infections on drupes. Moreover, some endophytic strains of A. pullulans provided high protection levels against Colletotrichum spp. when applied at the pre-flowering and veraison stages. Overall, data indicated that olive anthracnose can be controlled by using biological means and new products could be considered for introduction in the list of the organic product specification.

Background Metabolic reprogramming is commonly found in cancer but it is poorly understood in melanoma. Recent works [1,2] provided new insights concerning molecular mechanisms involved in mitochondrial biogenesis of melanoma. This work aims to find possible correlations between pathways involved in the onset and progression of the disease in order to provide supporting information in this field. In particular we studied the behaviour of the mitochondrial master regulator gene PGC1alpha in novel sporadic melanoma cell lines and its relations with BRAF mutational status.