Electron Injection in Metal Assisted Chemical Etching as a Fundamental Mechanism for Electroless Electricity Generation

Chemovoltaic effect for renewable liquid and vapor fuels on semiconductor surfaces

The chemovoltaic effect - generation of electronic excitation by exergonic redox reactions - has been observed on metallic surfaces of Schottky junctions and is proving to be pivotal in explaining in detail the momentum conservation relations of chemically active collisions. As shown in this work, it can hold keys for direct chemical energy harvesting by semiconductor solar cells. To study the possibilities of chemovoltaic energy conversion by semiconductors, we have modeled and designed an 'electrolyte-free fuel cell' formed by a GaAs diode that can host electrochemical fuel oxidation and oxidant reduction reactions on its conduction and valence bands and as a result convert renewable chemical energy (as well as light) into electricity. The experimental results show that exposing the surface of a suitably designed solar cell to methanol liquid or vapor in the presence of oxygen or hydrogen peroxide leads to the generation of electrical power.

Metagenomic analysis of the honey bee queen microbiome reveals low bacterial diversity and Caudoviricetes phages

In eusocial insects, the health of the queens-the colony founders and sole reproductive females-is a primary determinant for colony success. Queen failure in the honey bee Apis mellifera, for example, is a major concern of beekeepers who annually suffer colony losses, necessitating a greater knowledge of queen health. Several studies on the microbiome of honey bees have characterized its diversity and shown its importance for the health of worker bees, the female non-reproductive caste. However, the microbiome of workers differs from that of queens, which, in comparison, is still poorly studied. Thus, direct investigations of the queen microbiome are required to understand colony-level microbiome assembly, functional roles, and evolution. Here, we used metagenomics to comprehensively characterize the honey bee queen microbiome. Comparing samples from different geographic locations and breeder sources, we show that the microbiome of queens is mostly shaped by the environment experienced since early life and is predicted to play roles in the breakdown of the diet and protection from pathogens and xenobiotics. We also reveal that the microbiome of queens comprises only four candidate core bacterial species, Apilactobacillus kunkeei, Lactobacillus apis, Bombella apis, and Commensalibacter sp. Interestingly, in addition to bacteria, we show that bacteriophages infect the queen microbiome, for which Lactobacillaceae are predicted to be the main reservoirs. Together, our results provide the basis to understand the honey bee colony microbiome assemblage, can guide improvements in queen-rearing processes, and highlight the importance of considering bacteriophages for queen microbiome health and microbiome homeostasis in eusocial insects.IMPORTANCEThe queen caste plays a central role in colony success in eusocial insects, as queens lay eggs and regulate colony behavior and development. Queen failure can cause colonies to collapse, which is one of the major concerns of beekeepers. Thus, understanding the biology behind the queen's health is a pressing issue. Previous studies have shown that the bee microbiome plays an important role in worker bee health, but little is known about the queen microbiome and its function in vivo. Here, we characterized the queen microbiome, identifying for the first time the present species and their putative functions. We show that the queen microbiome has predicted nutritional and protective roles in queen association and comprises only four consistently present bacterial species. Additionally, we bring to attention the spread of phages in the queen microbiome, which increased in abundance in failing queens and may impact the fate of the colony.

Genetic mutation in Escherichia coli genome during adaptation to the murine intestine is optimized for the host diet

Mammalian gut microbes colonize the intestinal tract of their host and adapt to establish a microbial ecosystem. The host diet changes the nutrient profile of the intestine and has a high impact on microbiota composition. Genetic mutations in Escherichia coli, a prevalent species in the human gut, allow for adaptation to the mammalian intestine, as reported in previous studies. However, the extent of colonization fitness in the intestine elevated by genetic mutation and the effects of diet change on these mutations in E. coli are still poorly known. Here, we show that notable mutations in sugar metabolism-related genes (gatC, araC, and malI) were detected in the E. coli K-12 genome just 2 weeks after colonization in the germ-free mouse intestine. In addition to elevated fitness by deletion of gatC, as previously reported, deletion of araC and malI also elevated E. coli fitness in the murine intestine in a host diet-dependent manner. In vitro cultures of medium containing nutrients abundant in the intestine (e.g., galactose, N-acetylglucosamine, and asparagine) also showed increased E. coli fitness after deletion of the genes-of-interest associated with their metabolism. Furthermore, the host diet was found to influence the developmental trajectory of gene mutations in E. coli. Taken together, we suggest that genetic mutations in E. coli are selected in response to the intestinal environment, which facilitates efficient utilization of nutrients abundant in the intestine under laboratory conditions. Our study offers some insight into the possible adaptation mechanisms of gut microbes.IMPORTANCEThe gut microbiota is closely associated with human health and is greatly impacted by the host diet. Bacteria such as Escherichia coli live in the gut all throughout the life of a human host and adapt to the intestinal environment. Adaptive mutations in E. coli are reported to enhance fitness in the mammalian intestine, but to what extent is still poorly known. It is also unknown whether the host diet affects what genes are mutated and to what extent fitness is affected. This study suggests that genetic mutations in the E. coli K-12 strain are selected in response to the intestinal environment and facilitate efficient utilization of abundant nutrients in the germ-free mouse intestine. Our study provides a better understanding of these intestinal adaptation mechanisms of gut microbes.

Serum bile acids profiles are altered without change of the gut microbiota composition following a seven-day prednisolone therapy in severe alcoholic hepatitis

Severe Alcoholic Hepatitis (sAH) is an acute form of liver injury caused by chronic and heavy alcohol drinking. A one-month corticosteroids course is the only sAH reference treatment, and its interactions with the Gut Microbiota (GM), which is a key contributor to liver injury, remain unknown. To evaluate the evolution of the GM in sAH patients, we retrospectively investigated the composition of the GM of 27 sAH patients at the Amiens University Hospital before (D0) and after (D7) a 7-day corticotherapy course using fecal metagenomics sequencing. We also quantified fecal Short-Chain Fatty Acids (SCFA) and fecal and serum Bile Acids (BA), as well as serum Lipopolysaccharide-Binding Protein (LBP). Overall, the community and taxonomical analyses did not reveal any GM evolution between D0 and D7, nor did the SCFA profiles analysis. However, in serum but not fecal samples, the ratio of glyco-conjugated to tauro-conjugated BA was significantly reduced at D7, independently of the response to treatment, while two BA were enriched in non-responder patients. LBP concentration significantly diminished between D0 and D7, which may indicate an improvement of the gut barrier. The stability of the GM of sAH is interesting in the perspective of new treatments based on GM modulation.

Joining the bacterial conversation: increasing the cultivation efficiency of soil bacteria with acyl-homoserine lactones and cAMP

IMPORTANCE

Microorganisms are a repository of interesting metabolites and functions. Therefore, accessing them is an important exercise for advancing not only basic questions about their physiology but also to advance technological applications. In this sense, increasing the culturability of environmental microorganisms remains an important endeavor for modern microbiology. Because microorganisms do not live in isolation in their environments, molecules can be added to the cultivation strategies to "inform them" that they are present in growth-permissive environmental conditions. Signaling molecules such as acyl-homoserine lactones and 3',5'-cyclic adenosine monophosphate belong to the plethora of molecules used by bacteria to communicate with each other in a phenomenon called quorum sensing. Therefore, including quorum sensing molecules can be an incentive for microorganisms, specifically soil bacteria, to increase their numbers on solid media.

Biogeographic distribution and molecular epidemiology of Clostridioides (Clostridium) difficile in Western Australian soils

Clostridioides (Clostridium) difficile is a leading cause of infectious diarrhea in humans and production animals and can be found in a variety of environmental sources. The prevalence and diversity of multi-locus sequence type clade 5 strains of C. difficile in Australian production animals suggest Australia might be the ancestral home of this lineage of One Health importance. To better understand the role of the environment in the colonization of humans and animals in Australia, it is important to investigate these endemic sources. This study describes the prevalence, molecular epidemiology, and biogeographic distribution of C. difficile in soils of Western Australia. A total of 321 soil samples from remote geographical locations across the eight health regions of Western Australia were screened for C. difficile and isolates characterized by PCR ribotyping and toxin gene profiling. C. difficile was isolated from 31.15% of samples, with the highest prevalence in the Perth Metropolitan Health Region (49.25%, n = 33/67). Overall, 52 different strains [PCR ribotypes (RTs)] were identified, with 14 being novel, and 38% (38/100) of isolates being toxigenic, the most common of which was RT014/020. Five unique novel isolates showed characteristics similar to C. difficile clade 5. This is the first study of C. difficile isolated from soils in Australia. The high prevalence and heterogeneity of C. difficile strains recovered suggest that soils play a role in the survival and environmental dissemination of this organism, and potentially its transmission among native wildlife and production animals, and in community and hospital settings.IMPORTANCEClostridium difficile is a pathogen of One Health importance. To better understand the role of the environment in human and animal colonization/infection, it is critical that autochthonous reservoirs/sources of C. difficile be investigated. This is the first study of C. difficile isolated from soils of Western Australia (WA). Here, the ecology of C. difficile in WA is described by examining the geographic distribution, molecular epidemiology, and diversity of C. difficile isolated from soils across WA.

Geographical survey of the mycobiome and microbiome of Southern California glassy-winged sharpshooters

The glassy-winged sharpshooter, Homalodisca vitripennis Germar, is an invasive xylem-feeding leafhopper with a devastating economic impact on California agriculture through transmission of the plant pathogen, Xylella fastidiosa. While studies have focused on X. fastidiosa or known symbionts of H. vitripennis, little work has been done at the scale of the microbiome (the bacterial community) or mycobiome (the fungal community). Here, we characterize the mycobiome and the microbiome of H. vitripennis across Southern California and explore correlations with captivity and host insecticide resistance status. Using high-throughput sequencing of the ribosomal internal transcribed spacer 1 region and the 16S rRNA gene to profile the mycobiome and microbiome, respectively, we found that while the H. vitripennis mycobiome significantly varied across Southern California, the microbiome did not. We also observed a significant difference in both the mycobiome and microbiome between captive and wild H. vitripennis. Finally, we found that the mycobiome, but not the microbiome, was correlated with insecticide resistance status in wild H. vitripennis. This study serves as a foundational look at the H. vitripennis mycobiome and microbiome across Southern California. Future work should explore the putative link between microbes and insecticide resistance status and investigate whether microbial communities should be considered in H. vitripennis management practices. IMPORTANCE The glassy-winged sharpshooter is an invasive leafhopper that feeds on the xylem of plants and transmits the devastating pathogen, Xylella fastidiosa, resulting in significant economic damage to California's agricultural system. While studies have focused on this pathogen or obligate symbionts of the glassy-winged sharpshooter, there is limited knowledge of the bacterial and fungal communities that make up its microbiome and mycobiome. To address this knowledge gap, we explored the composition of the mycobiome and the microbiome of the glassy-winged sharpshooter across Southern California and identified differences associated with geography, captivity, and host insecticide resistance status. Understanding sources of variation in the microbial communities associated with the glassy-winged sharpshooter is an important consideration for developing management strategies to control this invasive insect. This study is a first step toward understanding the role microbes may play in the glassy-winged sharpshooter's resistance to insecticides.