Rumen Inoculum Enhances Cathode Performance in Single-Chamber Air-Cathode Microbial Fuel Cells

During the last decade, bioprospecting for electrochemically active bacteria has included the search for new sources of inoculum for microbial fuel cells (MFCs). However, concerning power and current production, a Geobacter-dominated mixed microbial community derived from a wastewater inoculum remains the standard. On the other hand, cathode performance is still one of the main limitations for MFCs, and the enrichment of a beneficial cathodic biofilm emerges as an alternative to increase its performance. Glucose-fed air-cathode reactors inoculated with a rumen-fluid enrichment and wastewater showed higher power densities and soluble chemical oxygen demand (sCOD) removal (Pmax = 824.5 mWm−2; ΔsCOD = 96.1%) than reactors inoculated only with wastewater (Pmax = 634.1 mWm−2; ΔsCOD = 91.7%). Identical anode but different cathode potentials suggest that differences in performance were due to the cathode. Pyrosequencing analysis showed no significant differences between the anodic community structures derived from both inocula but increased relative abundances of Azoarcus and Victivallis species in the cathodic rumen enrichment. Results suggest that this rarely used inoculum for single-chamber MFCs contributed to cathodic biofilm improvements with no anodic biofilm effects.

Enriching and characterizing an aerotolerant mixed microbial community capable of cellulose hydrolysis and ethanol production

Cellulosic ethanol produced via consolidated bioprocessing may one day be a viable alternative to fossil fuels However, efforts must focus on streamlining and simplifying its production in order to make this a reality. The aim of this study was to enrich a cellulolytic community and characterize its soluble end-products and bacterial diversity. The community degraded cellulose in the absence of reducing agent, and appeared to generate anaerobic conditions through oxygen-consuming aerobic respiration. Ethanol and acetate were the major fermentation products and the activity of the community was stable in aerobic and anaerobic media, as well as yeast extract-free aerobic media supplemented with other waste-based nutrient sources. Several community members showed high similarity to Clostridium species, suggesting the presence of some functional redundancy. Reducing agent and yeast extract both represent significant costs in the culturing of cellulolytic, ethanologenic microorganisms. The community described here exhibited this activity in the absence of both.

Enriching and characterizing an aerotolerant mixed microbial community capable of cellulose hydrolysis and ethanol production

Cellulosic ethanol produced via consolidated bioprocessing may one day be a viable alternative to fossil fuels However, efforts must focus on streamlining and simplifying its production in order to make this a reality. The aim of this study was to enrich a cellulolytic community and characterize its soluble end-products and bacterial diversity. The community degraded cellulose in the absence of reducing agent, and appeared to generate anaerobic conditions through oxygen-consuming aerobic respiration. Ethanol and acetate were the major fermentation products and the activity of the community was stable in aerobic and anaerobic media, as well as yeast extract-free aerobic media supplemented with other waste-based nutrient sources. Several community members showed high similarity to Clostridium species, suggesting the presence of some functional redundancy. Reducing agent and yeast extract both represent significant costs in the culturing of cellulolytic, ethanologenic microorganisms. The community described here exhibited this activity in the absence of both.

First steps in assessing microbial involvement in the geochemical evolution of uranium mine tailings : evaluation of iron reduction potential, biofilm formation and community heterogeneity

The high pH (~10) and elevated concentration of metals and oxyanions such as As, Fe, Ni, Mo and Se in the Deilmann tailings management facility (DTMF) presents a highly selective environment for microorganisms. The objective of this study was to assess the potential for metal and ion solubilization by the indigenous mixed microbial community in both optimum (high carbon) and

First steps in assessing microbial involvement in the geochemical evolution of uranium mine tailings : evaluation of iron reduction potential, biofilm formation and community heterogeneity

The high pH (~10) and elevated concentration of metals and oxyanions such as As, Fe, Ni, Mo and Se in the Deilmann tailings management facility (DTMF) presents a highly selective environment for microorganisms. The objective of this study was to assess the potential for metal and ion solubilization by the indigenous mixed microbial community in both optimum (high carbon) and

A Novel Approach to Studying the Problem of Sapronoses (on the Listeria monocytogenes Model)

Introduction: After a long period of non-recognition, sapronoses and saprozoonoses have taken their rightful place in the classification of infectious diseases, while the evolutionary features of these infections remain unclear. New facts related to the specifics of their circulation both in the external environment and in warm-blooded animals are revealed and the possibilities of their existence in hydrobionts and plants, as well as formation of uncultivated forms, etc., are being studied. However, recent studies have demonstrated the possibility of microorganisms to co-exist in certain consortia, interacting with other types of microorganisms of other species. In this regard, research on the issue of sapronosis remains sparse. Our objective was to evaluate the ability of saprotrophic bacteria isolated from soil and marine environment to form multicultural biofilms with Listeria monocytogenes, related to sapronoses, and to determine the nature of their interaction in model experiments. Materials and methods: The research was carried out in 2017–2019 using museum strains of different variants of Listeria monocytogenes from the collection of the the Research Institute of Epidemiology and Microbiology named after G.P. Somov and saprophytic bacteria isolated from marine environment and soil. Biofilms were analyzed by spectrophotometry, and the number of viable cells was determined by the number of colony-forming units in 1 ml (CFU/ml). The results showed that the bacteria of a mixed microbial community living in a biofilm could interact with each other through competition or cooperation. Conclusion: Cooperation between different strains of microorganisms in the soil or marine environment may contribute to a better adaptation and survival of L. monocytogenes, thus posing a potential hazard to the population. This fact highlights the epidemiological significance of the marine and soil environments.

Effects of Sulfamethoxazole on Growth and Antibiotic Resistance of A Natural Microbial Community

Diffuse environmental antibiotic and antibiotic resistance gene contamination is increasing human and animal exposure to these emerging compounds with a consequent risk of reduction in antibiotic effectiveness. The present work investigated the effect of the antibiotic sulfamethoxazole (SMX) on growth and antibiotic resistance genes of a microbial community collected from an anaerobic digestion plant fed with cattle manure. Digestate samples were used as inoculum for concentration-dependent experiments using SMX at various concentrations. The antibiotic concentrations affecting the mixed microbial community in terms of growth and spread of resistant genes (sul1, sul2) were investigated through OD (Optical Density) measures and qPCR assays. Moreover, SMX biodegradation was assessed by LC-MS/MS analysis. The overall results showed that SMX concentrations in the range of those found in the environment did not affect the microbial community growth and did not select for antibiotic-resistant gene (ARG) maintenance or spread. Furthermore, the microorganisms tested were able to degrade SMX in only 24 h. This study confirms the complexity of antibiotic resistance spread in real matrices where different microorganisms coexist and suggests that antibiotic biodegradation needs to be included for fully understanding the resistance phenomena among bacteria.

Evaluation of the Novel Culture-Based AtbFinder Test-System for the Selection of Optimal Antibiotics for Critically Ill Patients With Polymicrobial Infections Within 4 H

For polymicrobial infections, AtbFinder utilizes a novel paradigm of the population response to antibiotics, enabling bacterial growth in the form of a mixed microbial community and selecting the antibiotics targeting not only the principal pathogen, but also those bacteria that support their growth. TGV medium allowed culturing a more diverse set of bacteria from polymicrobial biospecimens, compared with that achieved with the standard media and enabled, already within 4h, accurate selection of the antibiotics that completely eliminated all cultivatable bacteria from clinical samples. In conclusion, AtbFinder system may be a valuable tool in improving antibiotic selection, enabling targeted empirical therapy and accurate antibiotic replacement, which is especially important in high-risk patients.

Effects of maize (Zea mays) genotypes and microbial sources in shaping fall armyworm (Spodoptera frugiperda) gut bacterial communities

Plants can have fundamental roles in shaping bacterial communities associated with insect herbivores. For larval lepidopterans (caterpillars), diet has been shown to be a driving force shaping gut microbial communities, where the gut microbiome of insects feeding on different plant species and genotypes can vary in composition and diversity. In this study, we aimed to better understand the roles of plant genotypes, sources of microbiota, and the host gut environment in structuring bacterial communities. We used multiple maize genotypes and fall armyworm (Spodoptera frugiperda) larvae as models to parse these drivers. We performed a series of experiments using axenic larvae that received a mixed microbial community prepared from frass from larvae that consumed field-grown maize. The new larval recipients were then provided different maize genotypes that were gamma-irradiated to minimize bacteria coming from the plant during feeding. For field-collected maize, there were no differences in community structure, but we did observe differences in gut community membership. In the controlled experiment, the microbial inoculation source, plant genotype, and their interactions impacted the membership and structure of gut bacterial communities. Compared to axenic larvae, fall armyworm larvae that received frass inoculum experienced reduced growth. Our results document the role of microbial sources and plant genotypes in contributing to variation in gut bacterial communities in herbivorous larvae. While more research is needed to shed light on the mechanisms driving this variation, these results provide a method for incorporating greater gut bacterial community complexity into laboratory-reared larvae.