Antibiotics at sub-inhibitory concentrations are often found in the environment. Here they could impose selective pressure on bacteria, leading to the selection and dissemination of antibiotic ...resistance, despite being under the inhibitory threshold. The goal of this study was to evaluate the effects of sub-inhibitory concentrations of gentamicin on environmental class 1 integron cassettes in natural river microbial communities. Gentamicin at sub-inhibitory concentrations promoted the integration and selection of gentamicin resistance genes (GmRG) in class 1 integrons after only a one-day exposure. Therefore, sub-inhibitory concentrations of gentamicin induced integron rearrangements, increasing the mobilization potential of gentamicin resistance genes and potentially increasing their dissemination in the environment. This study demonstrates the effects of antibiotics at sub-inhibitory concentrations in the environment and supports concerns about antibiotics as emerging pollutants.
Chitin is the second most produced biopolymer on Earth after cellulose. Chitin degrading enzymes are promising but untapped sources for developing novel industrial biocatalysts. Hidden amongst ...uncultivated micro-organisms, new bacterial enzymes can be discovered and exploited by metagenomic approaches through extensive cloning and screening. Enrichment is also a well-known strategy, as it allows selection of organisms adapted to feed on a specific compound. In this study, we investigated how the soil bacterial community responded to chitin enrichment in a microcosm experiment. An integrative metagenomic approach coupling phylochips and high throughput shotgun pyrosequencing was established in order to assess the taxonomical and functional changes in the soil bacterial community. Results indicate that chitin enrichment leads to an increase of Actinobacteria, γ-proteobacteria and β-proteobacteria suggesting specific selection of chitin degrading bacteria belonging to these classes. Part of enriched bacterial genera were not yet reported to be involved in chitin degradation, like the members from the Micrococcineae sub-order (Actinobacteria). An increase of the observed bacterial diversity was noticed, with detection of specific genera only in chitin treated conditions. The relative proportion of metagenomic sequences related to chitin degradation was significantly increased, even if it represents only a tiny fraction of the sequence diversity found in a soil metagenome.
This study has provided comprehensive insights into the intricate relationship between shear stress and the development, structure, and functionality of electroactive biofilms in Microbial Fuel Cells ...(MFCs). A multichannel microfluidic MFC reactors that created specific shear stress on the anode, were designed for the simultaneous study of multiple flow conditions using the same medium. Then, the evolution of the biofilm growth under different shear stress conditions (1, 5 and 10 mPa) were compared. The taxonomic and functional structure was studied by 16S rRNA gene and metagenomic sequencing and the physical biofilm characteristics were measured via fluorescence microscopy. The results demonstrate the pivotal role of shear stress in influencing the growth kinetics, electrical performance, and physical structure of anodic biofilms. Notably, the selection of specific EAB was observed to be shear stress-dependent, with a marked increase in specific EAB abundance as shear stress increased. The power density, while not directly correlated with the relative abundance of specific or nonspecific EAB, exhibited a strong linear relationship with biofilm coverage. This suggests that factors beyond the microbial composition, potentially including mass transport or electrochemical conditions, might be instrumental in determining electricity production. The functional metagenomic analysis further highlighted the complexities of extracellular electron transfer (EET) mechanisms in electroactive biofilm. While certain genes associated with EET in known species such as Geobacter and Shewanella were identified, the study also examined the limitations of solely relying on genetic markers to infer EET capabilities, emphasizing the need for complementary metaproteomic analyses. This study demonstrates the multifaceted impact of shear stress on electroactive biofilm and paves the way for future investigations aimed at harnessing the potential of electroactive biofilms in microbial fuel cell applications.
Antibiotic resistance, including multiresistance acquisition and dissemination by pathogens, is a critical healthcare issue threatening our management of infectious diseases 1–3. Rapid accumulation ...of resistance phenotypes implies a reservoir of transferable antibiotic resistance gene determinants (ARGDs) selected in response to inhibition of antibiotic concentrations, as found in hospitals 1, 3–5. Antibiotic resistance genes were found in environmental isolates, soil DNA 4–6, secluded caves 6, 7, and permafrost DNA 7, 8. Antibiotics target essential and ubiquitous cell functions, and resistance is a common characteristic of environmental bacteria 8–11. Environmental ARGDs are an abundant reservoir of potentially transferable resistance for pathogens 9–12. Using metagenomic sequences, we show that ARGDs can be detected in all (n = 71) environments analyzed. Soil metagenomes had the most diverse pool of ARGDs. The most common types of resistances found in environmental metagenomes were efflux pumps and genes conferring resistance to vancomycin, tetracycline, or β-lactam antibiotics used in veterinary and human healthcare. Our study describes the diverse and abundant antibiotic resistance genes in nonclinical environments and shows that these genes are not randomly distributed among different environments (e.g., soil, oceans or human feces).
•Antibiotic resistance DNA sequence screening is performed at the environment scale•Antibiotic resistance genes are detected in all ecosystems tested•ARGD distribution in the environment is ecosystem specific
Nesme et al. study show that resistance genes in nonclinical environments (e.g., soil, oceans, or human feces) are abundant and distributed depending on the habitat type. Soil is the most diverse environment, and genes found in the human gut are also detected in soil, emphasizing its resistance gene reservoir role for pathogens.
•In vial addition of salt, limiting the presence of salts in the LC-MS/MS system.•A sample preparation reduced to a simple addition of salt in the vial.•Low matrix effect allowing external ...calibration with solvent standards.
Aminoglycosides are mostly used as veterinary antibiotics. In France, their consumption accounts for about 10% of all prescribed animal medicine. Due to their high polarity nature (log Kow < -3), they require chromatographic separation by hydrophilic interaction liquid chromatography or ion-pairing chromatography. This study presents the development of an ion pairing liquid chromatography with alkanesulfonates coupled to tandem mass spectrometry for the analysis of 10 aminoglycosides (spectinomycin, streptomycin, dihydrostreptomycin, kanamycin, apramycin, gentamicin, neomycin and sisomicin) in wastewater samples. The novelty of this method lies in the addition of the ion paring salt directly and only into the sample vial and not in the mobile phase, lowering the amount of salt added and consequently reducing signal inhibition. The optimized method was validated and showed satisfactory resolution, performances suitable with the analysis of aminoglycosides in wastewater samples, with limits of quantifications less than 10 ng/mL for most of the compounds, low matrix effects, high accuracy (85%-115% recoveries) and reproducibility (2%-12%RSD). It was then applied successfully to raw and treated wastewater samples.
Low electrical conductivity of carbon materials is a source of potential loss for large carbonaceous electrode surfaces of MFCs due to the long distance traveled by electrons to the collector. In ...this paper, different configurations of titanium current collectors were used to connect large surfaces of carbon cloth anodes. The current collectors had different distances and contact areas to the anode. For the same anode surface (490 cm
), increasing the contact area from 28 cm
to 70 cm
enhanced power output from 58 mW·m
to 107 mW·m
. For the same contact area (28 cm
), decreasing the maximal distance of current collectors to anodes from 16.5 cm to 7.75 cm slightly increased power output from 50 mW·m
to 58 mW·m
. Molecular biology characterization (qPCR and 16S rRNA gene sequencing) of anodic bacterial communities indicated that the
number was not correlated with power. Moreover,
and
abundance increased with the drop in potential on the anode and with the presence of fermentative microorganisms. Electrochemical impedance spectroscopy (EIS) showed that biofilm resistance decreased with the abundance of electroactive bacteria. All these results showed that the electrical gradient arising from collectors shapes microbial communities. Consequently, current collectors influence the performance of carbon-based anodes for full-scale MFC applications.
Abstract
Polar regions are increasingly exposed to ultraviolet light due to ozone depletion. Snowpacks contain photochemically active particles that, when irradiated, can lead to the production and ...accumulation of reactive species that can induce oxidative stress on snow microorganisms. This could generate a selective pressure on snowpack bacteria. In this study, snow microcosms were buried in a snowpack at Ny-Ålesund (Svalbard), either exposed to solar irradiation or incubated in the dark for 10 days, and the bacterial response to solar irradiation was evaluated in situ using a metagenomics approach. Solar irradiation induced a significant decrease in bacterial abundance and richness. Genes involved in glutathione synthesis, sulphur metabolism, and multidrug efflux were significantly enriched in the light, whereas genes related to cell wall assembly and nutrient uptake were more abundant in the dark. This is the first study demonstrating the response of snow bacterial communities to solar irradiation in situ and providing insights into the mechanisms involved. Our research shows that polar sun irradiation is sufficiently intense to impose a selective pressure on snow bacteria and supports the concern that increased ultraviolet exposure due to anthropogenic activities and climatic change could drive critical changes in the structure and functioning of snow bacterial communities.
Genes involved in the response to oxidative stress were significantly enriched in snow exposed to solar irradiation, whereas genes related to cell wall assembly and nutrient uptake were more abundant in the dark.
In order to optimize energy production in MFCs, a better understanding of anodic communities is essential. Our objective was to determine the taxonomic structure of the bacterial communities present ...at the surface of the anode during the formation and development of electro-active biofilms in MFCs inoculated with fresh primary clarifier overflow. Quantitative microbial community dynamics were evaluated as a function of time and electrical performance using 16S rRNA gene-based phylogenetic microarrays and flow cytometry. Results show that the bacterial community stabilized partially but not completely when voltage output was stable. Geobacter appeared to be the predominant genus, whose growth was associated with voltage, while some other genus still developed or declined after the voltage stabilization. Flow cytometry revealed that some genus showing a decreasing proportional fluorescence intensity over time were still actively respiring bacteria, and thus, active albeit minor members of the biofilm. Finally, this study shows that anodic biofilm selection and maturation is still occurring after more than 20 days of operation and over ten days after voltage is stabilized.
•Anodic biofilm microbial communities continue to evolve even after voltage has stabilized.•Even minor (low proportion) members of the biofilm are active in the mature MFC.•Geobacter populations correlated with voltage increase, while other microorganisms were driven by other parameters.
In this study, the biodegradability of trifluoroacetate (TFA), perfluorooctanoic acid (PFOA), and perfluoro-2-methyl-3-oxahexanoic acid (HFPO-DA) by a native microbial community was evaluated over a ...10-month incubation period. The observed microbial defluorination ratios and removal efficiency were 3.46 ( ± 2.73) % and 8.03 ( ± 3.03) %, 8.44 ( ± 1.88) % and 13.52 ( ± 4.96) %, 3.02 ( ± 0.62) % and 5.45 ( ± 2.99) % for TFA, PFOA and HFPO-DA, respectively. The biodegradation intermediate products, TFA and pentafluoropropionic acid (PFA), of PFOA and HFPO-DA were detected in their biodegradation treatment groups. Furthermore, the concentrations of the PFOA metabolites, perfluorohexanoic acid (PFHxA) and perfluoroheptanoic acid (PFHpA), in the aqueous solutions after incubation were quantified to be 0.21 and 4.14 µg/L. TFA, PFOA and HFPO-DA significantly reduced the microbial diversity and changed the structure of the community. The co-occurrence network analysis showed that low abundance species, such as Flexilinea flocculi, Bacteriovorax stolpii, and g_Sphingomonas, are positively correlated with the generation of fluoride ion, implying their potential collaborative functions contributing to the observed biodefluorination. The findings in this study can provide insights for the biodegradation of perfluoroalkyl carboxylic acids and their emerging alternatives by indigenous microorganisms in the environment.
Display omitted
•The biodegradation of PFASs by a native microbial consortium was assessed under anoxic condition.•Fluoride production was confirmed in the biodegradation of TFA, PFOA and HFPO-DA.•Intermediate products of PFOA and HFPO-DA biodegradation were identified and quantitatively determined.•Species from the phyla of Nitrospirae, Proteobacteria, Actinobacteria, and Chloroflexi might be responsible for biodefluorination.
Microorganisms are ubiquitous in the atmosphere, and some airborne microbial
cells were shown to be particularly resistant to atmospheric physical and
chemical conditions (e.g., ultraviolet – UV – ...radiation, desiccation and the presence of radicals). In
addition to surviving, some cultivable microorganisms of airborne origin
were shown to be able to grow on atmospheric chemicals in laboratory
experiments. Metagenomic investigations have been used to identify specific
signatures of microbial functional potential in different ecosystems. We
conducted a comparative metagenomic study on the overall microbial
functional potential and specific metabolic and stress-related microbial
functions of atmospheric microorganisms in order to determine whether
airborne microbial communities possess an atmosphere-specific functional
potential signature as compared to other ecosystems (i.e., soil, sediment, snow, feces, surface seawater etc.). In the absence of a specific atmospheric signature, the atmospheric samples collected at nine sites around the world were similar to their underlying ecosystems. In addition, atmospheric samples were characterized by a relatively high proportion of fungi. The higher proportion of sequences annotated as genes involved in stress-related functions (i.e., functions related to the response to desiccation, UV radiation, oxidative stress etc.) resulted in part from the high concentrations of fungi that might resist and survive atmospheric physical stress better than bacteria.
PDF
