Sodium azide (NaN3) was evaluated as inhibitor of microbial growth and activity in marine sediment resuspensions by monitoring the abundance of free-living and sessile bacteria using both flow ...cytometry and qPCR methods. Results show that 50mM of NaN3 strongly inhibits bacterial growth under natural and enriched resource conditions.
•NaN3 efficiency on planktonic and sessile microorganisms depends on concentration and resource availability.•Under natural resource conditions 50mM NaN3 inhibits microbial growth and activity.•Under enhanced resource condition 5mM NaN3 only reduced microbial growth and activity.•Under enhanced resource condition 50mM NaN3 inhibited the growth of sessile bacteria for 11days.•Faint planktonic growth persisted with enhanced resource conditions and 50mM NaN3.
Denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR (qPCR) were successfully developed to monitor functional aoxB genes as markers of aerobic arsenite oxidizers. DGGE ...profiles showed a shift in the structure of the aoxB-carrying bacterial population, composed of members of the Alpha-, Beta- and Gammaproteobacteria, depending on arsenic (As) and Eh levels in Upper Isle River Basin waters. The highest aoxB gene densities were found in the most As-polluted oxic surface waters but without any significant correlation with environmental factors. Arsenite oxidizers seem to play a key role in As mobility in As-impacted waters.
Cigarette butts are the most common plastic form of litter found in the marine coast, threatening the quality of the seawater and marine life. However, the impact of cigarette butts known to contain ...toxic chemicals has been investigated to date in very few marine species. This study aimed to evaluate the effects of cigarette filters (smoked or unsmoked) on the microbial diversity inhabiting coastal sediments by high-throughput sequencing of the 16S rRNA genes. Both bacterial structure and metals distribution were impacted by cigarette filter addition in laboratory sediment experiments, compared to control sediment incubations without filter. Both smoked and unsmoked cigarette filters decreased pH and dissolved Cd, Mo and V concentrations in marine sediment incubations, while they increased dissolved Fe, Mn, Zn levels in the surrounding environment. Smoked filters dramatically decreased the relative abundance of the phyla Bacteroidetes and Cyanobacteria, while the members of the phyla Gammaproteobacteria, Firmicutes and Thermotogae were enriched by smoked filters in marine sediments. Bacterial taxa associated with deep marine environments or hydrothermal seep fields were selected by smoked cigarette filters. This study demonstrated for the first time the microbial community changes and impacts from toxic cigarette filters in coastal marine sediments.
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•Cigarette butts are the most littered plastic item in the world.•Cigarette filters changed the microbial diversity in coastal sediment.•Cigarette filters decreased pH and dissolved Cd, Mo and V levels in seawater.•Cigarette filters increased dissolved Fe, Mn, Zn levels in surrounding environment.•Smoked filters selected bacteria related to deep and hydrothermal ecosystems.
Serpentinite-hosted systems are amongst the most challenging environments for life on Earth. Serpentinization, a geochemical alteration of exposed ultramafic rock, produces hydrothermal fluids ...enriched in abiotically derived hydrogen (H
), methane (CH
), and small organic molecules. The hyperalkaline pH of these fluids poses a great challenge for metabolic energy and nutrient acquisition, curbing the cellular membrane potential and limiting electron acceptor, carbon, and phosphorous availability. Nevertheless, serpentinization supports the growth of diverse microbial communities whose metabolic make-up might shed light on the beginning of life on Earth and potentially elsewhere. Here, we outline current hypotheses on metabolic energy production, carbon fixation, and nutrient acquisition in serpentinizing environments. A taxonomic survey is performed for each important metabolic function, highlighting potential key players such as H
and CH
cycling
,
,
,
, and novel candidate phyla. Methodological biases of the available data and future approaches are discussed.
A new primer set was designed to specifically amplify ca. 1,100 bp of aoxB genes encoding the As(III) oxidase catalytic subunit from taxonomically diverse aerobic As(III)-oxidizing bacteria. ...Comparative analysis of AoxB protein sequences showed variable conservation levels and highlighted the conservation of essential amino acids and structural motifs. AoxB phylogeny of pure strains showed well-discriminated taxonomic groups and was similar to 16S rRNA phylogeny. Alphaproteobacteria-, Betaproteobacteria-, and Gammaproteobacteria-related sequences were retrieved from environmental surveys, demonstrating their prevalence in mesophilic As-contaminated soils. Our study underlines the usefulness of the aoxB gene as a functional marker of aerobic As(III) oxidizers.
We investigated the efficiency of a benthic diatom-associated bacteria in removing benzo(a)pyrene (BaP) and fluoranthene (Flt). The diatom, isolated from a PAH-contaminated sediment of the Bizerte ...Lagoon (Tunisia), was exposed in axenic and non-axenic cultures to PAHs over 7 days. The diversity of the associated bacteria, both attached (AB) and free-living bacteria (FB), was analyzed by the 16S rRNA amplicon sequencing. The diatom, which maintained continuous growth under PAH treatments, was able to accumulate BaP and Flt, with different efficiencies between axenic and non-axenic cultures. Biodegradation, which constituted the main process for PAH elimination, was enhanced in the presence of bacteria, indicating the co-metabolic synergy of microalgae and associated bacteria in removing BaP and Flt. Diatom and bacteria showed different capacities in the degradation of BaP and Flt. Nitzschia sp. harbored bacterial communities with a distinct composition between attached and free-living bacteria. The AB fraction exhibited higher diversity and abundance relative to FB, while the FB fraction contained genera with the known ability of PAH degradation, such as Marivita, Erythrobacter, and Alcaligenes. Moreover, strains of Staphylococcus and Micrococcus, isolated from the FB community, showed the capacity to grow in the presence of crude oil. These results suggest that a “benthic Nitzschia sp.-associated hydrocarbon-degrading bacteria” consortium can be applied in the bioremediation of PAH-contaminated sites.
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•An indigenous benthic diatom accumulated BaP and Flt, but biodegradation played the main role in the removal of PAH.•The biodegradation was enhanced by the presence of the diatom and its associated bacteria.•The diatom harbored bacterial genera identified as potential PAH degraders.•Strains isolated from the associated bacteria were able to grow in the presence of crude oil.
The southeastern part of New Caledonia main island (Grande Terre) is the location of a large ophiolitic formation that hosts several hyperalkaline springs discharging high pH (∼11) and warm (<40°C) ...fluids enriched in methane (CH
) and hydrogen (H
). These waters are produced by the serpentinization of the ultrabasic rock formations. Molecular surveys had previously revealed the prokaryotic diversity of some of these New Caledonian springs, especially from the submarine chimneys of Prony Bay hydrothermal field. Here we investigate the microbial community of hyperalkaline waters from on-land springs and their relationships with elevated concentrations of dissolved H
(21.1-721.3 μmol/L) and CH
(153.0-376.6 μmol/L). 16S rRNA gene analyses (metabarcoding and qPCR) provided evidence of abundant and diverse prokaryotic communities inhabiting hyperalkaline fluids at all the collected springs. The abundance of prokaryotes was positively correlated to the H
/CH
ratio. Prokaryotes consisted mainly of bacteria that use H
as an energy source, such as microaerophilic
/
(detected in all sources on land) or anaerobic sulfate-reducing
, which were exclusively found in the most reducing (E
ref H
∼ -700 mV) and the most H
-enriched waters discharging at the intertidal spring of the Bain des Japonais. The relative abundance of a specific group of uncultured Methanosarcinales that thrive in serpentinization-driven ecosystems emitting H
, considered potential H
-consuming methanogens, was positively correlated with CH
concentrations, and negatively correlated to the relative abundance of methylotrophic Gammaproteobacteria. Firmicutes were also numerous in hyperalkaline waters, and their relative abundance (e.g.,
or
) was proportional to the dissolved H
concentrations, but their role in the H
budget remains to be assessed. The prokaryotic communities thriving in New Caledonia hyperalkaline waters are similar to those found in other serpentinite-hosted high-pH waters worldwide, such as Lost City (North Atlantic) and The Cedars (California).
Both industrial effluent discharge and the resuspension of contaminated marine sediments are important sources of trace metals in seawater which potentially affect marine ecosystems. The aim of this ...study was to evaluate the impact of the industrial wastewaters having acidic pH (2-3) and containing trace metals on microbial diversity in the coastal ecosystem of the Gulf of Gabès (Tunisia, southern Mediterranean Sea) subjected to resuspension events of marine sediments. Four trace elements (As, Cd, U, and V) were monitored during 10-day sediment resuspension experiments. The highest enrichment in the seawater dissolved phase was observed for Cd followed by U, V, and As. Cd remobilization was improved by indigenous microbial community, while U release was mainly abiotic. Acidic effluent addition impacted both trace metal distribution and microbial diversity, particularly that of the abundant phylum
. Members of the order
were enriched from sediment in natural seawater (initial pH > 8), while the family
was favored by acidified seawater (initial pH < 8). Some
members were identified as dominant species in both initial sediment and experiments with acidic wastewater, in which their relative abundance increased with increasing dissolved Cd levels. It could be therefore possible to consider them as bioindicators of metal pollution and/or acidification in marine ecosystems.
Dark fermentation using mixed cultures is an attractive biological process for producing hydrogen (H2) from lignocellulosic biomass at a low cost. Physicochemical pretreatment is generally used to ...convert lignocellulosic materials into monosaccharides. However, the processes also involved release degradation byproducts which can, in turn, inhibit microbial growth and metabolism and, hence, impact substrate conversion. In this study, the impact on H2 production of lignocellulose-derived compounds (i.e. furan derivatives, phenolic compounds and lignins) was assessed along with their effect on bacterial communities and metabolisms. Batch tests were carried out using xylose as model substrate (1.67molH2molxylose−1 in the control test). All the putative inhibitory compounds showed a significant negative impact on H2 production performance (ranging from 0.34 to 1.39molH2molxylose−1). The H2 yields were impacted more strongly by furan derivatives (0.40–0.51molH2molxylose−1) than by phenolic compounds (1.28–1.39molH2molxylose−1). Except for the batch tests supplemented with lignins, the lag phase was shorter for inhibitors having the highest molecular weight (8 days versus 22 days for the lowest MW). Variability of the lag phase was clearly related to a shift in bacterial community structure, as shown by multivariate ordination statistics. The decrease in H2 yield was associated with a decrease in the relative abundance of several H2-producing clostridial species. Interestingly, Clostridium beijerinkii was found to be more resistant to the inhibitors, making this bacterium an ideal candidate for H2 production from hydrolyzates of lignocellulosic biomass.
► Lignocellulosic-derived compounds inhibited H2 production performances of mixed cultures. ► The H2 yields were more impacted by furan derivatives than phenolic compounds. ► The lag-phase time was negatively correlated to molecular mass of inhibitors. ► H2 production was related to different clostridial species and metabolic routes.
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