Bacterial biofilms on medical masks disposed in the marine environment: a hotspot of biological and functional diversity.

The present paper was aimed at investigating the role of disposable medical masks as a substrate for microbial biofilm growth and for the selection of specific microbial traits in highly impacted marine environments. In this view, we have immerged masks in a coastal area affected by a continuous input of artisanal fishery wastes and hydrocarbons pollution caused by intense maritime traffic. Masks maintained one month in the field were colonized by a bacterial community significantly different from that detected in the natural matrices from the same areas (seawater and sediments). The masks served as a viable substrate for the growth and enrichment of phototrophic microorganisms (Oxyphotobacteria), as well as Ruminococcaceae, Gracilibacteria, and Holophageae. In a follow-up investigation, masks previously colonized in the field were transferred in lab-scale microcosms which were supplemented with hydrocarbons and which contained also a piece of a virgin mask. After one month, a shift in the community composition, likely triggered by hydrocarbons addition, was observed in the previously colonized mask, with signatures characteristic of hydrocarbon-degrading microbial groups. Such hydrocarbon-degrading bacteria were also found to colonize the virgin mask. Remarkably, SEM micrographs provided indications of the occurrence of morphological modifications of the surface components of the virgin masks colonized by hydrocarbonoclastic bacteria. Overall, for the first time, we have demonstrated the potential risk for human and animal health determined by the uncorrected disposal of masks which are suitable substrates for pathogens colonization, permanence and spreading. Moreover, we have herein strengthened the knowledge on the role of hydrocarbon-degrading bacteria in the colonization and modification of fossil-based plastics in marine environment.

Correlations between maximum reductive dechlorination rates and specific biomass parameters in Dehalococcoides mccartyi consortia enriched on chloroethenes PCE, TCE and cis-1,2-DCE.

One of the challenges to implementing the modeling of the biological reductive dechlorination (RD) process is the evaluation of biological parameters that represent the abundance/activity levels of the microorganisms involved in the biodegradation of chloroethenes. Here we report a combined analysis of kinetic and specific biomass parameters conducted on three dechlorinating consortia enriched on PCE, TCE and cis-1,2-DCE. In these consortia, Dehalococcoides mccartyi (Dhc) represented ≥70% of the bacterial population identified via 16S rRNA gene amplicon sequencing. Quantitative biomolecular methods were used to generate specific biomass parameters targeting either the Dhc population (16S rRNA genes or cells) or specific genes encoding RD process-involved reductive dehalogenases. The correlation factor between the abundance of active Dhc cells or tceA gene copies and maximum RD rates allowed to predict an increment of 7E+09 of active Dhc cells or 5E+09 tceA gene copies/L under controlled conditions. Diversely, the utilization of gene transcripts as biomass parameters for RD modeling did not provide reliable correlations with kinetic performances. This study provides valuable insights for further modeling of the RD process through the utilization of specific biomass parameters.

Marine hydrocarbon-degrading bacteria breakdown poly(ethylene terephthalate) (PET).

Pollution of aquatic ecosystems by plastic wastes poses severe environmental and health problems and has prompted scientific investigations on the fate and factors contributing to the modification of plastics in the marine environment. Here, we investigated, by means of microcosm studies, the role of hydrocarbon-degrading bacteria in the degradation of poly(ethylene terephthalate) (PET), the main constituents of plastic bottles, in the marine environment. To this aim, different bacterial consortia, previously acclimated to representative hydrocarbons fractions namely, tetradecane (aliphatic fraction), diesel (mixture of hydrocarbons), and naphthalene/phenantrene (aromatic fraction), were used as inocula of microcosm experiments, in order to identify peculiar specialization in poly(ethylene terephthalate) degradation. Upon formation of a mature biofilm on the surface of poly(ethylene terephthalate) films, the bacterial biodiversity and degradation efficiency of each selected consortium was analyzed. Notably, significant differences on biofilm biodiversity were observed with distinctive hydrocarbons-degraders being enriched on poly(ethylene terephthalate) surface, such as Alcanivorax, Hyphomonas, and Cycloclasticus species. Interestingly, ATR-FTIR analyses, supported by SEM and water contact angle measurements, revealed major alterations of the surface chemistry and morphology of PET films, mainly driven by the bacterial consortia enriched on tetradecane and diesel. Distinctive signatures of microbial activity were the alteration of the FTIR spectra as a consequence of PET chain scission through the hydrolysis of the ester bond, the increased sample hydrophobicity as well as the formation of small cracks and cavities on the surface of the film. In conclusion, our study demonstrates for the first time that hydrocarbons-degrading marine bacteria have the potential to degrade poly(ethylene terephthalate), although their degradative activity could potentially trigger the formation of harmful microplastics in the marine environment.

Combining electrokinetic transport and bioremediation for enhanced removal of crude oil from contaminated marine sediments: Results of a long-term, mesocosm-scale experiment.

Marine sediments represent an important sink of harmful petroleum hydrocarbons after an accidental oil spill. Electrobioremediation techniques, which combine electrokinetic transport and biodegradation processes, represent an emerging technological platform for a sustainable remediation of contaminated sediments. Here, we describe the results of a long-term mesocosm-scale electrobioremediation experiment for the treatment of marine sediments contaminated by crude oil. A dimensionally stable anode and a stainless-steel mesh cathode were employed to drive seawater electrolysis at a fixed current density of 11 A/m2. This approach allowed establishing conditions conducive to contaminants biodegradation, as confirmed by the enrichment of Alcanivorax borkumensis cells harboring the alkB-gene and other aerobic hydrocarbonoclastic bacteria. Oil chemistry analyses indicated that aromatic hydrocarbons were primarily removed from the sediment via electroosmosis and low molecular weight alkanes (nC6 to nC10) via biodegradation.

Field distribution and activity of chlorinated solvents degrading bacteria by combining CARD-FISH and real time PCR.

Nowadays several advanced molecular techniques are applied for quantifying bacteria involved in contaminant degradation processes. However, despite the fact that significant efforts have been taken to make these tools more reliable and specific, their application for the analysis of field samples is hardly ever applied. In this study, a combination of three methods (CARD-FISH, qPCR and RT-qPCR) was successfully applied to evaluate the distribution and the activity of known chlorinated solvent dechlorinating bacteria in a contaminated site where no remedial actions have been undertaken. CAtalysed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) specifically provided the cell densities of known dechlorinating bacteria and was found to be more sensitive than quantitative PCR (qPCR) for the quantification of 'Dehalococcoides' cell numbers in the aquifer. Among the screened dechlorinators, 'Dehalococcoides' spp. were mainly found and nearly homogenously distributed in the aquifers at concentrations ranging from 8.1×10(5)±1.2×10(5) to 2.5×10(7)±5.6×10(6)cells per liter of groundwater (with a relative abundance out of the total Bacteria of 0.7-15%). Further, the dechlorination potentialities of 'Dehalococcoides' species living in the aquifer were evaluated by analyzing the abundance and the expression of 16S rRNA genes and reductive dehalogenase (RDase) encoding functional genes by qPCR and Reverse Transcription qPCR (RT-qPCR). 'Dehalococcoides'tceA gene, known to be associated to strains capable of reducing chlorinated solvents beyond cis-DCE, was found and expressed in the field. Overall, this study proved the existence of a well-established dechlorinating microbial community able to use contaminants as substrates for their metabolic activity and indicated the occurrence of reductive dechlorination at the site.

Use of poly-beta-hydroxy-butyrate as a slow-release electron donor for the microbial reductive dechlorination of TCE.

In situ anaerobic reductive dechlorination, using slow-release electron donors, is emerging as an effective and sustainable (low-cost and low-maintenance) technology to remediate aquifers contaminated by chloroethenes. In the present study, we investigated the use of poly-beta-hydroxy-butyrate (PHB), a fully biodegradable polymer, as a slow-release source of hydrogen and acetate for the reductive dechlorination of trichloroethene (TCE). Results of this study indicated that TCE dechlorination in PHB-amended microcosms was 2.3-times higher than in non-amended controls. This higher activity was explained by a higher H(2) level in PHB-amended microcosms. As usual, acetate was the major sink (approximately 90%) of reducing equivalents available from PHB degradation, whereas no acetotrophic dechlorination was observed.

Anaerobic transformation of tetrachloroethane, perchloroethylene, and their mixtures by mixed-cultures enriched from contaminated soils and sediments.

The focus of this research was to investigate the anaerobic transformation of tetrachloroethane (TeCA), perchloroethylene (PCE), and their mixtures by mixed cultures enriched from contaminated soils or sediments. Batch transformation studies were conducted using TeCA (60 microM), PCE (60 microM), or TeCA + PCE (each added at 60 microM) as electron acceptor(s) and H2 + acetate (each added at 3 mM) or butyrate (3mM) as electron donor(s). A Dehalococcoides spp.-containing, sediment-enrichment dechlorinated PCE rapidly to ethene (ETH) but slowly and incompletely dechlorinated TeCA. Moreover, when present in mixture with PCE, TeCA disrupted the ability of Dehalococcoides to dechlorinate vinyl chloride. In contrast, the soil-enrichment culture was able to completely dechlorinate TeCA and PCE to ETH, both when added as single contaminants and when added as a mixture.

Detection and quantitative estimation of Dehalococcoides spp. in a dechlorinating bioreactor by a combination of fluorescent in situ hybridisation (FISH) and kinetic analysis.

The unique capacity of Dehalococcoides ethenogenes of completely dechlorinating the common groundwater pollutant tetrachloroethene (PCE) to the harmless ethene makes this microorganism very attractive for application in natural or engineered bioremediation systems. In this study, the qualitative and quantitative determination of Dehalococcoides spp. in a lab-scale bioreactor was performed based on the combination of fluorescent in situ hybridisation (FISH) for specific detection, and kinetic batch tests at non-limiting hydrogen and PCE concentration for quantitative determination. The dechlorinating bioreactor was operated at a high and constant PCE loading rate of 255 micromol PCE [g volatile suspended solids (VSS)](-1) day(-1). Pale coccoid cells resembling the distinctive morphotype of D. ethenogenes were present in the microbial culture. These cocci hybridised with both eubacterial probes and the Dhe1259t probe recently designed for detecting Dehalococcoides spp. Positive hybridisation was also observed when the DHC1377 reverse primer was used as a specific probe and applied to the dechlorinating microbial consortium. The maximum dechlorination rate obtained under non-limiting hydrogen and PCE concentrations was 3.22 +/- 0.08 mmol Cl(-) l(-1 )day(-1). From the specific activity of D. ethenogenes [i.e. 0.055 +/- 0.008 mmol Cl(-) (mg VSS)(-1) day(-1)], as reported from pure culture study, this observed maximum rate corresponded to a concentration of this bacterium in the mixed liquor of the bioreactor of 59.0+/-10.4 mg VSS.l(-1) (41.5+/-11.2% of overall VSS). This calculated relative abundance of D. ethenogenes was in agreement with the percentage of methanol (in terms of reducing equivalents) channeled to reductive dechlorination (approximately 30%) supporting the assumption that most reductive dechlorination was actually due to this microorganism.