Bacterial Diversity and Bioremediation Potential of the Highly Contaminated Marine Sediments at El-Max District (Egypt, Mediterranean Sea)

Coastal environments worldwide are threatened by the effects of pollution, a risk particularly high in semienclosed basins like the Mediterranean Sea that is poorly studied from bioremediation potential perspective especially in the Southern coast. Here, we investigated the physical, chemical, and microbiological features of hydrocarbon and heavy metals contaminated sediments collected at El-Max bay (Egypt). Molecular and statistical approaches assessing the structure of the sediment-dwelling bacterial communities showed correlations between the composition of bacterial assemblages and the associated environmental parameters. Fifty strains were isolated on mineral media supplemented by 1% crude oil and identified as a diverse range of hydrocarbon-degrading bacteria involved in different successional stages of biodegradation. We screened the collection for biotechnological potential studying biosurfactant production, biofilm formation, and the capability to utilize different hydrocarbons. Some strains were able to grow on multiple hydrocarbons as unique carbon source and presented biosurfactant-like activities and/or capacity to form biofilm and owned genes involved in different detoxification/degradation processes. El-Max sediments represent a promising reservoir of novel bacterial strains adapted to high hydrocarbon contamination loads. The potential of the strains for exploitation for in situ intervention to combat pollution in coastal areas is discussed

A Recent Class of Chemosensory Neurons Developed in Mouse and Rat

In most animal species, the vomeronasal organ ensures the individual recognition of conspecifics, a prerequisite for a successful reproduction. The vomeronasal organ expresses several receptors for pheromone detection. Mouse vomeronasal type-2 receptors (V2Rs) are restricted to the basal neurons of this organ and organized in four families. Family-A, B and D (family ABD) V2Rs are expressed monogenically (one receptor per neuron) and coexpress with either Vmn2r1 or Vmn2r2, two members of family-C V2Rs. Thus, basal neurons are characterized by specific combinations of two V2Rs. To investigate this issue, we raised antibodies against all family-C V2Rs and analyzed their expression pattern. We found that six out of seven family-C V2Rs (Vmn2r2-7) largely coexpressed and that none of the anti-Vmn2r2-7 antibodies significantly stained Vmn2r1 positive neurons. Thus, basal neurons are divided into two complementary subsets. The first subset (Vmn2r1-positive) preferentially coexpresses a distinct group of family-ABD V2Rs, whereas the second subset (Vmn2r2-7-positive) coexpresses the remaining group of V2Rs. Phylogenetic reconstruction and the analysis of genetic loci in various species reveal that receptors expressed by this second neuronal subset are recent branches of the V2R tree exclusively present in mouse and rat. Conversely, V2Rs expressed in Vmn2r1 positive neurons, are phylogenetically ancient and found in most vertebrates including rodents. Noticeably, the more recent neuronal subset expresses a type of Major Histocompatibility Complex genes only found in murine species. These results indicate that the expansion of the V2R repertoire in a murine ancestor occurred with the establishment of a new population of vomeronasal neurons in which coexists the polygenic expression of a recent group of family-C V2Rs (Vmn2r2-7) and the monogenic expression of a recent group of family-ABD V2Rs. This evolutionary innovation could provide a molecular rationale for the exquisite ability in individual recognition and mate choice of murine species

Sequential Anaerobic/Aerobic Microbial Transformation of Chlorinated Ethenes: Use of Sustainable Approaches for Aquifer Decontamination

Chlorinated ethene contamination is a worldwide relevant health issue. In anaerobic aquifers, highly chlorinated ethenes are transformed by microbially-mediated organohalide respiration metabolism. For this reason, in the last few years, bioremediation interventions have been developed and employed in situ for aquifer decontamination. Biostimulation has been demonstrated to be efficient in enhancing organohalide respiration activity. The use of agrifood wastes that replace engineered substrates as biostimulants permits the low carbon impact of bioremediation treatment as part of a circular economy approach. The present work depicts the effects of available bio-based substrates and discusses their efficiency and impact on microbial communities when applied to contaminated aquifers. As a drawback of anaerobic organohalide respiration, there is the accumulation of more toxic lower-chlorinated ethenes. However, compounds such as dichloroethene (DCE) and vinyl chloride (VC) can be mineralized by metabolic and co-metabolic pathways in aerobic conditions. For this reason, sequential anaerobic/aerobic treatments proposed to stimulate the natural biotransformation activity can achieve complete degradation of chlorinated ethenes. The aim of this work is to provide an up-to-date revision of anaerobic/aerobic microbial transformation pathways towards chlorinated ethenes and to discuss their application in real scenarios and futurable microbial bioelectrochemical systems to remediate contaminated aquifers

EFFECTS OF REDUCING SUBSTRATES ADDITION ON CONTAMINATED AQUIFER MICROBIAL POPULATION AND THE DECHLORINATION ACTIVITY

Tetrachloroethene (PCE) and trichloroethene (TCE) (chloroethenes) are intensively used in industrial sector due to their physical and chemical characteristics (low inflammability) that makes them excellent solvents. These compounds are hardly degraded through physical and chemical remediation techniques; but some bacteria can transform them. In anaerobic and reductive conditions, chloroethenes can be dechlorinated through organohalide respiration (OHR) where one atom of chlorine was substituted with a hydrogen atom. This pathway is efficient in dechlorination of highly chlorinated compounds (PCE and TCE), but their daughter compounds (dichloroethene, DCE, and vinyl chloride, VC) are hardly transformed creating an accumulation of these compounds. They are oxidated in aerobic conditions. Chloroethenes are toxic for human being and TCE and VC are carcinogenic. In anaerobic conditions, fermentable substrates can be added to increase reducing power available for OHR bacteria (biostimulation). In the prospective of a more sustainable bioremediation techniques, chose of reducing substrates are focused on food industrial waste that are no longer used with food purposes. In this study two reducing substrates (engineering molasses and tomato peels) were tested to determine their effects on enhancement of OHR activity at laboratory scale. The microcosms were analyzed through monitoring of chloroethenes transformation by GC-MS, and chemical and physical parameters. In addition, through monitoring of dechlorination rate of chloroethenes (GC-MS analysis), and phylogenetic and functional biomarkers (qPCR analysis), the addition of engineering molasses was analyzed at filed scale. The addition of the two substrates effected OHR activity with an increase of dechlorination highly chloroethenes. In the aquifer, biomarkers characteristic of dechlorination pathways were present in high amount (105-106 gene copies L-1). The research was supported by Inail (National Institute for Insurance against Accidents at Work) in BRIC research fundin

Amplified ribosomal DNA restriction analysis for the characterization of <i>Azotobacteraceae</i>: a contribution to the study of these free-living nitrogen-fixing bacteria

A 16S rRNA gene-based fingerprinting method was developed for the identification of Azotobacteraceae and tested onto 48 soil isolates and 28 reference strains belonging to the free-living nitrogen-fixing bacterial group and to the most common species found in soil samples. According to this method, the 16S rRNA gene was amplified using universal primers for Eubacteria and PCR products were subsequently digested with RsaI, HhaI, HpaII, FnuDII, and AluI. The analysis of the restriction profiles obtained showed that the method is able to define a unique species-specific phylotype (SSP) for each of the eight Azotobacteraceae species tested. Cluster analysis was successfully employed for the identification of members of the family Azotobacteraceae, being assignation into species of the isolates confirmed by means of partial 16S rRNA gene sequencing

Dark Fermentation of <i>Arundo donax:</i> Characterization of the Anaerobic Microbial Consortium

The dark fermentation of lignocellulose hydrolysates is a promising process for the production of hydrogen from renewable sources. Nevertheless, hydrogen yields are often lower than those obtained from other carbohydrate sources due to the presence of microbial growth inhibitors in lignocellulose hydrolysates. In this study, a microbial consortium for the production of hydrogen by dark fermentation has been obtained from a wild methanogenic sludge by means of thermal treatments. The consortium has been initially acclimated to a glucose-based medium and then used as inoculum for the fermentation of Arundo donax hydrolysates. Hydrogen yields obtained from fermentation of A. donax hydrolysates were lower than those obtained from glucose fermentation using the same inoculum (0.30 ± 0.05 versus 1.11 ± 0.06 mol of H2 per mol of glucose equivalents). The hydrogen-producing bacteria belonged mainly to the Enterobacteriaceae family in cultures growing on glucose and to Clostridium in those growing on A. donax hydrolysate. In the latter cultures, Lactobacillus outcompeted Enterobacteriaceae, although Clostridium also increased. Lactobacillus outgrowth could account for the lower yields observed in cultures growing on A. donax hydrolysate