Genome-Wide Patterns of Sequence Divergence of Protein-Coding Genes Between Drosophila buzzatii and D. mojavensis.

Evolutionary rates for protein-coding genes are determined not only by natural selection but also by multiple genomic factors including mutation rates, recombination, gene expression levels, and chromosomal location. To investigate the joint effects of different genomic determinants on protein evolution, we compared the coding sequences of 9017 single-copy orthologs between 2 cactophilic species from the Drosophila subgenus, Drosophila mojavensis and D. buzzatii, whose genomes have been previously sequenced. We assessed the impact of 7 genomic determinants, that is, chromosome type, recombination, chromosomal inversions, expression breadth, expression level, gene length, and the number of exons, on divergence rates of protein-coding genes to understand patterns of evolutionary variation. Integrative analysis of these factors revealed that 1) X-linked and autosomal genes evolve at significantly different rates in agreement with the faster-X hypothesis, 2) genes located on the dot chromosome and pericentromeric regions have higher divergence rates, 3) genes located at chromosomes with more fixed inversions have higher pairwise divergence than those located at nearly collinear chromosomes, and 4) gene expression patterns can be considered the strongest determinant of protein evolution. In addition, the number of exons and protein length had a significant effect on pairwise divergence at synonymous sites. All in all, our results show the relative importance of each genomic factor on the rates of protein evolution and functional constraint in these 2 cactophilic Drosophila species.

Computational Sequence Analysis of Inversion Breakpoint Regions in the Cactophilic Drosophila mojavensis Lineage.

We investigated rates of chromosomal evolution in Drosophila mojavensis using whole-genome sequence information from D. mojavensis, Drosophila buzzatii, and Drosophila virilis. Drosophila mojavensis is a cactophilic species of the repleta group living under extreme ecological conditions in the deserts of the Southwestern United States and Northwestern México. The genome of D. buzzatii, another member of the repleta group, was recently sequenced and the largest scaffolds anchored to all chromosomes using diverse procedures. Chromosome organization between D. mojavensis and D. buzzatii was compared using MUMmer and GRIMM software. Our results corroborate previous cytological analyses that indicated chromosome 2 differed between these 2 species by 10 inversions, chromosomes X and 5 differed by one inversion each, and chromosome 4 was homosequential. In contrast, we found that chromosome 3 differed by 5 inversions instead of the expected 2 that were previously inferred by cytological analyses. Thirteen of these inversions occurred in the D. mojavensis lineage: 12 are fixed and one of them is a polymorphic inversion previously described in populations from Sonora and Baja California, México. We previously investigated the breakpoints of chromosome 2 inversions fixed in D. mojavensis. Here we characterized the breakpoint regions of the 5 inversions found in chromosome 3 in order to infer the molecular mechanism that generated each inversion and its putative functional consequences. Overall, our results reveal a number of gene alterations at the inversion breakpoints with putative adaptive consequences that point to natural selection as the cause for fast chromosomal evolution in D. mojavensis.

Concurrent Duplication of Drosophila Cid and Cenp-C Genes Resulted in Accelerated Evolution and Male Germline-Biased Expression of the New Copies.

Despite their essential role in the process of chromosome segregation in eukaryotes, kinetochore proteins are highly diverse across species, being lost, duplicated, created, or diversified during evolution. Based on comparative genomics, the duplication of the inner kinetochore proteins CenH3 and Cenp-C, which are interdependent in their roles of establishing centromere identity and function, can be said to be rare in animals. Surprisingly, the Drosophila CenH3 homolog Cid underwent four independent duplication events during evolution. Particularly interesting are the highly diverged Cid1 and Cid5 paralogs of the Drosophila subgenus, which are probably present in over one thousand species. Given that CenH3 and Cenp-C likely co-evolve as a functional unit, we investigated the molecular evolution of Cenp-C in species of Drosophila. We report yet another Cid duplication (leading to Cid6) within the Drosophila subgenus and show that not only Cid, but also Cenp-C is duplicated in the entire subgenus. The Cenp-C paralogs, which we named Cenp-C1 and Cenp-C2, are highly divergent. Both Cenp-C1 and Cenp-C2 retain key motifs involved in centromere localization and function, while some functional motifs are conserved in an alternate manner between the paralogs. Interestingly, both Cid5 and Cenp-C2 are male germline-biased and evolved adaptively. However, it is currently unclear if the paralogs subfunctionalized or if the new copies acquired a new function. Our findings point towards a specific inner kinetochore composition in a specific context (i.e., spermatogenesis), which could prove valuable for the understanding of how the extensive kinetochore diversity is related to essential cellular functions.

Exploration of the Drosophila buzzatii transposable element content suggests underestimation of repeats in Drosophila genomes.

BACKGROUND: Many new Drosophila genomes have been sequenced in recent years using new-generation sequencing platforms and assembly methods. Transposable elements (TEs), being repetitive sequences, are often misassembled, especially in the genomes sequenced with short reads. Consequently, the mobile fraction of many of the new genomes has not been analyzed in detail or compared with that of other genomes sequenced with different methods, which could shed light into the understanding of genome and TE evolution. Here we compare the TE content of three genomes: D. buzzatii st-1, j-19, and D. mojavensis. RESULTS: We have sequenced a new D. buzzatii genome (j-19) that complements the D. buzzatii reference genome (st-1) already published, and compared their TE contents with that of D. mojavensis. We found an underestimation of TE sequences in Drosophila genus NGS-genomes when compared to Sanger-genomes. To be able to compare genomes sequenced with different technologies, we developed a coverage-based method and applied it to the D. buzzatii st-1 and j-19 genome. Between 10.85 and 11.16 % of the D. buzzatii st-1 genome is made up of TEs, between 7 and 7,5 % of D. buzzatii j-19 genome, while TEs represent 15.35 % of the D. mojavensis genome. Helitrons are the most abundant order in the three genomes. CONCLUSIONS: TEs in D. buzzatii are less abundant than in D. mojavensis, as expected according to the genome size and TE content positive correlation. However, TEs alone do not explain the genome size difference. TEs accumulate in the dot chromosomes and proximal regions of D. buzzatii and D. mojavensis chromosomes. We also report a significantly higher TE density in D. buzzatii and D. mojavensis X chromosomes, which is not expected under the current models. Our easy-to-use correction method allowed us to identify recently active families in D. buzzatii st-1 belonging to the LTR-retrotransposon superfamily Gypsy.

Effectiveness and risk factors for virological outcome of darunavir-based therapy for treatment-experienced HIV-infected patients.

OBJECTIVE: We evaluated the effectiveness of darunavir (DRV) treatment plus an optimized background regimen in 120 HIV-1 treatment-experienced patients. DESIGN: Retrospective cohort, multicenter study. METHODS: Adults >16 years with virological treatment failure starting therapy with a DRV-containing regimen were included. Effectiveness was evaluated as the percentage of patients with an undetectable HIV-1 RNA viral load (<50 and <200 copies/mL) after 48 weeks, and changes in CD4+ cell counts. We evaluated the risk factors associated with treatment failure. RESULTS: Of the cohort, 83 % were men with a median age of 45 years (interquartile range, IQR 40-51). They had experienced treatment for a median of 13 years (IQR 9-17) with a median of six previous regimens (IQR 4-7), all using protease inhibitors. After treatment, 82 % (95 % confidence interval, CI 74-88 %) of patients had an HIV-1 RNA viral load <200 copies/mL and 69 % (95 % CI 60-76 %) had <50 copies/mL. The CD4+ cell count increased by 378 cells/µL (IQR 252-559; P < 0.001 vs. baseline). Risk factors associated with poor outcome were age >40 years [odds ratio, OR 0.15 (95 % CI 0.10-0.78); P = 0.015], use of raltegravir in the regimen [OR 0.37 (95 % CI 0.10-0.97); P = 0.046], and baseline CD4+ cell count <200 cells/µL [OR 2.79 (95 % CI 1.11-6.97); P = 0.028]. CONCLUSION: In this Mexican cohort Darunavir was metabolically safe, well tolerated and achieved high rates of virological suppression in highly treatment-experienced patients infected with HIV-1.

Structural and sequence diversity of the transposon Galileo in the Drosophila willistoni genome.

BACKGROUND: Galileo is one of three members of the P superfamily of DNA transposons. It was originally discovered in Drosophila buzzatii, in which three segregating chromosomal inversions were shown to have been generated by ectopic recombination between Galileo copies. Subsequently, Galileo was identified in six of 12 sequenced Drosophila genomes, indicating its widespread distribution within this genus. Galileo is strikingly abundant in Drosophila willistoni, a neotropical species that is highly polymorphic for chromosomal inversions, suggesting a role for this transposon in the evolution of its genome. RESULTS: We carried out a detailed characterization of all Galileo copies present in the D. willistoni genome. A total of 191 copies, including 133 with two terminal inverted repeats (TIRs), were classified according to structure in six groups. The TIRs exhibited remarkable variation in their length and structure compared to the most complete copy. Three copies showed extended TIRs due to internal tandem repeats, the insertion of other transposable elements (TEs), or the incorporation of non-TIR sequences into the TIRs. Phylogenetic analyses of the transposase (TPase)-encoding and TIR segments yielded two divergent clades, which we termed Galileo subfamilies V and W. Target-site duplications (TSDs) in D. willistoni Galileo copies were 7- or 8-bp in length, with the consensus sequence GTATTAC. Analysis of the region around the TSDs revealed a target site motif (TSM) with a 15-bp palindrome that may give rise to a stem-loop secondary structure. CONCLUSIONS: There is a remarkable abundance and diversity of Galileo copies in the D. willistoni genome, although no functional copies were found. The TIRs in particular have a dynamic structure and extend in different ways, but their ends (required for transposition) are more conserved than the rest of the element. The D. willistoni genome harbors two Galileo subfamilies (V and W) that diverged ~9 million years ago and may have descended from an ancestral element in the genome. Galileo shows a significant insertion preference for a 15-bp palindromic TSM.

Comparative performance of four single extreme outlier discordancy tests from Monte Carlo simulations.

Using highly precise and accurate Monte Carlo simulations of 20,000,000 replications and 102 independent simulation experiments with extremely low simulation errors and total uncertainties, we evaluated the performance of four single outlier discordancy tests (Grubbs test N2, Dixon test N8, skewness test N14, and kurtosis test N15) for normal samples of sizes 5 to 20. Statistical contaminations of a single observation resulting from parameters called δ from ±0.1 up to ±20 for modeling the slippage of central tendency or ε from ±1.1 up to ±200 for slippage of dispersion, as well as no contamination (δ = 0 and ε = ±1), were simulated. Because of the use of precise and accurate random and normally distributed simulated data, very large replications, and a large number of independent experiments, this paper presents a novel approach for precise and accurate estimations of power functions of four popular discordancy tests and, therefore, should not be considered as a simple simulation exercise unrelated to probability and statistics. From both criteria of the Power of Test proposed by Hayes and Kinsella and the Test Performance Criterion of Barnett and Lewis, Dixon test N8 performs less well than the other three tests. The overall performance of these four tests could be summarized as N2≅N15 > N14 > N8.

Segmental duplication, microinversion, and gene loss associated with a complex inversion breakpoint region in Drosophila.

Chromosomal inversions are usually portrayed as simple two-breakpoint rearrangements changing gene order but not gene number or structure. However, increasing evidence suggests that inversion breakpoints may often have a complex structure and entail gene duplications with potential functional consequences. Here, we used a combination of different techniques to investigate the breakpoint structure and the functional consequences of a complex rearrangement fixed in Drosophila buzzatii and comprising two tandemly arranged inversions sharing the middle breakpoint: 2m and 2n. By comparing the sequence in the breakpoint regions between D. buzzatii (inverted chromosome) and D. mojavensis (noninverted chromosome), we corroborate the breakpoint reuse at the molecular level and infer that inversion 2m was associated with a duplication of a ~13 kb segment and likely generated by staggered breaks plus repair by nonhomologous end joining. The duplicated segment contained the gene CG4673, involved in nuclear transport, and its two nested genes CG5071 and CG5079. Interestingly, we found that other than the inversion and the associated duplication, both breakpoints suffered additional rearrangements, that is, the proximal breakpoint experienced a microinversion event associated at both ends with a 121-bp long duplication that contains a promoter. As a consequence of all these different rearrangements, CG5079 has been lost from the genome, CG5071 is now a single copy nonnested gene, and CG4673 has a transcript ~9 kb shorter and seems to have acquired a more complex gene regulation. Our results illustrate the complex effects of chromosomal rearrangements and highlight the need of complementing genomic approaches with detailed sequence-level and functional analyses of breakpoint regions if we are to fully understand genome structure, function, and evolutionary dynamics.

Metagenomic binning of PacBio HiFi data prior to assembly reveals a complete genome of Cosmopolites sordidus (Germar) (Coleopterea: Curculionidae, Dryophthorinae) the most damaging arthropod pest of bananas and plantains.

PacBio HiFi sequencing was employed in combination with metagenomic binning to produce a high-quality reference genome of Cosmopolites sordidus. We compared k-mer and alignment reference based pre-binning and post-binning approaches to remove contamination. We were also interested to know if the post-binning approach had interspersed bacterial contamination within intragenic regions of Arthropoda binned contigs. Our analyses identified 3,433 genes that were composed with reads identified as of putative bacterial origins. The pre-binning approach yielded a C. sordidus genome of 1.07 Gb genome composed of 3,089 contigs with 98.6% and 97.1% complete and single copy genome and protein BUSCO scores respectively. In this article we demonstrate that in this case the pre-binning approach does not sacrifice assembly quality for more stringent metagenomic filtering. We also determine post-binning allows for increased intragenic contamination increased with increasing coverage, but the frequency of gene contamination increased with lower coverage. Future work should focus on developing reference free pre-binning approaches for HiFi reads produced from eukaryotic based metagenomic samples.

The impact of frailty on death, discharge destination and modelling accuracy in patients receiving organ support on the intensive care unit.

Background: This study aims to identify any effect of frailty in altering the risk of death or poor outcome already associated with receipt of organ support on ICU. It also aims to assess the performance of mortality prediction models in frail patients. Methods: All admissions to a single ICU over 1-year were prospectively allocated a Clinical Frailty Score (CFS). Logistic regression analysis was used to investigate the effect of frailty on death or poor outcome (death/discharge to a medical facility). Logistic regression analysis, area under the Receiver Operator Curve (AUROC) and Brier scores were used to investigate the ability of two mortality prediction models, ICNARC and APACHE II, to predict mortality in frail patients. Results: Of 849 patients, 700 (82%) patients were not frail, and 149 (18%) were frail. Frailty was associated with a stepwise increase in the odds of death or poor outcome (OR for each point rise of CFS = 1.23 ([1.03-1.47]; p = .024) and 1.32 ([1.17-1.48]; p = <.001) respectively). Renal support conferred the greatest odds of death and poor outcome, followed by respiratory support, then cardiovascular support (which increased the odds of death but not poor outcome). Frailty did not modify the odds already associated with organ support. The mortality prediction models were not modified by frailty (AUROC p = .220 and .437 respectively). Inclusion of frailty into both models improved their accuracy. Conclusions: Frailty was associated with increased odds of death and poor outcome, but did not modify the risk already associated with organ support. Inclusion of frailty improved mortality prediction models.

Gene alterations at Drosophila inversion breakpoints provide prima facie evidence for natural selection as an explanation for rapid chromosomal evolution.

BACKGROUND: Chromosomal inversions have been pervasive during the evolution of the genus Drosophila, but there is significant variation between lineages in the rate of rearrangement fixation. D. mojavensis, an ecological specialist adapted to a cactophilic niche under extreme desert conditions, is a chromosomally derived species with ten fixed inversions, five of them not present in any other species. RESULTS: In order to explore the causes of the rapid chromosomal evolution in D. mojavensis, we identified and characterized all breakpoints of seven inversions fixed in chromosome 2, the most dynamic one. One of the inversions presents unequivocal evidence for its generation by ectopic recombination between transposon copies and another two harbor inverted duplications of non-repetitive DNA at the two breakpoints and were likely generated by staggered single-strand breaks and repair by non-homologous end joining. Four out of 14 breakpoints lay in the intergenic region between preexisting duplicated genes, suggesting an adaptive advantage of separating previously tightly linked duplicates. Four out of 14 breakpoints are associated with transposed genes, suggesting these breakpoints are fragile regions. Finally two inversions contain novel genes at their breakpoints and another three show alterations of genes at breakpoints with potential adaptive significance. CONCLUSIONS: D. mojavensis chromosomal inversions were generated by multiple mechanisms, an observation that does not provide support for increased mutation rate as explanation for rapid chromosomal evolution. On the other hand, we have found a number of gene alterations at the breakpoints with putative adaptive consequences that directly point to natural selection as the cause of D. mojavensis rapid chromosomal evolution.

Testing chromosomal phylogenies and inversion breakpoint reuse in Drosophila. The martensis cluster revisited.

The chromosomal relationships of the four martensis cluster species are among the most complex and intricate within the entire Drosophila repleta group, due to the so-called sharing of inversions. Here, we have revised these relationships using comparative mapping of bacterial artificial chromosome (BAC) clones on the salivary gland chromosomes. A physical map of chromosome 2 of Drosophila uniseta (one of the cluster members) was generated by in situ hybridization of 82 BAC clones from the physical map of the Drosophila buzzatii genome (an outgroup that represents the ancestral arrangement). By comparing the marker positions, we determined the number, order, and orientation of conserved chromosomal segments between chromosome 2 of D. buzzatii and D. uniseta. GRIMM software was used to infer that a minimum of five chromosomal inversions are necessary to transform the chromosome 2 of D. buzzatii into that of D. uniseta. Two of these inversions have been overlooked in previous cytological analyses. The five fixed inversions entail two breakpoint reuses because only nine syntenic segments and eight interruptions were observed. We tested for the presence of the five inversions fixed in D. uniseta in the other three species of the martensis cluster by in situ hybridization of eight breakpoint-bearing BAC clones. The results shed light on the chromosomal phylogeny of the martensis cluster, yet leave a number of questions open.

Evaluation of Characteristics and Building Applications of Multi-Recycled Concrete Aggregates from Precast Concrete Rejects.

The construction industry must meet current environmental requirements, mostly those pertaining to the reduction in construction and demolition waste and the consumption of raw materials. The use of recycled concrete aggregates can be part of the solution, but one question that arises is how many times recyclables can be recycled. This unknown involves other related queries regarding the properties and possible uses of repeated recycled concrete aggregates. This research is derived from the precast concrete industry, where multi-recycling is a pressing need. From good-quality parent concretes, three cycles of recycled concrete aggregates were produced and analysed. The final results are promising due to the good quality of the recycled and multi-recycled concrete aggregates obtained. Not only can they be used in low-level applications (backfilling) as usual, but they can also be used for more demanding purposes, such as graded aggregates, cement-treated road bases and concrete pavements. Their use in structural concrete is feasible, but it will be dependent on the water absorption level and the amount of recycled aggregate substitution. This research proves the viability of multi-recycled concrete aggregates with all of the associated environmental benefits.

The Foldback-like element Galileo belongs to the P superfamily of DNA transposons and is widespread within the Drosophila genus.

Galileo is the only transposable element (TE) known to have generated natural chromosomal inversions in the genus Drosophila. It was discovered in Drosophila buzzatii and classified as a Foldback-like element because of its long, internally repetitive, terminal inverted repeats (TIRs) and lack of coding capacity. Here, we characterized a seemingly complete copy of Galileo from the D. buzzatii genome. It is 5,406 bp long, possesses 1,229-bp TIRs, and encodes a 912-aa transposase similar to those of the Drosophila melanogaster 1360 (Hoppel) and P elements. We also searched the recently available genome sequences of 12 Drosophila species for elements similar to Dbuz\Galileo by using bioinformatic tools. Galileo was found in six species (ananassae, willistoni, peudoobscura, persimilis, virilis, and mojavensis) from the two main lineages within the Drosophila genus. Our observations place Galileo within the P superfamily of cut-and-paste transposons and extend considerably its phylogenetic distribution. The interspecific distribution of Galileo indicates an ancient presence in the genus, but the phylogenetic tree built with the transposase amino acid sequences contrasts significantly with that of the species, indicating lineage sorting and/or horizontal transfer events. Our results also suggest that Foldback-like elements such as Galileo may evolve from DNA-based transposon ancestors by loss of the transposase gene and disproportionate elongation of TIRs.

Physical activity intention and attendance behaviour in Finnish youth with cerebral palsy - results from a physical activity intervention: an application of the theory of planned behaviour.

Physical activity is associated with better health in individuals with cerebral palsy (CP). Numerous physical activity interventions have been designed to promote physical activity among youth with CP. No previous studies have explored the factors contributing to the intention to participate and predicting attendance behaviour for these interventions. Using theory of planned behaviour (TPB), this study explored the prediction of physical activity intention and attendance behaviour in a physical activity intervention aiming to promote physical activity in a sample of young individuals with CP. Males with CP aged 9-21 years were asked to complete measures of attitude, subjective norms, perceived behavioural control and, intentions towards a physical activity intervention. Participants had no cognitive impairments to understand and follow instructions, were categorised into Gross Motor Function Classification System I-III, did not receive any specific lower limbs' medical treatment, or did not participate in a strength training program for lower limbs within 6 months before the study. Subjective norms were found to be the only significant predictor of intention, accounting for 83% of variance in intention. Intention and perceived behaviour control were found to be a nonsignificant predictor of attendance behaviour in youth with CP. The results show that TPB is a relevant tool in the prediction of intention towards a physical activity intervention in Finnish youth with CP.

Molecular analyses identifies new domains and structural differences among Streptococcus pneumoniae immune evasion proteins PspC and Hic.

The PspC and Hic proteins of Streptococcus pneumoniae are some of the most variable microbial immune evasion proteins identified to date. Due to structural similarities and conserved binding profiles, it was assumed for a long time that these pneumococcal surface proteins represent a protein family comprised of eleven subgroups. Recently, however, the evaluation of more proteins revealed a greater diversity of individual proteins. In contrast to previous assumptions a pattern evaluation of six PspC and five Hic variants, each representing one of the previously defined subgroups, revealed distinct structural and likely functionally regions of the proteins, and identified nine new domains and new domain alternates. Several domains are unique to PspC and Hic variants, while other domains are also present in other virulence factors encoded by pneumococci and other bacterial pathogens. This knowledge improved pattern evaluation at the level of full-length proteins, allowed a sequence comparison at the domain level and identified domains with a modular composition. This novel strategy increased understanding of individual proteins variability and modular domain composition, enabled a structural and functional characterization at the domain level and furthermore revealed substantial structural differences between PspC and Hic proteins. Given the exceptional genomic diversity of the multifunctional PspC and Hic proteins a detailed structural and functional evaluation need to be performed at the strain level. Such knowledge will also be useful for molecular strain typing and characterizing PspC and Hic proteins from new clinical S. pneumoniae strains.

Cloning and sequencing of the breakpoint regions of inversion 5g fixed in Drosophila buzzatii.

Chromosomal inversions are ubiquitous in Drosophila both as intraspecific polymorphisms and interspecific differences. Many gaps still remain in our understanding of the mechanisms that generate them. Previous work has shown that in Drosophila buzzatii, three polymorphic inversions were generated by ectopic recombination between copies of the transposon Galileo. In this study, we have characterized the breakpoint regions of inversion 5g, fixed in D. buzzatii and absent in Drosophila koepferae and other closely related species. A novel approach comprising four experimental steps was used. First, D. buzzatii BAC clones encompassing the breakpoints were identified and their ends sequenced. Then, breakpoint regions were mapped at high resolution in the Drosophila mojavensis genome sequence. Finally, breakpoint regions were isolated by polymerase chain reaction in D. buzzatii and D. koepferae and sequenced. Our aim was to shed light on the mechanism that generated inversion 5g and specifically to test for an implication of the transposon Galileo. No evidence implicates Galileo or other transposable elements in the origin of inversion 5g that was generated most likely by two independent breaks and non-homologous end-joining repair. Our results show that different inversion-generating mechanisms may coexist within the same lineage and suggest a hypothesis for the evolutionary time and mode of their operation.

HOM-C evolution in Drosophila: is there a need for Hox gene clustering?

The conservation of Homeotic (Hox) gene clustering and colinearity in many metazoans indicates that functional constraints operate on this genome organization. However, several studies have questioned its relevance in Drosophila. Here, we analyse the genomic organization of Hox and Hox-derived genes in 13 fruitfly species and the mosquito Anopheles gambiae. We found that at least seven different Homeotic complex (HOM-C) arrangements exist among Drosophila species, produced by three major splits, five microinversions and six gene transpositions. This dynamism contrasts with the stable organization of the complex in many other taxa. Although there is no evidence of an absolute requirement for Hox gene clustering in Drosophila, we found that strong functional constraints act on the individual genes.

Permeable reactive surface-biobarriers. Testing and evaluation of an ecotechnology for the removal of agrotoxic compounds carried by agricultural runoffs.

PURPOSE: The objective of the work is to determine the best operating conditions for variants of an ecological engineering tool (permeable reactive surface biobarrier -PRSB-) potentially useful for the protection of water resources, preventing the arrival of sediments and pesticides transported by runoffs and tile drainage from agricultural lands, to water bodies. METHODS: Four PRB-prototypes were constructed as fixed-bed horizontal channels packed with a porous material supporting an enriched microbial biofilm. Their dynamic and stoichiometric performance was evaluated in the presence or absence of granular activated carbon, with limiting or sufficient O2 supply. The removal of the pesticides and their leading catabolic derivatives were determined by HPLC. The most abundant cultivable microorganisms were isolated and identified by the sequencing of 16sDNA amplicons. RESULTS: The pollutant removal efficiencies obtained in the aerobic biobarriers or microaerophilia were similar. In addition, slight differences were observed in the presence of GAC as an adsorbent, meaning that the most economical and straightforward type of biobarrier was adequate to remove the pollutants studied. In addition, among the most abundant microorganisms isolated in the microbial biofilms colonizing the aerobic biobarriers, the microalgae Micractinium sp. showed the capacity to accumulate the insecticides permethrin and cypermethrin. CONCLUSIONS: The main observed role of Micractinium sp. in the aerobic barriers was the bioaccumulation of pyrethroids, meaning that biosorption is also a valuable removal mechanism operating in the aerobic PRBs. In this aspect, they behave analogously to subsurface constructed wetlands but, instead of superficial plant life, aerobic PRSBs host microalgae.