RESUMO
The microbial diversity and functioning around oceanic islands is poorly described, despite its importance for ecosystem homeostasis. Here, we aimed to verify the occurrence of microbe-driven phenanthrene co-oxidation in the seawater surrounding the Trindade Island (Brazil). We also used Next-Generation Sequencing to evaluate the effects of aliphatic and polycyclic aromatic hydrocarbons (PAHs) on these microbial community assemblies. Microcosms containing seawater from the island enriched with either labelled (9-14C) or non-labelled phenanthrene together with hexadecane, weathered oil, fluoranthene or pyrene, and combinations of these compounds were incubated. Biodegradation of phenanthrene-9-14C was negatively affected in the presence of weathered oil and PAHs but increased in the presence of hexadecane. PAH contamination caused shifts in the seawater microbial community-from a highly diverse one dominated by Alphaproteobacteria to less diverse communities dominated by Gammaproteobacteria. Furthermore, the combination of PAHs exerted a compounded negative influence on the microbial community, reducing its diversity and thus functional capacity of the ecosystem. These results advance our understanding of bacterial community dynamics in response to contrasting qualities of hydrocarbon contamination. This understanding is fundamental in the application and monitoring of bioremediation strategies if accidents involving oil spillages occur near Trindade Island and similar ecosystems.
Assuntos
Bactérias/efeitos dos fármacos , Bactérias/metabolismo , Hidrocarbonetos/efeitos adversos , Consórcios Microbianos/efeitos dos fármacos , Consórcios Microbianos/fisiologia , Fenantrenos/metabolismo , Água do Mar/microbiologia , Alcanos , Alphaproteobacteria/efeitos dos fármacos , Alphaproteobacteria/metabolismo , Bactérias/classificação , Bactérias/genética , Biodegradação Ambiental , Biodiversidade , Brasil , DNA Bacteriano/genética , Ecossistema , Gammaproteobacteria/efeitos dos fármacos , Gammaproteobacteria/metabolismo , Sequenciamento de Nucleotídeos em Larga Escala , Ilhas , Metagenômica , Consórcios Microbianos/genética , Poluição por Petróleo/efeitos adversos , Hidrocarbonetos Policíclicos Aromáticos/farmacologia , Pirenos , RNA Ribossômico 16S/metabolismo , Poluentes da ÁguaRESUMO
Biopurification systems (BPS) are complex soil-related and artificially-generated environments usually designed for the removal of toxic compounds from contaminated wastewaters. The present study has been conducted to isolate and characterize a collection of cultivable plasmid-carrying bacterial isolates recovered from a BPS established for the decontamination of wastewater generated in a farmyard. Out of 1400 isolates, a collection of 75 plasmid-containing bacteria was obtained, of which 35 representative isolates comprising in total at least 50 plasmids were chosen for further characterization. Bacterial hosts were taxonomically assigned by 16S ribosomal RNA gene sequencing and phenotypically characterized according to their ability to grow in presence of different antibiotics and heavy metals. The study demonstrated that a high proportion of the isolates was tolerant to antibiotics and/or heavy metals, highlighting the on-farm BPS enrichment in such genetic traits. Several plasmids conferring such resistances in the bacterial collection were detected to be either mobilizable or selftransmissible. Occurrence of broad host range plasmids of the incompatibility groups IncP, IncQ, IncN and IncW was examined with positive results only for the first group. Presence of the IS1071 insertion sequence, frequently associated with xenobiotics degradation genes, was detected in DNA obtained from 24 of these isolates, strongly suggesting the presence of yet-hidden catabolic activities in the collection of isolates. The results showed a remarkable diversity in the plasmid mobilome of cultivable bacteria in the BPS with the presence of abundant resistance markers of different types, thus providing a suitable environment to investigate the genetic structure of the mobile genetic pool in a model on-farm biofilter for wastewater decontamination in intensive agricultural production.
Assuntos
Gammaproteobacteria/isolamento & purificação , Plasmídeos/genética , Agricultura , Biodegradação Ambiental , DNA Bacteriano/genética , Gammaproteobacteria/efeitos dos fármacos , Gammaproteobacteria/genética , Metais Pesados/farmacologia , Testes de Sensibilidade Microbiana , Tipagem Molecular , Resíduos de Praguicidas/isolamento & purificação , RNA Ribossômico 16S/genética , Microbiologia do Solo , Poluentes Químicos da Água/isolamento & purificação , Purificação da ÁguaRESUMO
UNLABELLED: A major percentage (20 to 40%) of global marine fixed-nitrogen loss occurs in oxygen minimum zones (OMZs). Concentrations of O2 and the sensitivity of the anaerobic N2-producing processes of anammox and denitrification determine where this loss occurs. We studied experimentally how O2 at nanomolar levels affects anammox and denitrification rates and the transcription of nitrogen cycle genes in the anoxic OMZ off Chile. Rates of anammox and denitrification were reversibly suppressed, most likely at the enzyme level. Fifty percent inhibition of N2 and N2O production by denitrification was achieved at 205 and 297 nM O2, respectively, whereas anammox was 50% inhibited at 886 nM O2. Coupled metatranscriptomic analysis revealed that transcripts encoding nitrous oxide reductase (nosZ), nitrite reductase (nirS), and nitric oxide reductase (norB) decreased in relative abundance above 200 nM O2. This O2 concentration did not suppress the transcription of other dissimilatory nitrogen cycle genes, including nitrate reductase (narG), hydrazine oxidoreductase (hzo), and nitrite reductase (nirK). However, taxonomic characterization of transcripts suggested inhibition of narG transcription in gammaproteobacteria, whereas the transcription of anammox narG, whose gene product is likely used to oxidatively replenish electrons for carbon fixation, was not inhibited. The taxonomic composition of transcripts differed among denitrification enzymes, suggesting that distinct groups of microorganisms mediate different steps of denitrification. Sulfide addition (1 µM) did not affect anammox or O2 inhibition kinetics but strongly stimulated N2O production by denitrification. These results identify new O2 thresholds for delimiting marine nitrogen loss and highlight the utility of integrating biogeochemical and metatranscriptomic analyses. IMPORTANCE: The removal of fixed nitrogen via anammox and denitrification associated with low O2 concentrations in oceanic oxygen minimum zones (OMZ) is a major sink in oceanic N budgets, yet the sensitivity and dynamics of these processes with respect to O2 are poorly known. The present study elucidated how nanomolar O2 concentrations affected nitrogen removal rates and expression of key nitrogen cycle genes in water from the eastern South Pacific OMZ, applying state-of-the-art (15)N techniques and metatranscriptomics. Rates of both denitrification and anammox responded rapidly and reversibly to changes in O2, but denitrification was more O2 sensitive than anammox. The transcription of key nitrogen cycle genes did not respond as clearly to O2, although expression of some of these genes decreased. Quantifying O2 sensitivity of these processes is essential for predicting through which pathways and in which environments, from wastewater treatment to the open oceans, nitrogen removal may occur.
Assuntos
Amônia/metabolismo , Gammaproteobacteria/efeitos dos fármacos , Gammaproteobacteria/metabolismo , Expressão Gênica/efeitos dos fármacos , Oxigênio/metabolismo , Chile , Desnitrificação , Perfilação da Expressão Gênica , Dados de Sequência Molecular , Oxirredução , Análise de Sequência de DNARESUMO
High-altitude Andean wetlands are pristine environments with extreme conditions such as high UV radiation, high heavy metal content (mainly arsenic), high salinity, and oligotrophy. In this paper, the UV-B resistance and tolerance to arsenic of phylogenetically characterized bacteria (Actinobacteria [six isolates], Firmicutes [four isolates], and gamma-Proteobacteria [three isolates]) isolated from Laguna Vilama (4400-m altitude) and Laguna Azul (4560 m) were determined. In addition, given that multiple antibiotic resistances were also determined, a relationship between antibiotic resistances as a consequence of mutagenic ability or in relation to metal resistance is proposed. High UV-B resistances were found, since after 30 min (0.7 KJ m(-2)) and 60 min (1.4 KJ m(-2)) of irradiation, most of the studied bacteria did not show a decreased survival; what is more, many of them had an improved survival with the increased doses. Augmentations in mutagenesis rates were observed after UV-B irradiation in only 4 of the 13 tested isolates. Arsenite tolerance was also established in 8 of the 13 tested strains: Staphylococcus saprophyticus A3 and Micrococcus sp. A7, which were able to grow in media containing up to 10 mM As(III). Finally, predominance of antibiotic resistances (azithromycin, erythromycin, clarithromycin, roxithromycin, streptomycin, chloramphenicol, gentamycin, kanamycin, tetracycline, and ampicillin) was found, in all the isolated strains from both wetlands, with unexpectedly high minimal inhibitory concentrations (MICs; >2 mg mL(-1)) for macrolides. These results demonstrate that in extreme environments like high-altitude wetlands there is a correlation of multiresistances to UV-B radiation and arsenic, and that antibiotic resistances are also widespread in these pristine environments, where antibiotic selective pressure is supposed to be absent.
Assuntos
Actinobacteria , Farmacorresistência Bacteriana Múltipla , Água Doce/microbiologia , Gammaproteobacteria , Áreas Alagadas , Actinobacteria/efeitos dos fármacos , Actinobacteria/efeitos da radiação , Altitude , Argentina , Arsenitos/metabolismo , Gammaproteobacteria/efeitos dos fármacos , Gammaproteobacteria/efeitos da radiação , Testes de Sensibilidade Microbiana , Raios UltravioletaRESUMO
There is a wide offer of disinfectant products, for the food industry, available in the market, such as chlorine, iodine and quaternary ammonium compounds and their respective derivatives. However, new alternative products have emerged, for instance grapefruit seed extract, and peracetic and lactic acids. The present study was carried out in order to analyze in vitro the germicide effect, from the grapefruit seed extract (400 ppm), peracetic acid (2000 ppm) and lactic acid (20,000 ppm) at the manufacturer recommended action time, and other additional times. The germicide effect was tested against microorganisms such as Escherichia coli, Staphylococcus aureus, Streptococcus faecalis and Pseudomonas aeruginosa. In each case, the death kinetic was determined through the evaluation of the germicide effect (%), specific death rate (t-1) and the decimal reduction time (min). From the evaluated products, the best germicidal effect at the manufacturer conditions was reached by peracetic acid (2000 ppm) at 1 min, which presented the lower decimal reduction times compared with the other tested microorganisms. Generally speaking, Gram positive microorganisms showed a greater sensibility to the disinfectant action.
Assuntos
Desinfetantes/farmacologia , Indústria Alimentícia/instrumentação , Gammaproteobacteria/efeitos dos fármacos , Cocos Gram-Positivos/efeitos dos fármacos , Resistência Microbiana a Medicamentos , Contaminação de Equipamentos , Frutas , Ácido Láctico/farmacologia , Ácido Peracético/farmacologia , SementesRESUMO
AIMS: The aim of this study was to evaluate the diversity of Xylella fastidiosa isolated from citrus trees affected by Citrus Variegated Chlorosis (CVC). METHODS AND RESULTS: The antibiotic susceptibility by agar disc diffusion and minimum inhibitory concentration (MIC) methods was observed for all drug evaluated, except for penicillin-G. Genetic diversity by RAPD analysis revealed three major groups (citrus, coffee and grapevine), being the citrus group more similar with the coffee group than with the grapevine group. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the possibility to use these antibiotics susceptibility as markers in the development of a cloning vector and penicillin-G could be used as a selective marker for the isolation of X. fastidiosa from citrus plants.