Effects of different cultivation conditions on the production of ß-cyclocitral and ß-ionone in Microcystis aeruginosa.

BACKGROUND: Cyanobacteria blooms have become a major environmental problem and concern because of secondary metabolites produced by cyanobacteria released into the water. Cyanobacteria produce volatile organic compounds (VOCs), such as the compounds ß-cyclocitral and ß-ionone, which comprise odors, off-flavors, defense compounds, as well as growth regulators. Therefore, the general objective of this work was to evaluate the VOCs produced by two strains of Microcystis aeruginosa, differing in their ability to produce microcystins (LTPNA 01-non-producing and LTPNA 08-toxin-producing). The analysis of VOC production was carried out in (1) normal culture conditions, (2) under different light intensities (LI), and (3) after the external application of ß-ionone in both cultures. RESULTS: The results showed that ß-cyclocitral and ß-ionone are produced in all growth phases of LTPNA 01 and LTPNA 08. Both strains were producers of ß-cyclocitral and ß-ionone in normal culture conditions. It was observed that the ß-cyclocitral concentration was higher than ß-ionone in all light intensities investigated in this study. Additionally, the strain LTPNA 01 produced more ß-cyclocitral than LTPNA 08 at almost all times and LIs analyzed. However, the strain LTPNA 08 produced more ß-ionone, mainly at the initial times. In addition, the experiment results with the external addition of ß-ionone in the cultures showed that the strain LTPNA 01 produced more ß-cyclocitral in control conditions than in treatment. Nonetheless, ß-ionone production was higher in treatment conditions in LTPNA 08, indicating that the addition of ß-ionone may favor the production of these compounds and inhibit the production of ß-cyclocitral. CONCLUSION: Our results showed that some abiotic factors, such as different light intensities and external application of ß-ionone, can be triggers that lead to the production of VOCs.

Occurrence of clinically relevant antimicrobial resistance genes, including mcr-3 and mcr-7.1, in soil and water from a recreation club.

We researched clinically relevant antimicrobial resistance genes (ARGs) and mobile genetic elements (MGEs) in environmental samples from a recreation club in Brazil. A total of 172 amplicons (105 from soil and 67 from water) of 26 ARGs (20 among the soil and water samples; four only in soil samples; two only in water samples) were detected. Nine MGEs were detected, including plasmids and class 1 integron. The absolute abundance of the mcr-3 gene ranged from 1.12 × 102 to 1.81 × 103 copies/mL-1 in water samples. The rapid spread of mcr-like genes in several sources has generated a huge concern to public health. Accordingly, understanding of antimicrobial resistance, carry out surveillance studies may contribute to tackle antimicrobial resistance. As the environmental samples were collected from a popular recreation club in Brazil, this study points out to the risk and exposure to clinically relevant ARGs, especially to mcr-3 and mcr-7.1 genes.

Occurrence and abundance of clinically relevant antimicrobial resistance genes in environmental samples after the Brumadinho dam disaster, Brazil.

On January 25th 2019, the structure damming a pond containing ore mining wastes and iron burst at Brumadinho City, Brazil. About 11.7 million m3 of a tailings-mud mixture was released from the dam, causing destruction along 300 km of the Paraopeba River toward the São Francisco River. The environments with a high content of metals may provide a suitable environment for horizontal gene transfer, including antimicrobial resistance genes (ARGs). Therefore, this study aimed to detect and quantify clinically relevant ARGs in environmental samples after the Brumadinho dam disaster. Soil, sediment, and water samples were collected within 300 km of the Brumadinho dam disaster at unaffected and affected sites. Physical-chemical parameters of water samples were measured. Total DNA was extracted and 65 clinically relevant ARGs were researched by PCR. The most prevalent ARGs were selected for real-time quantitative PCR analysis. The average of the physical-chemical parameters was higher in the affected sites when compared to the unaffected sites, especially turbidity, concentration of Fe and Al. A total of 387 amplicons from 29 ARGs were detected, which confer resistance to ß-lactams, quinolones, aminoglycosides, tetracyclines, sulphonamides, phenicols, macrolides, glycopeptides, and polymyxins, including extended-spectrum ß-lactamases-encoding genes, and mcr-7.1. The sul1 gene had higher total concentrations than blaTEM, tetB and qnrB in the environmental samples, and the diversity and abundance of ARGs increased at the sites affected by the Brumadinho dam disaster. Therefore, we point out that the contamination by the Brumadinho dam disaster tailings resulted in an increase in the amount and abundance of ARGs in the environment.

A mini-review: current advances in polyethylene biodegradation.

Polyethylene (PE) has been described as the most abundant plastic worldwide since it is used for the manufacture of disposable recipients, such as bottles and bags. Consequently, large quantities of PE have been accumulating in the environment causing serious ecological problems. Although there are numerous plastic disposal methods, each one has its own inherent limitations, but biodegradation seems to be the least harmful method to deal with this type of contaminant. This mini-review summarizes current advances in PE contamination, focusing on the recent findings related to the biodegradation of PE in different environmental conditions, presenting the microorganisms, genes, and enzymes involved, as well as the mechanisms of PE biodegradation. It also attempts to address the main and current biodegradation methods used to minimize the impacts of this polymer on the environment.

Plasmids associated with heavy metal resistance and herbicide degradation potential in bacterial isolates obtained from two Brazilian regions.

The use of pesticides has been increasing due to the great agricultural production worldwide. The pesticides are used to eradicate pests and weeds; however, these compounds are classified as toxic to non-target organisms. Atrazine and diuron are herbicides widely used to control grassy and broadleaf weeds and weed control in agricultural crops and non-crop areas. Heavy metals are also important environmental contaminants that affect the ecological system. This study aimed to investigate the presence of herbicides-degrading genes and heavy metal resistance genes in bacterial isolates from two different soil samples from two Brazilian regions and to determine the genetic location of these genes. In this study, two isolates were obtained and identified as Escherichia fergusonii and Bacillus sp. Both isolates presented atzA, atzB, atzC, atzD, atzE, atzF, puhA, and copA genes and two plasmids each, being the major with ~ 60 Kb and a smaller with ~ 3.2 Kb. Both isolates presented the atzA-F genes inside the larger plasmid, while the puhA and copA genes were detected in the smaller plasmid. Digestion reactions were performed and showed that the ~ 60-Kb plasmid presented the same restriction profile using different restriction enzymes, suggesting that this plasmid harboring the complete degradation pathway to atrazine was found in both isolates. These results suggest the dispersion of these plasmids and the multi-herbicide degradation potential in both isolates to atrazine and diuron, which are widely used in different culture types worldwide.

Change in the antimicrobial resistance profile of Pseudomonas aeruginosa from soil after exposure to herbicides.

The extensive use of pesticides represents a risk to human health and to the environment. This study aimed to investigate if the exposure to atrazine and diuron, two herbicides widely used in Brazil, could induce changes in the susceptibility profile to aztreonam, colistin and polymyxin B antimicrobials in isolates of P. aeruginosa obtained from soil samples by using the determination of minimum inhibitory concentration (MIC) test. Three isolates had an increase of MIC to aztreonam after exposure to both herbicides and one isolate did not show any MIC change. The MexAB-OprM efflux pump has already been upregulated in these isolates and the herbicides atrazine and diuron did not increase MexAB-OprM overexpression. Therefore, the decrease in aztreonam susceptibility was not directly related to this pump, suggesting that probably other mechanisms should be involved.

Changes in bacterial community after application of three different herbicides.

The native soil microbiota is very important to maintain the quality of that environment, but with the intensive use of agrochemicals, changes in microbial biomass and formation of large quantities of toxic waste were observed in soil, groundwater and surface water. Thereby, the goal of this study was to evaluate if the selective pressure exerted by the presence of the herbicides atrazine, diuron and 2,4-D changes the bacterial community structure of an agricultural soil, using denaturing gradient gel electrophoresis technique. According to PERMANOVA analysis, a greater effect of the herbicide persistence time in the soil, the effect of the herbicide class and the effect of interaction between these two factors (persistence time and herbicide class) were observed. In conclusion, the results showed that the selective pressure exerted by the presence of these herbicides altered the composition of the local microbiota, being atrazine and diuron that most significantly affected the bacterial community in soil, and the herbicide 2,4-D was the one that less altered the microbial community and that bacterial community was reestablished first.

High prevalence of blaVIM-1 gene in bacteria from Brazilian soil.

This study investigated bacteria from soil samples to (i) determine the main bacterial genera and species having resistance to carbapenem and other ß-lactams and (ii) establish if the mechanism of resistance was due to the production of metallo-ß-lactamases. The isolates were characterized by PCR for metallo-ß-lactamases and integrons, by antimicrobial susceptibility testing, and by sequencing. The antimicrobial profile of 40 imipenem-resistant Gram-positive soil isolates from all Brazilian regions demonstrated that 31 (77.5%) of them were multidrug resistant. Among the 40 isolates, 19 presented the blaVIM gene and class 1 integrons by PCR. Six of the 19 isolates were identified as Paenibacillus sp., 12 as Bacillus sp., and just 1 was classified as Staphylococcus sp., by sequencing of the 16S rRNA gene. These results suggest that bacteria from soil can act as a source of blaVIM-1 genes, representing a threat to public health.