Field and soil microcosm studies on the survival and conjugation of aPseudomonas putidastrain bearing a recombinant plasmid, pADPTel

Biological valorization of pure and crude glycerol into 1,3-propanediol using a novel isolate Lactobacillus brevis N1E9.3.3

The aim of the study was to evaluate a novel onsite enrichment approach to isolate a crude glycerol utilizing facultative anaerobic bacteria. An onsite enrichment in natural conditions resulted an isolate, Lactobacillus brevis N1E9.3.3, that can utilize glycerol and produce 1,3-propanediol with a yield of 0.89g1,3-PDO/gGlycerol and productivity of 0.78g1,3-PDO/l/h at pH-8.5 under anaerobic conditions. Batch fermentation experiments with glycerol-glucose co-fermentation strategy was carried out to evaluate the production of 1,3-propanediol and other byproducts. The effect of other carbon sources as co-substrate was also evaluated. At the optimized condition, 18.6g/l 1,3-propanediol was monitored when biodiesel industry generated crude glycerol and 2.5% glucose were used as the substrate.

Establishment of multiple pesticide biodegradation capacities from pesticide-primed materials in on-farm biopurification system microcosms treating complex pesticide-contaminated wastewater

BACKGROUND

On-farm biopurification systems (BPSs) treat pesticide-containing wastewater at farms by biodegradation and sorption processes. The inclusion of pesticide-primed material carrying a pesticide-degrading microbial community is beneficial for improving biodegradation, but no data exist for treating wastewater containing multiple pesticides, as often occurs on farms. In a microcosm set-up, an examination was carried out to determine whether multiple pesticide degradation activities could be simultaneously established in the matrix of a BPS by the simultaneous inclusion of different, appropriate pesticide-primed materials. The microcosms were fed with a mixture of pesticides including the fungicide metalaxyl and the herbicides bentazon, isoproturon, linuron and metamitron, and pesticide-degrading activities were monitored over time.

RESULTS

The strategy immediately provided the microcosms with a multiple pesticide degradation/mineralisation capacity, which improved during feeding of the pesticide mixture. Not only did the degradation of the parent compound improve but also that of the produced metabolites and compound mineralisation. The time to achieve maximum degradation/mineralisation capacity depended on the pesticide degradation capacity of the pesticide-primed materials.

CONCLUSIONS

The data obtained show that the addition of pesticide-primed materials into the matrix of a BPS as an approach to improve biodegradation can be extended to the treatment of pesticide mixtures.

Microscopic and spectroscopic analyses of chlorhexidine tolerance in Delftia acidovorans biofilms

The physicochemical responses of Delftia acidovorans biofilms exposed to the commonly used antimicrobial chlorhexidine (CHX) were examined in this study. A CHX-sensitive mutant (MIC, 1.0 μg ml(-1)) was derived from a CHX-tolerant (MIC, 15.0 μg ml(-1)) D. acidovorans parent strain using transposon mutagenesis. D. acidovorans mutant (MT51) and wild-type (WT15) strain biofilms were cultivated in flow cells and then treated with CHX at sub-MIC and inhibitory concentrations and examined by confocal laser scanning microscopy (CLSM), scanning transmission X-ray microscopy (STXM), and infrared (IR) spectroscopy. Specific morphological, structural, and chemical compositional differences between the CHX-treated and -untreated biofilms of both strains were observed. Apart from architectural differences, CLSM revealed a negative effect of CHX on biofilm thickness in the CHX-sensitive MT51 biofilms relative to those of the WT15 strain. STXM analyses showed that the WT15 biofilms contained two morphochemical cell variants, whereas only one type was detected in the MT51 biofilms. The cells in the MT51 biofilms bioaccumulated CHX to a similar extent as one of the cell types found in the WT15 biofilms, whereas the other cell type in the WT15 biofilms did not bioaccumulate CHX. STXM and IR spectral analyses revealed that CHX-sensitive MT51 cells accumulated the highest levels of CHX. Pretreating biofilms with EDTA promoted the accumulation of CHX in all cells. Thus, it is suggested that a subpopulation of cells that do not accumulate CHX appear to be responsible for greater CHX resistance in D. acidovorans WT15 biofilm in conjunction with the possible involvement of bacterial membrane stability.

Bacterial diversity and composition of an alkaline uranium mine tailings-water interface

The microbial diversity and biogeochemical potential associated with a northern Saskatchewan uranium mine water-tailings interface was examined using culture-dependent and -independent techniques. Morphologically-distinct colonies from uranium mine water-tailings and a reference lake (MC) obtained using selective and non-selective media were selected for 16S rRNA gene sequencing and identification, revealing that culturable organisms from the uranium tailings interface were dominated by Firmicutes and Betaproteobacteria; whereas, MC organisms mainly consisted of Bacteroidetes and Gammaproteobacteria. Ion Torrent (IT) 16S rRNA metagenomic analysis carried out on extracted DNA from tailings and MC interfaces demonstrated the dominance of Firmicutes in both of the systems. Overall, the tailings-water interface environment harbored a distinct bacterial community relative to the MC, reflective of the ambient conditions (i.e., total dissolved solids, pH, salinity, conductivity, heavy metals) dominating the uranium tailings system. Significant correlations among the physicochemical data and the major bacterial groups present in the tailings and MC were also observed. Presence of sulfate reducing bacteria demonstrated by culture-dependent analyses and the dominance of Desulfosporosinus spp. indicated by Ion Torrent analyses within the tailings-water interface suggests the existence of anaerobic microenvironments along with the potential for reductive metabolic processes.

Microbial communities in low permeability, high pH uranium mine tailings: characterization and potential effects

AIMS

To describe the diversity and metabolic potential of microbial communities in uranium mine tailings characterized by high pH, high metal concentration and low permeability.

METHODS AND RESULTS

To assess microbial diversity and their potential to influence the geochemistry of uranium mine tailings using aerobic and anaerobic culture-based methods, in conjunction with next generation sequencing and clone library sequencing targeting two universal bacterial markers (the 16S rRNA and cpn60 genes). Growth assays revealed that 69% of the 59 distinct culturable isolates evaluated were multiple-metal resistant, with 15% exhibiting dual-metal hypertolerance. There was a moderately positive correlation coefficient (R = 0·43, P < 0·05) between multiple-metal resistance of the isolates and their enzyme expression profile. Of the isolates tested, 17 reduced amorphous iron, 22 reduced molybdate and seven oxidized arsenite. Based on next generation sequencing, tailings depth was shown to influence bacterial community composition, with the difference in the microbial diversity of the upper (0-20 m) and middle (20-40 m) tailings zones being highly significant (P < 0·01) from the lower zone (40-60 m) and the difference in diversity of the upper and middle tailings zone being significant (P < 0·05). Phylotypes closely related to well-known sulfate-reducing and iron-reducing bacteria were identified with low abundance, yet relatively high diversity.

CONCLUSIONS

The presence of a population of metabolically-diverse, metal-resistant micro-organisms within the tailings environment, along with their demonstrated capacity for transforming metal elements, suggests that these organisms have the potential to influence the long-term geochemistry of the tailings.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first investigation of the diversity and functional potential of micro-organisms present in low permeability, high pH uranium mine tailings.

Spatial variation in microbial community structure, richness, and diversity in an alluvial aquifer

Relatively little is known regarding the spatial variability of microbial communities in aquifers where well fouling is an issue. In this study 2 water wells were installed in an alluvial aquifer located adjacent to the North Saskatchewan River and an associated piezometer network developed to facilitate the study of microbial community structure, richness, and diversity. Carbon utilization data analysis revealed reduced microbial activity in waters collected close to the wells. Functional PCR and quantitative PCR analysis indicated spatial variability in the potential for iron-, sulphate-, and nitrate-reducing activity at all locations in the aquifer. Denaturing gradient gel electrophoresis analysis of aquifer water samples using principal components analyses indicated that the microbial community composition was spatially variable, and denaturing gradient gel electrophoresis sequence analysis revealed that bacteria belonging to the genera Acidovorax , Rhodobacter , and Sulfuricurvum were common throughout the aquifer. Shannon's richness (H') and Pielou's evenness (J') indices revealed a varied microbial diversity (H' = 1.488-2.274) and an even distribution of microbial communities within the aquifer (J' = 0.811-0.917). Overall, these analyses revealed that the aquifer's microbial community varied spatially in terms of composition, richness, and metabolic activity. Such information may facilitate the diagnosis, prevention, and management of fouling.

Effect of pumping on the spatio-temporal distribution of microbial communities in a water well field

A water well field adjacent to the North Saskatchewan River (City of North Battleford, Saskatchewan, Canada) with a history of rapid deterioration of both well water quality and yield was selected to study the spatial and temporal distribution of subsurface microbial communities and their response to water pumping. A range of conventional cultural, microscopic and molecular techniques, including confocal laser scanning microscopy (CLSM), Biolog, qPCR and Denaturing Gradient Gel Electrophoresis (DGGE), was used during this study. Redox data and water and sediment chemistry showed that the aquifer was anoxic and harbored substantial amounts of Fe and Mn. CLSM analyses of incubated coupons indicated extensive biofilm growth in the zone immediately surrounding the well and was coincident with reduced water well yield. PCR screening and qPCR analyses showed that the potential for iron- and sulfate-reducing activity increased with proximity to the well. Bacterial communities inhabiting the zone closest to the well showed the greatest changes and differences in metabolic activities and composition as revealed by PCA (Principal Components Analysis) of the Biolog and DGGE data. The sequence analysis of all the samples revealed that Sulfuricurvum spp., Methylobacter spp., Geobacter spp. and Rhodobacter spp. were most commonly detected in this aquifer. Overall the findings demonstrated that the microbial numbers, metabolic activities and the community composition changed in response to water pumping but effects did not extend beyond 1-2m zone from the well.

Agronomic and environmental implications of enhanced s-triazine degradation

Novel catabolic pathways enabling rapid detoxification of s-triazine herbicides have been elucidated and detected at a growing number of locations. The genes responsible for s-triazine mineralization, i.e. atzABCDEF and trzNDF, occur in at least four bacterial phyla and are implicated in the development of enhanced degradation in agricultural soils from all continents except Antarctica. Enhanced degradation occurs in at least nine crops and six crop rotation systems that rely on s-triazine herbicides for weed control, and, with the exception of acidic soil conditions and s-triazine application frequency, adaptation of the microbial population is independent of soil physiochemical properties and cultural management practices. From an agronomic perspective, residual weed control could be reduced tenfold in s-triazine-adapted relative to non-adapted soils. From an environmental standpoint, the off-site loss of total s-triazine residues could be overestimated 13-fold in adapted soils if altered persistence estimates and metabolic pathways are not reflected in fate and transport models. Empirical models requiring soil pH and s-triazine use history as input parameters predict atrazine persistence more accurately than historical estimates, thereby allowing practitioners to adjust weed control strategies and model input values when warranted.

The bacterial response to the chalcogen metalloids Se and Te

Microbial metabolism of inorganics has been the subject of interest since the 1970s when it was recognized that bacteria are involved in the transformation of metal compounds in the environment. This area of research is generally referred to as bioinorganic chemistry or microbial biogeochemistry. Here, we overview the way the chalcogen metalloids Se and Te interact with bacteria. As a topic of considerable interest for basic and applied research, bacterial processing of tellurium and selenium oxyanions has been reviewed a few times over the past 15 years. Oddly, this is the first time these compounds have been considered together and their similarities and differences highlighted. Another aspect touched on for the first time by this review is the bacterial response in cell-cell or cell-surface aggregates (biofilms) against the metalloid oxyanions. Finally, in this review we have attempted to rationalize the considerable amount of literature available on bacterial resistance to the toxic metalloids tellurite and selenite.