Assimilative and co-metabolic degradation of chloral hydrate by bacteria and their bioremediation potential

Role of cytochrome P450 genes of Trichoderma atroviride T23 on the resistance and degradation of dichlorvos

The Trichoderma has been extensively used to degrade the xenobiotics. In the present study, thirty-nine open reading frames of cytochrome P450 genes from T. atroviride T23 genome was cloned and it was found to be distributed in 29 families under 21 clades. Among them, 21 cytochrome P450 genes were involved in the degradation of xenobiotics. The quantitative expression of P450 genes in the presence of dichlorvos at 24 h showed 7 different expression patterns in the presence of 100 μg/mL, 300 μg/mL, 500 μg/mL and 1000 μg/mL of dichlorvos. The relative expression of P450 genes belongs to the family of TaCyp548, TaCyp620, TaCyp52, TaCyp528, TaCyp504 were upregulated at least 1-fold compared to the control. Significantly, the deletion of TaCyp548-2 reduced the concentration of 2,2-dichloroethanol. Further, it was observed that TaCyp548-2 belongs to the ω-hydroxylase family was responsible for fatty acid oxidation and the production of acetic acid, propionic acid, isobutyric acid and dibutyric acid to convert the 2,2-dichloroethanol to 2,2-dichloroethanolacetate. This study evidenced the involvement of Trichoderma P450 genes on dichlorvos degradation as an environmentally significant Biological control agent for the sustainable agriculture.

Microbial composition of a hydropower cooling water system reveals thermophilic bacteria with a possible role in primary biofilm formation

Microfouling, ie biofilm formation on surfaces, can have an economic impact and requires costly maintenance in water-powered energy generation systems. In this study, the microbiota of a cooling system (filter and heat exchanger) in the Irapé hydroelectric power plant in Brazil was examined. The goal was to identify bacteria that could be targeted to more efficiently reduce biofilm formation. Two sampling campaigns were made corresponding to two well-defined seasons of the Brazilian Cerrado biome: the dry (campaign 1) and the wet (campaign 2). Microfouling communities varied considerably over time in samples obtained at different times after the last clearance of the heat exchanger. The thermophilic bacteria Meiothermus, Thermomonas and Symbiobacterium were exclusive and abundant in the microfouling of the heat exchanger in campaign 2, while methanotrophs and iron-reducing bacteria were abundant only in filter sediments. These findings could help to guide strategies for ecofriendly measures to reduce biofilm fouling in hydroelectric power plants, minimizing environmental and economic losses.

Interactive effects of temperature, organic carbon, and pipe material on microbiota composition and Legionella pneumophila in hot water plumbing systems

BACKGROUND

Several biotic and abiotic factors have been reported to influence the proliferation of microbes, including Legionella pneumophila, in hot water premise plumbing systems, but their combined effects have not been systematically evaluated. Here, we utilize simulated household water heaters to examine the effects of stepwise increases in temperature (32-53 °C), pipe material (copper vs. cross-linked polyethylene (PEX)), and influent assimilable organic carbon (0-700 μg/L) on opportunistic pathogen gene copy numbers and the microbiota composition, as determined by quantitative polymerase chain reaction and 16S rRNA gene amplicon sequencing.

RESULTS

Temperature had an overarching influence on both the microbiota composition and L. pneumophila numbers. L. pneumophila peaked at 41 °C in the presence of PEX (1.58 × 105 gene copies/mL). At 53 °C, L. pneumophila was not detected. Several operational taxonomic units (OTUs) persisted across all conditions, accounting for 50% of the microbiota composition from 32 to 49 °C and 20% at 53 °C. Pipe material most strongly influenced microbiota composition at lower temperatures, driven by five to six OTUs enriched with each material. Copper pipes supported less L. pneumophila than PEX pipes (mean 2.5 log10 lower) at temperatures ≤ 41 °C, but showed no difference in total bacterial numbers. Differences between pipe materials diminished with elevated temperature, probably resulting from decreased release of copper ions. At temperatures ≤ 45 °C, influent assimilable organic carbon correlated well with total bacterial numbers, but not with L. pneumophila numbers. At 53 °C, PEX pipes leached organic carbon, reducing the importance of dosed organic carbon. L. pneumophila numbers correlated with a Legionella OTU and a Methylophilus OTU identified by amplicon sequencing.

CONCLUSIONS

Temperature was the most effective factor for the control of L. pneumophila, while microbiota composition shifted with each stepwise temperature increase. While copper pipe may also help shape the microbiota composition and limit L. pneumophila proliferation, its benefits might be constrained at higher temperatures. Influent assimilable organic carbon affected total bacterial numbers, but had minimal influence on opportunistic pathogen gene numbers or microbiota composition. These findings provide guidance among multiple control measures for the growth of opportunistic pathogens in hot water plumbing and insight into the mediating role of microbial ecological factors.

Kinetics of aerobic cometabolic biodegradation of chlorinated and brominated aliphatic hydrocarbons: A review

This review analyses kinetic studies of aerobic cometabolism (AC) of halogenated aliphatic hydrocarbons (HAHs) from 2001-2015 in order to (i) compare the different kinetic models proposed, (ii) analyse the estimated model parameters with a focus on novel HAHs and the identification of general trends, and (iii) identify further research needs. The results of this analysis show that aerobic cometabolism can degrade a wide range of HAHs, including HAHs that were not previously tested such as chlorinated propanes, highly chlorinated ethanes and brominated methanes and ethanes. The degree of chlorine mineralization was very high for the chlorinated HAHs. Bromine mineralization was not determined for studies with brominated aliphatics. The examined research period led to the identification of novel growth substrates of potentially high interest. Decreasing performance of aerobic cometabolism were found with increasing chlorination, indicating the high potential of aerobic cometabolism in the presence of medium- and low-halogenated HAHs. Further research is needed for the AC of brominated aliphatic hydrocarbons, the potential for biofilm aerobic cometabolism processes, HAH-HAH mutual inhibition and the identification of the enzymes responsible for each aerobic cometabolism process. Lastly, some indications for a possible standardization of future kinetic studies of HAH aerobic cometabolism are provided.

Community Analysis and Recovery of Phenol-degrading Bacteria from Drinking Water Biofilters

Phenol is a ubiquitous organic contaminant in drinking water. Biodegradation plays an important role in the elimination of phenol pollution in the environment, but the information about phenol removal by drinking water biofilters is still lacking. Herein, we study an acclimated bacterial community that can degrade over 80% of 300 mg/L phenol within 3 days. PCR detection of genotypes involved in bacterial phenol degradation revealed that the degradation pathways contained the initial oxidative attack by phenol hydroxylase, and subsequent ring fission by catechol 1,2-dioxygenase. Based on the PCR denatured gradient gel electrophoresis (PCR-DGGE) profiles of bacteria from biological activated carbon (BAC), the predominant bacteria in drinking water biofilters including Delftia sp., Achromobacter sp., and Agrobacterium sp., which together comprised up to 50% of the total microorganisms. In addition, a shift in bacterial community structure was observed during phenol biodegradation. Furthermore, the most effective phenol-degrading strain DW-1 that correspond to the main band in denaturing gradient gel electrophoresis (DGGE) profile was isolated and identified as Acinetobacter sp., according to phylogenetic analyses of the 16S ribosomal ribonucleic acid (rRNA) gene sequences. The strain DW-1 also produced the most important enzyme, phenol hydroxylase, and it also exhibited a good ability to degrade phenol when immobilized on granular active carbon (GAC). This study indicates that the enrichment culture has great potential application for treatment of phenol-polluted drinking water sources, and the indigenous phenol-degrading microorganism could recover from drinking water biofilters as an efficient resource for phenol removal. Therefore, the aim of this study is to draw attention to recover native phenol-degrading bacteria from drinking water biofilters, and use these native microorganisms as phenolic water remediation in drinking water sources.

Dechlorination of chloral hydrate is influenced by the biofilm adhesin protein LapA in Pseudomonas putida LF54

LapA is the largest surface adhesion protein of Pseudomonas putida that initiates biofilm formation. Here, by using transposon insertion mutagenesis and a conditional lapA mutant, we demonstrate for the first time that LapA influences chloral hydrate (CH) dechlorination in P. putida LF54.

Influence of hydraulic regimes on bacterial community structure and composition in an experimental drinking water distribution system

Microbial biofilms formed on the inner-pipe surfaces of drinking water distribution systems (DWDS) can alter drinking water quality, particularly if they are mechanically detached from the pipe wall to the bulk water, such as due to changes in hydraulic conditions. Results are presented here from applying 454 pyrosequencing of the 16S ribosomal RNA (rRNA) gene to investigate the influence of different hydrological regimes on bacterial community structure and to study the potential mobilisation of material from the pipe walls to the network using a full scale, temperature-controlled experimental pipeline facility accurately representative of live DWDS. Analysis of pyrosequencing and water physico-chemical data showed that habitat type (water vs. biofilm) and hydraulic conditions influenced bacterial community structure and composition in our experimental DWDS. Bacterial community composition clearly differed between biofilms and bulk water samples. Gammaproteobacteria and Betaproteobacteria were the most abundant phyla in biofilms while Alphaproteobacteria was predominant in bulk water samples. This suggests that bacteria inhabiting biofilms, predominantly species belonging to genera Pseudomonas, Zooglea and Janthinobacterium, have an enhanced ability to express extracellular polymeric substances to adhere to surfaces and to favour co-aggregation between cells than those found in the bulk water. Highest species richness and diversity were detected in 28 days old biofilms with this being accentuated at highly varied flow conditions. Flushing altered the pipe-wall bacterial community structure but did not completely remove bacteria from the pipe walls, particularly under highly varied flow conditions, suggesting that under these conditions more compact biofilms were generated. This research brings new knowledge regarding the influence of different hydraulic regimes on the composition and structure of bacterial communities within DWDS and the implication that this might have on drinking water quality.