Genetic modifications of metallothionein enhance the tolerance and bioaccumulation of heavy metals in Escherichia coli

The effect of wastewater on the sensitivity of toxicity and genotoxicity assays for the detection of heavy metals was evaluated. Five microbiological toxicity tests were used to compare the toxicity of cadmium, copper, chromium, mercury, nickel, and zinc, both in deionized water solutions and in wastewater. The toxicity assays employed were: Microtox®, two tests of growth inhibition using Pseudomonas fluorescens, and two spectrophotometric assays of the inhibition of respiration test using baker's yeast and P. fluorescens. Also, the genotoxic effect of the assayed metals was evaluated by using the Ames test, the Escherichia coli WP2 test, and the SOS test. The sensitivity to metals decreases in most of the toxicity and genotoxicity assays; in general, higher sensitivity thresholds (EC20) in wastewater than in water solutions were determined. Each test shows different sensitivities to each metal, which is related to different sensitivities of the organisms used in the assays, as well as to other factors.

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Roasted coffee wastes as a substrate for Escherichia coli to grow and produce hydrogen

FEMS Microbiology Letters ◽

10.1093/femsle/fnaa088 ◽

2020 ◽

Vol 367 (11) ◽

Cited By ~ 1

Author(s):

Hripsime Petrosyan ◽

Liana Vanyan ◽

Satenik Mirzoyan ◽

Armen Trchounian ◽

Karen Trchounian

Keyword(s):

Escherichia Coli ◽

H2 Production ◽

High Rate ◽

Main Role ◽

Wild Type ◽

Roasted Coffee ◽

Energy Needs ◽

Genetic Modifications ◽

Coffee Grounds ◽

And Control

ABSTRACT After brewing roasted coffee, spent coffee grounds (SCGs) are generated being one of the daily wastes emerging in dominant countries with high rate and big quantity. Escherichia coli BW25113 wild-type strain, mutants with defects in hydrogen (H2)-producing/oxidizing four hydrogenases (Hyd) (ΔhyaB ΔhybC, ΔhycE, ΔhyfG) and septuple mutant (ΔhyaB ΔhybC ΔhycA ΔfdoG ΔldhA ΔfrdC ΔaceE) were investigated by measuring change of external pH, bacterial growth and H2 production during the utilization of SCG hydrolysate. In wild type, H2 was produced with rate of 1.28 mL H2 (g sugar)−1 h−1 yielding 30.7 mL H2 (g sugar)−1 or 2.75 L (kg SCG)−1 during 24 h. In septuple mutant, H2 production yield was 72 mL H2 (g sugar)−1 with rate of 3 mL H2 (g sugar)−1 h−1. H2 generation was absent in hycE single mutant showing the main role of Hyd-3 in H2 production. During utilization of SCG wild type, specific growth rate was 0.72 ± 0.01 h−1 with biomass yield of 0.3 g L−1. Genetic modifications and control of external parameters during growth could lead to prolonged and enhanced microbiological H2 production by organic wastes, which will aid more efficiently global sustainable energy needs resulting in diversification of mobile and fixed energy sources.

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High-Efficiency Scarless Genetic Modification in Escherichia coli by Using Lambda Red Recombination and I-SceI Cleavage

Applied and Environmental Microbiology ◽

10.1128/aem.00313-14 ◽

2014 ◽

Vol 80 (13) ◽

pp. 3826-3834 ◽

Cited By ~ 44

Author(s):

Junjie Yang ◽

Bingbing Sun ◽

He Huang ◽

Yu Jiang ◽

Liuyang Diao ◽

...

Keyword(s):

Escherichia Coli ◽

Genetic Modification ◽

Target Gene ◽

Donor Plasmid ◽

Content Type ◽

Recognition Sites ◽

Genetic Modifications ◽

Pcr Targeting ◽

Λ Red ◽

Red Recombination

ABSTRACTGenetic modifications of bacterial chromosomes are important for both fundamental and applied research. In this study, we developed an efficient, easy-to-use system for genetic modification of theEscherichia colichromosome, a two-plasmid method involving lambda Red (λ-Red) recombination and I-SceI cleavage. An intermediate strain is generated by integration of a resistance marker gene(s) and I-SceI recognition sites in or near the target gene locus, using λ-Red PCR targeting. The intermediate strain is transformed with a donor plasmid carrying the target gene fragment with the desired modification flanked by I-SceI recognition sites, together with a bifunctional helper plasmid for λ-Red recombination and I-SceI endonuclease. I-SceI cleavage of the chromosome and the donor plasmid allows λ-Red recombination between chromosomal breaks and linear double-stranded DNA from the donor plasmid. Genetic modifications are introduced into the chromosome, and the placement of the I-SceI sites determines the nature of the recombination and the modification. This method was successfully used forcadAknockout,gdhAknock-in, seamless deletion ofpepD, site-directed mutagenesis of the essentialmetKgene, and replacement ofmetKwith theRickettsiaS-adenosylmethionine transporter gene. This effective method can be used with both essential and nonessential gene modifications and will benefit basic and applied genetic research.

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Evaluation of Chemical and Microbiological Contaminants in Fresh Fruits and Vegetables from Peasant Markets in Cundinamarca, Colombia

Journal of Food Protection ◽

10.4315/0362-028x/jfp-19-453 ◽

2020 ◽

Vol 83 (10) ◽

pp. 1726-1737

Author(s):

MANUEL PATIÑO ◽

MARÍA FERNANDA VALENCIA-GUERRERO ◽

EDWIN SAMIR BARBOSA-ÁNGEL ◽

MARÍA JOSÉ MARTÍNEZ-CORDÓN ◽

PILAR DONADO-GODOY

Keyword(s):

Escherichia Coli ◽

Heavy Metals ◽

Listeria Monocytogenes ◽

Fruits And Vegetables ◽

Integrated Management ◽

Management Strategies ◽

Escherichia Coli O157 ◽

Pathogenic Microorganisms ◽

Maximum Residue Limit ◽

Integrated Crop Management

ABSTRACT In this study, chemical and microbiological contaminants were detected in fresh fruits and vegetables in peasant markets in the Department of Cundinamarca to assess food safety. At least one pesticide was detected in 63% of the samples evaluated (n = 100, including fruits and vegetables), and in 41% of these, pesticides exceeded the maximum residue limit. Within the pesticides found, 60% do not use a registry from the Instituto Colombiano Agropecuario to be applied on the crops where they were detected and are included in the toxicological categories “highly toxic” (category IB) and “moderately toxic” (category II). Heavy metals were found in 45% of the samples, with cadmium (38%) and lead (14%) being the most frequent. The pathogenic microorganisms Escherichia coli O157:H7, Listeria monocytogenes, Salmonella, and Campylobacter sp. were detected in 4, 2, 1, and 0% of the samples, respectively. Factors concerning integrated crop management, contaminated inputs with chemicals and microorganisms, and the lack of hygiene in the postharvest stage favor the presence of pesticide residues, heavy metals, and the appearance of pathogenic microorganisms. The results suggest the need to strengthen the implementation of integrated management strategies that guarantee the safety of fresh fruits and vegetables in the country. HIGHLIGHTS

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