Cloning, Expression, and Bioinformatics Analysis of Heavy Metal Resistance Gene afe_1862 from Acidithiobacillus ferrooxidans L1 in Escherichia coli

Function of N-acetyltransferase in the biotransformation of aniline in the green alga Chlamydomonas reinhardtii

Phytoplankton plays a crucial role in the fate of pollutants in aquatic ecosystems by biotransformation and bioaccumulation. Aniline was listed in priority pollutants due to its toxicity and widespread distribution in the aquatic environment. This study focused on investigating the capacity and mechanism of eukaryotic alga Chlamydomonas reinhardtii in transforming aniline. Results showed that the total removal percentage of aniline was 56% within 8 days at an initial concentration of 10 mg · L-1. The percentage of the biotransformation by C. reinhardtii was 23.4%. The biotransformation product was identified as acetanilide, indicating that acetylation was the primary biotransformation pathway. To reveal the key enzyme of the biotransformation process, the N-acetyltransferase (NAT) gene was cloned from the C. reinhardtii genome, and the NAT protein was obtained through heterologous expression. Aniline was significantly transformed by the purified NAT protein in vitro, and the product was also acetanilide. The characteristics of C. reinhardtii NAT in biotransformation of aniline was analyzed by bioinformatics methods. The binding sites in C. reinhardtii NAT for ligands (aniline and acetyl-CoA) were identified. Three highly reserved valine residues (Glu85-Asp86-Val87-Val88-Val89) as well as GLU131 and Cys122 were the indispensable amino acid residues for the catalysis from aniline to acetanilide. These results demonstrated the capacity of C. reinhardtii in the biotransformation of aniline, and the transformation process was primarily through N-acetylation of aniline to acetanilide catalyzed by NAT enzyme. This study provides novel insights into the biotransformation mechanism of aniline in eukaryotic green alga C. reinhardtii, facilitating the evaluation of the fate of aniline within aquatic ecosystems.

Impact of lead (Pb2+) on the growth and biological activity of Serratia marcescens selected for wastewater treatment and identification of its zntR gene-a metal efflux regulator

Microorganisms isolated from contaminated areas play an important role in bioremediation processes. They promote heavy metal removal from the environment by adsorbing ions onto the cell wall surface, accumulating them inside the cells, or reducing, complexing, or precipitating these substances in the environment. Microorganism-based bioremediation processes can be highly efficient, low-cost and have low environmental impact. Thus, the present study aimed to select Pb²⁺-resistant bacteria and evaluate the growth rate, biological activity, and the presence of genes associated with metal resistance. Serratia marcescens CCMA 1010, that was previously isolated from coffee processing wastewater, was selected since was able to growth in Pb²⁺ concentrations of up to 4.0 mM. The growth rate and generation time did not differ from those of the control (without Pb²⁺), although biological activity decreased in the first hour of exposure to these ions and stabilized after this period. The presence of the zntR, zntA and pbrA genes was analysed, and only zntR was detected. The zntR gene encodes a protein responsible for regulating the production of ZntA, a transmembrane protein that facilitates Pb²⁺ extrusion out of the cell. S. marcescens CCMA 1010 demonstrated a potential for use as bioindicator that has potential to be used in bioremediation processes due to its resistance to high concentrations of Pb²⁺, ability to grow until 24 h of exposure, and possession of a gene that indicates the existence of mechanisms associated with resistance to lead (Pb²⁺).

Plastisphere community assemblage of aquatic environment: plastic-microbe interaction, role in degradation and characterization technologies

It is undeniable that plastics are ubiquitous and a threat to global ecosystems. Plastic waste is transformed into microplastics (MPs) through physical and chemical disruption processes within the aquatic environment. MPs are detected in almost every environment due to their worldwide transportability through ocean currents or wind, which allows them to reach even the most remote regions of our planet. MPs colonized by biofilm-forming microbial communities are known as the ''plastisphere". The revelation that this unique substrate can aid microbial dispersal has piqued interest in the ground of microbial ecology. MPs have synergetic effects on the development, transportation, persistence, and ecology of microorganisms. This review summarizes the studies of plastisphere in recent years and the microbial community assemblage (viz. autotrophs, heterotrophs, predators, and pathogens). We also discussed plastic-microbe interactions and the potential sources of plastic degrading microorganisms. Finally, it also focuses on current technologies used to characterize those microbial inhabitants and recommendations for further research.

Effects of ZmHIPP on lead tolerance in maize seedlings: Novel ideas for soil bioremediation

Extensive lead (Pb) absorption by plants affects their growth and development and causes damage to the human body by entering the food chain. In this study, we cloned ZmHIPP, a gene associated with Pb tolerance and accumulation in maize, using combined linkage mapping and weighted gene co-expression network analysis. We show that ZmHIPP, which encodes a heavy metal-associated isoprenylated plant protein, positively modulated Pb tolerance and accumulation in maize seedlings, Arabidopsis, and yeast. The genetic variation locus (A/G) in the promoter of ZmHIPP contributed to the phenotypic disparity in Pb tolerance among different maize inbred lines by altering the expression abundance of ZmHIPP. Knockdown of ZmHIPP significantly inhibited growth and decreased Pb accumulation in maize seedlings under Pb stress. ZmHIPP facilitated Pb deposition in the cell wall and prevented it from entering the intracellular organelles, thereby alleviating Pb toxicity in maize seedlings. Compared to that in the mutant zmhipp, the accumulated Pb in the wild-type line mainly consisted of the low-toxicity forms of Pb. Our study increases the understanding of the mechanism underlying Pb tolerance in maize and provides new insights into the bioremediation of Pb-polluted soil.

Techniques Used for Analyzing Microplastics, Antimicrobial Resistance and Microbial Community Composition: A Mini-Review

Antimicrobial resistance (AMR) is a global health threat. Antibiotics, heavy metals, and microplastics are environmental pollutants that together potentially have a positive synergetic effect on the development, persistence, transport, and ecology of antibiotic resistant bacteria in the environment. To evaluate this, a wide array of experimental methods would be needed to quantify the occurrence of antibiotics, heavy metals, and microplastics as well as associated microbial communities in the natural environment. In this mini-review, we outline the current technologies used to characterize microplastics based ecosystems termed "plastisphere" and their AMR promoting elements (antibiotics, heavy metals, and microbial inhabitants) and highlight emerging technologies that could be useful for systems-level investigations of AMR in the plastisphere.