Chimdi Mang Kalu

Introduction: The occurrence and abundance of heavy metal resistance genes (HMRGs) in drinking water treatment plants (DWTPs) and the stages at which they occur are a global challenge due to the risk of consuming contaminated water. Methods: The present study identified HMRGs associated with raw water sources, treatment stages (disinfection and filtration), final treated water, and produced sludge in three DWTPs across three provinces (Gauteng, Limpopo, and Mpumalanga) in South Africa, using a shotgun metagenomic approach. Results: In total, five classes of heavy metals (copper, arsenic, mercury, chromate, silver) and 50 resistance genes were identified across the three DWTPs. Most of the genes were obtained from the disinfection stages of the DWTPs. Discussion: This genomic dataset provides valuable information on the impact of disinfection stages on the relative abundance of HMRGs in drinking water treatment processes. Additionally, the transfer of genes into the final treated water consumed by the populace is a significant human health concern.

Contaminated water used for irrigation has been reported to trigger metabolic and physiological changes in plants. This study assessed the physicochemical status, pH, total dissolved solids (TDS), electrical conductivity (EC), salinity (SAL), and metals of Nwanedi River water and its influence on the primary metabolome of disordered tomato leaves (a physiological condition) irrigated with the Nwanedi River water. The physicochemical properties of water from Nwanedi River were measured by a multi-probe field meter, metal concentration by Inductively Coupled Optical Emission Spectrometer (ICP-OES), and primary metabolite profiling of disordered leaves done using LCMS-8040 triple quadrupole mass spectrometer. The pH, EC, TDS, Cd and Pb of river water were above the stipulated standards for irrigation purposes. Levels of hypoxanthine in tomato leaves were influenced negatively by pH (r = −0.91), TDS (r = −0.93), EC (r = −0.93), and SAL (r = −0.95) as revealed by Pearson correlation. Other metabolite quantities significantly swayed by the water’s condition were histamine, thymine, 4-hydroxyproline, acetylcarnitine and carnosine. The correlations between primary metabolites in the disordered leaves and the physicochemical parameters could indicate mitigation and adaptation mechanisms of the tomato plant.

Nanotechnology is a vast field applicable in various areas of study, including agriculture. Nanoparticles (NPs) can be used in plant disease control in many ways, including as fungicide delivery systems and to enhance cell-to-cell interactions in plants. Their ease of use can be manipulated not only for disease control in crop production but also for the identification of plant diseases. Information on the use of NPs for plant disease control and disease identification was collated. Mechanisms of action of NPs were outlined and discussed. Through these mechanisms, ZnO-NPs reduced Fusarium wilt symptoms in tomatoes by 28.57% and provided 67.99% protection. Ag-NPs promoted a 49.2% reduction of bacterial leaf blight disease in rice caused by Xanthomonas oryzae pv. oryzae. Various techniques involving NPs have been developed for plant disease identification and have shown promise. To ensure the sustainability of applications of NPs and crop production, several knowledge gaps need to be addressed. These include the timeliness of disease identification, the lack of standardised toxicity assessment protocols for NPs, and the paucity of information on NPs-microbiome-plant tri-interactions under field conditions. Furthermore, integration of NPs biosensing with remote sensing or innovative agricultural tools, and the unclear impact of NPs accumulation on soil enzyme activity and nutrient cycling, needs to be addressed. Further study is required to develop a novel technique for real-time identification of plant disease and to accurately identify and quantify the appropriate NPs for specific plant diseases.

Water treatment plants treat raw water making it suitable for consumption. Treatment stages are linked to the quality status of the treatment. The classes of antibiotic resistance genes as impacted by treatment stages remain under explored. We report the classes of antibiotic resistance genes (ARGs) from shotgun metagenomes as influenced by treatment stages.

Constant monitoring of the bacteriological indicators of drinking water and the associated Multiple Antibiotic Resistance (MAR) index as impacted by seasonal variations and different stages of Drinking Water Treatment Plants (DWTPs) may assist in understanding the pattern of their seasonal occurrences and the regular operations of the treatment plant that influence their removal. In this paper, the impact of the seasons and of the different stages of DWTPs on bacteriological indicator occurrence and the MAR-index of five treatment plants from three provinces in South Africa were assessed. Colilert-18 and Enterolert Quanti-Tray/2000 IDEXX methods were used to enumerate total coliform, E. coli, and Enterococcus spp. of water samples from the different treatment stages. Kirby–Bauer disc diffusion technique was used to assess the antibiotic susceptibility of the indicator bacteria isolates. All the measured physicochemical parameters were within the permissible limits. All the treatment plants essentially had a very high reduction of the indicator bacteria across all seasons. However, only two plants maintained the microbiological quality of the final treated water in compliance with the standards. A total of 121 isolates were obtained, and 106 isolates were multidrug resistant with the greatest resistance recorded for the Beta-lactams class of antibiotics. The MAR-index varied across seasons and with different plants. This implied that the usage of antibiotics is season- and site-dependent. The different stages of treatment reduced the indicator bacteria with the most reduction occurring in disinfection and candy stages. These findings extend the knowledge of how the treatment stages and seasons shape indicator bacteria and antibiotic resistance in drinking water.

In this study, high-throughput metagenomic amplicon sequencing and physicochemical analyses were used to evaluate the structural composition and functional diversity of the soil bacterial communities at different illegal waste dump sites. Results showed that while the litter-free soil was dominated by the phylum Proteobacteria, dumpsite soils were enriched with phylum Actinobacteria, followed by Proteobacteria, Firmicutes, Chloroflexi, Acidobacteria, Planctomycetes, Bacteroidetes, and Gemmatimonadetes. Bacterial diversity differed significantly (p > 0.05) between the litter-free and contaminated sites, with each dumpsite having distinct genera that demonstrate the impact of waste type on the bacterial community composition. Genus Nocardioides, a versatile organic and inorganic pollutant-degrading bacteria in the class Actinomycetia, was dominant in the dump site soils, raising the possibility that this genus could serve as a potential biomarker for dump site soil pollution. PICRUSt functional profiling also showed the presence of genes involved in putative degradative pathways in the dump site soils. Furthermore, community-level physiological profile (CLPP) analyses revealed that the dump site soils are habitats to active bacterial communities with significant catabolic and carbon utilization capacity. Overall, this study provides a theoretical insight into the diversity and unique soil bacterial assemblages in illegal dump sites that could encode biotechnologically significant genes for biosynthesis and biodegradation.

Despite root microecology playing critical role in plant growth and fidelity, relatively few studies have focused on the link between the microbial communities and root metabolome in the aquatic macrophytes under heavy metal (HM) pollution. Using high-throughput metagenomic sequencing, targeted metabolomics and community-level physiological profile analyses, we investigated the symbiotic associations between Phragmites australis with rhizospheric bacterial communities under differing acid mine drainage (AMD) pollution. Results indicated that AMD pollution and root localization significantly affected root metabolome profiles. Higher accumulation of adenosine monophosphate, inosine, methionine, carnitine and dimethylglycine were observed in the rhizosphere under AMD than non-AMD habitat. Overall, the bacterial diversity and richness, and functional (metabolic) diversity were lower under high-AMD pollution. While non-AMD site was enriched with members of phylum Firmicutes, Proteobacteria were the most abundant taxa in the rhizosphere and endosphere under AMD-polluted sites. Further, plant growth promoting rhizobacteria (Rhizobium, Delftia, Bradyrhizobium, and Mesorhizobium) and metal-tolerant bacteria (Bacillus, Arthrobacter, Massilia and Methylocystis) were most abundant in AMD-polluted than non-AMD habitat. Finally, pH, TDS (total dissolved solids), Cu, Cr, Fe, and Zn content were the key environmental factors that strongly contributed to the spatial perturbation of rhizospheric metabolites, proteobacterial and acidobacterial taxa. Overall, the study linked the differential endospheric and rhizospheric bacterial community and metabolite profiles in P. australis under AMD environment and provided insights into HM adaptability and phytoremediation potential.