The plastic and microplastic waste menace and bacterial biodegradation for sustainable environmental clean-up a review.

Environment plastic litter accumulation is a significant concern, needing urgent advancements in plastic waste management. Recent investigations into plastic biodegradation by bacteria and their enzymes are creating exciting unique opportunities for the development of biotechnological plastic waste treatment methods. This review summarizes information on bacterial and enzymatic biodegradation of plastic in a wide range of synthetic plastics such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyurethane (PUR), polytetrafluoroethylene (PTFE) and polyvinyl chloride (PVC). Plastic biodegradation is facilitated by Acinetobacter, Bacillus, Brevibacillus, Escherichia, Pseudomonas, Micrococcus, Streptomyces, and Rhodococcus bacteria, and enzymes such as proteases, esterases, lipases, and glycosidases. Molecular and analytical procedures used to analyze biodegradation processes are outlined, as are the obstacles in verifying plastic breakdown using these methods. Taken together, the findings of this study will contribute significantly to the construction of a library of high-efficiency bacterial isolates and consortiums and their enzymes for use in plastic biosynthesis. This information is useful to researchers investigating plastic bioremediation and a supplement to the scientific and grey literature already accessible. Finally, the review focuses on expanding the understanding of bacterial capacity to break-down plastic utilizing modern biotechnological methods, bio-nanotechnological-based materials, and their future role in resolving pollution problems.

Bioaugmentation potential of inoculum derived from anaerobic digestion feedstock for enhanced methane production using water hyacinth.

The utilisation of water hyacinth for production of biogas is considered to be a solution to both its control and the global renewable energy challenge. In this instance, an investigation was conducted to evaluate the potential of water hyacinth inoculum to enhance methane production during anaerobic digestion (AD). Chopped whole water hyacinth (10% (w/v)) was digested to prepare an inoculum consisting mainly of water hyacinth indigenous microbes. The inoculum was incorporated in the AD of freshly chopped whole water hyacinth to set up different ratios of water hyacinth inoculum and water hyacinth mixture with appropriate controls. The results of batch tests with water hyacinth inoculum showed a maximal cumulative volume of 211.67 ml of methane after 29 days of AD as opposed to 88.6 ml of methane generated from the control treatment without inoculum. In addition to improving methane production, inclusion of water hyacinth inoculum reduced the electrical conductivity (EC) values of the resultant digestate, and, amplification of nifH and phoD genes in the digestate accentuates it as a potential soil ameliorant. This study provides an insight into the potential of water hyacinth inoculum to enhance methane production and contribute to the feasibility of the digestate as a soil fertility enhancer.

Phytoremediation of soils contaminated by lead and cadmium in Ethiopia, using Endod (Phytolacca dodecandra L).

Phytoremediation is a cost effective and environmentally sustainable green technology for remediation of metal contaminated sites. In Addis Ababa, the capital of Ethiopia, large vegetable farms are grown on contaminated sites. This study evaluates the potential of Phytolacca dodecandra L to remediate Pb and Cd from contaminated sites in Addis Ababa. Pb and Cd in soil samples and different plant parts were determined using AAS. Phytoremediation potential of P. dodecandra in different seasons was estimated by calculating the Bioconcentration factor (BCF) and translocation factor (TF). The average BCF recorded for plant shoot in dry season samples varied from 0.87 to 1.74 for Pb and 1.06 to 2.00 for Cd, while in wet season it was within the range of 1.1-1.53 for Pb and 0.93-3.89 for Cd. The TF values for P. dodecandra ranged from 0.84 to 3.49 for Pb and 1.81 to 4.11 for Cd in dry season, whereas for wet season it varied between 1.34 and 2.01 for Pb and 1.78 and 2.97 for Cd. Since the mean values of BCF and TF were >1, it was concluded that P. dodecandra has considerable potential for phytoextraction of Pb and Cd in contaminated sites.

Effective treatment of acid mine drainage using a combination of MgO-nanoparticles and a series of constructed wetlands planted with Vetiveria zizanioides: A hybrid and stepwise approach.

In this novel study, acid mine drainage (AMD) was treated using a hybrid approach comprising a nano-and-biotic system synergistically integrated in a step-wise and modular fashion. Specifically, the treatment chains were made up of different stages, which comprise, neutralization using activated magnesite or MgO-nanoparticles (NPs) (Stage 1) and polishing the product water using a series of wetlands (Stage 2) in a step-wise connection. In stage One (1), real AMD was treated with MgO-NPs at a ratio of 1:100 (1 g/100 mL - w/v ratio), 500 rpm of mixing speed, and One (1) hour of hydraulic retention time (HRT) whilst in stage 2, the final water was fed into constructed wetlands, i.e. Three (3) interconnected wetland with different flow modalities [(I) subsurface vertical flow (SSVF-CW), (II) free water surface flow (FWS-CW), and (III) subsurface horizontal flow (SSHF-CW)], for further purification and polishing to the desired product. In this stage, i.e. stage 2, the product water and substrate were collected daily at the outlet and bottom of each wetland. After the treatment process, the pH of the product water was observed to have increased from 2.6 to 10.4. Significant removal of inorganic contaminants was also observed and the following removal sequence was registered, Fe (99.8%) ≥ Al (99.5%) ≥ Mn (99.24%) ≥ Zn (98.36%) ≥ Cu (97.38%) ≥ Ni (97.7%) ≥ SO42─ (80.59%). Reduction in electrical conductivity (EC) was also observed (86%). Specifically, the nano-part removed the metals and sulphate partially whereas the bio-part effectively removed SO42─ and EC levels, thus denoting stellar combination and complementary performance for the hybrid system in integrated fashion. The state-of-the-art analytical instruments were used to underpin and succinct the fate of chemical species in raw and product MgO-NPs, substrates, and the grass. Finally, the product water conformed to the prescribed standards for effluent discharge hence proving that the synergy of neutralization and bio-remediation, i.e. nano-and-biotic system, could potentially yield the desired results in mine water management and afield. This will go a long way in curtailing ecological footprints associated with mining activities thus fostering the concept of sustainable development.

Influences of geochemical factors and substrate availability on Gram-positive and Gram-negative bacterial distribution and bio-processes in ageing municipal landfills.

Bacteria are primary agents of organic substrate metabolisation and elemental cycling in landfills. Two major bacterial groups, namely, Gram-positive (GP) and Gram-negative (GN), drive independent metabolic functions that contribute to waste stabilisation. There is a lack of explicit exploration of how these different bacterial guilds respond to changing carbon (C) availability and substrate depletion as landfills age and how landfill geochemistry regulates their distribution. This study investigated and compared the abundance and vertical distribution of GP and GN bacteria in 14- and 36-year-old municipal landfills and explored linkages among bacterial groups, nutrient elements, heavy metals and soil texture. We found higher GP bacteria in the 14-year-old landfill, while GN bacteria dominated the 36-year-old landfill. The non-metric multidimensional scaling (nMDS) analysis showed that dissimilarities in the relative abundance of the GP and GN bacteria were linked distinctly to landfill age, and not depth. In support of this inference, we further found that GP and GN bacteria were negatively correlated with heavy metals and essential nutrients in the 14- and 36-year-old landfills, respectively. Notably, the GP/GN ratio, an indicator of relative C available for bacterial mineralisation, was greater in the14-year-old landfill, suggesting greater C availability. Conversely, the C to N ratio was higher in the 36-year-old landfill, indicating lower N mineralisation. Collectively, the results of the study reveal key insights into how landfill ageing and stabilisation influence distinct functional shifts in the abundance of GP and GN bacteria, and these are mainly driven by changes in C and N bioavailability.

Correlations Between Root Metabolomics and Bacterial Community Structures in the Phragmites australis Under Acid Mine Drainage-Polluted Wetland Ecosystem.

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.

Shifts in Bacterial Diversity During the Spontaneous Fermentation of Maize Meal as Revealed by Targeted Amplicon Sequencing.

Maize meal was allowed to undergo uncontrolled fermentation in the laboratory, in simulation of the traditional method of fermentation as practised in most African households. During the fermentation process, samples were collected daily for 11 days. Physico-chemical analysis of the fermenting slurry and metagenomics analysis of the microbial community using 16S rRNA demonstrated an interrelationship between the changes in the properties of the fermentation environment and the successional interplay of the microbial community. The first 24 h of fermentation at pH of 6.5 was characterised by the proliferation of probiotic Lactobacillus and Bifidobacterium, with their relative abundance being 40.7% and 29.9%, respectively. However, prolonged fermentation and a drop in pH from 5.3 to 3.7 caused a decline and finally an absence of these probiotic bacteria which were replaced by Clostridium spp. with a relative abundance of between 97% and 99% from day 5 to day 11. This study demonstrated that prolonged fermentation of maize meal is not ideally suited for the proliferation of probiotic nutritionally beneficial bacteria.

Distribution and comparison of bacterial communities in HVAC systems of two university buildings: Implications for indoor air quality and public health.

The installation of HVAC systems in building is meant to enhance indoor air quality as well as increase comfort to occupants. However, HVAC systems have also become a vehicle of contamination of indoor air with potentially pathogenic microorganisms. DNA was extracted from ten HVAC filter dust samples collected from two buildings and subjected to high throughput sequencing analysis to determine the bacterial community structure. Further, the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2) software was used to predict the potential functional capabilities of the bacterial communities. Sequencing analysis led to the identification of five major bacterial phyla, including Proteobacteria, Cyanobacteria, Actinobacteria, Firmicutes and Bacteroidetes. At genus level, Mycobacterium, Bacillus, Cupriavidus, Hyphomicrobium and Mesorhizobium were the most dominant. With the exception of the later two bacterial genera, the first three are potential pathogens whose presence in HVAC systems poses a significant public health risk, especially among immunocompromised individuals. Nine pathways associated with antibiotics resistance and bacterial pathogenicity were identified, including polymyxin resistance and peptidoglycan biosynthesis pathways. Further, investigation of the relationship between the detected bacterial meta-communities and predicted potential virulence factors (antibiotic resistance and pathogenic genes) led to the detection of 350 positive associations among 43 core bacteria, 2 pathogenic genes (sitA and uidA) and 14 resistance genes. Overall, the heterogeneous nature of microorganisms found in HVAC systems observed in this study shows that HVAC systems are the origin of airborne infections in indoor environments, and must be periodically cleaned and disinfected to avoid the build-up of pathogens, and the subsequent exposure of human occupants of these pathogens.

Microbiology of municipal solid waste landfills: a review of microbial dynamics and ecological influences in waste bioprocessing.

Municipal solid waste landfills are widely used as a waste management tool and landfill microbiology is at the core of waste degradation in these ecosystems. This review investigates the microbiology of municipal solid waste landfills, focusing on the current state of knowledge pertaining to microbial diversity and functions facilitating in situ waste bioprocessing, as well as ecological factors influencing microbial dynamics in landfills. Bioprocessing of waste in municipal landfills emanates from substrate metabolism and co-metabolism by several syntrophic microorganisms, resulting in partial transformation of complex substrates into simpler polymeric compounds and complete mineralisation into inorganic salts, water and gases including the biofuel gas methane. The substrate decomposition is characterised by evolution and interactions of different bacterial, archaeal and fungal groups due to prevailing biotic and abiotic conditions in the landfills, allowing for hydrolytic, fermentative, acetogenic and methanogenic processes to occur. Application of metagenomics studies based on high throughput Next Generation Sequencing technique has advanced research on profiling of the microbial communities in municipal solid waste landfills. However, functional diversity and bioprocess dynamics, as well as key factors influencing the in situ bioprocesses involved in landfill waste degradation; the very elements that are key in determining the efficiency of municipal landfills as tools of waste management, remain ambiguous. Such gaps also hinder progressive understanding of fundamentals that underlie technology development based on waste biodegradation, and exploration of municipal waste as a bioresource.

Occurrence and diversity of waterborne fungi and associated mycotoxins in treated drinking water distribution system in South Africa: implications on water quality and public health.

Despite increased public health concerns on the occurrences of potentially pathogenic/mycotoxigenic fungi in public drinking water system, dissemination of hygienically relevant fungi and their associated mycotoxins via distribution system under the dual burden of ageing infrastructure and ancillary distribution network lacking infrastructure for high-pressure water delivery systems is unknown. In this study, the diversity of fungi and occurrence of mycotoxins at 30 different points along treated piped water supply and ancillary distribution networks in Johannesburg, South Africa, were monitored for 12 months. Mycological analysis using cultural and molecular methods yielded 282 fungi belonging to phylum Ascomycota, having Aspergillus (91%), Penicillium (65%) and Trichoderma (31%) as dominant genera, with Aspergillus fumigatus, Penicillium citrinum, Purpureocillium lilacinum and Aspergillus flavus as the most prevalent species. Communal standpipe and reservoir outlets had significantly higher prevalence than other water samples. There was no strong correlation between total coliforms (r = 0.4266) and residual chlorine (r = - 0.1937), and fungal prevalence at p < 0.05. LC-MS/MS analysis detected aflatoxins B1, M1, G1 and G2 in 50, 9, 9 and 46% of water samples analysed, respectively, ranging between 0 and 3.18 ng/l. Deoxynivalenol (DON), 3-acetyl DON and 15-acetyl DON levels were between 8.4-96.1, 18.7-145.7 and 15.2-71.6 ng/l, respectively. However, the estimated average daily dose (ADD) for detected mycotoxins was below the tolerable daily intake (TDI), suggesting no toxicological risk. Presence of potentially mycotoxigenic fungi, despite the low toxicological risk, demonstrates a need for appropriate monitoring for fungi and mycotoxins in treated drinking water distribution systems for improved water quality and long-term public health assurance.

Targeted 16S rRNA amplicon analysis reveals the diversity of bacterial communities in carwash effluents.

This study aimed to analyze the bacterial diversity in carwash effluents and to determine their potential for use in microbial degradation of environmental contaminants. Nine carwash effluent samples were collected for physicochemical and bacterial community diversity analysis using multi-digital probes and 16S rRNA gene amplicon sequencing respectively. The pH of all effluent samples was neutral to slightly alkaline. Oil and grease concentrations ranged from 15.3 to 49.7 mg/L. 16S gene amplicon sequencing of the nine samples produced 45,934-sequence reads, which translated to 13 bacterial phyla, 26 classes, and 43 genera. The most dominant phyla were Proteobacteria, Bacteroidetes, Firmicutes, and Fusobacteria. Canonical correspondence analysis (CCA) showed that the distribution of the phyla Proteobacteria, Bacteroidetes, Acidobacteria, and Verrucomicrobia was influenced by the presence of oil and grease, total petroleum hydrocarbons-gasoline range organics (GRO-TPH), and metals species (Pb, Cu, and Zn). The dominant bacterial genera found in the present study were previously proven to biodegrade hydrocarbons, and their presence in carwash effluents could bode well for in situ natural bioremediation of these contaminated sites.

Prevalence and public health implications of mycotoxigenic fungi in treated drinking water systems.

Insufficient potable water resources and poorly treated drinking water quality are the world's number one cause for preventable morbidity and mortality from water-related pathogenic microorganisms. Pathogenic microorganisms, including mycotoxigenic fungi, have been identified in treated drinking water. This paper presents a review of mycotoxigenic fungi as a health risk to the public as these fungi are responsible for allergies, cancers and opportunistic infections mainly to immunocompromised patients. The exacerbating factors contributing to fungal presence in water distribution systems, factors that lead to fungi being resistant to water treatment and treated drinking water quality legislations are also discussed. This paper provides a review on the prevalence of mycotoxigenic fungi and their implications to public health in treated drinking water, and the need for inclusion in treated drinking water quality regulations.

Cultivable bacterial diversity, physicochemical profiles, and toxicity determination of car wash effluents.

Carwash effluents contain potentially toxic chemical and microbiological pollutants which may pose public health and ecotoxicological threats if directly discharged into surface waters. This work was aimed at determining the microbiological, physicochemical, and toxicological parameters of carwash effluents. Toxicity assays were determined using whole effluent toxicity (WET) using Danio rerio and Daphnia pulex. For microbiological analysis, sample aliquots were spread plated onto R2A Agar for the isolation of heterotrophic bacteria followed by DNA extraction from axenic cultures for sequencing analysis. The pH of effluent samples lay in the alkaline range, and ranged from pH 7 to pH 10. Sample salinity ranged from 0.2 to 0.3 g/Kg. Electrical conductivity values ranged from 274 to 554 µS/cm. Concentrations of Co, Pb, and Ni were < 1 mg/L in all samples while the concentrations of Cu ranged from 0.94 to 3.8 mg/L and Zn from 1.15 to 3 mg/L. Oil and grease concentrations ranged from 5 to 24 mg/L. The concentrations of TPH-GRO were low at < 1 mg/L in all samples. All the carwash effluents were categorised as acutely toxic, with ≥ 75% mortality recorded for both test organisms within the first 24 h of exposure to the test solutions. Heterotrophic bacteria counts ranged from 2800 to 4600 CFU/100 ml. Sequencing analysis revealed that 57% of the isolates were closely related to Aeromonas species, with 43% closely related to Pseudomonas species. We conclude that carwash effluents are veritable sources of microbiological contaminants and potentially toxic chemical pollutants of public health and ecotoxicological concern.

Diversity Analysis and Bioresource Characterization of Halophilic Bacteria Isolated from a South African Saltpan.

Though intensive research has been channeled towards the biotechnological applications of halophiles and other extremophilic microbes, these studies have not been, by any means, exhaustive. Saline environments still offer a vast diversity of microbes with potential to produce an array of natural products which can only be unlocked by concerted research efforts. In this study, a combination of culture and molecular approaches were employed to characterize halophilic bacteria from saltpan water samples and profile their potential biotechnological applications. Physicochemical analysis of the water samples showed that pH was alkaline (pH 8.8), with a salinity of 12.8%. 16S rRNA gene targeted amplicon analysis produced 10 bacterial phyla constituting of Bacteroidetes (30.57%), Proteobacteria (15.27%), Actinobacteria (9.05%), Planctomycetes (5.52%) and Cyanobacteria (3.18%). Eighteen strains were identified using sequencing analysis of the culturable bacterial strains. From these, the strains SP7 and SP9 were positive for cellulase production while the strains SP4, SP8 and SP22 were positive for lipase production. Quantitative enzyme assays showed moderate extracellular cellulase activity (1.95 U/mL) and lipase activity (3.71 U/mL) by the isolate SP9 and SP4 respectively. Further, of the six isolates, the isolate SP9 exhibited exploitable potential in the bioremediation of hydrocarbon pollution as demonstrated by its fairly high activity against benzanthracene (70% DCPIP reduction). Elucidation of the isolates secondary metabolites showed the production of the molecules 2,3-butanediol, hexahydro-3-(2-methylpropyl)pyrrole[1,2a]pyrazine-1,4-dione, aziridine, dimethylamine and ethyl acetate (GC-MS) and oxypurinol and 5-hydroxydecanoic acid (LC-MS), particularly by the isolate Salinivibrio sp. SP9. Overall, the study showed that the isolated halophiles can produce secondary metabolites with potential industrial and pharmaceutical application.

Occurrences and implications of pathogenic and antibiotic-resistant bacteria in different stages of drinking water treatment plants and distribution systems.

Different stages of drinking water treatment plants (DWTPs) play specific roles in diverse contaminants' removal present in natural water sources. Although the stages are recorded to promote adequate treatment of water, the occurrence of pathogenic bacteria (PB) and antibiotic-resistant bacteria (ARB) in the treated water and the changes in their diversity and abundance as it passed down to the end users through the drinking water distribution systems (DWDSs), is a great concern, especially to human health. This could imply that the different stages and the distribution system provide a good microenvironment for their growth. Hence, it becomes pertinent to constantly monitor and document the diversity of PB and ARB present at each stage of the treatment and distribution system. This review aimed at documenting the occurrence of PB and ARB at different stages of treatment and distribution systems as well as the implication of their occurrence globally. An exhaustive literature search from Web of Science, Science-Direct database, Google Scholar, Academic Research Databases like the National Center for Biotechnology Information, Scopus, and SpringerLink was done. The obtained information showed that the different treatment stages and distribution systems influence the PB and ARB that proliferate. To minimize the human health risks associated with the occurrence of these PB, the present review, suggests the development of advanced technologies that can promote quick monitoring of PB/ARB at each treatment stage and distribution system as well as reduction of the cost of environomics analysis to promote better microbial analysis.

Metagenomics datasets of water and sediments from eutrophication-impacted artificial lakes in South Africa.

We present metagenomes of 16 samples of water and sediment from two lakes, collected from eutrophic and non-eutrophic areas, including pooled samples enriched with phosphate and nitrate. Additionally, we assembled 167 bacterial metagenome-assembled genomes (MAGs). These MAGs were de-replicated into 83 unique genomes representing different species found in the lakes. All the MAGs exhibited >70% completeness and <10% contamination, with 79 MAGs being classified as 'nearly complete' (completeness >90%), while 54 falling within 80-90% range and 34 between 75-80% complete. The most abundant MAGs identified across all samples were Proteobacteria (n = 80), Firmicutes_A (n = 35), Firmicutes (n = 13), and Bacteriodota (n = 22). Other groups included Desulfobacteria_I (n = 2), Verrucomicrobiota (n = 4), Campylobacterota (n = 4) and Actinobacteriota (n = 6). Importantly, phylogenomic analysis identified that approximately 50.3% of the MAGs could not be classified to known species, suggesting the presence of potentially new and unknown bacteria in these lakes, warranting further in-depth investigation. This study provides valuable new dataset on the diverse and often unique microbial communities living in polluted lakes, useful in developing effective strategies to manage pollution.

Assessing the impact of COVID-19 restrictions on the microbial quality of an urban water catchment and the associated probability of waterborne infections.

The World Health Organization reported that COVID-19 cases reached 611,421,786 globally by September 23, 2022. Six months after the first reported case, the disease had spread rapidly, reaching pandemic status, leading to numerous preventive measures to curb the spread, including a complete shutdown of many activities worldwide. Such restrictions affected services like waste management, resulting in waste accumulation in many communities and increased water pollution. Therefore, the current study investigated if lockdown impacted surface water microbial quality within an urban water catchment in South Africa. Using quantitative microbial risk assessment, the study further assessed changes in the probability of infection (Pi) with gastrointestinal illnesses from exposure to polluted water in the catchment. Escherichia coli data for 2019, 2020 and 2021 - pre-COVID, lockdown, and post-lockdown periods, respectively - were collected from the area's wastewater treatment management authorities. The Pi was determined using a beta-Poisson model. Mean overall E. coli counts ranged from 2.93 ± 0.16 to 5.30 ± 1.07 Log10 MPN/100 mL. There was an overall statistically significant increase in microbial counts from 2019 to 2021. However, this difference was only accounted for between 2019 and 2021 (p = 0.008); the increase was insignificant between 2019 and 2020, and 2020 and 2021. The Pi revealed a similar trend for incidental ingestion of 100 mL and 1 mL of polluted water. No statistically significant difference was observed between the years based on multiple exposures. Although the overall microbial load and Pi estimated within the catchment exceeded the local and international limits recommended for safe use by humans, especially for drinking and recreation, these were not significantly affected by the COVID-19 restrictions. Nevertheless, these could still represent a health hazard to immunocompromised individuals using such water for personal and household hygiene, especially in informal settlements without access to water and sanitation services.

Multivariate analysis of enriched landfill soil consortia provide insight on the community structural perturbation and functioning during low-density polyethylene degradation.

Plastic-enriched sites like landfills have immense potential for discovery of microbial consortia that can efficiently degrade plastics. In this study, we used a combination of culture enrichment, high-throughput PacBio sequencing of 16 S rRNA and the ITS gene, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) to examine the compositional and diversity perturbations of bacterial and fungal consortia from landfill soils and their impact on low-density polyethylene (LDPE) film biodegradation over a 90-day period. Results showed that enrichment cultures effectively utilized LDPE as a carbon source for cellular growth, resulting in significant weight reduction (22.4% and 55.6%) in the films. SEM analysis revealed marked changes in the micrometric surface characteristics (cracks, fissures, and erosion) and biofilm formation in LDPE films. FTIR analyses suggested structural and functional group modification related to C-H (2831-2943 cm⁻¹), and CH2 (1400 cm⁻¹) stretching, CO and CC (680-950 cm⁻¹) scission, and CO incorporation (3320-3500 cm⁻¹) into the carbon backbone, indicative of LDPE polymer biodegradation. Enrichment cultures had lower diversity and richness of microbial taxa compared to soil samples, with LDPE as a carbon source having a direct influence on the structure and functioning of the microbial consortia. A total of 26 bacterial and 12 fungal OTU exhibiting high relative abundance and significant associations (IndVal > 0.7, q < 0.05) were identified in the enrichment culture. Bacterial taxa such as unclassified Parvibaculum FJ375498, Achromobacter xylosoxidans, unclassified Chitinophagaceae PAC002331, unclassified Paludisphaera and unclassified Comamonas JX898122, and six fungal species (Galactomyces candidus, Trichosporon chiropterorum, Aspergillus fumigatus, Penicillium chalabudae, Talaromyces thailandensis, and Penicillium citreosulfuratum) were identified as the putative LDPE degraders in the enrichment microbial consortium cultures. PICRUSt2 metagenomic functional profiling of taxonomic bacterial taxa abundances in both landfill soil and enrichment microbial consortia also revealed differential enrichment of energy production, stress tolerance, surface attachment and motility pathways, and xenobiotic degrading enzymes important for biofilm formation and hydrolytic/oxidative LDPE biodegradation. The findings shed light on the composition and structural changes in landfill soil microbial consortia during enrichment with LDPE as a carbon source and suggest novel LDPE-degrading bacterial and fungal taxa that could be explored for management of polyethylene pollution.

Characterization of the physicochemical composition of anaerobically digested (digestate) high throughput red meat abattoir waste in South Africa and the determination of its quality as a potential biofertilizer.

Anaerobic digestion as a treatment option for waste produced in high throughput red meat abattoirs in South Africa is now gaining interest in both private and government sectors. The resultant digested slurry (digestate) is currently being regarded as waste despite its nutritional value for soil and plants which can be harnessed if digestate is utilized as biofertilizer to ensure nutrient cycling. The study investigated the physicochemical and microbial characteristics of digestate emanating from anaerobic digestion of red meat abattoir waste in South Africa, as well as evaluating its potential use as biofertilizer. The pH, total solids, volatile solids, chemical oxygen demand, electrical conductivity, total volatile fatty acids and chemical composition were determined using standard methods. Microbial analyses were determined according to the serial dilution method (101- 1010). The results were benchmarked with Public Available Specifications (PAS) 110 standards for quality control of digestate intended to be used as biofertilizer for agricultural purposes. Results for pH, total solids, electrical conductivity, chemical oxygen demand, and total volatile fatty acids fell within the required PAS110 standard which requires standard limits of 6.5-9, 30 %-50 %, <1500 mg/L, <3000 µS/cm, and 0.43 COD/g VS respectively. Moisture content in all red meat abattoir digestate ranged from 92.05 ± 0.5 % to 95.49 ± 0.38 % and did not meet the required limit of <35 %. E. coli in untreated cattle and pig abattoir digestate were 1023 ± 35 cfu/mL and 1068 ± 51 cfu/mL, respectively, and also did not meet the required standard limit of <1000 cfu/mL. Chemical composition showed that abattoir digestate was abundant in both macronutrients and micronutrients, and heavy metal concentrations in all digestate samples fell within the PAS 110. In conclusion, abattoir digestate was observed to be highly abundant in nutrients essential for soil health and plant growth, and mostly met the required EU PAS110 standard for utilization as biofertilizer in agricultural land.

Contribution of pollution gradient to the sediment microbiome and potential pathogens in urban streams draining into Lake Victoria (Kenya).

In sub-Saharan Africa (SSA), urban rivers/streams have long been subjected to anthropogenic pollution caused by urbanization, resulting in significantly altered chemical and biological properties of surface water and sediments. However, little is known about the diversity and structure of river microbial community composition and pathogens, as well as how they respond to anthropogenic inputs. High-throughput 16S rRNA amplicon sequencing and PICRUSt predictive function profiling were used in this study to conduct a comprehensive analysis of the spatial bacterial distribution and metabolic functions in sediment of two urban streams (Kisat and Auji) flowing through Kisumu City, Kenya. Results revealed that sediment samples from the highly urbanized mid and lower stream catchment zones of both streams had significantly higher levels of total organic carbon (TOC), total nitrogen (TN), total phosphorous (TP) than the less urbanized upper catchment zone, and were severely polluted with toxic heavy metals lead (Pb), cadmium (Cd), and copper (Cu). Differential distribution of Actinobacteria, Proteobacteria, Chloroflexi, and Verrucomicrobia in sediment bacterial composition was detected along stream catchment zones. The polluted mid and lower catchment zones were rich in Actinobacteria and Proteobacteria, as well as a variety of potential pathogenic taxa such as Corynebacterium, Staphylococcus, Cutibacterium, Turicella, Acinetobacter, and Micrococcus, as well as enteric bacteria such as Faecalibacterium, Shewanella, Escherichia, Klebsiella, Enterococcus, Prevotella, Legionella, Vibrio and Salmonella. Furthermore, PICRUSt metabolic inference analysis revealed an increasing enrichment in the sediments of genes associated with carbon and nitrogen metabolism, disease pathogenesis, and virulence. Environmental factors (TOC, Pb, Cd, TN, pH) and geographical distance as significant drivers of sediment bacterial community assembly, with the environmental selection to play a dominant role. In polluted river catchment zone sediment samples, Pb content was the most influential sediment property, followed by TOC and Cd content. Given the predicted increase in urbanization in SSA, further alteration of surface water and sediment microbiome due to urban river pollution is unavoidable, with potential long-term effects on ecosystem function and potential health hazards. As a result, this study provides valuable information for ecological risk assessment and management of urban rivers impacted by diffuse and point source anthropogenic inputs, which is critical for future proactive and sustainable urban waste management, monitoring, and water pollution control in low-income countries.