Do environmentally induced DNA variations mediate adaptation in Aspergillus flavus exposed to chromium stress in tannery sludge?

An animal charcoal contaminated cottage industry soil highlighted by halophilic archaea dominance and decimation of bacteria

An animal charcoal contaminated cottage industry soil in Lagos, Nigeria (ACGT) was compared in an ex post facto study with a nearby unimpacted soil (ACGC). Hydrocarbon content was higher than regulatory limits in ACGT (180.2 mg/kg) but lower in ACGC (19.28 mg/kg). Heavy metals like nickel, cadmium, chromium and lead were below detection limit in ACGC. However, all these metals, except cadmium, were detected in ACGT, but at concentrations below regulatory limits. Furthermore, copper (253.205 mg/kg) and zinc (422.630 mg/kg) were above regulatory limits in ACGT. Next generation sequencing revealed that the procaryotic community was dominated by bacteria in ACGC (62%) while in ACGT archaea dominated (76%). Dominant phyla in ACGC were Euryarchaeota (37%), Pseudomonadota (16%) and Actinomycetota (12%). In ACGT it was Euryarchaeota (76%), Bacillota (9%), Pseudomonadota (7%) and Candidatus Nanohaloarchaeota (5%). Dominant Halobacteria genera in ACGT were Halobacterium (16%), Halorientalis (16%), unranked halophilic archaeon (13%) Salarchaeum (6%) and Candidatus Nanohalobium (5%), whereas ACGC showed greater diversity dominated by bacterial genera Salimicrobium (7%) and Halomonas (3%). Heavy metals homeostasis genes, especially for copper, were fairly represented in both soils but with bacterial taxonomic affiliations. Sites like ACGT, hitherto poorly studied and understood, could be sources of novel bioresources.

Genomic and proteomic analyses reveal the reduction mechanism of hexavalent chromium by the culturing supernatant of strain Pediococcus acidilactici 13-7

This study used lactic acid bacteria with high antioxidative properties to screen for strains capable of reducing hexavalent chromium [Cr (VI)] in their culturing supernatants. The strain Pediococcus acidilactici 13-7 exhibited potent Cr (VI)-reducing capability and remarkable resistance to Cr (VI) even at concentration as high as 24 mM. Comparative genomics analysis revealed a unique gene, ChrR, associated with Cr (VI) reduction in this strain, distinguishing it from four reference strains of P. acidilactici. The proteomic investigation identified proteins linked to the ChrR gene, such as nqo1, frdA, and gshR, indicating significant enrichment in redox-related functions and oxidative phosphorylation pathways. These findings suggest that P. acidilactici 13-7 possesses superior electron transfer capacity compared to other strains, making it more adaptable under highly oxidative conditions by modulating the external environment to mitigate oxidative stress. Collectively, the results demonstrated the potential application of this lactic acid bacterial strain for bioremediation of heavy metals by its ability to reduce Cr (VI), and shed light on the molecular mechanisms underlying Cr (VI) reduction of the strain P. acidilactici 13-7.

Disinfection and Photocatalytic Degradation of Organic Contaminants Using Visible Light-Activated GCN/Ag2CrO4 Nanocomposites

Visible-light-driven photocatalysts have gained increasing attention in the past few decades in treating emerging contaminants in water and wastewater. In this work, the photocatalytic activity of the coupled graphitic carbon nitride (GCN) and silver chromate (Ag2CrO4), herein denoted as GCN/Ag2CrO4, nanocomposites was evaluated for degrading organic pollutants and inactivating microorganisms under visible light irradiation using a royal blue light-emitting diode (LED). The organic pollutants studied were 2,4-dichlorophenoxyacetic acid (2,4-D) and methyl chlorophenoxy propionic acid (MCPP or Mecoprop-P) present in KillexR, a commercially available herbicide, bovine serum albumin (BSA) protein, and SARS-CoV-2 spike protein. The disinfection experiments were conducted on wastewater secondary effluent. The results showed that over 85% degradation was achieved for both 2,4-D and Mecoprop-P in 120 min while 100% of BSA protein and 77.5% of SARS-CoV-2 protein were degraded in 20 min and 30 min, respectively. Additionally, GCN/Ag2CrO4 nanocomposites led to over one log reduction of cellular ATP (cATP), total coliforms, and E. coli in wastewater treatment plant (WWTP) secondary effluent after 60 min of royal blue LED irradiation. It was observed that the degradation performance of a photocatalyst under light irradiation is contaminant-specific. The binding affinity of the released metal ions from GCN/Ag2CrO4 with protein and ATP functional groups was responsible for the degradation of proteins and the reduction of cATP, while the generated ROS was responsible for the disinfection of total coliforms and E. coli. Overall, the results indicate that GCN/Ag2CrO4 nanocomposite is a promising photocatalyst in degrading organic pollutants and disinfecting microorganisms under visible light irradiation within a reasonable time.

Oxidative stress, DNA, and membranes targets as modes of antibacterial and antibiofilm activity of facile synthesized biocompatible keratin-copper nanoparticles against multidrug resistant uro-pathogens

Escherichia coli and Enterococcus faecalis are two of the most prevalent uro-pathogens and are difficult to treat as they acquire multidrug-resistant traits. In this study, the main objective was to develop biocompatible copper nanoparticles using chicken feather keratin protein (CuNPs-K) and to investigate their impact on multidrug-resistant (MDR) uro-pathogens, E. coli and E. faecalis, under both single and mixed culture conditions. CuNPs-K were characterised by UV-Vis spectroscopy, dynamic light scattering, X-ray diffraction, Fourier transform infrared spectroscopy, and docking experiments. The MIC values of CuNPs-K against single and mixed planktonic cultures were 50 μg/ml and 75 μg/ml, respectively. CuNPs-K efficiently disrupted the biofilm of single and mixed uro-pathogen cultures by eliminating sessile cells. This biofilm disruption may be attributed to a decline in the production of extracellular polymeric substances in both single and mixed bacterial cultures treated with CuNPs-K. Moreover, selective antimicrobial activity was determined by selectivity assays using T24 cells. CuNPs-K targets both the bacterial membrane and DNA with elevated reactive oxygen species (ROS) as their bactericidal mode of action. This comprehensive antimicrobial activity of CuNPs-K was further confirmed in vivo by using the zebra fish model. In this study, CuNPs-K effectively reduced bacterial load with increased survivability of infected zebrafish. All these results suggest that CuNPs-K can be explored as an exceptional antibacterial agent against MDR uro-pathogenic E. coli and E. faecalis.

Microbial Response to Fungal Infection in a Fungus-Growing Termite, Odontotermes formosanus (Shiraki)

The crosstalk between gut microbiota and host immunity has emerged as one of the research foci of microbiome studies in recent years. The purpose of this study was to determine how gut microbes respond to fungal infection in termites, given their reliance on gut symbionts for food intake as well as maintaining host health. Here, we used Metarhizium robertsii, an entomopathogenic fungus, to infect Odontotermes formosanus, a fungus-growing termite in the family Termitidae, and documented changes in host gut microbiota via a combination of bacterial 16S rDNA sequencing, metagenomic shotgun sequencing, and transmission electron microscopy. Our analyses found that when challenged with Metarhizium, the termite gut showed reduced microbial diversity within the first 12 h of fungal infection and then recovered and even surpassed pre-infection flora levels. These combined results shed light on the role of gut flora in maintaining homeostasis and immune homeostasis in the host, and the impact of gut flora dysbiosis on host susceptibility to infection.

Draft genome sequence of Aspergillus flavus isolate TERIBR1, a highly tolerant fungus to chromium stress

Objectives

Aspergillus flavus isolate TERIBR1 was isolated from tannery sludge highly contaminated with chromium. During characterization process, it exhibited capability to adapt and grow in fungal growth media amended with chromium concentration as high as 250 mg/l. In order to understand the genetic underpinnings of the chromium tolerance trait, whole genome sequencing of the TERIBR1 genome was carried out. Information from the current genome will facilitate an understanding of the mechanisms underlying fungal adaptation to heavy metal stress and also heavy metal bioremediation.

Data description

Here, we report the draft genome sequence along with the assembly and annotation methods used for genome sequence of the A. flavus isolate TERIBR1. The draft genome assembly size is estimated at 37.7 Mb coding for 13,587 genes and has high similarity to the reference genome of A. flavus strain NRRL3357.