Ligninolytic fungi are promising organisms in developing bioremediation technologies due to their ability to degrade various pollutants. Fungi and their extracellular enzymes in soil inevitably collide with metabolites produced by other organisms. Here, we investigated the effect of some natural metabolites on the degradation of a model mixture of polycyclic aromatic hydrocarbons (PAHs) by the fungus Pleurotus ostreatus var. Florida.
Fungus was grown in the liquid medium containing PAHs with or without the addition of natural metabolites. The degraded PAHs and the identification of metabolites were checked using high-performance liquid chromatography (HPLC). Enzymatic activities were measured spectrophotometrically using test substrates. The metabolite effects on the pure laccase and versatile peroxidase were also checked. All experimental treatments were analyzed using Excel 2019 (Microsoft Office 2019, USA).
Indole-3-acetic acid (IAA) and salicylic acid increased PAH degradation by 25–70%. However, tryptophan, a precursor to IAA biosynthesis, slightly increased the degradation of only three-ring PAHs. The tested flavonoids reduced the PAH degradations, which may have resulted from the inhibition of mycelial growth by these compounds. Ferulic and cinnamic acids, precursors to lignin biosynthesis, also inhibited PAH degradation. Of the tested fungal metabolites, only veratryl alcohol promoted PAH degradation: the four-ring PAHs became more accessible to fungal degradation (43.5 and 38.1% for fluoranthene and pyrene, respectively). Oxalic and malonic acids, the most actively produced fungal organic acids, reduced the degradation of all PAHs but fluoranthene. HPLC led us to identify 9,10-phenanthrenequinone, 9,10-anthraquinone, and 9-fluorenone as the main metabolites of PAH degradation. P. ostreatus is a strong producer of extracellular laccases and peroxidases, whose involvement in PAH degradation is also well known. In our study, the most vigorous laccase inducers were tryptophan and ferulic acid (40 and 60%, respectively), whereas IAA and salicylic acid were weaker inducers (about 20%). Ferulic and salicylic acids increased versatile peroxidase activity by 1.5–2 times, whereas other effectors reduced it to varying degrees.
These results are important for developing environmental biotechnologies that combine phyto- and mycoremediation.
The contamination of soil with toxic heavy metals is considered a significant environmental concerns, with the problem intensifying rapidly due to shifts in industrial practices. Even in trace quantities, heavy metals and metalloids, such as chromium, lead, mercury, cadmium and arsenic, are toxic and carcinogenic, representing a significant threat to agricultural production and human health. Additionally, prolonged exposure to these heavy metals can cause adverse health effects in humans and other living organisms. Heavy metals are non-degradable and tend to accumulate in soil, meaning their removal is necessary. One of the more sophisticated techniques for the remediation of heavy metals is utilizing biological methods, which employ naturally occurring microorganisms, such as Pseudomonas. Bioremediation is a superior method for the elimination of heavy metals in comparison to other approaches due to its environmentally benign nature, economic viability, and minimal labor and effort requirements, bioremediation is a superior method for the elimination of heavy metals in comparison to other approaches. Pseudomonas species can absorb heavy metals from soil and utilize these toxic contaminants in their metabolic processes, or transforming them into less or non-toxic forms. This review is focused on the studies that used the Pseudomonas genus is utilized for heavy metal bioremediation in contaminated soil. Notably, applying this strategy as a sustainable environmental technology in the near future has shown synergistic benefits with marked-fold increases in removing heavy metals from soil.
Red clover (Trifolium pratense L.) is an important forage crop throughout the world due to its high forage quality, nitrogen fixation capacity and beneficial effects on the soil fertility. But aluminum (Al) toxicity limits significantly red clover production in acid soils, which represent more than one third of the world's agricultural lands. Natural variation for Al3+ ions resistance has been identified in many crop species so development of tolerant accessions and varieties is a promising approach for red clover breeding. In this context the objectives of this article were to select in vitro and evaluate using different DNA markers the tolerant to toxic aluminum breeding samples of red clover.
Seeds of the experimental hybrid population were germinated under various aluminum concentrations, including control without aluminum. Epicotyls of seedlings without roots and with roots not less than 4–5 mm were subcultivated on agar's medium of Gamborg B5 with 2 mg/L of 6-benzylaminopurine and 100 mg/L of Al3+ and then planted in the cassettes with soil. Seedlings and adult plants F2, tolerant to 50 and 100 mg/L of Al3+ were selected, grown in vegetative pots and used further for molecular analyses. Genetic variability between tolerant and susceptible red clover genotypes was evaluated based on DNA markers: sequence-related amplified polymorphism (SRAP), retrotransposon microsatellite amplified polymorphism (REMAP) and inter-primer binding site polymorphism (iPBS).
Aluminum-tolerant red clover samples were obtained by in vitro selection on the medium with toxic aluminum ions. F2 seedlings in the variants with 50 mg/L and 100 mg/L of Al3+ were characterized by longer length and roots size compared with F1 seedlings and variety-standard at the same aluminum concentration. Subsequent molecular analysis showed that REMAP and iPBS were efficient markers to detect distinguishes among red clover accessions. The average level of polymorphism was identified as 45.8 using REMAP and 68.2% with iPBS; the average values of polymorphism information content (PIC) were 0.764 and 0.746 accordingly, higher compared to SRAP (0.741).
Combination of the biotechnology methods and the current DNA-technologies based on REMAP and iPBS markers is effective approach to improve precision and reliability of selection and assessing of red clover genotypes with tolerance to toxic aluminum ions (Al3+). Breeding samples identified in this study, can be used as a promising initial material for development the new varieties with stable inheritability of the aimed trait.
Low retinal blood flow and/or vasospasm represent major risk factors for the development of glaucomatous optic neuropathy (GON), a potentially blinding eye disease. Bradykinin (BK), a nonapeptide, is endogenously produced and released, which can cause smooth muscles to contract and relax in different tissues depending on the physiological/pathological situation and the presence or absence of vascular tone. Several reports have shown the presence of BK receptor mRNAs, and in some cases, B1- and B2-receptor proteins, in ocular tissues, including the retina. However, the function of these receptors remains to be determined, especially in retinal blood vessels.
We pharmacologically characterized the ability of BK and any related peptide agonists to promote the contraction of isolated bovine posterior ciliary arteries (PCAs) in an organ bath setup using a cumulative compound addition and tension development recording process. Receptor-selective kinin agonists and subtype-selective BK receptor antagonists were utilized to define the possible heterogeneity in the functional BK receptors for PCAs.
All agonist kinin peptides concentration-dependently contracted the PCA rings bi-phasically over a 5-log unit range (0.1 nM–10 μM). The relative potencies (EC50 values; n = 4–5) regarding the high-affinity receptor site were: Lys–BK = 0.9 ± 0.4 nM; Des–Arg9–BK = 0.9 ± 0.4 nM; RMP-7 = 1.1 ± 0.6 nM; Met–Lys–BK = 1.3 ± 0.5 nM; Hyp3–BK = 2.7 ± 0.5 nM; BK = 3.0 ± 0.7 nM. The low-affinity receptor site activated by these peptides mostly exhibited EC50 values ranging from 0.3 μM to 3 μM. The concentration–response curves to Des–Arg9–BK (B1-selective agonist) were shifted to the left in the presence of increasing concentrations of a B1-receptor antagonist (R715: 1–10 μM; n = 3). Similarly, WIN-64338 (a B2-receptor antagonist: 1–10 μM; n = 3) moved the BK concentration–response curves to the left.
The pharmacological characteristics of BK and analog-induced contractions, and their inhibition by receptor-selective antagonists, indicated the presence of both B1- and B2-receptors, and perhaps another subtype, which mediate the PCA contractions. These results have potential implications for the involvement of heterogeneous kinin receptors, narrowing PCA diameters in vivo, restricting blood flow to the retina, causing GON, and subsequent visual impairment that can eventually cause blindness.
Klebsiella pneumoniae possesses a range of virulence factors that enable this bacterium to colonize, persist, adhere to host tissues, invade, and cause disease. The pathogen poses a significant risk to immunocompromised individuals and those with pre-existing health conditions. This research focused on assessing the virulence traits and biofilm-forming abilities of K. pneumoniae isolates in Nigeria.
Clinical samples were collected from 420 patients across seven tertiary hospitals in Southwestern Nigeria between February 2018 and July 2019. Standard microbiological procedures were employed to identify Klebsiella isolates. The presence of six specific virulence genes was determined using polymerase chain reaction (PCR): fimH, kfu, rmpA, uge, wcaG, and aero_1. Additionally, PCR was utilized to identify capsular serotypes K1, K2, and K5.
A substantial proportion (82%) of K. pneumoniae isolates demonstrated the ability to form biofilms. Of these, 51 isolates (39.8%) were classified as strong biofilm producers, 54 (42.2%) as moderate, and 23 (17.9%) showed no biofilm production. Among the virulence genes detected, uge was the most common (68.0%), followed by fimH (65.6%), aero_1 (63.3%), kfu (29.7%), rmpA (28.1%), and wcaG (14.1%). Statistically significant correlations were found between biofilm formation and the presence of aero_1, fimH, kfu, and rmpA. In terms of capsular serotypes, the majority of isolates were non-K1/K2/K5 (84.4%), with lower frequencies observed for K2 (7.0%), K1 (5.5%), and K5 (3.1%).
This study highlights that the aero_1, fimH, and uge genes are frequently present in K. pneumoniae isolates from this region, and that these strains often carry multiple virulence genes. The strong virulence potential and biofilm-forming capacity of these isolates underscore a significant public health threat, particularly in vulnerable populations.
Healthcare-associated infections (HAIs) are a source of constant risk for inpatients and healthcare workers and a serious challenge to human health services worldwide. Common surfaces, such as doorknobs, tables, and bedrails, can become contaminated and develop into a reservoir of pathogens; thus, common surfaces can play an important role in the fomite-mediated pathway through which HAIs are transmitted. Non-critical disinfection techniques are common practice in the nosocomial setting, aiming to reduce the bioburden of common surfaces and prevent the spread of HAIs. However, these techniques are limited by factors such as the need for frequent disinfectant reapplication and the potential recontamination that can occur at any moment after cleaning. Light-activated antimicrobial nanocoatings are an interesting alternative to overcome these issues, since these nanocoatings can confer self-disinfection capacities to nosocomial common surfaces, to supplement non-critical disinfection. Thus, this review aims to discuss the relevance of fomites and gaps in common disinfection strategies that favor the propagation of HAIs. In addition, nanotechnology-based antimicrobial coatings are considered, along with strategies for nanoparticle-based antimicrobial coating development. Furthermore, the use of titanium oxide nanoparticles to formulate photo-responsive antimicrobial nanocomposites/nanocoatings and concerns related to toxicity, environmental fate, and bacterial resistance development are discussed. Finally, emerging photo-responsive antimicrobial nanotechnologies and future perspectives are considered.
Pesticides spread into the air, contaminate soil and water, and can affect various objects, contributing to secondary pollution regardless of the employed type or application method. Currently, organophosphorus pesticides (OPs) are widely utilized in agriculture, forestry, and livestock farming worldwide. These chemicals enter the body through multiple exposure routes and can harm the nervous system, endocrine system, and other organs. Owing to the environmental persistence and elevated toxicity exhibited by these pesticides, certain OPs are difficult to break down biologically, thus posing serious threats to human health and ecosystems. Disinfection or destruction of those pesticides remaining in the environment represents one of the important tasks scientists face. This review presents information on OPs, some of their properties, environmental impacts, and mechanisms for the effective decomposition of these pesticide residues by microorganisms. Bacteria and fungi isolated from samples contaminated with various OPs were analyzed. New metabolites formed during OP degradation by these microorganisms, as well as microbial enzymes involved in OP degradation and the molecular mechanisms of the process, are presented. The methods used in these studies and recommendations for future research are also detailed.