Individual Microorganisms Research Articles

Portable impedance-sensing device for microorganism characterization in the field

A variety of biosensors have been proposed to quickly detect and measure the properties of individual microorganisms among heterogeneous populations, but challenges related to cost, portability, stability, sensitivity, and power consumption limit their applicability. This study proposes a portable microfluidic device based on impedance flow-cytometry and electrical impedance spectroscopy that can detect and quantify the size of microparticles larger than 45 µm, such as algae and microplastics. The system is low cost ($300), portable (5 cm times 5 cm), low-power (1.2 W), and easily fabricated utilizing a 3D-printer and industrial printed circuit board technology. The main novelty we demonstrate is the use of square wave excitation signal for impedance measurements with quadrature phase-sensitive detectors. A linked algorithm removes the errors associated to higher order harmonics. After validating the performance of the device for complex impedance models, we used it to detect and differentiate between polyethylene microbeads of sizes between 63 and 83 µm, and buccal cells between 45 and 70 µm. A precision of 3% is reported for the measured impedance and a minimum size of 45 µm is reported for the particle characterization.

Microbial Surfactants to the Rescue

Microbial Surfactants to the Rescue

Analysis of the activated sludge composition using artificial neural networks

The object of research is electron microscopic images of activated sludge, which were used to train a convolutional neural network. An important task of the process of biological wastewater treatment is the prompt determination of quantitative and qualitative changes in activated sludge, as well as the assessment of the impact of the identified changes on the efficiency of the treatment. Microscopic examination, which is a traditional tool for controlling the quality of the water-sludge mixture, does not allow to quickly detect the deterioration of the activated sludge, which can lead to its degradation, and in difficult cases – to the death of the sludge. Violation of the microbiological composition of sludge leads to improper formation of flocs, violation of the process of formation of flakes, filamentous or sludge swelling, toxicity, etc. The combination of artificial intelligence methods with existing methods of quality control of activated sludge will increase the reliability and validity of the assessment of the quality of biological treatment. A proposed methodology for analyzing the state of activated sludge using convolutional neural networks. For the purpose of training the network, images of activated sludge were prepared, which were classified into two categories – «flocs» and «bacteria with microorganisms». There are 4 subcategories in the «flocks» category: size, shape, structure, edge of the floc; in the category «bacteria with microorganisms» there are 2 subcategories: «individual bacteria and microorganisms» and «colonies». Data sets of 250, 500 and 1000 images were created for each category. The task of learning the image processing model and the criteria for evaluating the success of learning are formulated. The task of training the network was to find such a recognition function that, with a given degree of accuracy, approximates the unknown recognition function over the entire domain of its definition. The accuracy of image recognition is chosen as a learning success criterion. The model training results show that the image recognition accuracy reaches 99.98 %, and the training quality is affected by the sample size and training duration. The trained model can be used as a fast and efficient tool to detect problems with activated sludge.

In vitro comparative study of antimicrobial efficacy of endodontic sealers against common pathogens in the dental pulp.

Different types of bacterial species, Enterococcus faecalis (E. faecalis), Fusobacterium nucleatum (F. nucleatum), and Porphyromonas gingivalis (P. gingivalis), cause pulpal and periradicular diseases. Hence, the antibacterial efficacy of endodontic sealers is of utmost importance from a clinical point of view. The main objective of the study is to test the antibacterial efficacy of endodontic sealers against endo microflora belonging to E. faecalis, F. nucleatum, and P. gingivalis species. The antibacterial effectiveness of five endodontic sealers (AH plus, Apexit, EndoRez, Endomethasone, and Tubliseal) was tested by means of the agar-diffusion test (ADT) and direct contact test (DCT). The bacterial suspension of individual microorganisms was applied separately onto the agar plates for ADT. Subsequently, freshly mixed and set sealer was applied on to the sterile discs. After 48 h of incubation, the inhibition zones were measured. For DCT, the sealers were put in 96-well cell culture plates and overlaid with bacterial suspension and brain heart infusion broth. The bacterial growth density of the liquid was tested by spectrophotometry at 0, 2, 4, 6, and 24 h. The data were analyzed using ANOVA and post hoc Turkey's test. The present study showed that Endomethasone and AH Plus had a good antibacterial effect. In the ADT and DCT, Endomethasone showed the greatest antimicrobial effect against E. faecalis when compared to other endodontic sealers. In the ADT, Apexit had no antimicrobial effect on E. faecalis, whereas AH Plus had the greatest antibacterial effect on F. nucleatum and P gingivalis. Whereas in DCT, EndoRez and Endomethasone showed the greatest effect against F. nucleatum and P. gingivalis.

Caracterização bioquímica de micro-organismos promotores de crescimento de plantas individuais e combinados

ABSTRACT The increasing demand for using microorganisms in agriculture to improve food production requires constantly assessing microbial diversity. This study aimed to investigate the biochemical properties of individual and combined multifunctional microorganisms, as well as to identify potential applications in biotechnology or agriculture. The experiment comprised 29 treatments, with 7 single and 21 combined microorganisms: M01 (Serratia marcescens), M02 (Bacillus toyonensis), M03 (Phanerochaete australis), M04 (Trichoderma koningiopsis), M05 (Azospirillum brasilense), M06 (Azospirillum sp.), M07 (Bacillus sp.), M08 to M28 (combination among these microorganisms) and M29 (control - no microorganisms). All the single and combined treatments assimilated nitrogen, produced siderophores and indoleacetic acid and solubilized phosphate. Only the treatments M04, M13 and M26 produced HCN. Additionally, all treatments, except for M03, produced biofilm. Only M03, M07, M09, M10, M12 and M13 solubilized potassium.

Impact of direct physical association and motility on fitness of a synthetic interkingdom microbial community

Mutualistic exchange of metabolites can play an important role in microbial communities. Under natural environmental conditions, such exchange may be compromised by the dispersal of metabolites and by the presence of non-cooperating microorganisms. Spatial proximity between members during sessile growth on solid surfaces has been shown to promote stabilization of cross-feeding communities against these challenges. Nonetheless, many natural cross-feeding communities are not sessile but rather pelagic and exist in turbulent aquatic environments, where partner proximity is often achieved via direct cell-cell adhesion, and cooperation occurs between physically associated cells. Partner association in aquatic environments could be further enhanced by motility of individual planktonic microorganisms. In this work, we establish a model bipartite cross-feeding community between bacteria and yeast auxotrophs to investigate the impact of direct adhesion between prokaryotic and eukaryotic partners and of bacterial motility in a stirred mutualistic co-culture. We demonstrate that adhesion can provide fitness benefit to the bacterial partner, likely by enabling local metabolite exchange within co-aggregates, and that it counteracts invasion of the community by a non-cooperating cheater strain. In a turbulent environment and at low cell densities, fitness of the bacterial partner and its competitiveness against a non-cooperating strain are further increased by motility that likely facilitates partner encounters and adhesion. These results suggest that, despite their potential fitness costs, direct adhesion between partners and its enhancement by motility may play key roles as stabilization factors for metabolic communities in turbulent aquatic environments.

Degradation of Polyethylene Using Bacteria from Waste Dump Sites in Obio/Akpor Local Government Area in Rivers State, Nigeria

All around the world today, different types of plastics are used for packaging materials, especially in form of low density polyethylene (LDPE). The aim of the study was to degrade polyethylene using bacteria from waste dump sites in Alakahia and Ogbogoro of Obio/ Apkor Local Government Area, Rivers State. Soil samples were randomly collected from Alakahia and Ogbogoro dump sites in Obio/Apkor Local Government Area, in Rivers state. Polyethylene degraders were determined using microscopy and weight loss methods. The total heterotrophic bacterial counts recorded were 3.03 x 106 CFU/g and 1.12 x 106 CFU/g for Ogbogoro and Alakahia samples. The total count of Pseudomonas recorded were 5.0 x 104 CFU/g and 4.9 x 104 CFU/g for Ogbogoro and Alakahia sample. There was no significant difference (P ≤ 0.05) within the counts of the samples. The bacteria isolated from the soil collected from the dumpsites were Bacillus sp, Klebsiella sp, Pseudomonas sp, Staphylococcus sp, Serratia sp, Escherichia coli, Shigella sp, Salmonella sp. The identified bacteria were Pseudomonas proteolytica NR025588.1, Pseudomonas aeruginosa CP0296051 and Bacillus circulans CP026031.1. From the result of the degradative ability by the individual microorganism using weight loss measurement, Pseudomonas aeruginosa CP0296051 showed a greater percentage of degradation of polyethylene of 5% to 27.03% (after 150 days) followed by Pseudomonas proteolytica NR025588.1 which recorded percentage degradation of 6.0% to 23.28% (after 150 days) while Bacillus circulans CP02603.1 recorded the least percentage of 5% to 19.9% (after 150 days). The result of degradative potential of the microbes in consortium set ups showed that the consortium of Pseudomonas aeruginosa CP0296051 and Bacillus circulans CP02603.1 (B8+B6) showed the highest degradation potential producing degradation percentage range of 8.7 to 46.80% after 150 days of the study and the least degradation potential of polyethylene was observed in Pseudomonas aeruginosa CP0296051 and Pseudomonas proteolytica NRO255SS.1 (B6+B3) with the percentage range of 5% to 27.03% after 150 days. From the study, Pseudomonas sp, Bacillus sp and their consortium showed higher potential to degrade low density polyethylene (LDPE) hence the prospect in remediation of polyethylene.

Source and Route of Microplastics in Terrestrial, Atmospheric, and Aquatic Environments, and Effects of Microplastics on Organisms

Objectives : Microplastics, known as pieces of polymer debris less than 5 mm, result from plastic particles originally manufactured to small size or fragmentation from larger plastic items. Due to the persistence, microplastics can remain and accumulate in land and ocean for a prolonged period. Microplastics enter ecosystems and cause various problems. Trophic transfer of microplastics can be occurred in food chain, accordingly humans also can ingest microplastics. The accumulation of microplastics raises concerns regarding impacts on human health and terrestrial and aquatic ecosystems. Here, we discuss the source and route of microplastics found in environments, and ecological effects of microplastics on organisms.Methods : We explore how microplastics enter terrestrial, atmospheric, and aquatic environments and influence individual animals, plants, and microorganisms living in diverse ecosystems. Research literature is reviewed microplastics in terms of ecological risk published between 2010s and June 2022.Results and Discussion : Diverse human activities (e.g., industrial and agricultural activity) accelerate the production of microplastics and result in a release of microplastics to surrounding ecosystems. The microplastics can circulate among the terrestrial, atmospheric, and aquatic environments. The exposure of microplastics can induce oxidative stress, damage of intestinal cells, and reduce the body size in animals. In plants, length of root, biomass, and chlorophyll content are decreased upon exposure to microplastics. In addition, microplastics inhibit the growth of microalgae by reducing algal chlorophyll contents and cause oxidative stress.Conclusion : This paper includes basic information regarding the occurrence and accumulation of microplastics and their ecological effects on organisms. The contents will help to understand behavior of microplastics in diverse environments and to further evaluate ecological impacts of microplastics.

Environmental biodiversity, human microbiota and association with allergies

Background. The article presents modern views on the role of microbiota in the occurrence of atopic pathology. The reasons for the decline in biodiversity, changes in the dynamic balance between macro-microorganisms, violation of the colonization of human ecological niches, which are important in the formation of local and systemic immunity, are considered; the main causes of dysbiosis at an early age, which precedes the formation of allergic diseases (food allergy, atopic dermatitis, allergic rhinitis, asthma), a significant increase in which has been noted in recent decades. Aim: to analyze reviews, articles devoted to the study of the role of the human microbiota, a decrease in its biodiversity in the formation of allergic pathology. Methods: the use of analytical reviews, articles posted in electronic databases: PubMed, Scopus, Web of Science, position of the European Academy of Allerogology and Clinical Immunology (EAACI). Conclusion: the analysis made it possible to present the modern role of microorganisms inhabiting the ecological niches of the human body, their dynamic balance on the function of all organs and systems, with consideration of the reasons for the decrease in biodiversity and the subsequent development of allergic diseases; the need to further study the role of not individual pathogens, but the general properties of the microbial population, which will help to change the approach to disease therapy, based not on replacing individual microorganisms, but on restoring the all population.

Microbial compost tea properties affect suppression of strawberry grey mould (Botrytis cinerea Pers.)

ABSTRACT Compost teas are aqueous filtrates of steeped composted materials, which can be applied to the phyllosphere or rhizosphere of plants. Compost teas possess beneficial effects including reducing the impact of plant pathogens. Six compost teas were prepared and tested for their ability to inhibit mycelial growth of strawberry pathogens and to suppress grey mould of strawberry. All compost teas inhibited the growth of Alternaria alternata, Botrytis cinerea, Phytophthora fragariae, and Verticillium dahliae, by 45–73%. Compost teas prepared from forest, sea, sheep, shrimp, and vermicomposts reduced grey mould lesions on strawberry leaves by 38–62% up to 12 days. Heat and cold sterilised compost teas did not provide inhibition of B. cinerea, indicating that presence of microorganisms seemed key to the activity of the compost tea. Total bacteria, Gram negative bacteria, and fungal/oomycete population numbers did not relate to effectiveness of the compost teas. Three isolates from sheep compost tea showed antibiosis-like activity. Isolates SH1 and SH2 resembled Bacillus velezensis and isolate SH3 resembled Pseudomonas azotoformans, following sequence analysis and phylogenetic relatedness testing. Results indicated that pathogen inhibition and grey mould suppression did not seem related to different microbial community groups or population numbers, but rather to the general presence of specific microbial groups or individual antagonistic microorganisms.

Microbiota as a new pathogenetic factor in the development of chronic hyperuricemia and gout. Part I: the current state of the problem

The gut microbiota plays a key role in metabolism and immune regulation, and imbalance in microbial composition can contribute to various diseases. We present up-to-date data on the role of the gut microbiota in the occurrence of chronic hyperuricemia (HU) and gout, which is associated with the influence of the microbiota on the synthesis of purine-metabolizing enzymes and pro-inflammatory cytokines. It has been shown that the gut microbiota plays an important role in the pathophysiology of gout and can serve as a new target for therapy. Currently, the microbial index of gout is considered as a potential method for early diagnosis of the disease, possibly already at the preclinical stage. The gut microbiota can be a starting point in the study of the pathogenesis of HU and gout. This makes it necessary to assess the pathogenetic relationship between individual specific microorganisms, the microbiota as a whole, and the development of uric acid (UA) metabolism disorders that contribute to the onset of HU and its transformation into gout. It is assumed that this approach will provide a more complete understanding of the gut microbiota participation in the synthesis of UA and its extrarenal excretion, as well as of bacteria and bacterial enzymes that can be used as a probiotic coadjuvant for the treatment and prevention of gout.

Acoustic tethering of microorganisms.

We show how to construct and apply a setup to acoustically tether and enable behavioral observations of individual microorganisms using simple laboratory equipment and a standard light microscope. We explore the capability of the setup with the freely swimming dinoflagellate Alexandrium minutum as the study organism. The setup allows us to tether cells in focus in the mid-plane of the sample chamber and make observations of individual organisms at high magnification without affecting their flagellar beat frequencies. We discuss the prospect of the method to explore appendage motion and swimming kinematics of other flagellates and ciliates, and we argue that the method will be applicable to a broad range of cell sizes and shapes.

Biodegradation of renewable polyurethane foams in marine environments occurs through depolymerization by marine microorganisms

Accumulation of plastics in the Earth's oceans is causing widespread disruption to marine ecosystems. To help mitigate the environmental burden caused by non-degradable plastics, we have previously developed a commercially relevant polyurethane (PU) foam derived from renewable biological materials that can be depolymerized into its constituent monomers and consumed by microorganisms in soil or compost. Here we demonstrate that these same PU foams can be biodegraded by marine microorganisms in the ocean and by isolated marine microorganisms in an ex situ seawater environment. Using Fourier-transform infrared (FTIR) spectroscopy, we tracked molecular changes imparted by microbial breakdown of the PU polymers; and utilized scanning electron microscopy (SEM) to demonstrate the loss of physical structure associated with colonization of microorganisms on the PU foams. We subsequently enriched, isolated, and identified individual microorganisms, from six marine sites around San Diego, CA, that are capable of depolymerizing, metabolizing, and accumulating biomass using these PU foams as a sole carbon source. Analysis using SEM, FTIR, and gas chromatography–mass spectrometry (GCMS) confirmed that these microorganisms depolymerized the PU into its constitutive diols, diacids, and other PU fragments. SEM and FTIR results from isolated organismal biodegradation experiments exactly matched those from ex situ and ocean biodegradation samples, suggesting that these PU foam would undergo biodegradation in a natural ocean environment by enzymatic depolymerization of the PU foams and eventual uptake of the degradation products into biomass by marine microorganisms, should these foams unintentionally end up in the marine environment, as many plastics do.

Isolation, Solubilization of Inorganic Phosphate, and Production of Organic Acids by Individual and Co-inoculated Microorganisms

Phosphate solubilizing microorganisms (PSMs) mineralize phosphate (PO4³−) to make phosphorous available for plant uptake. This study is designed to isolate the PSMs from the subtropical environmental samples. Total 35 bacterial and 18 fungal isolates were found to be effective P solubilizers depend on their ability of P solubilization that were determined qualitatively and quantitatively using National Botanical Research Institute Phosphorus media. Efficient PSMs that were solubilizing phosphate in maximum amount were identified as Pseudomonas aeruginosa, Serratia marcescens, Pseudomonas mosselii, Bacillus licheniformis, Bacillus subtilis, Bacillus species, Aspergillus flavus, Aspergillus foetidus, Aspergillus niger, Aspergillus tubingensis, and Penicillium chrysogenum. Among them, A. tubingensis was observed as the most efficient phosphate solubilizing strain. For the first time, combined phosphate solubilization activity of A. tubingensis with other efficient phosphate solubilizers was checked and found that A. tubingensis and P. aeruginosa acted synergistically and solubilized phosphate in increased amount. High-performance liquid chromatography results revealed that A. tubingensis produced variety of organic acids including succinic, gluconic, oxalic, and citric acids. Scanning electron microscopy results confirmed the presence of firmly attached large fungal hyphae on tri-calcium phosphate (Ca3(PO4)2). Thus, the results suggest that the use of these PSMs either single or combined as bioinoculants will help to increase the availability of soluble phosphorous.

Identification of Functional Microbial Modules Through Network-Based Analysis of Meta-Microbial Features Using Matrix Factorization

As the microbiome is composed of a variety of microbial interactions, it is imperative in microbiome research to identify a microbial sub-community that collectively conducts a specific function. However, current methodologies have been highly limited to analyzing conditional abundance changes of individual microorganisms without considering group-wise collective microbial features. To overcome this limitation, we developed a network-based method using nonnegative matrix factorization (NMF) to identify functional meta-microbial features (MMFs) that, as a group, better discriminate specific environmental conditions of samples using microbiome data. As proof of concept, large-scale human microbiome data collected from different body sites were used to identify body site-specific MMFs by applying NMF. The statistical test for MMFs led us to identify highly discriminative MMFs on sample classes, called synergistic MMFs (SYMMFs). Finally, we constructed a SYMMF-based microbial interaction network (SYMMF-net) by integrating all of the SYMMF information. Network analysis revealed core microbial modules closely related to critical sample properties. Similar results were also found when the method was applied to various disease-associated microbiome data. The developed method interprets high-dimensional microbiome data by identifying functional microbial modules on sample properties and intuitively representing their systematic relationships via a microbial network.

Efficient elimination of airborne pathogens: a study on aerosolized Mycobacterium tuberculosis and SARS-CoV-2 using ZeBox technology

BackgroundDespite multifactorial evidence, the safe and effective elimination of free-floating micro-organisms remains a significant scientific challenge. ZeBox Technology exploits microbial Zeta Potential, to extract and eliminate them from free-flowing air, using a non-ionizing electric field, in combination with a microbicidal surface.AimEvaluation of ZeBox Technology against aerosolized SARS-CoV-2 and Mycobacterium tuberculosis under controlled conditions.MethodsSARS-CoV-2 and M. tuberculosis H37Ra were used in this study. Individual micro-organisms were aerosolized using a Collison nebulizer inside an air-sealed test chamber. Air samples were collected from the chamber on to a Mixed Cellulose Ester membrane, at various time points, and used for enumeration. SARS-CoV-2 was enumerated using qRT-PCR, while M. tuberculosis H37Ra was quantified using standard microbiological procedures.FindingsWe established a viable aerosolized microbial load of ∼10E9 and ∼10E6 for SARS-CoV-2 and M. tuberculosis H37Ra, respectively, inside the test chamber. Under ideal conditions, the floating microbial load was at a steady-state level of 10E9 for SARS-CoV-2 and 10E6 for M. tuberculosis. When the ZeBox-Technology-enabled device was operated, the microbial load reduced significantly. A reduction of ∼10E4.7 was observed for M. tuberculosis, while a reduction of ∼10E7 for SARS-CoV-2 was observed within a short duration. The reduction in airborne SARS-CoV-2 load was qualitatively and quantitatively measured using fluorescence analysis and qRT-PCR methods, respectively.ConclusionThis validation demonstrates the efficacy of the developed technology against two of the deadliest micro-organisms that claim millions of lives worldwide. In conjunction with the existing reports, the present validation proved the true broad-spectrum elimination capability of ZeBox technology.

Profiling of d-alanine production by the microbial isolates of rat gut microbiota.

d-alanine (d-Ala) and several other d-amino acids (d-AAs) act as hormones and neuromodulators in nervous and endocrine systems. Unlike the endogenously synthesized d-serine in animals, d-Ala may be from exogenous sources, e.g., diet and intestinal microorganisms. However, it is unclear if the capability to produce d-Ala and other d-AAs varies among different microbial strains in the gut. We isolated individual microorganisms of rat gut microbiota and profiled their d-AA production in vitro, focusing on d-Ala. Serial dilutions of intestinal contents from adult male rats were plated on agar to obtain clonal cultures. Using MALDI-TOF MS for rapid strain typing, we identified 38 unique isolates, grouped into 11 species based on 16S rRNA gene sequences. We then used two-tier screening to profile bacterial d-AA production, combining a d-amino acid oxidase-based enzymatic assay for rapid assessment of non-acidic d-AA amount and chiral LC-MS/MS to quantify individual d-AAs, revealing 19 out of the 38 isolated strains as d-AA producers. LC-MS/MS analysis of the eight top d-AA producers showed high levels of d-Ala in all strains tested, with substantial inter- and intra-species variations. Though results from the enzymatic assay and LC-MS/MS analysis aligned well, LC-MS/MS further revealed the existence of d-glutamate and d-aspartate, which are poor substrates for this enzymatic assay. We observed large inter- and intra-species variation of d-AA production profiles from rat gut microbiome species, demonstrating the importance of chemical profiling of gut microbiota in addition to sequencing, furthering the idea that microbial metabolites modulate host physiology.

Potential of Microbes Containing Formulations to Alter Growth and Phytochemicals of Medicinal Aromatic Plant- Foeniculum Vulgare

Sustainable plant production with the integration of eco-friendly agricultural practices, low chemical inputs, minimal deleterious effects on human health and low cost methods, is the need of the moment. In this direction, scientific/industrial community, continuously exploring novel and reliable methods. Plant growth promoting microbes are proving more promising to achieve eco-friendly and sustainable agricultural outcomes. In the present study, individuals of Foeniculum vulgare, a valuable aromatic plant species with potential medicinal value, were inoculated with different plant growth promoting microorganisms: (1) Arbuscular mycorrhizal like fungi (Sebacina vermifera) (2) Phosphate solubilizing bacteria (Pseudomonas fluorescens) (3) Azotobacter (Azotobacter chroococcum). Response of individual microorganism species was evaluated with reference to the emergence, plant growth and yield of essential oil along with qualitative effects on essential oil. Comparatively, significant response of Sebacina vermifera, in the stimulation of emergence of seeds, growth of plant and yield enhancement of essential oil was observed. An enhanced synthesis of anethole (major chemical constituent) was also recorded. Moreover, the enhancement in growth of plants was dependent on the extent of colonization percentage. A periodic study of growth parameters indicates plant’s health and vitality influenced by Sebacina vermifera. The enhanced essential oil of seeds along with enhanced synthesis of anethole was in agreement with the assumption that Sebacina vermifera trigger defensive responses and hence improve phytochemical production. A mechanistic insight is also illustrated. In conclusion Sebacina vermifera possesses immense potentials in the pursuit of agro-ecological attributes of medicinal plant cultivation and crop production. It exerts excellent growth effects and enhances phytochemical production in medicinal plants.

Effects of Heavy Metals on Bacterial Growth, Biochemical Properties and Antimicrobial Susceptibility

Heavy metals are metallic elements that occur naturally and have a high atomic weight and a density which is five times greater than the density of water. Several studies have demonstrated that metal contamination in natural environments could have an important role in the development and spread of antimicrobial resistance. This is of particular concern, considering that heavy metals usually occur at higher levels than pharmaceutically produced antimicrobials. Also, the bio-accumulative and non-biodegradable nature of heavy metals may result in long- term antimicrobial resistance selection pressure. Therefore, this study assessed the effects of Copper, Cobalt, Cadmium, Zinc and Lead salts on growth, biochemical properties and antimicrobial susceptibility of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus to commonly used antimicrobials. The selected bacteria were exposed to varying concentrations of the heavy metal salts ranging from 1 ppm to 1000 ppm after which growth was measured using a spectrophotometer. The effect on biochemical reactions and antimicrobial susceptibility were also tested by the use of conventional biochemical tests and Kirby-Bauer disk diffusion methods respectively. Different heavy metals affected the growth of each individual microorganism differently. Despite that, the growth of E. coli, P. aeruginosa and S. aureus was observed to be inversely proportional to the concentrations of the heavy metals used. Following exposure to heavy metals, E. coli and S. aureus showed no changes in their biochemical properties but P. aeruginosa gave a positive urease result contrary to the control. E. coli developed resistance to Levofloxacin, Meropenem and Tetracycline while S. aureus to Azithromycin and Gentamicin and P. aeruginosa developed resistance only to Meropenem. These results confirm the adverse effects of heavy metals on bacterial growth and reveals that heavy metals can cause changes in some biochemical properties of bacteria that produce any of these properties under stressful growing conditions. This research also supports the findings that heavy metals enhance the development of antimicrobial resistance in otherwise antimicrobial sensitive strains of bacteria. This study therefore, gives insight into the likely state of the proliferation of heavy metal induced antimicrobial resistance in heavy metal contaminated areas.

Laboratory Analysis of the Anti-Infectious Activity of Quantum Dots and Bioconjugates Based on Them in the Aspect of the Prospects for the Treatment of Inflammatory Diseases of the Eye. Experimental Research (Part 3)

This article presents the third part of an experimental study on the prospects and possibilities of using quantum dots and bioconjugates created on their basis in the treatment of inflammatory diseases of the eye. Taking into account the previously obtained results on the possibility of “safe” use of CdTe/Cd and InP/ZnSe/ZnS quantum dots on an animal model under conditions of intravitreal administration, the aim of the current stage was to analyze their antimicrobial activity in a bacteriological laboratory.Materials and methods. As QDs, we took two types of artificial fluorophores capable of generating superoxide radicals synthesized according to a special technical assignment at the Federal State Unitary Enterprise “Research Institute of Applied Acoustics”, Dubna, Moscow Region: type 1 — colloidal solution of QD CdTe / Cd MPA 710 10 % of the mass. Type 2 — colloidal solution of QD InP / ZnSe / ZnS 650 10 % wt. The study included “museum” and nosocomial strains of microorganisms, and the activity of points was assessed using the diskdiffusion method, followed by an assessment of the zones of inhibition of bacterial growth. Concentrations of 0.1 %, 0.01 %, and 0.001 % quantum dots were tested, as well as solutions of bioconjugates (antibiotic + quantum dots) of Vancomycin, Levofloxacin, Ceftazidime and Cefotaxime.Results. Based on the data obtained, it was concluded that quantum dots potentiate the action of the sensitivity of individual microorganisms, both outpatient and hospital strains.