Characterization of Xenorhabdus and Photorhabdus bacteria by Fourier transform mid-infrared spectroscopy with attenuated total reflection (FT-IR/ATR)

Preliminary Screening on Antibacterial Crude Secondary Metabolites Extracted from Bacterial Symbionts and Identification of Functional Bioactive Compounds by FTIR, HPLC and Gas Chromatography-Mass Spectrometry

Secondary metabolites, bioactive compounds produced by living organisms, can unveil symbiotic relationships in nature. In this study, soilborne entomopathogenic nematodes associated with symbiotic bacteria (Xenorhabdus stockiae and Photorhabdus luminescens) were extracted from solvent supernatant containing secondary metabolites, demonstrating significant inhibitory effects against E. coli, S. aureus, B. subtilus, P. mirabilis, E. faecalis, and P. stutzeri. The characterization of these secondary metabolites by Fourier transforms infrared spectroscopy revealed amine groups of proteins, hydroxyl and carboxyl groups of polyphenols, hydroxyl groups of polysaccharides, and carboxyl groups of organic acids. Furthermore, the obtained crude extracts were analyzed by high-performance liquid chromatography for the basic identification of potential bioactive peptides. Gas chromatography-mass spectrometry analysis of ethyl acetate extracts from Xenorhabdus stockiae identified major compounds including nonanoic acid derivatives, proline, paromycin, octodecanal derivatives, trioxa-5-aza-1-silabicyclo, 4-octadecenal, methyl ester, oleic acid, and 1,2-benzenedicarboxylicacid. Additional extraction from Photorhabdus luminescens yielded functional compounds such as indole-3-acetic acid, phthalic acid, 1-tetradecanol, nemorosonol, 1-eicosanol, and unsaturated fatty acids. These findings support the potential development of novel natural antimicrobial agents for future pathogen suppression.

Investigation of Corrosion Inhibition of Mild Steel in 0.5 M H2SO4 with Lachancea fermentati Inhibitor Extracted from Rotten Grapefruits (Vitis vinifera): Adsorption, Thermodynamic, Electrochemical, and Quantum Chemical Studies

Corrosion inhibition of mild steel (MS) was studied using Lachancea fermentati isolate in 0.5 M H2SO4, which was isolated from rotten grapes (Vitis vinifera) via biofilm formation. Biofilm over the MS surface was asserted by employing FT-IR and FE-SEM with EDXS, electrochemical impedance spectroscopy (EIS), AFM, and DFT-ESP techniques. The weight loss experiments and temperature studies supported the physical adsorption behavior of the corrosion inhibitors. The maximum inhibition efficiency (IE) value (90%) was observed at 293 K for 9 × 106 cfu/mL of Lachancea fermentati isolate. The adsorption of Lachancea fermentati isolate on the surface of MS confirms Langmuir's adsorption isotherm model, and the -ΔG values indicate the spontaneous adsorption of inhibitor over the MS surface. Electrochemical studies, such as potentiodynamic polarization (PDP) and EIS were carried out to investigate the charge transfer (CT) reaction of the Lachancea fermentati isolate. Tafel polarization curves reveal that the Lachancea fermentati isolate acts as a mixed type of inhibitor. The Nyquist plots (EIS) indicate the increase in charge transfer resistance (Rct) and decrease of double-layer capacitance (Cdl) values when increasing the concentration of Lachancea fermentati isolate. The spectral studies, such as UV-vis and FT-IR, confirm the formation of a complex between MS and the Lachancea fermentati isolate inhibitor. The formation of biofilm on the MS surface was confirmed by FE-SEM, EDXS, and XPS analysis. The proposed bioinhibitor shows great potential for the corrosion inhibition of mild steel in acid media.

Rapid Identification of Insecticide- and Herbicide-Tolerant Genetically Modified Maize Using Mid-Infrared Spectroscopy

Genetically modified (GM) technology is of great significance for increasing crop production, protecting biodiversity, and reducing environmental pollution. However, with the frequent occurrence of safety events regarding GM foods, more and more disputes have arisen over the potential safety of transgenic technology. It is particularly necessary to find a fast and accurate method for transgenic product identification. In this research, mid-infrared spectroscopy, coupled with chemometric methods, was applied to discriminate GM maize from its non-GM parent. A total of 120 GM maize and 120 non-GM maize samples were prepared, and the spectral information in the range of 400–4000 cm−1 was collected. After acquiring the spectra, wavelet transform (WT) was used to preprocess the data, and k-means was carried out to split all samples into calibration and prediction sets in the ratio of 2:1. Principal component analysis (PCA) was then conducted to qualitatively distinguish the two types of samples, and an apparent cluster was observed. Since the full spectrum covered a large amount of data and redundant information, we adopted the successive projections algorithm (SPA) to select optimal wavelengths for further analysis. Chemometrics, including partial least squares-discriminant analysis (PLS-DA), the k-nearest neighbor algorithm (KNN), and the extreme learning machine (ELM), were performed to establish classification models based on full spectra and optimal wavelengths. The overall results indicated that ELM models based on full spectra and optimal spectra showed better accuracy and reliability, with a 100% recognition rate in the calibration set and a 98.75% recognition rate in the prediction set. It has been confirmed that mid-infrared spectroscopy, combined with chemometric methods, can be a novel approach to identify transgenic maize.

An exopolysaccharide-producing novel Agrobacterium pusense strain JAS1 isolated from snake plant enhances plant growth and soil water retention

A peculiar bacterial growth was very often noticed in leaf-initiated tissue cultures of Sansevieria trifasciata, a succulent belonging to the Asparagaceae family. The isolate left trails of some highly viscous material on the walls of the suspension vessels or developed a thick overlay on semisolid media without adversities in plant growth. FTIR identified this substance to be an extracellular polysaccharide. Various morphological, biochemical tests, and molecular analyses using 16S rRNA, atpD, and recA genes characterized this isolate JAS1 as a novel strain of Agrobacterium pusense. Its mucoidal growth over Murashige and Skoog media yielded enormous exopolysaccharide (7252 mg l^-1), while in nutrient agar it only developed fast-growing swarms. As a qualifying plant growth-promoting bacteria, it produces significant indole-3-acetic acid (86.95 mg l^-1), gibberellic acid (172.98 mg l^-1), ammonia (42.66 µmol ml^-1). Besides, it produces siderophores, 1-aminocyclopropane-1-carboxylic acid deaminase, fixes nitrogen, forms biofilms, and productively solubilizes soil inorganic phosphates, and zinc. Under various treatments with JAS1, wheat and chickpea resulted in significantly enhanced shoot and root growth parameters. PGP effects of JAS1 positively enhanced plants' physiological growth parameters reflecting significant increments in overall chlorophyll, carotenoids, proline, phenols, flavonoids, and sugar contents. In addition, the isolated strain maintained both plant and soil health under an intermittent soil drying regime, probably by both its PGP and EPS production attributes, respectively.

Silver Nanoparticles Incorporated on Natural Clay as an Inhibitor against the New ISO SS Bacteria Isolated from Sewage Sludge, Involved in Malachite Green Dye Oxidation

A facile, ecofriendly, and cost-effective method was developed to prepare a microporous material based on natural chemically modified bentonite with silver ions (BN-Ag⁰). This material presents a good catalytic activity against Malachite Green (MG) dye and bacteriostatic activity against a newly isolated bacterium from sewage sludge named hereafter “ISO SS” and Escherichia coli (E. coli). BN-Ag⁰ was characterized by the following methods: energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), Fourier-transform infrared (FTIR) spectroscopy, temperature programmed desorption (TPD) and X-ray Diffraction (XRD). The new bacterium ISO SS, was isolated using the technique of isolating a pure culture of anaerobically stabilized sludge. A mandatory characterization of ISO SS isolated strains from anaerobic stabilized sludge was performed in the process of identifying bacterial species. The cationic clay-based nanomaterial showed appreciable antibacterial activity against ISO SS, a Gram-negative bacterium. It also showed good activity against E. coli bacteria. As a catalyst in the catalytic ozonation of MG dye, BN-Ag⁰ significantly improves the oxidation time of the dye, due to its good adsorption and catalytic properties. The catalytic and antibacterial activities of the natural bentonite (BN) and of BN-Ag⁰ were examined using performant characterization techniques. The lifetime of the BN-Ag⁰ catalyst was also evaluated. Results obtained are expected to provide valuable findings for the preparation of a good microporous material with multiple functionalities.

Survival and efficacy of entomopathogenic nematodes on exposed surfaces

Entomopathogenic nematodes (EPN) species differ in their capability to withstand rapid desiccation (RD). Infective juveniles of Steinernema carpocapsae are a better adaptable and tolerant than Steinernema feltiae or Heterorhabditis bacteriophora as, an optimal RH of > 90% is required by S. feltiae and H. bacteriophora while maintaining RH equivalent to 74% could sustain survival of S. carpocapsae under RD. Our findings from infectivity suggest that following application, shrunk IJs are acquired passively by the larvae, probably rehydrate and resume infection within the insect gut. Water loss rate is a key factor affecting survival of S. carpocapsae on exposed surfaces. The present study provides the foundation for characterizing mechanism of rapid rate of water loss in EPN. ATR-FTIR is a rapid and reliable method for analysis of water loss. Changes in peak intensity was observed at 3100-3600 cm-1 (OH bonds of water), 2854 cm-1 (CH stretching of symmetric CH2, acyl chains), 2924 cm-1 (CH stretching of anti-symmetric CH2, lipid packing heterogeneity), 1634 cm-1 (amide I bonds) indicate major regions for hydration dependent changes in all EPN species. FTIR data also indicates that, S. carpocapsae contains strong water interacting regions in their biochemical profile, which could be an influencing factor in their water holding capacity under RD. ATR-FTIR were correlated to water content determined gravimetrically by using Partial Least square -Regression and FTIR multivariate method, which could be used to screen a formulation's potential to maintain or delay the rate of water loss in a rapid and efficient manner.

Infrared Spectroscopy of Blood

The magnitude of infectious diseases in the twenty-first century created an urgent need for point-of-care diagnostics. Critical shortages in reagents and testing kits have had a large impact on the ability to test patients with a suspected parasitic, bacteria, fungal, and viral infections. New point-of-care tests need to be highly sensitive, specific, and easy to use and provide results in rapid time. Infrared spectroscopy, coupled to multivariate and machine learning algorithms, has the potential to meet this unmet demand requiring minimal sample preparation to detect both pathogenic infectious agents and chronic disease markers in blood. This focal point article will highlight the application of Fourier transform infrared spectroscopy to detect disease markers in blood focusing principally on parasites, bacteria, viruses, cancer markers, and important analytes indicative of disease. Methodologies and state-of-the-art approaches will be reported and potential confounding variables in blood analysis identified. The article provides an up to date review of the literature on blood diagnosis using infrared spectroscopy highlighting the recent advances in this burgeoning field.

In vitro and in vivo antibacterial activity of environmental bacteriophages against Pseudomonas aeruginosa strains from cystic fibrosis patients

The goal of the study was to determine the relationship between in vitro/in vivo efficacy of environmental Pseudomonas phages and certain phenotypical properties of Pseudomonas aeruginosa (PA) strains. We studied the diversity between particular isolates and determined phage sensitivity in vitro and in vivo in the Galleria mellonella insect model. Twenty-eight lytic bacteriophages specific for PA were tested against 121 CF PA isolates including 29 mucoid PA strains. Most strains from cystic fibrosis (CF) patients were lysed by at least three phages (93.6 %), but completely insensitive strains were also present (6.4 %). Two phages PA5oct and KT28 exhibited high rates of lytic potency on 55–68 % of PA strains (72–86 % of mucoid isolates). We further explored phage activity against six PA strains (CF and non-CF) in vitro, comparing clonal differences in phage susceptibility with bacterial properties such as the ability to form biofilms, mucosity, twitching motility, and biochemical profiles. We observed the relationship between variation in phage susceptibility and Fourier transform infrared spectroscopy (FTIR) analysis in the spectra window of carbohydrates. The protective efficacy of two selected phages against PA PAO1 and 0038 infection was confirmed in vivo in G. mellonella larvae. Generally, the wax moth model results confirmed the data from in vitro assays, but in massive infection of CF isolates, the application of lytic phages probably led to the release of toxic compound causing an increase in larvae mortality. We assumed that apart of in vitro phage activity testing, a simple and convenient wax moth larvae model should be applied for the evaluation of in vivo effectiveness of particular phage preparations.

Identification and discrimination of bacteria using Fourier transform infrared spectroscopy

Bacterial spectra were obtained in the wavenumber range of 4000-600 cm(-1) using FTIR spectroscopy. FTIR spectral patterns were analyzed and matched with 16S-rRNA signatures of bacterial strains OS1 and OS2, isolated from oil sludge. Specific spectral bands obtained from OS1 (FJ226761), reference strain Bacillus flexus (ATCC 49095), OS2 (FJ215874) and reference strain Stenotrophomonas maltophilia (ATCC 19861) respectively, suggested that OS1 and ATCC 49095 were closely related whereas OS2 was different. The bands probably represent groups of proteins and lipids of specific bacteria. Separate peaks found in B. flexus were similar to those of OS1. The S. maltophilia (ATCC 19861) and OS2 exhibited a similar peak at 3272 cm(-1). Amide bands (I, II and III) exhibited that OS1 and B. flexus were closely related, but were different from OS2. In the fingerprint region, peak at 1096 cm(-1) and 1360 cm(-1) exhibited the specific fingerprints of OS2 and reference strain S. maltophilia (ATCC 19861), respectively. The specific fingerprint signature was found at 1339 cm(-1) for OS1 and at 1382 cm(-1) for B. flexus ATCC 49095, allowing these two strains of B. flexus to be differentiated. This spectral signature originated from phospholipid and RNA components of the cell. Principle components analysis (PCA) of spectral regions exhibited with distinct sample clusters between Bacillus flexus (ATCC 49095), S. maltophilia (ATCC 19861), OS1 and OS2 in amide and fingerprint region.