Vellasamy Shanmugaiah

Antibacterial Activity of Essential Oil Components and Their Potential Use in Seed Disinfection

Among the main (> or = 0.7%) components of some essential oils, considerable antibacterial activity was shown by terpenoid and phenylpropanoid derivatives containing phenol and alcohol functionalities. A reduced or no activity was shown by those derivatives containing ketones, aldehydes, ethers, and ester functionalities as well as the remaining terpenoids. Eugenol emulsion treatments (1-8 mg/mL) of bean seeds bearing about 2.6 x 10(6) cfu/seed of strain ICMP239 of Xanthomonas campestris pv. phaseoli var. fuscans determined a highly significant reduction of the bacteria on seeds. In particular, eugenol at 4 mg/mL disinfect seeds bearing about 7.0 x 10(2) cfu/seed and lower densities. However, after 72 h, incubation treatments with 2, 4, and 8 mg/mL of eugenol caused germination reduction of 3%, 7%, and 16%, respectively, which was significantly different from the controls. No effect on germination was observed with 1 mg/mL eugenol emulsion treatment. These data indicate eugenol as potentially useful for bean seed disinfection from X. campestris pv. phaseoli var. fuscans. Further studies on the effects on seed vitality and on formulation of essential oils are needed.

Novel bioactive metabolites producing endophytic fungus Colletotrichum gloeosporioides against multidrug-resistant Staphylococcus aureus

The emergence of antibiotic-resistant bacteria such as Staphylococcus aureus calls for inventive research and development strategies. Inhibition of this bacterial pathogenesis may be a promising therapeutic approach. The screening of antimicrobial compounds from endophytes is a promising way to meet the increasing threat of drug-resistant strains of human and plant pathogens. In the present study, a novel endophytic fungus, Colletotrichum gloeosporioides, was isolated from the medicinal plant Vitex negundo L. Extracts of C. gloeosporioides were obtained using hexane, ethyl acetate and methanol solvents. The fungal extracts exhibited an effective antimicrobial activity against bacterial and fungal strains. The extracts were also analysed for antibacterial activity against methicillin-, penicillin- and vancomycin-resistant S. aureus strains (1-10). The methanol extract showed an effective antibacterial activity against S. aureus strain 9, with a minimal inhibitory concentration of 31.25 μg mL(-1) . The synergistic action of endophytic fungal extract with antibiotics such as methicillin, penicillin and vancomycin was observed against S. aureus strain 6. The fractional inhibitory concentration index of methanol extract with methicillin, penicillin and vancomycin was 1.0, 0.5 and 0.375, respectively. These results clearly indicate that the metabolite of endophytic fungus C. gloeosporioides is a potential source of new antibiotics.

An eco-friendly and water mediated product selective synthesis of 2-aminopyrimidines and their in vitro anti-bacterial evaluation

A greener water mediated protocol for the efficient synthesis of a library of 2-amino-6-styryl pyrimidines (4) and their dihydro analogues (3) has been reported. Most of the saturated compounds (3) rather than their unsaturated analogues (4) showed better anti-bacterial (in vitro) activity against three human pathogens viz. Staphylococcus aureus, Klebsiella pneumonia and Escherichia coli. In particular, three of them (3 b, 3 i &3 k) exhibited high inhibition against the growth of all the three pathogens comparable with that of the reference drug, tetracycline.

Biological evaluation and molecular docking studies of new curcuminoid derivatives: Synthesis and characterization.

In the present study, three series of dimethylamino curcuminoids viz. 4-phenylaminomethyl curcumin (3a-d), arylidene curcumin (3e) and pyrazole curcumin (3f-i) derivatives have been synthesized and studied for their in vitro anti-inflammatory, antioxidant and antibacterial activities. Synthesized dimethylamino curcuminoid derivatives namely 3d, 3e, 3h and 3i have shown potent anti-inflammatory properties than parent curcumin. Molecular docking interactions of dimethylamino curcuminoids derivatives against cyclooxygenase enzymes (COX-1 and COX-2) were studied.

Synthesis of (Z)-1,3-diaryl-2-(4-aryl-1H-1,2,3-triazol-1-yl)prop-2-en-1-ones and their antibacterial studies

The cyclization of 1,3-diaryl-2-azido-2-propen-1-ones with various alkynes in the presence of a catalytic amount of copper sulfate–sodium ascorbate in DMSO–water mixture under microwave irradiation led to the formation of (Z)-1,3-diaryl-2-(4-substituted-1H-1,2,3-triazol-1-yl)prop-2-en-1-ones. The structure and stereochemistry of the products have been elucidated by spectroscopic and single crystal X-ray analyses. All the newly synthesized compounds have been tested for their antibacterial activity against four strains of bacteria and found to have moderate to good inhibition.

Rhizobacteria isolated from common bean in southern Italy as potential biocontrol agents against common bacterial blight

Common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli and its variety fuscans, leads to important crop loss and, due to limited bactericides availability and effectiveness in agriculture practices, it appears necessary to develop alternative control strategies. The aim of this study was to assess the potential of bacteria isolated from bean rhizosphere to control the above mentioned disease. Sixty out of 162 bean rhizobacteria inhibited the growth in vitro of selected virulent strains of both varieties of X. a. pv. phaseoli and, when applied to seeds before sowing, six of them reduced disease symptoms on bean in in vitro and greenhouse pathogenicity assays. In order to deepen bacteria characterization, the six rhizobacteria were evaluated for lytic enzymes, hydrogen cyanide, ammonia, siderophores, indoles production, for inorganic phosphates solubilisation and environmental adaptability in terms of salinity, pH and temperature gradients variation. Altogether the findings of this study indicate the above six rhizobacteria as potential biocontrol candidates.

Effect of improved Trichoderma fusants and their parent strains in control of sheath blight of rice and wilt of tomato

The biological efficacy of Trichoderma species may differ due to variations in strains and ecosystems. It has been shown that fusant strains, obtained by protoplast fusion, may have enhanced biocontrol efficacy. A study was conducted under in vitro and pot conditions to assess the biocontrol efficacy of Trichoderma harzianum, T. viride, their intra-fusants ThSF3 and TvSF5, and inter-fusant HF9 against Rhizoctonia solani, Fusarium oxysporum f. sp. lycopersici, Bipolaris oryzae, Curvularia lunata and Pythium sp. In vitro the inhibition potential towards either mycelial growth or conidia, sclerotia and oospores germination of F. oxysporum f. sp. lycopersici, B. oryzae, C. lunata, R. solani and Pythium sp. respectively, was evaluated. Among these, the highest mycelial growth inhibition was observed for inter-fusant HF9 followed by the intrafusants and the effect was significantly higher towards inhibition of R. solani, B. oryzae and Pythium sp. In rice pot culture experiments, T. harzianum and T. viride parental strains, intra-fusants ThSF3 and TvSF5, and inter-fusant HF9 suppressed sheath blight of rice by 62%, 58%, 66%, 61% and 81%, respectively. Similarly in tomato T. harzianum, T. viride parental strains, intra-fusants ThSF3 and TvSF5, and interfusant HF9 suppressed the Fusarium wilt of tomato by 71%, 64%, 75%, 69%, 80%, respectively. Inter-fusant strain HF9 was found to significantly control all the fungal pathogens and lowers down the disease incidence significantly in both rice and tomato plants when compared to the other antagonists. Fusant strains exhibited higher biocontrol activity in both in vitro and green house condition, they increased shoot and root growth of tomato and rice plants and they also showed a better survival feature in soil.

Molecular Cloning and Docking of speB Gene Encoding Cysteine Protease With Antibiotic Interaction in Streptococcus pyogenes NBMKU12 From the Clinical Isolates

Streptococcus pyogenes causes a variety of diseases ranging from mild diseases to severe invasive infections which result in significant morbidity and mortality. This study focuses on the antibiotic resistance of S. pyogenes and their interaction with cysteine protease. Around 36 beta-hemolytic isolates were collected from the clinical lab, of which seven isolates (19.4%) were identified as Streptococcus pyogenes. One of the seven isolates was collected from a urinary tract infection, which was identified by antibody agglutination and MALTI-TOF-MS, and it is designated as S. pyogenes NBMKU12. Around 8.3 to 66.6 % of the isolates were found to be resistant to one or more antimicrobial agents, especially, penicillin-G resistance was exhibited by 29.1% of the isolates. In the NBMKU12 isolate, the beta lactem (TEM) gene was detected among the 13 antibiotic genes for which it was tested. Furthermore, when analysis for presence of 13 virulence genes were carried out in NBMKU12 isolate, only speJ and speB were detected. The speB (streptococcal pyrogenic exotoxin B) encoding cysteine protease gene was cloned. This was followed by performing DNA sequencing to understand the putative cysteine protease interaction with antibiotics, inhibitors, and substrate. The speB gene consists of 1197 nucleotides and encodes a protein with multiple domains, including a signal peptide (aa 1–22), an inhibitor region (aa 27–156), and a catalytic cysteine domain (aa 160–367). The signal peptide cleavage site is predicted between Ala22 and Asn23. The putative 398 amino acid residues were found to have a theoretical pI of 8.76 and a molecular mass of 43,204.36 Da. The tested culture supernatants of NBMKU12 isolate exhibited the proteolytic activity against casein, papaya and pineapple used as substrates. The proteolytic activity suggests the expression of speB gene. Molecular docking analysis of cysteine protease showed that erythromycin (bond length 2.41 Å), followed by chloramphenicol (2.51 Å), exhibited a strong interaction; while penicillin-G (3.24 Å) exhibited a weak interaction, and this factor could be considered as a cause for penicillin-G resistance. The present study contributes to a better understanding of speB gene encoding cysteine protease, antibiotic resistance, and their interaction in the isolate, S. pyogenes NBMKU12. The antibiotics and cysteine protease interaction study confirms the resistance or sensitivity of S. pyogenes. Hence, it could be hypothesized that the isolate NBMKU12 is resistant to most of the tested antibiotics, and this resistance might be a cause for mutation.

Nanocerium oxide increases the survival of adult rod and cone photoreceptor in culture by abrogating hydrogen peroxide-induced oxidative stress

In vitro cell culture system for adult rod and cone photoreceptor (PR) is an effective and economical model for screening drug candidates against all kinds of age related retinal blindness. Interestingly, adult PR cells have a limited survival in the culture system, thus preventing full exploitation of this in vitro approach for drug screening applications. The limited survival of the adult PR cells in culture is due to their inherently high oxidative stress and photic injury. Mixed valence-state ceria nanoparticles have the ability to scavenge free radicals and reduce oxidative stress. Here, ceria nanoparticles of 5-10 nm dimensions have been synthesized, possessing dual oxidation state (+3 and +4) as evident from x-ray photoelectron spectroscopy and exhibiting real time reduction of hydrogen peroxide (H2O2) as quantified by absorbance spectroscopy and cyclic voltammogram analysis. Using flow cytometry and cell culture assay, it has been shown that, upon one time addition of 10 nM of nanoceria in the PR culture of the 18 months old adult common carp (Cyprinus carpio) at the time of plating the cells, the oxidative stress caused due to hydrogen peroxide assault could be abrogated. A further single application of nanoceria significantly increases the survival of these fragile cells in the culture, thus paving way for developing a more robust photoreceptor culture model to study the aging photoreceptor cells in a defined condition.