Diversity and biosynthetic potential of culturable aerobic heterotrophic bacteria isolated from Magura Cave, Bulgaria

Biocapacity of bacteria inhabiting karstic caves to produce valuable biologically active compounds is still slightly investigated. A total of 46 culturable heterotrophic bacteria were isolated under aerobic conditions from the Gallery with pre-historical drawings in Magura Cave, Bulgaria. Phylogenetic analysis revealed that most of bacterial isolates aff iliated with Proteobacteria (63%), followed by Actinobacteria (10.9%), Bacteroidetes (10.9%), and Firmicutes (6.5%). A strong domination of Gram-negative bacteria (total 81%) belonging to nine genera: Serratia, Pseudomonas, Enterobacter, Sphingobacterium, Stenotrophomonas, Commamonas, Acinetobacter, Obesumbacterium, and Myroides, was observed. Gram-positive isolates were represented by the genera Bacillus, Arthrobacter, and Micrococcus. One isolate showed a signif icant phylogenetic distance to the closest neighbor and could represent а novel species. Heterotrophic bacterial isolates from Magura Cave were investigated for hydrolytic enzymes production, antimicrobial and hemolytic activity. Predominance of producers of protease (87%), followed by xanthan lyase (64%), lipase (40%), β-glycosidase (40%), and phytase (21%) was observed. Over 75% of the isolates demonstrated antimicrobial and hemolytic activity. The results suggest that heterotrophic bacteria isolated from Magura Cave could be a valuable source of industrially relevant psychrotolerant enzymes and bioactive metabolites. This study is a f irst report on the taxonomic composition and biological activity of culturable bacteria inhabiting a cave in Bulgaria

Surface Functionalization of Cotton Fabric with Fluorescent Dendrimers, Spectral Characterization, Cytotoxicity, Antimicrobial and Antitumor Activity

Poly(propylenimine) dendrimers from first and third generations modified with 1,8-naphthalimide units and their Zn(II) complexes have been investigated by absorption and fluorescence spectroscopy. These dendrimers have been deposited on a cotton cloth by the extraction method, producing yellow-colored textile materials. They have been characterized by defining their color coordinates L*a*b*, XYZ and xy. The antimicrobial activity of dendrimers has been investigated in vitro against model gram-positive and gram-negative bacteria and yeasts. Being deposited onto the surface of cotton fabric, the studied dendrimers reduced bacterial growth and prevented the formation of bacterial biofilm. Anticancer and cytotoxicity activities have also been performed against HeLa and Lep-3 human tumor cell lines as model systems

Enhanced Photodynamic Efficacy Using 1,8-Naphthalimides: Potential Application in Antibacterial Photodynamic Therapy

This study addresses the need for antibacterial medication that can overcome the current problems of antibiotics. It does so by suggesting two 1,8-naphthalimides (NI1 and NI2) containing a pyridinium nucleus become attached to the imide-nitrogen atom via a methylene spacer. Those fluorescent derivatives are covalently bonded to the surface of a chloroacetyl-chloride-modified cotton fabric. The iodometric method was used to study the generation of singlet oxygen (1O2) by irradiation of KI in the presence of monomeric 1,8-naphthalimides and the dyed textile material. Both compounds generated reactive singlet oxygen, and their activity was preserved even after they were deposited onto the cotton fabric. The antibacterial activity of NI1 and NI2 in solution and after their covalent bonding to the cotton fabric was investigated. In vitro tests were performed against the model gram-positive bacteria B. cereus and gram-negative P. aeruginosa bacteria in dark and under light iradiation. Compound NI2 showed higher antibacterial activity than compound NI1. The light irradiation enhanced the antimicrobial activity of the compounds, with a better effect achieved against B. cereus

Phylogenetic analysis of the bacterial community in a crystallizer pond, Pomorie salterns, Bulgaria

The aim of this study was to investigate the bacterial community habituating P18, the biggest crystallizer pond in Pomorie salterns (34% salinity). The obtained results showed that the bacterial community differs from many previous reports of low bacterial diversity in hypersaline environments and demonstrates unusually high diversity of presented taxa, some unusual domination of diverse genera not reported before as dominant and identification of previously unknown 16S rRNA sequences. The retrieved 23 bacterial operational taxonomic units (OTUs) affiliated with 15 bacterial genera from four phyla – Firmicutes, 47.5%; Proteobacteria, 23.1%; Bacteroidetes, 22%; Deinococcus–Thermus, 2.4%; and one-candidate division SR1, 4.8%. Representatives of the phylum Firmicutes predominated in the bacterial community with almost half of the retrieved sequences. Almost all clones branched together with cultured halophiles or uncultured clones retrieved from saline niches. Despite of the high salt concentration, some of the closest phylogenetic neighbours were moderate halophiles. New sequences represented 42.3% of bacterial OTUs. Some of them formed separate branches with similarity less than 85%

Cotton Fabric Modified with a PAMAM Dendrimer with Encapsulated Copper Nanoparticles: Antimicrobial Activity

A new methodology for modifying textile materials with dendrimers containing nanoparticles was developed. This involved a combination of eosin Y and N-methyldiethanolamine (MDEA) for reducing the copper ions in the dendrimer complex by enabling a photochemical reaction under visible light and ambient conditions. The conversion of copper ions into nanoparticles was monitored using scanning electron microscopy (SEM) and by performing colorimetric, fluorescence, and electron paramagnetic resonance (EPR) studies. Regardless of the concentration of the photoinitiator eosin Y, it discolored completely upon illumination. Three types of cotton fabrics were compared as antimicrobial materials against Bacillus cereus. One of the fabrics was dyed with a first-generation PAMAM dendrimer which had been functionalized with eight 1,8-naphthalimide fluorophores. Another fabric was dyed with a dendrimer–copper complex, and the third was treated by conversion of the complex into copper nanoparticles encapsulated into the dendrimer. An enhancement in the antimicrobial activity of the textiles was achieved at higher dendrimer concentrations, under illumination with visible light. The fabric modified with the copper nanoparticles encapsulated inside the dendrimer exhibited the best antibacterial activity because it had two photosensitizers (PS), as both 1,8-naphthalimide fluorophores and copper nanoparticles were contained in the dendrimer molecules. The presence of oxygen and suitable illumination activated the photosensitizers to generate the reactive oxygen species (singlet oxygen (1O2) and other oxygenated products, e.g., anion radicals, hydroxyl radicals, and hydrogen peroxide) responsible for destroying the bacteria

Synthesis, structural characterization and antibacterial activity of cotton fabric modified with a hydrogel containing barium hexaferrite nanoparticles

Barium hexaferrite nanoparticles were synthesized by co-precipitation of Ba2+ and Fe3+ cations with NaOH under of high-power ultrasound. The nanoparticles were dispersed in an aqueous solution of the hydrogel precursors. This solution was used to impregnate the cotton fabric dyed with a photoinitiator. The composite material BaFe12O19 nanoparticles-hydrogel-cotton fabric was prepared by surface initiated photopolymerization under visible light. The modification of the cotton fabric and uniform distribution of the nanoparticles in the structure of the hydrogel were analyzed by scanning electron microscopy (SEM), IR spectroscopy, X-ray diffraction analysis (XRD), fluorescence and colourimetric analyses. The antibacterial efficacy of the material was evaluated against Gram-negative Escherichia coli and Pseudomonas aeruginosa. © 2016 Elsevier B.V. All rights reserved

Keratinase production by newly isolated antarctic actinomycete strains

International audienc

Photophysical and antibacterial activity of light-activated quaternary eosin Y

The functional characteristics of a new eosin dye with biocidal quaternary ammonium group (E) were studied in aqueous solution and in organic solvents of different polarity. The spectral properties depend on the nature and polarity of the respective solvents. The antimicrobial activity of compound E has been tested in vitro against Gram-negative bacteria (Escherichia coli, Acinetobacter johnsoni and Pseudomonas aeruginosa), Gram-positive bacteria (Sarcina lutea and Bacillus cereus) and the antifungal activity was tested against the yeasts Candida lipolytica in solution and after treated on cotton fabric. Broth dilution test has been used for quantitative evaluation of the antimicrobial activity of compound E against the model strains. The ability of compound E to inhibit the growth of model Gram-negative P. aeruginosa strain was assessed after 16 h of incubation in presence and absence of light. These experiments were conducted in planktonic format in solution and on cotton fabric. The results suggest that the new compound is effective in treating the relevant pathogens with better results being obtained by irradiation with light. In this case the quaternary ammonium group promotes the binding of eosin Y moiety to the bacterial cell wall thus accelerating bacterial photo inactivation

Unusually High Archaeal Diversity in a Crystallizer Pond, Pomorie Salterns, Bulgaria, Revealed by Phylogenetic Analysis

Recent studies on archaeal diversity in few salterns have revealed heterogeneity between sites and unique structures of separate places that hinder drawing of generalized conclusions. Investigations on the archaeal community composition in P18, the biggest crystallizer pond in Pomorie salterns (PS) (34% salinity), demonstrated unusually high number of presented taxa in hypersaline environment. Archaeal clones were grouped in 26 different operational taxonomic units (OTUs) assigned to 15 different genera from two orders, Halobacteriales and Haloferacales. All retrieved sequences were related to culturable halophiles or unculturable clones from saline (mostly hypersaline) niches. New sequences represented 53.9% of archaeal OTUs. Some of them formed separate branches with 90% similarity to the closest neighbor. Present results significantly differed from the previous investigations in regard to the number of presented genera, the domination of some genera not reported before in such extreme niche, and the identification of previously undiscovered 16S rRNA sequences