Extremophiles as sources of inorganic bio-nanoparticles

Industrial use of nanotechnology in daily life has produced an emphasis on the safe and efficient production of nanoparticles (NPs). Traditional chemical oxidation and reduction methods are seen as inefficient, environmentally unsound, and often dangerous to those exposed and involved in NP manufacturing. However, utilizing microorganisms for biosynthesis of NPs allows efficient green production of a range of inorganic NPs, while maintaining specific size, shape, stability, and dispersity. Microorganisms living under harsh environmental conditions, called “Extremophiles,” are one group of microorganisms being utilized for this biosynthesis. Extremophiles’ unique living conditions have endowed them with various processes that enable NP biosynthesis. This includes a range of extremophiles: thermophiles, acidophilus, halophiles, psychrophiles, anaerobes, and some others. Fungi, bacteria, yeasts, and archaea, i.e. Ureibacillus thermosphaericus, and Geobacillus stearothermophilus, among others, have been established for NP biosynthesis. This article highlights the extremophiles and methods found to be viable candidates for the production of varying types of NPs, as well as interpreting selective methods used by the organisms to synthesize NPs.     

A review on the biosynthesis of metallic nanoparticles (gold and silver) using bio-components of microalgae: Formation mechanism and applications

The synthesis of nanoparticles (NP) using algae has been underexploited and even unexplored. In recent times, there are few reports on the synthesis of NP using algae, which are being used as a bio-factory for the synthesis. Moreover, the algae are a renewable source, so that it could be effectively explored in the green synthesis of NP. Hence, this review reports on the biosynthesis of NP especially gold and silver NP using algae. The most widely reported NP from algae are silver and gold than any other metallic NP, which might be due to their enormous biomedical field applications. The NP synthesized by this method is mainly in spherical shape; the reports are revealing the fact that the cell free extracts are highly exploited for the synthesis than the biomass, which is associated with the problem of recovering the particles. Besides, mechanism involving in the reduction and stabilization is well demonstrated to deepen the knowledge towards enhancement possibilities for the synthesis and applications.     

Prediction of chlortetracycline adsorption on the Fe3O4 nanoparticle using molecular dynamics simulation

Abstract

Molecular dynamics (MD) simulation was applied to investigate the adsorption mechanism of chlortetracycline (CTC) antibiotic molecule as the aqueous pollutant on the Fe₃O₄ nanoparticle (NP). Two different NP sizes with a diameter of about 1.4?nm and 3.5?nm were selected. Initially, the stability of both NPs in water was investigated by calculating radial distribution function curves of NP atoms. Simulation results confirmed the stable crystallographic structures of both NPs. However, small NP induce greater structural stabilization. Then, CTC molecules were adsorbed on NPs surface in various pollutant concentrations. Electrostatic and hydrogen bond were the major types of interactions between CTC molecules and the adsorbent surface. CTC molecules formed a complex with NP surface from their amine side chains; while they were parallel to each other in their aromatic rings and π-π bond between two CTC molecules was formed. Diffusion rate of CTC molecules could predict the adsorption mechanism. At lower concentration of CTC, CTC molecules tend to adsorb on the NP surface. At these concentrations, the diffusion rate of CTC was high. By increasing the CTC concentration, the pollutant agglomeration was enhanced which decreased the diffusion rate. At this time, the surface of NP was saturated. In addition, the results of isotherm curves showed that CTC adsorption on small NPs could be defined with both Langmuir and Freundlich isotherm models, while Freundlich isotherm model was more appropriate for larger NPs. In conclusion, observations confirmed that MD simulation could successfully predict the behavior of CTC adsorption on the Fe₃O₄ NP surface.

Communicated by Ramaswamy H. Sarma     

Altered Host Cell–Bacteria Interaction due to Nanoparticle Interaction with a Bacterial Biofilm

Nanoparticle (NP) use in everyday applications creates the potential for NPs to enter the environment where, in aquatic systems, they are likely to settle on substrates and interact with microbial communities. Legionella pneumophila biofilms are found as part of microbial communities in both natural and man-made environments, especially in man-made cooling systems. The bacterium is the causative agent of Legionnaires' disease. Legionella requires a host cell for replication in the environment, and amoebae commonly serve as this host cell. Our previous work demonstrated significant changes in Legionella biofilm morphology after exposure to 0.7 μg/L gold NPs (AuNPs). Here, we investigate how these morphology changes alter host–bacteria interactions using Acanthamoeba polyphaga as a model. Host–bacteria–NP interactions are affected by NP characteristics. Biofilms exposed to 4- and 18-nm, citrate-capped, spherical AuNPs significantly altered the grazing ability of A. polyphaga, which was not observed in biofilms exposed to 24-nm polystyrene beads. Uptake and replication of NP-exposed planktonic L. pneumophila within A. polyphaga were not altered regardless of NP size or core chemistry. Nanomaterial effects on the interaction of benthic organisms and bacteria may be directly or, as shown here, indirectly dependent on bacterial morphology. NP contamination therefore may alter interactions in a normal ecosystem function.     

Metabolic engineering for plant natural product biosynthesis in microbes

Plant natural products (NPs) not only serve many functions in an organism's survivability but also demonstrate important pharmacological activities. Isolation of NPs from native sources is frequently limited by low abundance and environmental, seasonal, and regional variation while total chemical synthesis of what are often complex structures is typically commercially infeasible. Reconstruction of biosynthetic pathways in heterologous microorganisms offers significant promise for a scalable means to provide sufficient quantities of a desired NP while using inexpensive renewable resources. To this end, metabolic engineering provides the technological platform for enhancing NP production in these engineered heterologous hosts. Recent advancements in the production of isoprenoids, phenylpropanoids, and alkaloids were made possible by utilizing a variety of techniques including combinatorial biosynthesis, codon optimization, expression of regulatory elements, and protein engineering of P450s.     

A green chemical approach for the synthesis of gold nanoparticles: characterization and mechanistic aspect

This IRCSET-EMPOWER (Irish Research Council for Science, Engineering and Technology Postdoctoral Research Grant) project aims to improve current methodology for the synthesis of metal nanoparticles (NPs). The development of efficient methodology for metal nanomaterials synthesis is an economical and environmental challenge. While the current methods for NPs synthesis are often energy-intensive and involve toxic chemicals, NPs biosynthesis can be carried on at circumneutral pH and mild temperature, resulting in low cost and environmental impact. Nanomaterial biosynthesis has been already observed in magnetotactic bacteria, diatoms, and S-layer bacteria, however, controlled NPs biosynthesis is a relatively new area of research with considerable potential for development. A thorough understanding of the biochemical mechanism involved in NPs biosynthesis is needed, before biosynthetic methods can be economically competitive. The analysis and identification of active species in the nucleation and growth of metal NPs is a daunting task, due to the complexity of the microbial system. This project work focuses on the controlled biosynthesis of gold NPs by fungal microorganisms and aims to determine the biochemical mechanism involved in nucleation and growth of the particles.     

Extra and Intracellular Synthesis of Nickel Oxide Nanoparticles Mediated by Dead Fungal Biomass

The use of dead biomass of the fungus Hypocrea lixii as a biological system is a new, effective and environmentally friendly bioprocess for the production and uptake of nickel oxide nanoparticles (NPs), which has become a promising field in nanobiotechnology. Dead biomass of the fungus was successfully used to convert nickel ions into nickel oxide NPs in aqueous solution. These NPs accumulated intracellularly and extracellularly on the cell wall surface through biosorption. The average size, morphology and location of the NPs were characterized by transmission electron microscopy, high-resolution transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The NPs were mainly spherical and extra and intracellular NPs had an average size of 3.8 nm and 1.25 nm, respectively. X-ray photoelectron spectroscopy analysis confirmed the formation of nickel oxide NPs. Infrared spectroscopy detected the presence of functional amide groups, which are probable involved in particle binding to the biomass. The production of the NPs by dead biomass was analyzed by determining physicochemical parameters and equilibrium concentrations. The present study opens new perspectives for the biosynthesis of nanomaterials, which could become a potential biosorbent for the removal of toxic metals from polluted sites.     

Ferritin in the field of nanodevices

Biomineralization of ferritin core has been extended to the artificial synthesis of homogeneous metal complex nanoparticles (NPs) and semiconductor NPs. The inner cavity of apoferritin is an ideal spatially restricted chemical reaction chamber for NP synthesis. The obtained ferritin (biocomplexes, NP and the surrounding protein shell) has attracted great interest among researchers in the field of nanodevices. Ferritins were delivered onto specific substrate locations in a one-by-one manner or a hexagonally close-packed array through ferritin outer surface interactions. After selective elimination of protein shells from the ferritin, bare NPs were left at the positions where they were delivered. The obtained NPs were used as catalysts for carbon nanotube (CNT) growth and metal induced lateral crystallization (MILC), charge storage nodes of floating gate memory, and nanometer-scale etching masks, which could not be performed by other methods.     

Chemical defenses of seaweeds against microbial colonization

Any living or non-living surface immersed in seawaterrapidly acquires a bacterial biofilm. For living marineorganisms, biofilm formation can result in the death ofthe host, and thus there is strong evolutionary pressure formarine eukaryotes to evolve mechanisms which inhibit orcontrol the development of biofilms on their surfaces.Some marine eukaryotes are indeed successful incontrolling biofilms on their surfaces, and in manyinstances this control is achieved by the production ofinhibitory chemicals which act at or near the surface ofthe organism. In some cases these natural inhibitors aresimply toxic to bacteria. However, increasingly it appearsthat at least some of these compounds act by interferingspecifically with bacterial characteristics which effect theability of bacteria to colonize their hosts, such asattachment, surface spreading, or the production ofextracellular macromolecules. As an example, theAustralian seaweed Delisea pulchra appears tocontrol bacterial colonization by interfering with abacterial regulatory system (the acylated homoserinelactone system) that regulates several colonizationrelevant bacterial traits. Understanding how marineorganisms control specific bacterial colonization traitsshould provide us with insights into new technologies forthe control of biofilms on artificial surfaces.     

Assessing protein oxidation by inorganic nanoparticles with enzyme‐linked immunosorbent assay (ELISA)

Growth in the nanotechnology industry is leading to increased production of engineered nanoparticles (NPs). This has given rise to concerns about the potential adverse and toxic effects to biological system and the environment. An important mechanism of NP toxicity is oxidative stress caused by the formation of reactive oxygen species (ROS) or via direct oxidation of biomolecules. In this study, a protein oxidation assay was developed as an indicator of biomolecule oxidation by NPs. The oxidation of the protein, bovine serum albumin (BSA) was evaluated with an enzyme‐linked immunosorbent assay (ELISA) to measure the protein carbonyl derivatives formed from protein oxidation. The results showed that some NPs such as Cu(0), CuO, Mn₂O₃, and Fe(0) caused oxidation of BSA; whereas, many of the other NPs tested were not reactive or very slowly reactive with BSA. The mechanisms involved in the oxidation of BSA protein by the reactive NPs could be attributed to the combined effects of ROS‐dependent and direct protein oxidation mechanisms. The ELISA assay is a promising method for the assessment of protein oxidation by NPs, which can provide insights on NP toxicity mechanisms. Biotechnol. Bioeng. 2013; 110: 694–701. © 2012 Wiley Periodicals, Inc.     

Reactive Oxygen Species Mediated Bacterial Biofilm Inhibition via Zinc Oxide Nanoparticles and Their Statistical Determination

The formation of bacterial biofilm is a major challenge in clinical applications. The main aim of this study is to describe the synthesis, characterization and biocidal potential of zinc oxide nanoparticles (NPs) against bacterial strain Pseudomonas aeruginosa. These nanoparticles were synthesized via soft chemical solution process in a very short time and their structural properties have been investigated in detail by using X-ray diffraction and transmission electron microscopy measurements. In this work, the potential of synthesized ZnO-NPs (∼10–15 nm) has been assessed in-vitro inhibition of bacteria and the formation of their biofilms was observed using the tissue culture plate assays. The crystal violet staining on biofilm formation and its optical density revealed the effect on biofilm inhibition. The NPs at a concentration of 100 µg/mL significantly inhibited the growth of bacteria and biofilm formation. The biofilm inhibition by ZnO-NPs was also confirmed via bio-transmission electron microscopy (Bio-TEM). The Bio-TEM analysis of ZnO-NPs treated bacteria confirmed the deformation and damage of cells. The bacterial growth in presence of NPs concluded the bactericidal ability of NPs in a concentration dependent manner. It has been speculated that the antibacterial activity of NPs as a surface coating material, could be a feasible approach for controlling the pathogens. Additionally, the obtained bacterial solution data is also in agreement with the results from statistical analytical methods.     

Role for Rhizobium rhizogenes K84 cell envelope polysaccharides in surface interactions

Rhizobium rhizogenes strain K84 is a commercial biocontrol agent used worldwide to control crown gall disease. The organism binds tightly to polypropylene substrate and efficiently colonizes root surfaces as complex, multilayered biofilms. A genetic screen identified two mutants in which these surface interactions were affected. One of these mutants failed to attach and form biofilms on the abiotic surface although, interestingly, it exhibited normal biofilm formation on the biological root tip surface. This mutant is disrupted in a wcbD ortholog gene, which is part of a large locus predicted to encode functions for the biosynthesis and export of a group II capsular polysaccharide (CPS). Expression of a functional copy of wcbD in the mutant background restored the ability of the bacteria to attach and form normal biofilms on the abiotic surface. The second identified mutant attached and formed visibly denser biofilms on both abiotic and root tip surfaces. This mutant is disrupted in the rkpK gene, which is predicted to encode a UDP-glucose 6-dehydrogenase required for O-antigen lipopolysaccharide (LPS) and K-antigen capsular polysaccharide (KPS) biosynthesis in rhizobia. The rkpK mutant from strain K84 was deficient in O-antigen synthesis and exclusively produced rough LPS. We also show that strain K84 does not synthesize the KPS typical of some other rhizobia strains. In addition, we identified a putative type II CPS, distinct from KPS, that mediates cell-surface interactions, and we show that O antigen of strain K84 is necessary for normal cell-cell interactions in the biofilms.     

Induction of holomycin production and complex metabolic changes by the argR mutation in Streptomyces clavuligerus NP1

In bacteria, arginine biosynthesis is tightly regulated by a universally conserved regulator, ArgR, which regulates the expression of arginine biosynthetic genes, as well as other important genes. Disruption of argR in Streptomyces clavuligerus NP1 resulted in complex phenotypic changes in growth and antibiotic production levels. To understand the metabolic changes underlying the phenotypes, comparative proteomic studies were carried out between NP1 and its argR disruption mutant (designated CZR). In CZR, enzymes involved in holomycin biosynthesis were overexpressed; this is consistent with its holomycin overproduction phenotype. The effects on clavulanic acid (CA) biosynthesis are more complex. Several proteins from the CA cluster were moderately overexpressed, whereas several proteins from the 5S clavam biosynthetic cluster and from the paralog cluster of CA and 5S clavam biosynthesis were severely downregulated. Obvious changes were also detected in primary metabolism, which are mainly reflected in the altered expression levels of proteins involved in acetyl-coenzyme A (CoA) and cysteine biosynthesis. Since acetyl-CoA and cysteine are precursors for holomycin synthesis, overexpression of these proteins is consistent with the holomycin overproduction phenotype. The complex interplay between primary and secondary metabolism and between secondary metabolic pathways were revealed by these analyses, and the insights will guide further efforts to improve production levels of CA and holomycin in S. clavuligerus.     

Microbial Synthesis of Nanoparticles: Mechanisms,Characteristics, and Applications

Cadmium sulfide (CdS) and zinc sulfide (ZnS) biogenic nanoparticles (NPs) were produced by microbial synthesis using bacteria of different taxonomic groups: Gram-negative (Shewanella oneidensis MR-1) and Gram-positive (Bacillus subtilis 168) bacteria in a liquid medium under aerobic conditions in the presence of salts of the respective metals and sulfur. It was shown that the stabilization of nanoparticles in aqueous suspensions is due to the presence of certain protein molecules of the outer membrane of cells, that is, proteins of the families of various receptors, porins, and flagellin, on the nanoparticle (NP) surface. The effect of the protein coating on stability, luminescence, zeta-potential, hydrodynamics diameter and other physiochemical characteristics of nanoparticles was studied. Decolorization of methylene blue dye under the exposure to UV irradiation was used as a model to demonstrate the photocatalytic properties of NPsCdS. This opens the possibility of using biogenic nanoparticles in photocatalysis for industrial wastewater treatment.

     

生物被膜主动分散机制研究进展

细菌生物被膜(bacterial biofilm, BBF)为微生物栖息提供了所需要的保护屏障和生长微环境。生物被膜对抗菌药物的耐受性使得它在医学治疗等领域产生了严重的危害。因此如何分散被膜显得意义重大。综述了生物被膜主动分散的几种主要机制,包括降解酶的合成、运动力的恢复、表面活性剂的产生和细胞死亡。     

Dextran Nanoparticle Synthesis and Properties

Dextran is widely exploited in medical products and as a component of drug-delivering nanoparticles (NPs). Here, we tested whether dextran can serve as the main substrate of NPs and form a stable backbone. We tested dextrans with several molecular masses under several synthesis conditions to optimize NP stability. The analysis of the obtained nanoparticles showed that dextran NPs that were synthesized from 70 kDa dextran with a 5% degree of oxidation of the polysaccharide chain and 50% substitution with dodecylamine formed a NP backbone composed of modified dextran subunits, the mean diameter of which in an aqueous environment was around 100 nm. Dextran NPs could be stored in a dry state and reassembled in water. Moreover, we found that different chemical moieties (e.g., drugs such as doxorubicin) can be attached to the dextran NPs via a pH-dependent bond that allows release of the drug with lowering pH. We conclude that dextran NPs are a promising nano drug carrier.     

Impact of RGD nanopatterns grafted onto titanium on osteoblastic cell adhesion

This work reports on the synthesis of titanium bone implants functionalized with nanoparticles (NPs) containing Arg-Gly-Asp-Cys peptide (RGDC) and shows the adhesion behavior of cells seeded on these materials. RGDC peptides were first conjugated to a norbornenyl-poly(ethylene oxide) macromonomer (Nb-PEO). Then, functional NPs with a size of ～300 nm and constituted of polynorbornene core surrounded by poly(ethylene oxide) shell were prepared by ring-opening metathesis polymerization in dispersed medium. The grafting density of these NPs on the titanium surface is up to 2 NPs·μm(-2) (80 pmol of RGDC per cm(-2) of NP surface). Cell adhesion was evaluated using preosteoblast cells (MC3T3-E1). Results of cells cultured for 24 h showed that materials grafted with NPs functionalized with RGDC peptides enhance specific cell adhesion and can create filopodia-like structures among NP sites by stressing the cells.     

Bacterial biofilms as a natural form of existence of bacteria in the environment and host organism

Advances in microscopic analysis and molecular genetics research methods promoted the acquisition of evidence that natural bacteria populations exist predominately as substrate attached biofilms. Bacteria in biofilms are able to exchange signals and display coordinated activity that is inherent to multicellular organisms. Formation of biofilm communities turned out to be one of the main survival strategies of bacteria in their ecological niche. Bacteria in attached condition in biofilm are protected from the environmental damaging factors and effects of antibacterial substances in the environment and host organism during infection. According to contemporary conception, biofilm is a continuous layer of bacterial cells that are attached to a surface and each other, and contained in a biopolymer matrix. Such bacterial communities may be composed of bacteria of one or several species, and composed of actively functioning cells as well as latent and uncultured forms. Particular attention has recently been paid to the role of biofilms in the environment and host organism. Microorganisms form biofilm on any biotic and abiotic surfaces which creates serious problems in medicine and various areas of economic activity. Currently, it is established that biofilms are one of the pathogenetic factors of chronic inflection process formation. The review presents data on ubiquity of bacteria existence as biofilms, contemporary methods of microbial community analysis, structural-functional features of bacterial biofilms. Particular attention is paid to the role of biofilm in chronic infection process formation, heightened resistance to antibiotics of bacteria in biofilms and possible mechanisms of resistance. Screening approaches for agents against biofilms in chronic infections are discussed.