Rhodococcus aetherivorans BCP1 as cell factory for the production of intracellular tellurium nanorods under aerobic conditions

Background: Tellurite (TeO32-) is recognized as a toxic oxyanion to living organisms. However, mainly anaerobic or facultative-anaerobic microorganisms are able to tolerate and convert TeO32- into the less toxic and available form of elemental Tellurium (Te0), producing Te-deposits or Te-nanostructures. The use of TeO32--reducing bacteria can lead to the decontamination of polluted environments and the development of "green-synthesis" methods for the production of nanomaterials. In this study, the tolerance and the consumption of TeO32- have been investigated, along with the production and characterization of Te-nanorods by Rhodococcus aetherivorans BCP1 grown under aerobic conditions. Results: Aerobically grown BCP1 cells showed high tolerance towards TeO32- with a minimal inhibitory concentration (MIC) of 2800μg/mL (11.2mM). TeO32- consumption has been evaluated exposing the BCP1 strain to either 100 or 500μg/mL of K2TeO3 (unconditioned growth) or after re-inoculation in fresh medium with new addition of K2TeO3 (conditioned growth). A complete consumption of TeO32- at 100μg/mL was observed under both growth conditions, although conditioned cells showed higher consumption rate. Unconditioned and conditioned BCP1 cells partially consumed TeO32- at 500μg/mL. However, a greater TeO32- consumption was observed with conditioned cells. The production of intracellular, not aggregated and rod-shaped Te-nanostructures (TeNRs) was observed as a consequence of TeO32- reduction. Extracted TeNRs appear to be embedded in an organic surrounding material, as suggested by the chemical-physical characterization. Moreover, we observed longer TeNRs depending on either the concentration of precursor (100 or 500μg/mL of K2TeO3) or the growth conditions (unconditioned or conditioned grown cells). Conclusions:Rhodococcus aetherivorans BCP1 is able to tolerate high concentrations of TeO32- during its growth under aerobic conditions. Moreover, compared to unconditioned BCP1 cells, TeO32- conditioned cells showed a higher oxyanion consumption rate (for 100μg/mL of K2TeO3) or to consume greater amount of TeO32- (for 500μg/mL of K2TeO3). TeO32- consumption by BCP1 cells led to the production of intracellular and not aggregated TeNRs embedded in an organic surrounding material. The high resistance of BCP1 to TeO32- along with its ability to produce Te-nanostructures supports the application of this microorganism as a possible eco-friendly nanofactory

Assembly, growth and conductive properties of tellurium nanorods produced by Rhodococcus aetherivorans BCP1

Tellurite (TeO32-) is a hazardous and toxic oxyanion for living organisms. However, several microorganisms can bioconvert TeO32- into the less toxic form of elemental tellurium (Te0). Here, Rhodococcus aetherivorans BCP1 resting (non-growing) cells showed the proficiency to produce tellurium-based nanoparticles (NPs) and nanorods (NRs) through the bioconversion of TeO32-, depending on the oxyanion initial concentration and time of cellular incubation. Te-nanostructures initially appeared in the cytoplasm of BCP1 cells as spherical NPs, which, as the exposure time increased, were converted into NRs. This observation suggested the existence of an intracellular mechanism of TeNRs assembly and growth that resembled the chemical surfactant-assisted process for NRs synthesis. The TeNRs produced by the BCP1 strain showed an average length (>700 nm) almost doubled compared to those observed in other studies. Further, the biogenic TeNRs displayed a regular single-crystalline structure typically obtained for those chemically synthesized. The chemical-physical characterization of the biogenic TeNRs reflected their thermodynamic stability that is likely derived from amphiphilic biomolecules present in the organic layer surrounding the NRs. Finally, the biogenic TeNRs extract showed good electrical conductivity. Thus, these findings support the suitability of this strain as eco-friendly biocatalyst to produce high quality tellurium-based nanomaterials exploitable for technological purposes

Growth of Rhodococcus sp. strain BCP1 on gaseous n-alkanes: New metabolic insights and transcriptional analysis of two soluble di-iron monooxygenase genes

Rhodococcus sp. strain BCP1 was initially isolated for its ability to grow on gaseous n-alkanes, which act as inducers for the co-metabolic degradation of low-chlorinated compounds. Here, both molecular and metabolic features of BCP1 cells grown on gaseous and short-chain n-alkanes (up to n-heptane) were examined in detail. We show that propane metabolism generated terminal and sub-terminal oxidation products such as 1- and 2-propanol, whereas 1-butanol was the only terminal oxidation product detected from n-butane metabolism. Two gene clusters, prmABCD and smoABCD-coding for Soluble Di-Iron Monooxgenases (SDIMOs) involved in gaseous n-alkanes oxidation-were detected in the BCP1 genome. By means of Reverse Transcriptase-quantitative PCR (RT-qPCR) analysis, a set of substrates inducing the expression of the sdimo genes in BCP1 were assessed as well as their transcriptional repression in the presence of sugars, organic acids, or during the cell growth on rich medium (Luria-Bertani broth). The transcriptional start sites of both the sdimo gene clusters were identified by means of primer extension experiments. Finally, proteomic studies revealed changes in the protein pattern induced by growth on gaseous- (n-butane) and/or liquid (n-hexane) short-chain n-alkanes as compared to growth on succinate. Among the differently expressed protein spots, two chaperonins and an isocytrate lyase were identified along with oxidoreductases involved in oxidation reactions downstream of the initial monooxygenase reaction step

The Neurobiology of Time Processing

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A hidden integral structure endows absolute concentration robust systems with resilience to dynamical concentration disturbances: A hidden integral structure endows absolute concentration robust systems with resilience to dynamical concentration disturbances

Biochemical systems that express certain chemical species of interest at the same level at any positive steady state are called 'absolute concentration robust' (ACR). These species behave in a stable, predictable way, in the sense that their expression is robust with respect to sudden changes in the species concentration, provided that the system reaches a (potentially new) positive steady state. Such a property has been proven to be of importance in certain gene regulatory networks and signaling systems. In the present paper, we mathematically prove that a well-known class of ACR systems studied by Shinar and Feinberg in 2010 hides an internal integral structure. This structure confers these systems with a higher degree of robustness than was previously known. In particular, disturbances much more general than sudden changes in the species concentrations can be rejected, and robust perfect adaptation is achieved. Significantly, we show that these properties are maintained when the system is interconnected with other chemical reaction networks. This key feature enables the design of insulator devices that are able to buffer the loading effect from downstream systems - a crucial requirement for modular circuit design in synthetic biology. We further note that while the best performance of the insulators are achieved when these act at a faster timescale than the upstream module (as typically required), it is not necessary for them to act on a faster timescale than the downstream module in our construction

Polarization-Dependent Phase of Light Propagating in Optical Fibers

As it propagates in a real single-mode fiber, light accumulates a phase delay and undergoes variations of its polarization state. These two phenomena are partly related to each other, owing to both well known geometric effects, i.e. the Pancharatnam's phase, and less known dynamic ones. This paper aims at reviewing these concepts, highlighting the polarization-depended phase of light that propagates in a single-mode fiber. We present a mathematical treatment using the familiar language of Jones and Stokes vectors and report experiments supporting the theory. The presented analysis has a general validity, and it can describe phase variation with respect to several parameters, such as distance, frequency and time. Its extension to multimode and multi-core fibers is also discussed. The results can be used for a better modelling and understanding of coherent transmission systems and interferometric fiber optic sensors

The different story of π bonds

We revisit “classical” issues in multiply bonded systems between main groups elements, namely the structural distortions that may occur at the multiple bonds and that lead, e.g., to trans-bent and bond-length alternated structures. The focus is on the role that orbital hybridization and electron correlation play in this context, here analyzed with the help of simple models for σ-and π-bonds, numerically exact solutions of Hubbard Hamiltonians and first principles (density functional theory) investigations of an extended set of systems

ALTERED HOMEOSTASIS OF PERIPHERAL BLOOD B CELLS IN PATIENTS WITH CHRONIC HUMAN HERPESVIRUS-8 INFECTION AND KAPOSI\ubfS SARCOMA: IMPLICATION FOR INFLUENZA VACCINATION

Background: Human herpesvirus-8 (HHV-8) is the etiological agent of classic Kaposi\u2019s sarcoma (cKS), a lymphoangioproliferative disease found mainly in older men of Eastern European and Mediterranean origin. Due to the dual role of B cells in HHV-8 infection, virus reservoir as well as agents of humoral immune control, we analyzed the subset distribution and the functional state of peripheral blood B cells in HHV-8- infected individuals with and without cKS. Furthermore, in order to investigate whether the chronic HHV-8 infection in B cells could alter the functionality of these cells and particularly may impact on humoral responses to antigenic stimulation, we investigated cKS patients\u2019 response to influenza vaccination, in terms of clinical efficacy, antibody production and safety. Methodology: Circulating B cells and their subsets were analyzed by 6-color flow cytometry in the following groups: 1- patients HHV-8 positive with classic KS (cKS); 2- subjects HHV-8 positive and cKS negative (HSP); 3- healthy controls, HHV-8 negative and cKS negative. Adjuvated trivalent influenza vaccine was administered to cKS patients and age- and sex-matched healthy controls. Influenza symptoms and side effects were recorded by daily diary cards supplied to the patients. Blood analysis and measurement of serum antibodies against vaccine antigens (H1N1, H3N2 and B) were performed before, 1 and 3 months post vaccination. Principal Finding: The number of B cells belonging to the preimmune/natural effector compartment, including transitional, pre-na\u131\ua8ve, na\u131\ua8ve and MZ-like subsets, was significantly higher among HHV-8 positive subjects, with or without cKS, while was comparable to healthy controls in the antigen experienced T-cell dependent compartment. The increased number of preimmune/natural effector B cells was associated with increased resistance to spontaneous apoptosis, while did not correlate with HHV-8 viral load. The clinical efficacy of vaccination was similar in cKS patients and controls. Seroconversion and seroprotection occurred equally in both groups. A mild increase in HHV-8 viremia was observed in a proportion of cKS patients after vaccination, without concomitant worsening of cKS lesions. The safety of vaccination did not differ between cKS patients and controls. The frequency of B cell subpopulations was evaluated and did not change after vaccination both in cKS patients and in healthy controls. Conclusions: For the first time to our knowledge, in this study we report that HHV-8 chronic infection promotes a perturbation of peripheral B cell homeostasis characterized by expansion of B cells of the preimmune/natural effector compartment, in patients with or without cKS. The alterations observed in cKS patients did not lead to an altered response to influenza vaccination that resulted safe and immunogenic in cKS patients as well as in age- and sex-matched controls. This observation may broaden our understanding of the complex interplay between viral and immune factors leading HHV-8-infected individuals to develop HHV-8-associated malignancies. Furthermore, our results have clinical importance because annual influenza vaccination may be particularly recommended for cKS patients considering their advanced age and comorbidity

Aerobic growth of Rhodococcus aetherivorans BCP1 using selected naphthenic acids as the sole carbon and energy sources

Naphthenic acids (NAs) are an important group of toxic organic compounds naturally occurring in hydrocarbon deposits. This work shows that Rhodococcus aetherivorans BCP1 cells not only utilize a mixture of eight different NAs (8XNAs) for growth but they are also capable of marked degradation of two model NAs, cyclohexanecarboxylic acid (CHCA) and cyclopentanecarboxylic acid (CPCA) when supplied at concentrations from 50 to 500 mgL-1. The growth curves of BCP1 on 8XNAs, CHCA, and CPCA showed an initial lag phase not present in growth on glucose, which presumably was related to the toxic effects of NAs on the cell membrane permeability. BCP1 cell adaptation responses that allowed survival on NAs included changes in cell morphology, production of intracellular bodies and changes in fatty acid composition. Transmission electron microscopy (TEM) analysis of BCP1 cells grown on CHCA or CPCA showed a slight reduction in the cell size, the production of EPS-like material and intracellular electron-transparent and electron-dense inclusion bodies. The electron-transparent inclusions increased in the amount and size in NA-grown BCP1 cells under nitrogen limiting conditions and contained storage lipids as suggested by cell staining with the lipophilic Nile Blue A dye. Lipidomic analyses revealed significant changes with increases of methyl-branched (MBFA) and polyunsaturated fatty acids (PUFA) examining the fatty acid composition of NAs-growing BCP1 cells. PUFA biosynthesis is not usual in bacteria and, together with MBFA, can influence structural and functional processes with resulting effects on cell vitality. Finally, through the use of RT (Reverse Transcription)-qPCR, a gene cluster (chcpca) was found to be transcriptionally induced during the growth on CHCA and CPCA. Based on the expression and bioinformatics results, the predicted products of the chcpca gene cluster are proposed to be involved in aerobic NA degradation in R. aetherivorans BCP1. This study provides first insights into the genetic and metabolic mechanisms allowing a Rhodococcus strain to aerobically degrade NAs

On Markov operators preserving polynomials

The paper is concerned with a special class of positive linear operators acting on the space C(K) of all continuous functions defined on a convex compact subset K of R^d, d \geq 1, having non-empty interior. Actually, this class consists of all positive linear operators T on C(K) which leave invariant the polynomials of degree at most 1 and which, in addition, map polynomials into polynomials of the same degree. Among other things, we discuss the existence of such operators in the special case where K is strictly convex by also characterizing them within the class of positive projections. In particular we show that such operators exist if and only if ∂K is an ellipsoid. Furthermore, a characterization of balls of R^d in terms of a special class of them is furnished. Additional results and illustrative examples are presented as well