Microalga Broths Synthesize Antibacterial and Non-Cytotoxic Silver Nanoparticles Showing Synergy with Antibiotics and Bacterial ROS Induction and Can Be Reused for Successive AgNP Batches.

The era of increasing bacterial antibiotic resistance requires new approaches to fight infections. With this purpose, silver-based nanomaterials are a reality in some fields and promise new developments. We report the green synthesis of silver nanoparticles (AgNPs) using culture broths from a microalga. Broths from two media, with different compositions and pHs and sampled at two growth phases, produced eight AgNP types. Nanoparticles harvested after several synthesis periods showed differences in antibacterial activity and stability. Moreover, an evaluation of the broths for several consecutive syntheses did not find relevant kinetics or activity differences until the third round. Physicochemical characteristics of the AgNPs (core and hydrodynamic sizes, Z-potential, crystallinity, and corona composition) were determined, observing differences depending on the broths used. AgNPs showed good antibacterial activity at concentrations producing no or low cytotoxicity on cultured eukaryotic cells. All the AgNPs had high levels of synergy against Escherichia coli and Staphylococcus aureus with the classic antibiotics streptomycin and kanamycin, but with ampicillin only against S. aureus and tetracycline against E. coli. Differences in the synergy levels were also dependent on the types of AgNPs. We also found that, for some AgNPs, the killing of bacteria started before the massive accumulation of ROS.

Green Extracellular Synthesis of Silver Nanoparticles by Pseudomonas alloputida, Their Growth and Biofilm-Formation Inhibitory Activities and Synergic Behavior with Three Classical Antibiotics.

Bacterial resistance to antibiotics is on the rise and hinders the fight against bacterial infections, which are expected to cause millions of deaths by 2050. New antibiotics are difficult to find, so alternatives are needed. One could be metal-based drugs, such as silver nanoparticles (AgNPs). In general, chemical methods for AgNPs' production are potentially toxic, and the physical ones expensive, while green approaches are not. In this paper, we present the green synthesis of AgNPs using two Pseudomonas alloputida B003 UAM culture broths, sampled from their exponential and stationary growth phases. AgNPs were physicochemically characterized by transmission electron microscopy (TEM), total reflection X-ray fluorescence (TXRF), infrared spectroscopy (FTIR), dynamic light scattering (DLS), and X-ray diffraction (XRD), showing differential characteristics depending on the synthesis method used. Antibacterial activity was tested in three assays, and we compared the growth and biofilm-formation inhibition of six test bacteria: Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. We also monitored nanoparticles' synergic behavior through the growth inhibition of E. coli and S. aureus by three classical antibiotics: ampicillin, nalidixic acid, and streptomycin. The results indicate that very good AgNP activity was obtained with particularly low MICs for the three tested strains of P. aeruginosa. A good synergistic effect on streptomycin activity was observed for all the nanoparticles. For ampicillin, a synergic effect was detected only against S. aureus. ROS production was found to be related to the AgNPs' antibacterial activity.

Los hábitos de lectura reducen la procrastinación académica en estudiantes de enfermería / Reading Habits Reduce Academic Procrastination in Nursing Students

Introducción: La procrastinación académica es la conducta negativa de postergar sin razón diversas tareas. Se ha relacionado con diferentes variables, sin embargo, se desconoce si los hábitos de lectura influyen en su reducción. Objetivo: Determinar la influencia de los hábitos de lectura en la procrastinación académica en estudiantes de enfermería. Métodos: Estudio descriptivo, correlacional causal, con una muestra de 271 estudiantes de enfermería de primero a quinto año de formación en la Universidad Nacional de San Agustín de Arequipa, Perú. Se usaron dos instrumentos: el Inventario de hábitos de lectura de Muñoz y la escala de procrastinación de Busko. Se aplicó la prueba r de Pearson y el análisis de regresión lineal. Resultados: Las estudiantes de enfermería tuvieron edades que fluctúan entre los 16 y 25 años, con predominio del sexo femenino. Los hábitos de lectura fueron de nivel medio en el 66,79 por ciento y alto en el 30,99 por ciento de los casos. El 97,05 por ciento de estudiantes tuvo algún nivel de procrastinación, de los cuales 2,58 por ciento registró un nivel alto. Existe asociación significativa tanto entre hábitos de lectura y edad, como entre procrastinación y año de estudios. Conclusión: Los hábitos de lectura se relacionan de forma inversa con la procrastinación académica y predicen su disminución(AU)

Introduction: Academic procrastination is the negative behavior of putting off various tasks without reason. It has been related to different variables; however, it is unknown whether reading habits influence its reduction. Objective: To determine the influence of reading habits on academic procrastination in nursing students. Methods: Descriptive study, causal correlation, with a sample of 271 nursing students from first to fifth year of training at the National University of San Agustín de Arequipa, Peru. Two instruments were used: Muñoz Reading Habits Inventory and Busko Procrastination Scale. Pearson's r test and linear regression analysis were applied. Results: The nursing students had ages that fluctuate between 16 and 25 years, with a predominance of females. Reading habits were medium level in 66.79 percent and high in 30.99 percent of the cases. Certain level of procrastination was identified in 97.05 percent of students, 2.58 percent of them registered a high level. There is significant association between reading habits and age, as well as between procrastination and year of studies. Conclusion: Reading habits are inversely related to academic procrastination and predict its decline(AU)

Nonuniversality of front fluctuations for compact colonies of nonmotile bacteria.

The front of a compact bacterial colony growing on a Petri dish is a paradigmatic instance of non-equilibrium fluctuations in the celebrated Eden, or Kardar-Parisi-Zhang (KPZ), universality class. While in many experiments the scaling exponents crucially differ from the expected KPZ values, the source of this disagreement has remained poorly understood. We have performed growth experiments with B. subtilis 168 and E. coli ATCC 25922 under conditions leading to compact colonies in the classically alleged Eden regime, where individual motility is suppressed. Non-KPZ scaling is indeed observed for all accessible times, KPZ asymptotics being ruled out for our experiments due to the monotonic increase of front branching with time. Simulations of an effective model suggest the occurrence of transient nonuniversal scaling due to diffusive morphological instabilities, agreeing with expectations from detailed models of the relevant biological reaction-diffusion processes.

Prokaryotic diversity and community composition in the Salar de Uyuni, a large scale, chaotropic salt flat.

Salar de Uyuni (SdU), with a geological history that reflects 50 000 years of climate change, is the largest hypersaline salt flat on Earth and is estimated to be the biggest lithium reservoir in the world. Its salinity reaches saturation levels for NaCl, a kosmotropic salt, and high concentrations of MgCL2 and LiCl, both salts considered important chaotrophic stressors. In addition, extreme temperatures, anoxic conditions, high UV irradiance, high albedo and extremely low concentrations of phosphorous, make SdU a unique natural extreme environment in which to contrast hypotheses about limiting factors of life diversification. Geophysical studies of brines from different sampling stations show that water activity is rather constant along SdU. Geochemical measurements show significant differences in magnesium concentration, ranging from 0.2 to 2M. This work analyses the prokaryotic diversity and community structure at four SdU sampling stations, selected according to their location and ionic composition. Prokaryotic communities were composed of both Archaea (with members of the classes Halobacteria, Thermoplasmata and Nanohaloarchaea, from the Euryarchaeota and Nanohaloarcheota phyla respectively) and Bacteria (mainly belonging to Bacteroidetes and Proteobacteria phyla). The important differences in composition of microbial communities inversely correlate with Mg2+ concentration, suggesting that prokaryotic diversity at SdU is chaotropic dependent.

Microbial community composition of Tirez lagoon (Spain), a highly sulfated athalassohaline environment.

BACKGROUND: The aim was to study the seasonal microbial diversity variations of an athalassohaline environment with a high concentration of sulfates in Tirez lagoon (La Mancha, Spain). Despite the interest in these types of environments there is scarce information about their microbial ecology, especially on their anoxic sediments. RESULTS: We report the seasonal microbial diversity of the water column and the sediments of a highly sulfated lagoon using both molecular and conventional microbiological methods. Algae and Cyanobacteria were the main photosynthetic primary producers detected in the ecosystem in the rainy season. Also dinoflagelates and filamentous fungi were identified in the brines. The highest phylotype abundance in water and sediments corresponded to members of the bacterial phylum Proteobacteria, mainly of the Gamma- and Alphaproteobacteria classes. Firmicutes and Actinobacteria were isolated and identified in Tirez brines and sediment samples. Halophilic sulfate reducing Deltaproteobacteria were also detected (Desulfohalobium). CONCLUSIONS: Important differences have been found in the microbial diversity present in the Tirez water column and the sediments between the wet and dry seasons. Also the Tirez lagoon showed a high richness of the bacterial Alpha- and Deltaproteobacteria, Bacteroidetes, Firmicutes, Actinobacteria and for the archaeal Euryarchaeota.

The sulfate-rich and extreme saline sediment of the ephemeral tirez lagoon: a biotope for acetoclastic sulfate-reducing bacteria and hydrogenotrophic methanogenic archaea.

Our goal was to examine the composition of methanogenic archaea (MA) and sulfate-reducing (SRP) and sulfur-oxidizing (SOP) prokaryotes in the extreme athalassohaline and particularly sulfate-rich sediment of Tirez Lagoon (Spain). Thus, adenosine-5'-phosphosulfate (APS) reductase α (aprA) and methyl coenzyme M reductase α (mcrA) gene markers were amplified given that both enzymes are specific for SRP, SOP, and MA, respectively. Anaerobic populations sampled at different depths in flooded and dry seasons from the anoxic sediment were compared qualitatively via denaturing gradient gel electrophoresis (DGGE) fingerprint analysis. Phylogenetic analyses allowed the detection of SRP belonging to Desulfobacteraceae, Desulfohalobiaceae, and Peptococcaceae in ∂-proteobacteria and Firmicutes and SOP belonging to Chromatiales/Thiotrichales clade and Ectothiorhodospiraceae in γ-proteobacteria as well as MA belonging to methylotrophic species in Methanosarcinaceae and one hydrogenotrophic species in Methanomicrobiaceae. We also estimated amino acid composition, GC content, and preferential codon usage for the AprA and McrA sequences from halophiles, nonhalophiles, and Tirez phylotypes. Even though our results cannot be currently conclusive regarding the halotolerant strategies carried out by Tirez phylotypes, we discuss the possibility of a plausible "salt-in" signal in SRP and SOP as well as of a speculative complementary haloadaptation between salt-in and salt-out strategies in MA.

The status of the species Beijerinckia fluminensis Dobereiner and Ruschel 1958. Request for an Opinion.

In a previous article [Oggerin M., Arahal, D. R., Rubio, V. & Marin, I. (2009). Int J Syst Evol Microbiol 59, 2323-2328], it has been shown that strain Beijerinckia fluminensis UQM 1685(T) and its derived equivalent B. fluminensis CIP 106281(T) do not conform to the description of the type strain of Beijerinckia fluminensis Döbereiner and Ruschel 1958. Indeed, both strains were identified as members of the species Rhizobium radiobacter and exhibited marked phenotypic and genotypic differences with members of the genus Beijerinckia. It was concluded that both strains, and any other equivalents derived from them, do not descend from the nomenclatural type. Since then, our attempts to find older deposits of the type strain, hopefully derived from the original isolate, or other existing strains of Beijerinckia fluminensis that could be proposed as a neotype strain, have been in vain. It is therefore proposed that the Judicial Commission should place the name Beijerinckia fluminensis Döbereiner and Ruschel 1958 on the list of rejected names if a suitable replacement type strain or a neotype cannot be found within two years following the publication of this Request (Rule 18c).

Bacterial diversity in Fez tanneries and Morocco's Binlamdoune River, using 16S RNA gene based fingerprinting.

Tannery wastewater causes serious ecological and sanitary damage. Chemical analysis of water from Binlamdoune River of the medina of Fez was conducted and the results revealed the presence of toxic elements from tanneries and other industrial activities, which strongly affected water quality. To determine the effectiveness of bioremediation for depollution, we studied the abundance and diversity of bacteria residing in these polluted environments. Conducting denaturing gradient gel electrophoresis (PCR-DGGE) of the 16S rDNA area using primers related to bacteria showed a bacterial community belonging to eubacterial groups, that is, Epsilonproteobacteria, Clostridia, Lactobacillales, Bacteroidetes, Gammaproteobacteria, and Alphaproteobacteria. In addition, cloning displayed the presence of clones belonging to the Firmicutes group. Moreover, scanning electron microscopy revealed a significant heterogeneity of microorganism forms and structures. These endogenous microbes could have a significant role in the purification of Binlamdoune River and Fez tannery wastewater.

Identification of Beijerinckia fluminensis strains CIP 106281T and UQM 1685T as Rhizobium radiobacter strains, and proposal of Beijerinckia doebereinerae sp. nov. to accommodate Beijerinckia fluminensis LMG 2819.

During the course of a research project with free-living, nitrogen-fixing bacteria, we determined the 16S rRNA gene sequence of Beijerinckia fluminensis strains UQM 1685T and CIP 106281T and discovered that they were only 90.6-91.2% similar to the sequences of strains of other Beijerinckia species and subspecies. Moreover, the highest similarity to these sequences (99.7%) corresponded to strains of Rhizobium radiobacter (including Agrobacterium tumefaciens). Other diagnostic features confirmed that the two strains have the same origin but do not descend from the nomenclatural type. At the same time, B. fluminensis LMG 2819 was characterized and it was found that its properties also do not agree with the original description of the species, although it can be considered a member of the genus. Further characterization, including chemotaxonomic and other phenotypic traits, allows us to propose (i) the identification of B. fluminensis strains CIP 106281T and UQM 1685T as strains of Rhizobium radiobacter and (ii) the designation of strain LMG 2819T (=CECT 7311T) as the type strain of a novel species, Beijerinckia doebereinerae sp. nov.

Enzymatic permeabilization of the thecate dinoflagellate Alexandrium minutum (Dinophyceae) yields detection of intracellularly associated bacteria via catalyzed reporter deposition-fluorescence in situ hybridization.

The enzymatic permeabilization procedure described here allows the detection of intracellular bacteria in the thecate dinoflagellate Alexandrium minutum by using catalyzed reporter deposition-fluorescence in situ hybridization. The combined use of propidium iodide and calcofluor for confocal laser scanning microscopy, together with general and specific fluorescent bacterial probes, demonstrated the intracellular presence of bacteria, including members of the phylum Bacteroidetes.

Hoeflea alexandrii sp. nov., isolated from the toxic dinoflagellate Alexandrium minutum AL1V.

A Gram-negative, aerobic, non-symbiotic bacterium (AM1V30(T)) was isolated from the toxic dinoflagellate Alexandrium minutum AL1V. On the basis of 16S rRNA gene sequence similarity, strain AM1V30(T) was most closely related (97.4 % similarity) to the type strain of Hoeflea marina, which belongs to the family Phyllobacteriaceae within the order Rhizobiales of the class Alphaproteobacteria. A polyphasic approach was used to clarify the taxonomic position of strain AM1V30(T). During the course of this study, a second species was described by others as belonging to the genus Hoeflea, namely Hoeflea phototrophica; it showed a somewhat higher level of 16S rRNA gene sequence similarity with respect to strain AM1V30(T) (98.2 %) and was also taken into account. The fatty acid profiles, physiological and biochemical data and DNA G+C content (59.7 mol%) support the classification of strain AM1V30(T) as a member of the genus Hoeflea. The characteristics of the novel strain were sufficiently distinct to indicate that it represents a separate species. To confirm this conclusion, DNA-DNA hybridizations were performed: low values (between 15.8 and 29.8 %) were obtained in all cases. Thus, AM1V30(T) represents a novel species within the genus Hoeflea, for which the name Hoeflea alexandrii sp. nov. is proposed. Strain AM1V30(T) (=CECT 5682(T)=DSM 16655(T)) is the type strain.