Antimicrobial and Antibiofilm Peptides

The increasing onset of multidrug-resistant bacteria has propelled microbiology research towards antimicrobial peptides as new possible antibiotics from natural sources. Antimicrobial peptides are short peptides endowed with a broad range of activity against both Gram-positive and Gram-negative bacteria and are less prone to trigger resistance. Besides their activity against planktonic bacteria, many antimicrobial peptides also show antibiofilm activity. Biofilms are ubiquitous in nature, having the ability to adhere to virtually any surface, either biotic or abiotic, including medical devices, causing chronic infections that are difficult to eradicate. The biofilm matrix protects bacteria from hostile environments, thus contributing to the bacterial resistance to antimicrobial agents. Biofilms are very difficult to treat, with options restricted to the use of large doses of antibiotics or the removal of the infected device. Antimicrobial peptides could represent good candidates to develop new antibiofilm drugs as they can act at different stages of biofilm formation, on disparate molecular targets and with various mechanisms of action. These include inhibition of biofilm formation and adhesion, downregulation of quorum sensing factors, and disruption of the pre-formed biofilm. This review focuses on the proprieties of antimicrobial and antibiofilm peptides, with a particular emphasis on their mechanism of action, reporting several examples of peptides that over time have been shown to have activity against biofilm

Aprovechamiento de materiales locales en la estructura de pavimentos urbanos económicos

Se estudiaron las propiedades de un suelo representativo del partido de 25 de Mayo (Prov. de Buenos Aires) y su zona de influencia, con el objeto de conocer la posibilidad de utilizarlo como base y sub-base de pavimentos urbanos. Se analizó el comportamiento del suelo, realizando mezclas con emulsión bituminosa superestable EBL2, como así también mezclas de suelo-cemento. De la comparación de ambos casos surgen consideraciones técnico-económicas, en base a las cuales se dan posibles soluciones de pavimento.In this paper were studied the properties of a representative soil of 25 de Mayo district, in the Buenos Aires Province, with the object to establish the possibility of its use as a base and sub-base in urban pavements. The soil behaviour vms analyzed making mixtures with su- perstnble EBL2 bituminous emulsions and also with soil-cement mixtures. The results obtained with both mixtures were compared and technical and economical considerations were given

Characterization of the proteins involved in the DNA repair mechanism in M. smegmatis.

: Several alkylating agents that either occur in the environment or are self-produced can cause DNA-damaging injuries in bacterial cells. Therefore, all microorganisms have developed repair systems that are able to counteract DNA alkylation damage. The adaptive response to alkylation stress in Escherichia coli consists of the Ada operon, which has been widely described; however, the homologous system in Mycobacterium tuberculosis (MTB) has been shown to have a different genetic organization but it is still largely unknown. In order to describe the defense system of MTB, we first investigated the proteins involved in the repair mechanism in the homologous non-pathogenic mycobacterium M. smegmatis. Ogt, Ada-AlkA and FadE8 proteins were recombinantly produced, purified and characterized. The biological role of Ogt was examined using proteomic experiments to identify its protein partners in vivo under stress conditions. Our results suggested the formation of a functional complex between Ogt and Ada-AlkA, which was confirmed both in silico by docking calculations and by gel filtration chromatography. We propose that this stable association allows the complex to fulfill the biological roles exerted by Ada in the homologous E. coli system. Finally, FadE8 was demonstrated to be structurally and functionally related to its E. coli homologous, Aid

Effect of Levamisole on the Incidence of Spontaneous Mammary Tumors in C3H Mice

Spontaneous mammary carcinoma in C3H mice is preceded by premalignant hyperplastic alveolar nodules. When a primary tumor is evident, examination of the other mammae will reveal a number of microscopic precancerous lesions in various stages of transformation to overt malignant tumors. In an effort to inhibit the development of additional malignant tumors after surgical removal of the first apparent tumor, we treated female C3H/HeJ mice with subcutaneous injections of levamisole (0.6 mg per kg of body weight) on a twice weekly regimen. All further tumors were surgically excised when they became palpable. The surgical excision of bulk tumor burden, immunorestoration by levamisole, and the presence in the tumor cells of immunogenic surface antigens related to the virus all might be expected to enhance immunodulation of tumor cell growth or immunorejection of tumor cells. Immune activity measured by assaying macrophage migration inhibition factor, extractable from splenocytes, was significantly greater in the levamisole-treated mice than in the controls throughout the experiment. Although fewer tumors developed in the treated animals during the first eight weeks, this apparent effect of immunopertubation was only transitory. By the end of 14 weeks, there was no longer a statistically significant difference in cumulative tumor index between the two groups

Structure of amyloid-β (20-34) with Alzheimer's-associated isomerization at Asp23 reveals a distinct protofilament interface.

Amyloid-β (Aβ) harbors numerous posttranslational modifications (PTMs) that may affect Alzheimer's disease (AD) pathogenesis. Here we present the 1.1 Å resolution MicroED structure of an Aβ 20-34 fibril with and without the disease-associated PTM, L-isoaspartate, at position 23 (L-isoAsp23). Both wild-type and L-isoAsp23 protofilaments adopt β-helix-like folds with tightly packed cores, resembling the cores of full-length fibrillar Aβ structures, and both self-associate through two distinct interfaces. One of these is a unique Aβ interface strengthened by the isoaspartyl modification. Powder diffraction patterns suggest a similar structure may be adopted by protofilaments of an analogous segment containing the heritable Iowa mutation, Asp23Asn. Consistent with its early onset phenotype in patients, Asp23Asn accelerates aggregation of Aβ 20-34, as does the L-isoAsp23 modification. These structures suggest that the enhanced amyloidogenicity of the modified Aβ segments may also reduce the concentration required to achieve nucleation and therefore help spur the pathogenesis of AD

Sobre la identidad taxonómica de Polycarpon apurense (Caryophyllaceae) con una aclaración sobre su distribución en Sudamérica

As part of the ongoing studies of the genus Polycarpon (Caryophyllaceae) and the preparation of its treatment for the Argentinian Flora, we here present a taxonomic note concerning the identity of the name P. apurense. A specimen preserved at P is designated as the lectotype of this name. Its identity was discussed and the synonymy with P. prostratum, recurring in the literature, was discarded on the basis of its habit and leaf shape and size. A nomenclatural change (i.e. P. tetraphyllum subsp. apurense) is proposed here on the basis of the current concept in the genus Polycarpon. Concerning the distribution of this taxon, it is excluded from Brazil and Uruguay and its presence in Peru is uncertain.Key words: Como parte de los estudios en curso del género Polycarpon (Caryophyllaceae) y la preparación de su tratamiento para la Flora Argentina, presentamos aquí una nota taxonómica sobre la identidad del nombre P. apurense. Un espécimen preservado en P es designado como el lectotipo de este nombre. Se discute su identidad y se descarta la sinonimia con P. prostratum, recurrente en la literatura, sobre la base de algunos caracteres morfológicos como el hábito, forma y tamaño de las hojas. Se propone un cambio nomenclatural (P. tetraphyllum subsp. apurense), sobre la base del concepto actual en el género Polycarpon. Sobre la distribución de este taxon, se excluye de las floras de Brasil y Uruguay y, se considera un registro dudoso para Perú

The antimicrobial peptide Temporin L impairs E. coli cell division by interacting with FtsZ and the divisome complex

Background: The comprehension of the mechanism of action of antimicrobial peptides is fundamental for the design of new antibiotics. Studies performed looking at the interaction of peptides with bacterial cells offer a faithful picture of what really happens in nature. Methods: In this work we focused on the interaction of the peptide Temporin L with E. coli cells, using a variety of biochemical and biophysical techniques that include: functional proteomics, docking, optical microscopy, TEM, DLS, SANS, fluorescence. Results: We identified bacterial proteins specifically interacting with the peptides that belong to the divisome machinery; our data suggest that the GTPase FtsZ is the specific peptide target. Docking experiments supported the FtsZ-TL interaction; binding and enzymatic assays using recombinant FtsZ confirmed this hypothesis and revealed a competitive inhibition mechanism. Optical microscopy and TEM measurements demonstrated that, upon incubation with the peptide, bacterial cells are unable to divide forming long necklace-like cell filaments. Dynamic light scattering studies and Small Angle Neutron Scattering experiments performed on treated and untreated bacterial cells, indicated a change at the nanoscale level of the bacterial membrane. Conclusions: The peptide temporin L acts by a non-membrane-lytic mechanism of action, inhibiting the divisome machinery. General significance: Identification of targets of antimicrobial peptides is pivotal to the tailored design of new antimicrobials

Structural and functional characterization of a novel recombinant antimicrobial peptide from hermetia illucens

Antibiotics are commonly used to treat pathogenic bacteria, but their prolonged use con-tributes to the development and spread of drug-resistant microorganisms raising the challenge to find new alternative drugs. Antimicrobial peptides (AMPs) are small/medium molecules ranging 10–100 residues synthesized by all living organisms and playing important roles in the defense sys-tems. These features, together with the inability of microorganisms to develop resistance against the majority of AMPs, suggest that these molecules might represent effective alternatives to clas-sical antibiotics. Because of their high biodiversity, with over one million described species, and their ability to live in hostile environments, insects represent the largest source of these molecules. However, production of insect AMPs in native forms is challenging. In this work we investigate a defensin-like antimicrobial peptide identified in the Hermetia illucens insect through a combination of transcriptomics and bioinformatics approaches. The C-15867 AMP was produced by recombi-nant DNA technology as a glutathione S-transferase (GST) fusion peptide and purified by affinity chromatography. The free peptide was then obtained by thrombin proteolysis and structurally characterized by mass spectrometry and circular dichroism analyses. The antibacterial activity of the C-15867 peptide was evaluated in vivo by determination of the minimum inhibitory concentration (MIC). Finally, crystal violet assays and SEM analyses suggested disruption of the cell membrane architecture and pore formation with leaking of cytosolic material

Structure-based inhibitors of amyloid beta core suggest a common interface with tau.

Alzheimer's disease (AD) pathology is characterized by plaques of amyloid beta (Aβ) and neurofibrillary tangles of tau. Aβ aggregation is thought to occur at early stages of the disease, and ultimately gives way to the formation of tau tangles which track with cognitive decline in humans. Here, we report the crystal structure of an Aβ core segment determined by MicroED and in it, note characteristics of both fibrillar and oligomeric structure. Using this structure, we designed peptide-based inhibitors that reduce Aβ aggregation and toxicity of already-aggregated species. Unexpectedly, we also found that these inhibitors reduce the efficiency of Aβ-mediated tau aggregation, and moreover reduce aggregation and self-seeding of tau fibrils. The ability of these inhibitors to interfere with both Aβ and tau seeds suggests these fibrils share a common epitope, and supports the hypothesis that cross-seeding is one mechanism by which amyloid is linked to tau aggregation and could promote cognitive decline