A Critical Review of Short Antimicrobial Peptides from Scorpion Venoms, Their Physicochemical Attributes, and Potential for the Development of New Drugs.

Scorpion venoms have proven to be excellent sources of antimicrobial agents. However, although many of them have been functionally characterized, they remain underutilized as pharmacological agents, despite their evident therapeutic potential. In this review, we discuss the physicochemical properties of short scorpion venom antimicrobial peptides (ssAMPs). Being generally short (13-25 aa) and amidated, their proven antimicrobial activity is generally explained by parameters such as their net charge, the hydrophobic moment, or the degree of helicity. However, for a complete understanding of their biological activities, also considering the properties of the target membranes is of great relevance. Here, with an extensive analysis of the physicochemical, structural, and thermodynamic parameters associated with these biomolecules, we propose a theoretical framework for the rational design of new antimicrobial drugs. Through a comparison of these physicochemical properties with the bioactivity of ssAMPs in pathogenic bacteria such as Staphylococcus aureus or Acinetobacter baumannii, it is evident that in addition to the net charge, the hydrophobic moment, electrostatic energy, or intrinsic flexibility are determining parameters to understand their performance. Although the correlation between these parameters is very complex, the consensus of our analysis suggests that there is a delicate balance between them and that modifying one affects the rest. Understanding the contribution of lipid composition to their bioactivities is also underestimated, which suggests that for each peptide, there is a physiological context to consider for the rational design of new drugs.

A paratransgenic strategy to block transmission of Xylella fastidiosa from the glassy-winged sharpshooter Homalodisca vitripennis.

BACKGROUND: Arthropod-borne diseases remain a leading cause of human morbidity and mortality and exact an enormous toll on global agriculture. The practice of insecticide-based control is fraught with issues of excessive cost, human and environmental toxicity, unwanted impact on beneficial insects and selection of resistant insects. Efforts to modulate insects to eliminate pathogen transmission have gained some traction and remain future options for disease control. RESULTS: Here, we report a paratransgenic strategy that targets transmission of Xylella fastidiosa, a leading bacterial pathogen of agriculture, by the Glassy-Winged Sharpshooter (GWSS), Homalodisca vitripennis. Earlier, we identified Pantoea agglomerans, a bacterial symbiont of the GWSS as the paratransgenic control agent. We genetically engineered P. agglomerans to express two antimicrobial peptides (AMP)-melittin and scorpine-like molecule (SLM). Melittin and SLM were chosen as the effector molecules based on in vitro studies, which showed that both molecules have anti-Xylella activity at concentrations that did not kill P. agglomerans. Using these AMP-expressing strains of P. agglomerans, we demonstrated disruption of pathogen transmission from insects to grape plants below detectable levels. CONCLUSION: This is the first report of halting pathogen transmission from paratransgenically modified insects. It is also the first demonstration of paratransgenic control in an agriculturally important insect vector.

Recombinant expression of Intrepicalcin from the scorpion Vaejovis intrepidus and its effect on skeletal ryanodine receptors.

BACKGROUND: Scorpion venoms contain toxins that modulate ionic channels, among which are the calcins, a small group of short, basic peptides with an Inhibitor Cystine Knot (ICK) motif that target calcium release channels/ryanodine receptors (RyRs) with high affinity and selectivity. Here we describe the heterologous expression of Intrepicalcin, identified by transcriptomic analysis of venomous glands from Vaejovis intrepidus. METHODS: Recombinant Intrepicalcin was obtained in Escherichia coli BL21-DE3 (periplasm) by fusing the Intrepicalcin gene to sequences coding for signal-peptide, thioredoxin, His-tag and enterokinase cleavage site. RESULTS: [3H]Ryanodine binding, used as a functional index of RyR activity, revealed that recombinant Intrepicalcin activates skeletal RyR (RyR1) dose-dependently with Kd=17.4±4.0nM. Intrepicalcin significantly augments the bell-shaped [Ca2+]-[3H]ryanodine binding curve at all [Ca2+] ranges, as is characteristic of the calcins. In single channel recordings, Intrepicalcin induces the appearance of a subconductance state in RyR1 with a fractional value ∼55% of the full conductance state, very close to that of Vejocalcin. Furthermore, Intrepicalcin stimulates Ca2+ release at an initial dose=45.3±2.5nM, and depletes ~50% of Ca2+ load from skeletal sarcoplasmic reticulum vesicles. CONCLUSIONS: We conclude that active recombinant Intrepicalcin was successfully obtained without the need of manual oxidation, enabling it to target RyR1s with high affinity. GENERAL SIGNIFICANCE: This is the first calcin heterologously expressed in the periplasma of Escherichia coli BL21-DE3, shown to be pharmacologically effective, thus paving the way for the generation of Intrepicalcin variants that are required for structure-function relationship studies of calcins and RyRs.

Structure, molecular modeling, and function of the novel potassium channel blocker urotoxin isolated from the venom of the Australian scorpion Urodacus yaschenkoi.

This communication reports the structural and functional characterization of urotoxin, the first K(+) channel toxin isolated from the venom of the Australian scorpion Urodacus yaschenkoi. It is a basic peptide consisting of 37 amino acids with an amidated C-terminal residue. Urotoxin contains eight cysteines forming four disulfide bridges with sequence similarities resembling the α-potassium channel toxin 6 (α-KTx-6) subfamily of peptides; it was assigned the systematic number of α-KTx-6.21. Urotoxin is a potent blocker of human voltage-gated potassium channel (Kv)1.2 channels, with an IC50 of 160 pM, whereas its affinity for other channels tested was in the nanomolar range (hKv1.1, IC50 = 253 nM; hKv1.3, IC50 = 91 nM; and hKCa3.1, IC50 = 70 nM). The toxin had no effect on hKv1.4, hKv1.5, human ether-à-go-go-related gene type 1 (hERG1), or human ether-à-go-go-like (hELK2) channels. Multiple sequence alignments from the venom gland transcriptome showed the existence of four other new peptides similar to urotoxin. Computer modeling of urotoxin's three-dimensional structure suggests the presence of the α/ß-scaffold characteristic of other scorpion toxins, although very likely forming an uncommon disulfide pairing pattern. Using molecular dynamics, a model for the binding of this peptide to human Kv1.2 and hKv1.1 channels is presented, along with the binding of an in silico mutant urotoxin (Lys25Ala) to both channels. Urotoxin enriches our knowledge of K(+) channel toxins and, due to its high affinity for hKv1.2 channels, it may be a good candidate for the development of pharmacologic tools to study the physiologic functions of K(+) channels or related channelopathies and for restoring axonal conduction in demyelinated axons.

Emerging Applications of Bacteriocins as Antimicrobials, Anticancer Drugs, and Modulators of The Gastrointestinal Microbiota.

The use of bacteriocins holds great promise in different areas such as health, food, nutrition, veterinary, nanotechnology, among others. Many research groups worldwide continue to advance the knowledge to unravel a novel range of therapeutic agents and food preservatives. This review addresses the advances of bacteriocins and their producer organisms as biocontrol agents for applications in the medical industry and agriculture. Furthermore, the bacteriocin mechanism of action and structural characteristics will be reviewed. Finally, the potential role of bacteriocins to modulate the signaling in host-associated microbial communities will be discussed.

Growth inhibition of pathogenic microorganisms by Pseudomonas protegens EMM-1 and partial characterization of inhibitory substances.

The bacterial strain, EMM-1, was isolated from the rhizosphere of red maize ("Rojo Criollo") and identified as Pseudomonas protegens EMM-1 based on phylogenetic analysis of 16S rDNA, rpoB, rpoD, and gyrB gene sequences. We uncovered genes involved in the production of antimicrobial compounds like 2,4-diacetylphloroglucinol (2,4-DAPG), pyoluteorin, and lectin-like bacteriocins. These antimicrobial compounds are also produced by other fluorescent pseudomonads alike P. protegens. Double-layer agar assay showed that P. protegens EMM-1 inhibited the growth of several multidrug-resistant (MDR) bacteria, especially clinical isolates of the genera Klebsiella and ß-hemolytic Streptococcus. This strain also displayed inhibitory effects against diverse fungi, such as Aspergillus, Botrytis, and Fusarium. Besides, a crude extract of inhibitory substances secreted into agar was obtained after the cold-leaching process, and physicochemical characterization was performed. The partially purified inhibitory substances produced by P. protegens EMM-1 inhibited the growth of Streptococcus sp. and Microbacterium sp., but no inhibitory effect was noted for other bacterial or fungal strains. The molecular weight determined after ultrafiltration was between 3 and 10 kDa. The inhibitory activity was thermally stable up to 60°C (but completely lost at 100°C), and the inhibitory activity remained active in a wide pH range (from 3 to 9). After treatment with a protease from Bacillus licheniformis, the inhibitory activity was decreased by 90%, suggesting the presence of proteic natural compounds. All these findings suggested that P. protegens EMM-1 is a potential source of antimicrobials to be used against pathogens for humans and plants.

Smp76, a Scorpine-Like Peptide Isolated from the Venom of the Scorpion Scorpio maurus palmatus, with a Potent Antiviral Activity Against Hepatitis C Virus and Dengue Virus.

Growing global viral infections have been a serious public health problem in recent years. This current situation emphasizes the importance of developing more therapeutic antiviral compounds. Hepatitis C virus (HCV) and dengue virus (DENV) belong to the Flaviviridae family and are an increasing global health threat. Our previous study reported that the crude venom of Scorpio maurus palmatus possessed anti-HCV and anti-DENV activities in vitro. We report here the characterization of a natural antiviral peptide (scorpion-like peptide Smp76) that prevents HCV and DENV infection. Smp76 was purified from S. m. palmatus venom and contains 76 amino acids with six residues of cysteine. Smp76 antiviral activity was evaluated using a cell culture technique utilizing Huh7it-1, Vero/SLAM, HCV (JFH1, genotype 2a) and DENV (Trinidad 1751, type 2). A potential antiviral activity of Smp76 was detected in culture cells with an approximate IC50 of 0.01 µg/ml. Moreover, Smp76 prevents HCV infection and suppresses secondary infection, by inactivating extra-cellular infectious particles without affecting viral replication. Interestingly, Smp76 is neither toxic nor hemolytic in vitro at a concentration 1000-fold higher than that required for antiviral activity. Conclusively, this report highlights novel anti-HCV and anti-DENV activities of Smp76, which may lay the foundation for developing a new therapeutic intervention against these flaviviruses.

Structural characterization of scorpion peptides and their bactericidal activity against clinical isolates of multidrug-resistant bacteria.

Scorpion venom peptides represent a novel source of antimicrobial peptides (AMPs) with broad-spectrum activity. In this study, we determined the minimum bactericidal concentration (MBC) of three scorpion AMPs, Uy234, Uy17, and Uy192, which are found in the venomous glands of the Urodacus yaschenkoi scorpion, against the clinical isolates of multidrug-resistant (MDR) bacteria. In addition, we tested the activity of a consensus AMP designed in our laboratory based on some previously reported IsCT-type (cytotoxic linear peptide) AMPs with the aim of obtaining higher antimicrobial activity. All peptides tested showed high antimicrobial activity against MDR clinical isolates, with the highest activity against ß-hemolytic Streptococcus strains. The hemolytic activity was determined against human red blood cells and was significantly lower than that of previously reported AMPs. The α-helical structure of the four AMPs was confirmed by circular dichroism (CD). These results suggest that the four peptides can be valuable tools for the design and development of AMPs for use in the inhibition of MDR pathogenic bacteria. A clear index of synergism and additivity was found for the combination of QnCs-BUAP + Uy234, which makes these peptides the most promising candidates against pathogenic bacteria.

Desiccation-induced viable but nonculturable state in Pseudomonas putida KT2440, a survival strategy.

The potential of Pseudomonas putida KT2440 to act as a plant-growth promoter or as a bioremediator of toxic compounds can be affected by desiccation. In the present work, the bacterial survival ratio (BSR) in response to air desiccation was evaluated for P. putida KT2440 in the presence of different protectors. The BSR in the presence of nonreducing disaccharides, such as trehalose, was high after 15 days of desiccation stress (occurring at 30°C and 50% relative humidity), whereas in the absence of a protector the bacterial counts diminished to nondetectable numbers (ca 2.8 log CFU/mL). The LIVE/DEAD staining method showed that bacteria protected with trehalose maintained increased numbers of green cells after desiccation while cells without protection were all observed to be red. This indicated that nonprotected bacteria had compromised membrane integrity. However, when nonprotected bacteria subjected to 18 days of desiccation stress were rehydrated for a short time with maize root exudates or for 48 h with water (prolonged rehydration), the bacterial counts were as high as that observed for those not subjected to desiccation stress, suggesting that the cells entered the viable but nonculturable (VBNC) state under desiccation and that they returned to a culturable state after those means of rehydration. Interestingly an increase in the green color intensity of cells that returned to a culturable state was observed using LIVE/DEAD staining method, indicating an improvement in their membrane integrity. Cellular activity in the VBNC state was determined. A GFP-tagged P. putida strain expressing GFP constitutively was subjected to desiccation. After 12 days of desiccation, the GFP-tagged strain lost culturability, but it exhibited active GFP expression, which in turn made the cells green. Furthermore, the expression of 16S rRNA, rpoN (housekeeping), mutL, mutS (encoding proteins from the mismatch repair complex), and oprH (encoding an outer membrane protein) were examined by RT-PCR. All evaluated genes were expressed by both types of cells, culturable and nonculturable, indicating active molecular processes during the VBNC state.

The change of the scFv into the Fab format improves the stability and in vivo toxin neutralization capacity of recombinant antibodies.

The antigen-binding fragment (Fab) has been considered a more functionally stable version of recombinant antibodies than single chain antibody fragments (scFvs), however this intuitive consideration has not been sufficiently proven in vivo. This communication shows that three out of four specific scFvs against a scorpion toxin, with different affinities and stabilities, become neutralizing in vivo when expressed as Fabs, despite the fact that they are not neutralizing in the scFv format. A scFv fragment previously obtained from a neutralizing mouse antibody (BCF2) was used to produce three derived scFvs by directed evolution. Only one of them was neutralizing, however when expressed as Fab, all of them became neutralizing fragments in vivo. The initial scFvBCF2 (earlier used for directed evolution) was not neutralizing in the scFv format. After expressing it as Fab did not become a neutralizing fragment, but did reduce the intoxication symptoms of experimental mice. The stability of the four Fabs derived from their respective scFvs was improved when tested in the presence of guanidinium chloride. The in vitro stability of the Fab format has been shown earlier, but the physiological consequences of this stability are shown in this communication. The present results indicate that improved functional stability conferred by the Fab format can replace additional maturation steps, when the affinity and stability are close to the minimum necessary to be neutralizing.

Next generation of microbial inoculants for agriculture and bioremediation.

In this Crystal Ball we describe the negative effects of the scheme of intensive agriculture of the green revolution technology. To recover the contaminated soils derived from intensive farming is necessary introduce new successful technologies to replace the use of chemical fertilizer and toxic pesticides by organic fertilizers and biological control agents. Our principal speculation is that in a short time authors in the field of PGPB and bioremediation will be expanding the knowledge on the development of different formulations containing super-bacteria or a mixture of super-bacteria able to provide beneficial effect for agriculture and bioremediation.

Targeting antigens to Dec-205 on dendritic cells induces a higher immune response in chickens: Hemagglutinin of avian influenza virus example.

It is widely known that targeting a variety of antigens to the DEC-205 receptor on dendritic cells (DCs) significantly potentiate immunity. This communication reports the development of a new murine monoclonal antibody (mAb) against the chicken DEC-205, using as immunogen the carbohydrate recognition domain-2 (CRD-2) heterologously expressed. This mAb recognizes a protein band of 250kDa by immunoprecipitation analysis and shows strong cross-reactivity with human and pig DEC-205. Furthermore, the hemagglutinin (HA) of avian influenza H5N2 virus was cloned and expressed using insect cell-baculovirus expression system. We chemically conjugated the anti-chicken DEC-205 antibody with the highly purified HA to direct the antigen to the dendritic cells and evaluate the immune response elicited in vivo by this conjugate. A single dose of chemical conjugate was sufficient to elicit a strong immune response in chickens as early as fourteen days after priming. In addition, the conjugate induced an earlier and higher response compared to unconjugated HA. These results suggest that the strategy described here has potential to be used in the future design and development of successful vaccines against different chicken infectious diseases with direct impact in biotechnology and veterinary fields.

Compatible bacterial mixture, tolerant to desiccation, improves maize plant growth.

Plant growth-promoting rhizobacteria (PGPR) increase plant growth and crop productivity. The inoculation of plants with a bacterial mixture (consortium) apparently provides greater benefits to plant growth than inoculation with a single bacterial strain. In the present work, a bacterial consortium was formulated containing four compatible and desiccation-tolerant strains with potential as PGPR. The formulation had one moderately (Pseudomonas putida KT2440) and three highly desiccation-tolerant (Sphingomonas sp. OF178, Azospirillum brasilense Sp7 and Acinetobacter sp. EMM02) strains. The four bacterial strains were able to adhere to seeds and colonize the rhizosphere of plants when applied in both mono-inoculation and multi-inoculation treatments, showing that they can also coexist without antagonistic effects in association with plants. The effects of the bacterial consortium on the growth of blue maize were evaluated. Seeds inoculated with either individual bacterial strains or the bacterial consortium were subjected to two experimental conditions before sowing: normal hydration or desiccation. In general, inoculation with the bacterial consortium increased the shoot and root dry weight, plant height and plant diameter compared to the non-inoculated control or mono-inoculation treatments. The bacterial consortium formulated in this work had greater benefits for blue maize plants even when the inoculated seeds underwent desiccation stress before germination, making this formulation attractive for future field applications.

Contributions and difficulties of soil metagenomics and its impact on agricultura / Aportes y dificultades de la metagenómica de suelos y su impacto en la agricultura

RESUMEN Los microorganismos son de gran interés porque colonizan todo tipo de ambiente, sin embargo, uno de los problemas al que nos enfrentamos para conocer su diversidad biológica es que no todos los microorganismos son cultivables. El desarrollo de nuevas tecnologías como la generación de vectores de clonación aunado al desarrollo de técnicas de secuenciación de alto rendimiento ha favorecido el surgimiento de una nueva herramienta llamada metagenómica, la cual nos permite estudiar genomas de comunidades enteras de microorganismos. Debido a que ningún ambiente es idéntico a otro, es importante mencionar que dependiendo del tipo de muestra a analizar será el tipo de reto al cual nos enfrentaremos al trabajar con metagenómica, en el caso específico del suelo existen diversas variantes como la contaminación del suelo con metales pesados o diversos compuestos químicos que podrían limitar los estudios. Sin embargo, pese a las limitaciones que el mismo ambiente presenta, la metagenómica ha permitido tanto el descubrimiento de nuevos genes como la caracterización de las comunidades microbianas que influyen positivamente en el desarrollo de plantas, lo cual en un futuro podría generar un gran impacto en la agricultura. En este artículo se realizó una revisión de diversas investigaciones que han empleado metagenómica, reportadas en las bases de datos de PudMed y Google Schoolar, con el objetivo de examinar los beneficios y limitaciones de las diversas metodologías empleadas en el tratamiento del ADN metagenómico de suelo y el impacto de la metagenómica en la agricultura.

ABSTRACT Microorganisms are of great interest because they colonize all types of environment, however, one of the problems we face in knowing biological diversity is that not all microorganisms are cultivable. The development of new technologies such as the generation of cloning vectors coupled with the development of high performance sequencing techniques, have favored the emergence of a new tool in science called metagenomics, which allows us to study genomes of entire communities. Since all environments are different, the type of challenge that we will face when working with metagenomics is going to change depending of the type of sample, in the specific case of soils, there are several variables, such as soil contamination with heavy metals or chemical compounds that could limit metagenomic studies. However, despite the limitations that the environment presents, with the help of metagenomics, both gene discovery and the characterization of microbial communities that positively influence plant development have been achieved, which could generate a greater impact on agriculture in the future. In this article a review of several investigations that have used metagenomics, reported in the PudMed and Google Schoolar databases was carried out, with the aim of examining the benefits and limitations of the various methodologies used in the treatment of metagenomic DNA from soil and the impact of metagenomics in agriculture.

Whole Transcriptome of the Venom Gland from Urodacus yaschenkoi Scorpion.

Australian scorpion venoms have been poorly studied, probably because they do not pose an evident threat to humans. In addition, the continent has other medically important venomous animals capable of causing serious health problems. Urodacus yaschenkoi belongs to the most widely distributed family of Australian scorpions (Urodacidae) and it is found all over the continent, making it a useful model system for studying venom composition and evolution. This communication reports the whole set of mRNA transcripts produced by the venom gland. U. yaschenkoi venom is as complex as its overseas counterparts. These transcripts certainly code for several components similar to known scorpion venom components, such as: alpha-KTxs, beta-KTxs, calcins, protease inhibitors, antimicrobial peptides, sodium-channel toxins, toxin-like peptides, allergens, La1-like, hyaluronidases, ribosomal proteins, proteasome components and proteins related to cellular processes. A comparison with the venom gland transcriptome of Centruroides noxius (Buthidae) showed that these two scorpions have similar components related to biological processes, although important differences occur among the venom toxins. In contrast, a comparison with sequences reported for Urodacus manicatus revealed that these two Urodacidae species possess the same subfamily of scorpion toxins. A comparison with sequences of an U. yaschenkoi cDNA library previously reported by our group showed that both techniques are reliable for the description of the venom components, but the whole transcriptome generated with Next Generation Sequencing platform provides sequences of all transcripts expressed. Several of which were identified in the proteome, but many more transcripts were identified including uncommon transcripts. The information reported here constitutes a reference for non-Buthidae scorpion venoms, providing a comprehensive view of genes that are involved in venom production. Further, this work identifies new putative bioactive compounds that could be used to seed research into new pharmacological compounds and increase our understanding of the function of different ion channels.

Transcriptome analysis of scorpion species belonging to the Vaejovis genus.

Scorpions belonging to the Buthidae family have traditionally drawn much of the biochemist's attention due to the strong toxicity of their venoms. Scorpions not toxic to mammals, however, also have complex venoms. They have been shown to be an important source of bioactive peptides, some of them identified as potential drug candidates for the treatment of several emerging diseases and conditions. It is therefore important to characterize the large diversity of components found in the non-Buthidae venoms. As a contribution to this goal, this manuscript reports the construction and characterization of cDNA libraries from four scorpion species belonging to the Vaejovis genus of the Vaejovidae family: Vaejovis mexicanus, V. intrepidus, V. subcristatus and V. punctatus. Some sequences coding for channel-acting toxins were found, as expected, but the main transcribed genes in the glands actively producing venom were those coding for non disulfide-bridged peptides. The ESTs coding for putative channel-acting toxins, corresponded to sodium channel ß toxins, to members of the potassium channel-acting α or κ families, and to calcium channel-acting toxins of the calcin family. Transcripts for scorpine-like peptides of two different lengths were found, with some of the species coding for the two kinds. One sequence coding for La1-like peptides, of yet unknown function, was found for each species. Finally, the most abundant transcripts corresponded to peptides belonging to the long chain multifunctional NDBP-2 family and to the short antimicrobials of the NDBP-4 family. This apparent venom composition is in correspondence with the data obtained to date for other non-Buthidae species. Our study constitutes the first approach to the characterization of the venom gland transcriptome for scorpion species belonging to the Vaejovidae family.

Novel monoclonal antibody against alphaX subunit from horse CD11c/CD18 integrin.

The αX I-domain of the horse integrin CD11c was successfully expressed in Escherichia coli, purified, biochemically characterized and used as immunogen to generate murine monoclonal antibodies against horse CD11c, which are not yet commercially available. One monoclonal antibody mAb-1C4 against the αX I-domain, is an IgG2a able to interact with the recombinant I-domain, showing an EC50=2.4ng according to ELISA assays. By western blot with horse PBMCs lysates the mAb-1C4 recognized a protein of 150kDa which corresponds well with the CD11c molecule. Using immunohistochemistry in horse lymph node tissue sections, mAb-1C4 marked cells in situ, some with apparent dendritic morphology. Thus the mAb generated to a recombinant epitope from horse CD11c identified the molecule in intact cells within horse lymphoid tissue. By the labelling intensity, the histological location (paracortical and interfollicular areas) and the apparent morphology of the marked cells, we can say that these are putative horse dendritic cells (DCs). The development of a mAb to horse CD11c provides a new tool to better study the horse DC biology and opens other biotechnological avenues, such as DC targeting-based vaccines.

Importancia de compuestos antimicrobianos producidos por bacterias benéficas en el biocontrol de fitopatógenos / The importance of antimicrobial compounds produced by beneficial bacteria on the biocontrol of phytopathogens

ABSTRACT Bacteria produce antimicrobial compounds to compete for nutrients and space in a particular habitat. Antagonistic interactions can be evaluated by several methodologies including the double-layer agar and simultaneous inhibition assays. Among the well-known inhibitory substances produced by bacteria are the broad-spectrum antibiotics, organic acids, siderophores, antifungal, and bacteriocins. The most studied bacterial genera able to produce these inhibitory substances are Enterococcus, Lactococcus, Streptomyces, Bacillus, Pseudomonas, Klebsiella, Escherichia, and Burkholderia. Some beneficial bacteria can promote plant growth and degrade toxic compounds in the environment representing an attractive solution to diverse issues in agriculture and soil pollution, particularly in fields with damaged soils where pesticides and fertilizers have been indiscriminately used. Beneficial bacteria may increase plant health by inhibiting pathogenic microorganisms; some examples include Gluconacetobacter diazotrophicus, Azospirullum brasilense, Pseudomonas fluorescens, Pseudomonas protegens, and Burkholderia tropica. However, most studies showing the antagonistic potential of these bacteria have been performed in vitro, and just a few of them have been evaluated in association with plants. Several inhibitory substances involved in pathogen antagonism have not been elucidated yet; in fact, we know only 1 % of the bacterial diversity in a natural environment leading us to assume that many other inhibitory substances remain unexplored. In this review, we will describe the characteristics of some antimicrobial compounds produced by beneficial bacteria, the principal methodologies performed to evaluate their production, modes of action, and their importance for biotechnological purposes.

RESUMEN Las bacterias producen compuestos antimicrobianos para competir por nutrientes y espacio en un hábitat particular. Las interacciones antagónicas pueden evaluarse mediante varias metodologías, incluido el agar de doble capa y los ensayos de inhibición simultánea. Las sustancias inhibidoras mejor conocidas producidas por bacterias incluyen antibióticos, ácidos orgánicos, sideróforos, antifúngicos y bacteriocinas. Entre los géneros bacterianos más estudiados que producen sustancias inhibidoras se incluyen Enterococcus, Lactococcus, Streptomyces, Bacillus, Pseudomonas, Klebsiella, Escherichia y Burkholderia. Algunas bacterias beneficiosas tienen la capacidad de promover el crecimiento de las plantas y degradar compuestos tóxicos en el ambiente, por lo que podrían incrementar el rendimiento de los cultivos y disminuir problemas de contaminación del suelo, especialmente donde los pesticidas y fertilizantes han sido utilizados indiscriminadamente. Algunas bacterias beneficiosas pueden aumentar la salud de las plantas al inhibir microorganismos patógenos, por ejemplo, Gluconacetobacter diazotrophicus, Azospirullum brasilense, Pseudomonas fluorescens, Pseudomonas protegens y Burkholderia tropica. Sin embargo, la mayoría de los estudios que muestran el potencial antagónico de estas bacterias se han realizado in vitro, y pocos de ellos se han evaluado en asociación con plantas. Varias sustancias inhibitorias implicadas en el antagonismo de los patógenos aún son desconocidas; de hecho, sabemos que solo se ha aislado el 1 % de la diversidad bacteriana en un ambiente natural, lo que sugiere que hay muchas otras sustancias inhibitorias que no han sido exploradas. En esta revisión describimos las características de algunos compuestos antimicrobianos producidos por bacterias beneficiosas, las principales metodologías usadas para evaluar su producción, modos de acción y su importancia para fines biotecnológicos.

Venom proteomic and venomous glands transcriptomic analysis of the Egyptian scorpion Scorpio maurus palmatus (Arachnida: Scorpionidae).

Proteomic analysis of the scorpion venom Scorpio maurus palmatus was performed using reverse-phase HPLC separation followed by mass spectrometry determination. Sixty five components were identified with molecular masses varying from 413 to 14,009 Da. The high percentage of peptides (41.5%) was from 3 to 5 KDa which may represent linear antimicrobial peptides and KScTxs. Also, 155 expressed sequence tags (ESTs) were analyzed through construction the cDNA library prepared from a pair of venomous gland. About 77% of the ESTs correspond to toxin-like peptides and proteins with definite open reading frames. The cDNA sequencing results also show the presence of sequences whose putative products have sequence similarity with antimicrobial peptides (24%), insecticidal toxins, ß-NaScTxs, κ-KScTxs, α-KScTxs, calcines and La1-like peptides. Also, we have obtained 23 atypical types of venom molecules not recorded in other scorpion species. Moreover, 9% of the total ESTs revealed significant similarities with proteins involved in the cellular processes of these scorpion venomous glands. This is the first set of molecular masses and transcripts described from this species, in which various venom molecules have been identified. They belong to either known or unassigned types of scorpion venom peptides and proteins, and provide valuable information for evolutionary analysis and venomics.

Characterization of the venom from the Australian scorpion Urodacus yaschenkoi: Molecular mass analysis of components, cDNA sequences and peptides with antimicrobial activity.

The Urodacidae scorpions are the most widely distributed of the four families in Australia and represent half of the species in the continent, yet their venoms remain largely unstudied. This communication reports the first results of a proteome analysis of the venom of the scorpion Urodacus yaschenkoi performed by mass fingerprinting, after high performance liquid chromatography (HPLC) separation. A total of 74 fractions were obtained by HPLC separation allowing the identification of approximately 274 different molecular masses with molecular weights varying from 287 to 43,437 Da. The most abundant peptides were those from 1 K Da and 4-5 K Da representing antimicrobial peptides and putative potassium channel toxins, respectively. Three such peptides were chemically synthesized and tested against Gram-positive and Gram-negative bacteria showing minimum inhibitory concentration in the low micromolar range, but with moderate hemolytic activity. It also reports a transcriptome analysis of the venom glands of the same scorpion species, undertaken by constructing a cDNA library and conducting random sequencing screening of the transcripts. From the resultant cDNA library 172 expressed sequence tags (ESTs) were analyzed. These transcripts were further clustered into 120 unique sequences (23 contigs and 97 singlets). The identified putative proteins can be assorted in several groups, such as those implicated in common cellular processes, putative neurotoxins and antimicrobial peptides. The scorpion U. yaschenkoi is not known to be dangerous to humans and its venom contains peptides similar to those of Opisthacanthus cayaporum (antibacterial), Scorpio maurus palmatus (maurocalcin), Opistophthalmus carinatus (opistoporines) and Hadrurus gerstchi (scorpine-like molecules), amongst others.