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Fluorescent in situ hybridization (FISH) is a powerful tool that for more than 30 years has allowed to detect and quantify microorganisms as well as to study their spatial distribution in three-dimensional structured environments such as biofilms. Throughout these years, FISH has been improved in order to face some of its earlier limitations and to adapt to new research objectives. One of these improvements is related to the emergence of Nucleic Acid Mimics (NAMs), which are now employed as alternatives to the DNA and RNA probes that have been classically used in FISH. NAMs such as peptide and locked nucleic acids (PNA and LNA) have provided enhanced sensitivity and specificity to the FISH technique, as well as higher flexibility in terms of applications. In this review, we aim to cover the state-of-the-art of the different NAMs and explore their possible applications in FISH, providing a general overview of the technique advancement in the last decades.

26 p.-6 fig.-3 tab., Antibiotic resistance is a global current threat of increasing importance. Moreover, biofilms represent a medical challenge since the inherent antibiotic resistance of their producers demands the use of high doses of antibiotics over prolonged periods. Frequently, these therapeutic measures fail, contributing to bacterial persistence, therefore demanding the development of novel antimicrobials. Esters of bicyclic amines (EBAs), which are strong inhibitors of Streptococcus pneumoniae growth, were initially designed as inhibitors of pneumococcal choline-binding proteins on the basis of their structural analogy to the choline residues in the cell wall. However, instead of mimicking the characteristic cell chaining phenotype caused by exogenously added choline on planktonic cultures of pneumococcal cells, EBAs showed an unexpected lytic activity. In this work we demonstrate that EBAs display a second, and even more important, function as cell membrane destabilizers. We then assayed the inhibitory and disintegrating activity of these molecules on pneumococcal biofilms. The selected compound (EBA 31) produced the highest effect on S. pneumoniae (encapsulated and non-encapsulated) biofilms at very low concentrations. EBA 31 was also effective on mixed biofilms of non-encapsulated S. pneumoniae plus non-typeable Haemophilus influenzae, two pathogens frequently forming a self-produced biofilm in the human nasopharynx. These results support the role of EBAs as a promising alternative for the development of novel, broad-range antimicrobial drugs encompassing both Gram-positive and Gram-negative pathogens., This work was supported by grants from the Spanish Ministry of Economy, Industry and Competitiveness (BIO2013-47684-R, BIO2016-79323-R and SAF2017-88664-R), and the RETICS-FEDER RICET RD16/0027/0010.

35 p.-5 fig.-1 tab.-1 schem., The human protozoan parasites Leishmania donovani and L. infantum are the causative agents of visceral leishmaniasis, as such, responsible for approximately 30,000 deaths annually. The available chemotherapeutic treatments are reduced to a few drugs whose effectiveness is limited by rising drug resistance/therapeutic failure, and noxious side-effects. Therefore, new therapeutic hits are needed. Compounds displaying the imidazo[2,1-a]isoindole skeleton have shown antichagasic, anti-HIV, antimalarial and anorectic activities. Here, we report the leishmanicidal activity of thirty one imidazo[2,1-a]isoindol-5-ol derivatives on promastigotes and intracellular amastigotes of L. donovani. Eight out of thirty one assayed compounds showed EC50 values ranging between 1 and 2 μM with selectivity indexes from 29 to 69 on infected THP-1 cells. Six compounds were selected for further elucidation of their leishmanicidal mechanism. In this regard, compound 29, the imidazoisoindolol with the highest activity on intracellular amastigotes, induced an early decrease of intracellular ATP levels, as well as mitochondrial depolarization, together with a partial plasma membrane destructuration, as assessed by transmission electron microscopy. Consequently, the inhibition of the energy metabolism of Leishmania plays an important role in the leishmanicidal mechanism of this compound, even when other additional targets cannot be ruled out. In all, the results supported the inclusion of the imidazoisoindole scaffold for the development of new leishmanicidal drugs., Financial support from FIS-PI-060782, FIS-PI-052026, MINECO: RETOS (AGL2016-79813-C2-2, to EO), the Spanish Ministerio de Ciencia, Innovación y Universidades (RTI2018-097210-B-I00 to FG), ISCIII-RICET-FEDER: RD16/0027/0018 (EO) and RD16/0027/0010 (LR), and SAF2015-65740 (LR), as the CSIC grant PIE 201620E038 are acknowledged.

58 p.-6 fig.-1 tab.-5 schem.-1 graph.abst, A new class of quinoline derivatives, bearing amino chains at C-4 and a styryl group at C-2, were tested on Leishmania donovani promastigotes and axenic and intracellular Leishmania pifanoi amastigotes. The introduction of the C-4 substituent improves the activity, which is due to interference with the mitochondrial activity of the parasite and its concomitant bioenergetic collapse by ATP exhaustion. Some compounds show a promising antileishmanial profile, with low micromolar or submicromolar activity on promastigote and amastigote forms and a good selectivity index., This research was supported by the following grants; (a) MLB: MIUR, PRIN 201274BNKN_003; (b) JCM: Universidad Complutense (GR3/14) and MINECO (CTQ2015-68380-R); (c) LR: RD16/0027/0010, CSIC PIE-201020E054 and MINECO SAF2015-65740-R. A predoctoral contracts to MS from Universidad Complutense and a FPI contract to MP from MINECO (BES-2016–076410P) are also gratefully acknowledged.

13 p.-5 fig.-2 tab.-1 graph.abs + supp.inf. 38 p.-2 fig.supl.-5 tab. supl., Previous reports have validated the glycogen synthase kinase-3 (GSK-3) as a druggable target against the human protozoan parasite Leishmania. This prompted us to search for new leishmanicidal scaffolds as inhibitors of this enzyme from our in-house library of human GSK-3β inhibitors, as well as from the Leishbox collection of leishmanicidal compounds developed by GlaxoSmithKline. As a result, new leishmanicidal inhibitors acting on Leishmania GSK-3 at micromolar concentrations were found. These inhibitors belong to six different chemical classes (thiadiazolidindione, halomethylketone, maleimide, benzoimidazole, N-phenylpyrimidine-2-amine and oxadiazole). In addition, the binding mode of the most active compounds into Leishmania GSK-3 was approached using computational tools. On the whole, we have uncovered new chemical scaffolds with an appealing prospective in the development and use of Leishmania GSK-3 inhibitors against this infectious protozoan., Funding from MINECO [Grant SAF2015-65740-R], Instituto de Salud Carlos III RETICS programme RICET [RD16/0027/0010] with associated FEDER funds and MECD [Grant FPU15/1465 to V. S.-P.] is acknowledged. P. M. acknowledges the contract from the European Social Fund (Youth Employment Initiative) and FEDER funds.

42 p.-8 fig., Drug repurposing affords the implementation of new treatments at a moderate cost and under a faster time-scale. Most of the clinical drugs against Leishmania share this origin. The antidepressant sertraline has been successfully assayed in a murine model of visceral leishmaniasis. Nevertheless, sertraline targets in Leishmania were poorly defined. In order to get a detailed insight into the leishmanicidal mechanism of sertraline on Leishmania infantum, unbiased multiplatform metabolomics and transmission electron microscopy were combined with a focused insight into the sertraline effects on bioenergetics metabolism of the parasite. Sertraline induced respiration uncoupling, a significant decrease of intracellular ATP level, and oxidative stress in L. infantum promastigotes. Metabolomics evidenced an extended metabolic disarray caused by sertraline. This encompasses a remarkable variation of the levels of thiol-redox and polyamine biosynthetic intermediates, as well as shortage of intracellular amino acids used as metabolic fuel by Leishmania Sertraline killed Leishmania through a multitarget mechanism of action, tackling essential metabolic pathways of the parasite. As such, sertraline is a valuable candidate for visceral leishmaniasis treatment under a drug repurposing strategy., This work was supported by grants of the Fondo de Investigaciones Sanitarias-ISCIII-FEDER (PI12-02706), and (RD16/0027/0010, Red de Enfermedades Tropicales, subprogram RETICS del Plan Estatal de I+D+i (2013-2016) co-financed with FEDER funds, SAF2015-65740-R, and CSIC PIE 201620E038 to L. R., São Paulo State Research Foundation (FAPESP 2015/23403-9 to A. G.T.); EADS-CASA/ Brazilian Air Force (FAB) mobility program to M.L.L., and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) to M.L.L.

36 p.-7 fig.-1 tab.-1 fig. supl., Viral infections in the aquaculture of salmonids can lead to high mortality and substantial economic losses. Thus, there is industrial interest in new molecules active against these viruses. Here we describe the production, purification, and the physicochemical and structural characterization of high molecular weight dextrans synthesized by Lactobacillus sakei MN1 and Leuconostoc mesenteroides RTF10. The purified dextrans, and commercial dextrans with molecular weights ranging from 10 to 2000 kDa, were assayed in infected BF-2 and EPC fish cell-line monolayers for antiviral activity. Only T2000 and dextrans from MN1 and RTF10 had significant antiviral activity. This was similar to results obtained against infectious pancreatic necrosis virus. However the dextran from MN1 showed ten-fold higher activity against hematopoietic necrosis virus than T2000. In vivo assays using the MN1 polymer confirmed the in vitro results and revealed immunomodulatory activity. These results together with the high levels of dextran production (2 g L−1) by Lb. sakei MN1, indicate the compounds potential utility as an antiviral agent in aquaculture., This study was supported by grants AGL2009-12998-C03-03, AGL2012-40084-C03-01 and CSD2007-00063 from the Spanish Ministry of Economics and Competitiveness and grants PIE2010-20E084 and PIE2013-20E017 from Consejo Superior de Investigaciones Científicas.

Antimicrobial peptides (AMPs) are ubiquitous through living organisms from different kingdoms. Their role is either defense against invading pathogens, or to strive for survival against microorganisms sharing the same ecological niche. Many AMPs are active against a broad variety of target microorganisms. This, together with their low induction of resistance, heralded the use of AMPs as a new generation of antibiotics. However, studies addressing the feasibility of AMP implementation on leishmaniasis are scarce. This review describes the different approaches to leishmaniasis carried out with AMPs regardless their biological origin. The chapter encompasses studies of AMPs both in vitro and in animal models of Leishmania infection. The mechanisms of action of AMPs both on Leishmania and on the macrophage are described, as well as the underlying molecular determinants of AMPs driving their effectiveness on Leishmania. Finally, the prospects for the feasible implementation of a pharmacological strategy for leishmaniasis based on peptide-based therapies are outlined.

40 p.-7 fig.-4 fig.supl., In this work we have investigated two dextran-producing lactic acid bacteria, Lactobacillus sakei MN1 and Leuconostoc mesenteroides RTF10, isolated from fermented meat products. These bacteria synthesise dextran when sucrose, but not glucose, is present in the growth medium. The influence of dextran on bacterial aggregation, adhesion and biofilm formation was investigated in cultures challenged with sucrose or glucose. For Lb. sakei MN1, the synthesis of the dextran drastically impaired the three processes; in contrast it had no effect on Lc. mesenteroides RTF10. Therefore, the influence of dextran on probiotic properties of Lb. sakei MN1 was tested in vivo using gnotobiotic zebrafish models. The bacterium efficiently colonised the fish gut and inhibited the killing activity of Vibrio anguillarum NB10[pOT11]. Furthermore, under conditions of dextran synthesis, the adhesion of Lb. sakei MN1 to the epithelial cells decreased, without greatly affecting its anti V. anguillarum activity., This work was supported by the Spanish Ministry of Economics and Competitiveness [grants AGL2012-40084C03-01 and AGL2015-65010-C3-1-R] and by the Agriculture and Fisheries Department of the Basque Government [project VIVAQUA], and II is the recipient of a PhD fellowship from Technological centres foundation-Iñaki Goenaga.

The exopolysaccharide synthesized by Lactobacillus sakei MN1 is a dextran with antiviral and immunomodulatory properties of potential utility in aquaculture. In this work we have investigated the genetic basis of dextran production by this bacterium. Southern blot hybridization experiments demonstrated the plasmidic location of the dsrLS gene, which encodes the dextransucrase involved in dextran synthesis. DNA sequencing of the 11,126 kbp plasmid (pMN1) revealed that it belongs to a family which replicates by the theta mechanism, whose prototype is pUCL287. The plasmid comprises the origin of replication, repA, repB, and dsrLS genes, as well as seven open reading frames of uncharacterized function. Lb. sakei MN1 produces dextran when sucrose, but not glucose, is present in the growth medium. Therefore, plasmid copy number and stability, as well as dsrLS expression, were investigated in cultures grown in the presence of either sucrose or glucose. The results revealed that pMN1 is a stable low-copy-number plasmid in both conditions. Gene expression studies showed that dsrLS is constitutively expressed, irrespective of the carbon source present in the medium. Moreover, dsrLS is expressed from a monocistronic transcript as well as from a polycistronic repA-repB-orf1-dsrLS mRNA. To our knowledge, this is the first report of a plasmid-borne dextransucrase-encoding gene, as well as the first time that co-transcription of genes involved in plasmid maintenance and replication with a gene encoding an enzyme has been established., This work was supported by the Spanish Ministry of Economy and Competitiveness (grant AGL2015-65010-C3-1-R).

Polysaccharides produced by a variety of bacteria have properties as viscosifiers, thickening and gelling agents, which contribute to the rheology and texture of fermented food. In addition, some can act as prebiotic agents by enhancing the development of a microbiota that is beneficial to the human and animal gastrointestinal tract, as well as possibly possessing an immunomodulating effect. These aspects constitute an important field of research that could lead to the production of fermented functional foods which benefit human and animal health. Therefore, in this chapter, in addition to describing the nature and structure of bacterial exopolysaccharides (EPS), we review the current knowledge concerning the functional properties of EPS as well as describing their actual usages and future potential applications.

2 figuras, 2 tablas, Lactic acid bacteria (LAB) produce homopolysaccharides (HoPS) and heteropolysaccharides (HePS) with potential functional properties. In this work, we have performed a comparative analysis of production and purification trials of these biopolymers from bacterial culture supernatants. LAB strains belonging to four different genera, both natural as well as recombinant, were used as model systems for the production of HoPS and HePS. Two well characterized strains carrying the gft gene were used for β-glucan production, Pediococcus parvulus 2.6 (P. parvulus 2.6) isolated from cider, and the recombinant strain Lactococcus lactis NZ9000[pGTF] (L. lactis NZ9000[pGTF]). In addition, another cider isolate, Lactobacillus suebicus CUPV225 (L. suebicus CUPV225), and Leuconostoc mesenteroides RTF10 (L. mesenteroides RTF10), isolated from meat products were included in the study. Chemical analysis of the EPS revealed that L. mesenteroides produces a dextran, L. suebicus a complex heteropolysaccharide, and the β-glucan producing-strains the expected 2-substituted (1,3)-β-glucan, This study was supported by grants AGL2009-12998-C03 and CSD2007-00063 from the Spanish Ministry of Science and Innovation, ACOMP/2009/257 from the Generalitat Valenciana, and IT335-10 from the Basque Government. M. N-V and S. N. are the recipients of JAE pre-doctor grants from the “Consejo Superior de Investigaciones Científicas” (CSIC)