A Drosophila model for Meniere's disease: Dystrobrevin is required for support cell function in hearing and proprioception.

Meniere's disease (MD) is an inner ear disorder characterised by recurrent vertigo attacks associated with sensorineural hearing loss and tinnitus. Evidence from epidemiology and Whole Exome Sequencing (WES) suggests a genetic susceptibility involving multiple genes, including α-Dystrobrevin (DTNA). Here we investigate a Drosophila model. We show that mutation, or knockdown, of the DTNA orthologue in Drosophila, Dystrobrevin (Dyb), results in defective proprioception and impaired function of Johnston's Organ (JO), the fly's equivalent of the inner ear. Dyb and another component of the dystrophin-glycoprotein complex (DGC), Dystrophin (Dys), are expressed in support cells within JO. Their specific locations suggest that they form part of support cell contacts, thereby helping to maintain the integrity of the hemolymph-neuron diffusion barrier, which is equivalent to a blood-brain barrier. These results have important implications for the human condition, and notably, we note that DTNA is expressed in equivalent cells of the mammalian inner ear.

The human microbiome in sickness and in health.

The study of the human microbiome has led to an exceptional increase in the current understanding of the importance of microbiota for health throughout all stages of life. Human microbial colonization occurs in the skin, genitourinary system and, mainly, in the oral cavity and intestinal tract. In these locations, the human microbiota establishes a symbiotic relationship with the host and helps maintain physiological homeostasis. Lifestyle, age, diet and use of antibiotics are the main regulators of the composition and functionality of human microbiota. Recent studies have indicated the reduction in microbial diversity as one of the contributors to the development of diseases. In addition to phylogenetic diversity studies, further metagenomic studies are needed at the functional level of the human microbiome to improve our understanding of its involvement in human health.

Microbioma humano en la salud y la enfermedad / The human microbiome in sickness and in health

El estudio del microbioma humano ha incrementado de manera excepcional el conocimiento actual del que disponemos sobre la importancia de la microbiota en la salud durante todas las etapas de la vida. La colonización microbiana humana ocurre en la piel, en el sistema genitourinario y, principalmente, en la cavidad oral y el tracto intestinal. En todos estos lugares, la microbiota humana establece una relación simbiótica con el hospedador y ayuda a mantener la homeostasis fisiológica. El estilo de vida, la edad, la dieta y el uso de antibióticos son los principales reguladores de la composición y la funcionalidad de la microbiota humana. Estudios recientes apuntan al descenso de la diversidad microbiana como uno de los aspectos que contribuye al desarrollo de enfermedades. Además de los estudios de diversidad filogenética, es necesario profundizar en estudios metagenómicos a nivel funcional del microbioma humano para mejorar el conocimiento sobre su participación en la salud humana (AU)

The study of the human microbiome has led to an exceptional increase in the current understanding of the importance of microbiota for health throughout all stages of life. Human microbial colonization occurs in the skin, genitourinary system and, mainly, in the oral cavity and intestinal tract. In these locations, the human microbiota establishes a symbiotic relationship with the host and helps maintain the physiological homeostasis. Lifestyle, age, diet and use of antibiotics are the main regulators of the composition and functionality of human microbiota. Recent studies have indicated the reduction in microbial diversity as one of the contributors to the development of diseases. In addition to phylogenetic diversity studies, further metagenomic studies are needed at the functional level of the human microbiome to improve our understanding of its involvement in human health (AU)

The human microbiome in sickness and in health. / Microbioma humano en la salud y la enfermedad.

The study of the human microbiome has led to an exceptional increase in the current understanding of the importance of microbiota for health throughout all stages of life. Human microbial colonization occurs in the skin, genitourinary system and, mainly, in the oral cavity and intestinal tract. In these locations, the human microbiota establishes a symbiotic relationship with the host and helps maintain the physiological homeostasis. Lifestyle, age, diet and use of antibiotics are the main regulators of the composition and functionality of human microbiota. Recent studies have indicated the reduction in microbial diversity as one of the contributors to the development of diseases. In addition to phylogenetic diversity studies, further metagenomic studies are needed at the functional level of the human microbiome to improve our understanding of its involvement in human health.

Diet and microbiota linked in health and disease.

Diet has shaped microbiota profiles through human evolution. Traditional gut microbiomes are described to be driven by high levels of Prevotella. In the present, however, it is consistently described a lower microbial richness in urban industrialized populations compared with individuals living in rural settings, Bacteroides being predominant among urban-industrial gut microbiomes. Components of diet are highly influential in shaping the gut microbiota, being fiber, fat, proteins, polyphenols and micronutrients differentially metabolized by generalist and specialized microorganisms alone or through the phenomenon of cross-feeding. The progressive loss of microbial diversity over generations in industrialized societies along with the emerging increase of chronic non-transmissible diseases have been related to the decline in the consumption of dietary fiber. Diet and derived microbial metabolites have strong implications with the development of food associated diseases such as obesity and metabolic syndrome, malnutrition and eating disorders, intestinal inflammatory diseases and colorectal cancer, among others. Still, there is a need of further studies in order to identify microbiota-related biomarkers of risk for these disorders. In turn, healthy diets and specific nutritional interventions, including increase of dietary fiber and the consumption of probiotics and prebiotics, could be valuable for restoration of beneficial bacteria and microbiota diversity capable to shift from disease to health promoting states.

Lactobacillus plantarum IFPL935 impacts colonic metabolism in a simulator of the human gut microbiota during feeding with red wine polyphenols.

The colonic microbiota plays an important role in the bioavailibility of dietary polyphenols. This work has evaluated the impact on the gut microbiota of long-term feeding with both a red wine polyphenolic extract and the flavan-3-ol metabolizer strain Lactobacillus plantarum IFPL935. The study was conducted in the dynamic Simulator of the Human Intestinal Microbial Ecosystem (SHIME). The feeding of the gut microbiota model with red wine polyphenols caused an initial decrease in the counts of total bacteria in the ascending colon (AC), with Bacteroides, Clostridium coccoides/Eubacterium rectale and Bifidobacterium being the most affected bacterial groups. The bacterial counts recovered to initial numbers faster than the overall microbial fermentation and proteolysis, which seemed to be longer affected by polyphenols. Addition of L. plantarum IFPL935 helped to promptly recover total counts, Lactobacillus and Enterobacteriaceae and led to an increase in lactic acid formation in the AC vessel at the start of the polyphenol treatment as well as butyric acid in the transverse (TC) and descending (DC) vessels after 5 days. Moreover, L. plantarum IFPL935 favoured the conversion in the DC vessel of monomeric flavan-3-ols and their intermediate metabolites into phenylpropionic acids and in particular 3-(3'-hydroxyphenyl)propionic acid. The results open the possibilities of using L. plantarum IFPL935 as a food ingredient for helping individuals showing a low polyphenol-fermenting metabotype to increase their colonic microbial capacities of metabolizing dietary polyphenols.

In Vitro Models for Studying Secondary Plant Metabolite Digestion and Bioaccessibility.

There is an increased interest in secondary plant metabolites, such as polyphenols and carotenoids, due to their proposed health benefits. Much attention has focused on their bioavailability, a prerequisite for further physiological functions. As human studies are time consuming, costly, and restricted by ethical concerns, in vitro models for investigating the effects of digestion on these compounds have been developed and employed to predict their release from the food matrix, bioaccessibility, and assess changes in their profiles prior to absorption. Most typically, models simulate digestion in the oral cavity, the stomach, the small intestine, and, occasionally, the large intestine. A plethora of models have been reported, the choice mostly driven by the type of phytochemical studied, whether the purpose is screening or studying under close physiological conditions, and the availability of the model systems. Unfortunately, the diversity of model conditions has hampered the ability to compare results across different studies. For example, there is substantial variability in the time of digestion, concentrations of salts, enzymes, and bile acids used, pH, the inclusion of various digestion stages; and whether chosen conditions are static (with fixed concentrations of enzymes, bile salts, digesta, and so on) or dynamic (varying concentrations of these constituents). This review presents an overview of models that have been employed to study the digestion of both lipophilic and hydrophilic phytochemicals, comparing digestive conditions in vitro and in vivo and, finally, suggests a set of parameters for static models that resemble physiological conditions.

Familial clustering and genetic heterogeneity in Meniere's disease.

The aims of this study were to estimate the prevalence of familial cases in patients with Meniere's disease (MD) and to identify clinical differences between sporadic and familial MD. We recruited 1375 patients with definite MD according to the American Academy of Otolaryngology-Head and Neck Surgery criteria, obtaining the familial history of hearing loss or episodic vertigo by direct interview or a postal survey in 1245 cases in a multicenter study. Familial clustering was estimated by the recurrence risk ratio in siblings (λs ) and offspring (λo ) using intermediate and high prevalence values for MD in European population. A total of 431 patients (34%) reported a familial history of hearing loss or recurrent vertigo and 133 patients had a relative with possible MD. After clinical reevaluation, 93 relatives in 76 families were diagnosed of definite MD (8.4%), including three pairs of monozygotic twins. λs and λo were 16-48 and 4-12, respectively. We observed genetic heterogeneity, but most families had an autosomal dominant inheritance with anticipation. No clinical differences were found between sporadic and familial MD, except for an early onset in familial cases. We may conclude that MD has a strong familial aggregation and that sporadic and familial MDs are clinically identical.

¿Existe una relación entre la microbiota intestinal, el consumo de probióticos y la modulación del peso corporal? / Is there a relationship between gut microbiota, probiotics and body weight modulation?

Introducción: Estudios científicos recientes indican que la microbiota intestinal puede jugar un papel importante en la modulación del peso corporal del hospedador. Objetivo: En este artículo se presenta una revisión actualizada de la literatura científica sobre el papel potencial de la microbiota intestinal y del consumo de probióticos en el peso corporal del hospedador, incluyendo la predisposición y la prevención del sobrepeso y la obesidad. Resultados y conclusiones: El empleo de probióticos en diferentes etapas de crecimiento, tanto en el hospedador animal como el humano, está habitualmente asociado a beneficios en la salud. Es evidente que los beneficios asociados al crecimiento no implican necesariamente un aumento del tejido adiposo ni tampoco una predisposición al sobrepeso o la obesidad. Hasta el momento, los datos que asocian un tipo de microorganismos específicos con la obesidad humana no son concluyentes ya que no determinan si es dicha microbiota la que juega una función causativa de la obesidad (fenómeno primario), o si es la microbiota intestinal la que está modulada en respuesta a dietas obesogénicas u otros factores relacionados con la patogénesis de esta condición (fenómeno secundario). Los estudios dirigidos a la modulación de la microbiota intestinal para prevenir o controlar la obesidad del hospedador, incluido el uso de probióticos, muestran resultados prometedores. De hecho, el consumo de probióticos en el entorno materno-infantil podría contribuir al control del peso corporal en etapas posteriores mediante la modulación de la microbiota intestinal infantil. Sin embargo, son necesarios más estudios que empleen ensayos aleatorizados, doble ciego y controlados por placebo para poder demostrar la eficacia de cepas probióticas específicas para la prevención o el tratamiento del sobrepeso y la obesidad. En el marco de la actual pandemia de obesidad, el empleo de cepas probióticas de las que se disponga de evidencia científica sobre un efecto beneficioso frente a determinados factores de riesgo asociados a la obesidad podría servir, junto con cambios en la dieta y el fomento de la actividad física, a la modulación del peso corporal (AU)

Introduction: Recent scientific studies show that gut microbiota may play an important role in the modulation of the body weight of the host. Objective: The aim of this article is to present an updated review of the scientific literature dealing with the potential roles of the gut microbiota and probiotics on the body weight of the host, including the predisposition to and prevention of overweight and obesity. Results and conclusions: The use of probiotics in different growth stages, both in human and animal hosts, is usually associated to a beneficial effect to the host's health. Admittedly, benefits associated to growth do not necessarily imply an increase in the adipose tissue or a predisposition to overweight or obesity. At present, the data that link the presence of specific gut microbial groups with obesity are controversial since it is unknown if they represent a cause or a consequence of obesity-associated diets and/or any other factor related to the pathogenesis of this condition. Studies dealing with the modulation of the gut microbiota to prevent or control obesity in the host, including the use of probiotics, are promising. In fact, probiotic intake in the mother-infant context might contribute to the control of the adult body weight by modulating the infant gut microbiota. However, well-designed randomized double-blind placebo-controlled trials are required to demonstrate the efficacy of specific probiotic strains for prevention or treatment of overweight and obesity. In the frame of the current obesity pandemics, use of probiotic strains with scientifically-substantiated properties against obesity risk factors may constitute a future approach, complementary to changes in diet and life style, for the modulation of the body weight (AU)

Antibacterial activity of wine phenolic compounds and oenological extracts against potential respiratory pathogens.

AIMS: To investigate the effect of seven wine phenolic compounds and six oenological phenolic extracts on the growth of pathogenic bacteria associated with respiratory diseases (Pseudomonas aeruginosa, Staphylococcus aureus, Moraxella catarrhalis, Enterococcus faecalis, Streptococcus sp Group F, Streptococcus agalactiae and Streptococcus pneumoniae). METHODS AND RESULTS: Antimicrobial activity was determined using a microdilution method and quantified as IC(50) . Mor. catarrhalis was the most susceptible specie to phenolic compounds and extracts. Gallic acid and ethyl gallate were the compounds that showed the greatest antimicrobial activity. Regarding phenolic extracts, GSE (grape seed extract) and GSE-O (oligomeric-rich fraction from GSE) were the ones that displayed the strongest antimicrobial effects. CONCLUSIONS: Results highlight the antimicrobial properties of wine phenolic compounds and oenological extracts against potential respiratory pathogens. The antimicrobial activity of wine phenolic compounds was influenced by the type of phenolic compounds. Gram-negative bacteria were more susceptible than Gram-positive bacteria to the action of phenolic compounds and extracts; however, the effect was species-dependent. SIGNIFICANCE AND IMPACT OF STUDY: The ability to inhibit the growth of respiratory pathogenic bacteria as shown by several wine phenolic compounds and oenological extracts warrants further investigations to explore the use of grape and wine preparations in oral hygiene.

Consensus statements from the Workshop 'Probiotics and Health: Scientific Evidence' / Declaraciones consensuadas del Workshop: “Probióticos y Salud: Evidencia Científica”

This report shows the level of scientific consensus on definition, characteristics and health benefits of probiotics. The content of the report has derived from the scientific meeting: Workshop on Probiotics and Health. Scientific evidence, that congregated several Spanish experts, including gastroenterologists, microbiologists, nutritionists, immunologists and food technologists, among others, who have agreed with the statements shown in this document. Each statement has been sustained with the most relevant scientific aspects that were discussed during the Workshop and the following evaluation of there port by all experts who approved and signed it (AU)

En este documento se muestra una base de consenso entorno a la definición, características y propiedades beneficiosas de los probióticos. El contenido fue generado a partir de la reunión científica Workshop Probióticos y Salud. Evidencia Científica, que agrupó a una variedad de expertos españoles gastroenterólogos, microbiólogos, nutricionistas, inmunólogos y tecnólogos de alimentos, entre otros, que se han adherido en su mayoría a las sentencias que constituyen este documento. Para cada sentencia se establecen las aspectos científicos más relevantes que la respaldan y que son consecuencia del acuerdo al que se ha llegado tras el debate surgido en la reunión y la evaluación posterior del contenido por todos los expertos que han firmado este documento (AU)

Consensus statements from the Workshop "Probiotics and Health: Scientific evidence".

This report shows the level of scientific consensus on definition, characteristics and health benefits of probiotics. The content of the report has derived from the scientific meeting: Workshop on Probiotics and Health. Scientific evidence, that congregated several Spanish experts, including gastroenterologists, microbiologists, nutritionists, immunologists and food technologists, among others, who have agreed with the statements shown in this document. Each statement has been sustained with the most relevant scientific aspects that were discussed during the Workshop and the following evaluation of the report by all experts who approved and signed it.

Key enzymes involved in methionine catabolism by cheese lactic acid bacteria.

Cheese microbiota and their enzymatic conversion of l-methionine to volatile sulphur compounds (VSCs) play an important role in aroma formation during cheese ripening. Here, lactic acid bacteria (LAB) strains isolated from raw goats' milk cheeses were screened for the major enzymes critical to the formation of VSCs from l-methionine. A large natural biodiversity in enzyme capabilities and high inter- and intra-species variability was found among the LAB isolates investigated. From those isolates tested, lactococci displayed higher C-S lyase specificities towards the sulphur-containing compounds examined than did Lactobacillus and Leuconostoc, in some cases generating higher levels of VSCs than B. linens, known to be an efficient producer of methanethiol (MTL) and related VSCs. Moreover, these differences in C-S lyase activities (determined spectrophotometrically by measuring the formation of free thiol groups) were shown to correspond with the enzymatic potential of the isolates as determined by visualization of enzymatic activities. This technique could therefore prove valuable for the detection and preliminary characterization of C-S lyase activities among LAB isolates. Lactococci were also found to possess higher aminotransferase activities than lactobacilli and leuconostocs, while glutamate dehydrogenase activities were observed to be highest among Leuconostoc and Lactobacillus spp. Meanwhile, alpha-keto acid decarboxylase activities were highly variable and were measurable in only a limited number of isolates, mainly lactobacilli. From these data, combining indigenous isolates showing high VSCs-producing capabilities with those that facilitate the completion of the metabolic pathway responsible for degrading l-methionine into volatile compounds may provide an efficient approach to enhance cheese aroma development.

Discrepancies between the phenotypic and genotypic characterization of Lactococcus lactis cheese isolates.

AIMS: The use of randomly amplified polymorphic DNA (RAPD)-PCR fingerprinting and plasmid profiles to determine at the strain level, the similarity of Lactococcus lactis isolates obtained during sampling of traditional cheeses and to verify its correspondence to the selected phenotypic characteristics. METHODS AND RESULTS: A total of 45 L. lactis isolates were genotypically analysed by RAPD-PCR fingerprinting and plasmid patterns. Phenotypic traits used to compare strains were proteolytic, acidifying, aminotransferase (aromatic and branched chain aminotransferase) and alpha-ketoisovalerate decarboxylase (Kivd) activities. The results show that 23 isolates could be grouped in clusters that exhibited 100% identity in both their RAPD and plasmid patterns, indicating the probable isolation of dominant strains during the cheese sampling process. However, there were phenotypic differences between isolates within the same cluster that included the loss of relevant technological properties such as proteinase activity and acidifying capacity or high variation in their amino acid converting enzyme activities. Likewise, the analysis of a specific attribute, Kivd activity, indicated that 7 of 15 isolates showed no detectable activity despite the presence of the encoding (kivd) gene. CONCLUSION: Phenotypic differences found between genotypically similar strains of L. lactis strains could be linked to differences in enzymatic expression. SIGNIFICANCE AND IMPACT OF THE STUDY: Phenotypic analysis of L. lactis isolates should be considered when selecting strains with new cheese flavour forming capabilities.

Enzymatic ability of Bifidobacterium animalis subsp. lactis to hydrolyze milk proteins: identification and characterization of endopeptidase O.

The proteolytic system of Bifidobacterium animalis subsp. lactis was analyzed, and an intracellular endopeptidase (PepO) was identified and characterized. This work reports the first complete cloning, purification, and characterization of a proteolytic enzyme in Bifidobacterium spp. Aminopeptidase activities (general aminopeptidases, proline iminopeptidase, X-prolyl dipeptidylaminopeptidase) found in cell extracts of B. animalis subsp. lactis were higher for cells that had been grown in a milk-based medium than for those grown in MRS. A high specific proline iminopeptidase activity was observed in B. animalis subsp. lactis. Whole cells and cell wall-bound protein fractions showed no caseinolytic activity; however, the combined action of intracellular proteolytic enzymes could hydrolyze casein fractions rapidly. The endopeptidase activity of B. animalis subsp. lactis was examined in more detail, and the gene encoding an endopeptidase O in B. animalis subsp. lactis was cloned and overexpressed in Escherichia coli. The deduced amino acid sequence for B. animalis subsp. lactis PepO indicated that it is a member of the M13 peptidase family of zinc metallopeptidases and displays 67.4% sequence homology with the predicted PepO protein from Bifidobacterium longum. The recombinant enzyme was shown to be a 74-kDa monomer. Activity of B. animalis subsp. lactis PepO was found with oligopeptide substrates of at least 5 amino acid residues, such as met-enkephalin, and with larger substrates, such as the 23-amino-acid peptide alpha s1-casein(f1-23). The predominant peptide bond cleaved by B. animalis subsp. lactis PepO was on the N-terminal side of phenylalanine residues. The enzyme also showed a post-proline secondary cleavage site.

[Evaluation of a pharmaceutical care program to improve adherence to antiretroviral therapy]. / Evaluación de un programa de atención farmacéutica dirigido a mejorar la adherencia al tratamiento antirretroviral.

OBJECTIVE: To establish the impact of a pharmaceutical care program on the improvement of adherence to antiretroviral therapy, and on patient immunologic and virologic outcome. MATERIALS AND METHODS: A multicenter, observational, prospective study in a HIV-infected patient cohort under treatment with antiretrovirals selected by random sampling in 19 Spanish hospitals. The study lasted 12 months, in which the program was applied through a baseline preprocedural visit and 4 quarterly visits. Adherence estimation was based on pill counting. An adherence > or = 90, or > or = 95% was considered adequate (in two time points). RESULTS: 541 patients were included, most of them were males (68.8%) between 20 and 78 years of age. Major risk groups included injecting drug users (43.4%) and heterosexuals (29.4%). Sixty percent had already received treatment for more than 3 years. Mean baseline viral load and CD4 count values were 32,866 copies/ml and 485 cells/mm3, respectively. Throughout the study a slight increase in the percentage of adherent patients was seen; however, statistical significance was not reached (64.3 and 79.2% of patients showed an adherence > 95 and > 90%, respectively, during the fourth quarter, versus 59.8 and 75.5% at baseline). A statistically significant decrease in viral load and increase in CD4 cells was seen following program application. The percentage of patients with a viral load < 200 copies/ml was 72.2, 76.7, and 75.0% at the 2nd, 3rd, and 4th quarters, respectively, versus 64.2% at baseline. CD4 cell counts increased by 50 cells/mm3 on average from the start to the end of follow-up. CONCLUSIONS: Patients included in the program had a good immunologic and virologic outcome, and a trend towards an increased percentage of patients with good adherence was also seen. These results confirm the need to implement follow-up programs for patients receiving antiretrovirals in order to ensure maximum therapeutic benefits.

Conversion of methionine to methional by Lactococcus lactis.

Lactic acid bacteria were screened for methional production from 4-methylthio-2-ketobutanoate. Only Lactococcus lactis IFPL730 produced high amounts of methional. It was demonstrated that production of this compound was an exclusively enzymatic reaction. The present work describes for the first time that L. lactis can convert enzymatically methionine to methional in a process mediated by aminotransferase and alpha-ketoacid decarboxylase activities. The activity seems to be strain dependent.

Lactobacillus casei and Lactobacillus plantarum initiate catabolism of methionine by transamination.

AIMS: To study the ability of Lactobacillus casei and Lact. plantarum strains to convert methonine to cheese flavour compounds. METHODS AND RESULTS: Strains were assayed for methionine aminotransferase and lyase activities, and amino acid decarboxylase activity. About 25% of the strains assayed showed methionine aminotransferase activity. The presence of glucose in the reaction mixture increased conversion of methionine to 4-methylthio-2-ketobutanoate (KMBA) and 4-methylthio-2-hydroxybutanoate (HMBA) in all strains. The methionine aminotransferase activity in Lact. plantarum and Lact. casei showed variable specificity for the amino group acceptors glyoxylate, ketoglutarate, oxaloacetate and pyruvate. None of the strains showed methionine lyase or glutamate and methionine decarboxylase activities. CONCLUSION: The presence of amino acid converting enzymes in lactobacilli is strain specific. SIGNIFICANCE AND IMPACT OF THE STUDY: The findings of this work suggest that lactobacilli can be used as adjuncts for flavour formation in cheese manufacture.

Use of a bacteriocin-producing transconjugant as starter in acceleration of cheese ripening.

The non-conjugative 46 kb plasmid that encodes the biosynthesis of lacticin 3147 in Lactococcus lactis IFPL105 has been transferred to the starter L. lactis IFPL359, used in goat's milk cheesemaking. The accelerating effect exerted on proteolysis and development of sensory characteristics of semi-hard cheese by the bacteriocin-producing transconjugant L. lactis IFPL3593 (Lac+ Bac+ Imm+), which is able to induce cell lysis in starter adjuncts with high peptidase activity, has been studied. It has been demonstrated that the use of IFPL3593 as starter accelerates cheese ripening as it increases the level of amino nitrogen correlated with early cell lysis of adjuncts. The fact that the bacteriocin-producing microorganism used is immune to the bacteriocin. allowed proper acidification of the curd without altering the cheese-making process.

Biological and molecular characterization of a two-peptide lantibiotic produced by Lactococcus lactis IFPL105.

The lactic acid bacterium Lactococcus lactis IFPL105 secretes a broad spectrum bacteriocin produced from the 46 kb plasmid pBAC105. The bacteriocin was purified to homogeneity by ionic and hydrophobic exchange and reverse-phase chromatography. Bacteriocin activity required the complementary action of two distinct peptides (alpha and beta) with average molecular masses of 3322 and 2848 Da, respectively. The genes encoding the two peptides were cloned and sequenced and were found to be identical to the ltnAB genes from plasmid pMRC01 of L. lactis DPC3147. LtnA and LtnB contain putative leader peptide sequences similar to the known 'double glycine' type. The predicted amino acid sequence of mature LtnA and LtnB differed from the amino acid content determined for the purified alpha and beta peptides in the residues serine, threonine, cysteine and alanine. Post-translational modification, and the formation of lanthionine or methyllanthionine rings, could partly explain the difference. Hybridization experiments showed that the organization of the gene cluster in pBAC105 responsible for the production of the bacteriocin is similar to that in pMRC01, which involves genes encoding modifying enzymes for lantibiotic biosynthesis and dual-function transporters. In both cases, the gene clusters are flanked by IS946 elements, suggesting an en bloc transposition. The findings from the isolation and molecular characterization of the bacteriocin provide evidence for the lantibiotic nature of the two peptides.