Control strategies for biofilm control in reclaimed water distribution systems from the perspective of microbial antagonism and electrochemistry.

Biofilm formation in reclaimed water (RW) distribution systems presents significant technical challenges to RW utilization. Two main technologies to control biofilm formation, microbial antagonism (MA) and electrochemical oxidation (EO), are not yet widely used in drip irrigation systems (DIS) and their mechanisms of action need further clarification. In this study, we first showed that the MA and EO treatments reduced biofilm formation by about 62% and 68%, respectively, and extracellular polymeric substance (EPS) content by 14% and 49%, respectively, in biofilms compared with raw RW type 1 (R-RW1) in unused pipes, thus effectively improving the performance of DIS. When MA-RW and EO-RW were applied to already clogged systems, the degree of clogging alleviation varied depending on the severity of the original clogging. We recommend adding the antagonist, Bacillus subtilis, to RW at 25% clogging for the maximum effect and to slow the microbial adaptation process. Compared to MA, the recovery effect of EO was slower initially but lasted longer and had a significantly better alleviating effect on severely clogged pipelines. Illumina Mi-SEQ high-throughput sequencing data showed that both MA and EO resulted in a significant decrease in microbial diversity, dynamic changes in bacterial community structure, and disruption of network interaction and network modularity. Meanwhile, both treatments promoted the growth of specific microorganisms, enhanced the interaction between certain microbial components, and improved the efficiency of information, matter, and energy exchange within the modules. In summary, we verified the dredging effect of two strategies on DIS under different water conditions, revealed the differences in their mechanisms of action, and proposed their application scenarios. Our results will help improve the efficiency of RW in agricultural drip irrigation systems and effectively reduce maintenance costs.

Effect of polymicrobial interactions on antimicrobial resistance: an in vitro analysis in human ocular infections.

Purpose: Investigate the effect of polymicrobial interactions on antimicrobial resistance (AMR) of ocular pathogens in polymicrobial settings, compared with monomicrobial infections. Methods: Polymicrobial interactions were labeled as antagonistic, synergistic or indifferent based on a reduction, an increase or no change, respectively, in antibiotics' MIC by the Vitek 2 compact system, compared with monomicrobial pathogens. Results:Staphylococcus epidermidis showed antagonistic polymicrobial interactions (22.6%); Pseudomonas aeruginosa showed synergistic interactions (62.5%); multidrug-resistant Acinetobacter baumannii showed increased susceptibility to select antibiotics; Serratia ficaria (inherently colistin resistant) became colistin-susceptible in polymicrobial combinations. Conclusion: Both antagonistic and synergistic interactions exist among human pathogens in polymicrobial settings. Gram-positive pathogens had significantly higher antagonistic polymicrobial interactions (increased MICs: 20.4%) compared with Gram-negative ones (synergistic: 59.4%).

Uninvited Guests: a Chronology of Petri Dish Contaminations.

Petri dish contaminations are commonplace and personally witnessed by every microbiologist. The vast majority of such contaminations result in nothing more than annoyance following which the Petri dishes are discarded. However, a handful of incidents of contaminations have led to momentous outcomes, the most renowned of which being that perceived by Alexander Fleming on the basis of the immense number of lives saved by penicillin. Petri dish contaminations as reported upon in the literature fall broadly into two categories; those in which the contaminant caused antagonism toward the species being cultured, and those in which the contaminant was established to be a species novum. Accounts of both of these categories of contaminations are set out here.

A fungal member of the Arabidopsis thaliana phyllosphere antagonizes Albugo laibachii via a GH25 lysozyme.

Plants are not only challenged by pathogenic organisms but also colonized by commensal microbes. The network of interactions these microbes establish with their host and among each other is suggested to contribute to the immune responses of plants against pathogens. In wild Arabidopsis thaliana populations, the oomycete pathogen Albugo laibachii plays an influential role in structuring the leaf phyllosphere. We show that the epiphytic yeast Moesziomyces bullatus ex Albugo on Arabidopsis, a close relative of pathogenic smut fungi, is an antagonistic member of the A. thaliana phyllosphere, which reduces infection of A. thaliana by A. laibachii. Combination of transcriptomics, reverse genetics, and protein characterization identified a GH25 hydrolase with lysozyme activity as a major effector of this microbial antagonism. Our findings broaden the understanding of microbial interactions within the phyllosphere, provide insights into the evolution of epiphytic basidiomycete yeasts, and pave the way for novel biocontrol strategies.

Much like the 'good bacteria' that live in our guts, many microscopic organisms can co-exist with and even benefit the plants they live on. For instance, the yeast Moesziomyces bullatus ex Albugo (MbA for short) can shield the leaves of its plant host against white rust, a disease caused by the organism Albugo laibachii. Studies have started to unveil how the various microbes at the surface of leaves interact and regulate their own community, yet the genetic mechanisms at play are less well-known. To investigate these processes, Eitzen et al. examined the genes that were switched on when MbA cells were in contact with A. laibachii on a leaf. This experiment revealed a few gene candidates that were then deleted, one by one, in MbA cells. As a result, a gene emerged as being key to protect the plant from white rust. It produces an enzyme known as the GH25 hydrolase, which, when purified, could reduce A. laibachii infections on plant leaves. Bacteria, fungi and other related microorganisms cause many diseases which, like white rust, can severely affect crops. Chemical methods exist to prevent these infections but they can have many biological and ecological side effects. A solution inspired by natural interactions may be safer and more effective at managing plant diseases that affect valuable crops. Harnessing the interactions between microbes living on plants, and the GH25 enzyme, may offer better disease control.

Biomanagement of rice root-knot nematode Meloidogyne graminicola using five indigenous microbial isolates under pot and field trials.

AIMS: To ascertain the effectiveness of Aspergillus niger, Trichoderma harzianum, Pochonia chlamydosporia, Bacillus subtilis and Pseudomonas fluorescens against rice root-knot nematode, Meloidogyne graminicola, and to optimize their application methods. METHODS AND RESULTS: The relative effectiveness of five indigenous biocontrol agents (BCA) against M. graminicola on rice cv. PS-5 was tested initially in pot culture. The BCAs, A. niger, P. chlamydosporia and P. fluorescens proved more effective, and significantly reduced the nematode disease. It is hypothesized that success of a biocontrol module may vary with the BCA and application methods. Hence, the effectiveness of the above three BCAs as well as seven different treatment schemes were evaluated in naturally infested farmer's fields during 2 consecutive years. In nematode-infested plots without any BCA treatments, terminal galls formed on the roots, and plants suffered a 19-31% decrease in the growth and yield. The treatments with P. chlamydosporia or A. niger through root-dip (RD) plus one soil application (SA) at 15 days after planting were found to be highly effective against the nematode. CONCLUSIONS: Relatively greater nematode control was achieved with RD plus two SAs (15 + 30 DAP) but statistically the effect was on par with RD + one SA at 15 DAP. These treatments significantly reduced galling (22-25%), egg mass production (21-29%) and reproduction factor (63-70%) of M. graminicola, and subsequently increased the grain yield (11-21%). SIGNIFICANCE AND IMPACT OF THE STUDY: Application methods enhanced the effectiveness of BCAs against M. graminicola. The RD plus one SA at 15 DAP proved to be most effective treatment to control root-knot disease in rice. Use of multiple treatments (root dip and SA) appears cumbersome, but in view of effectiveness and limitation of chemical control in rice paddies, farmers may adopt the above module that may lead to 11-21% yield improvement.

Biocontrol yeasts: mechanisms and applications.

Yeasts occur in all environments and have been described as potent antagonists of various plant pathogens. Due to their antagonistic ability, undemanding cultivation requirements, and limited biosafety concerns, many of these unicellular fungi have been considered for biocontrol applications. Here, we review the fundamental research on the mechanisms (e.g., competition, enzyme secretion, toxin production, volatiles, mycoparasitism, induction of resistance) by which biocontrol yeasts exert their activity as plant protection agents. In a second part, we focus on five yeast species (Candida oleophila, Aureobasidium pullulans, Metschnikowia fructicola, Cryptococcus albidus, Saccharomyces cerevisiae) that are or have been registered for the application as biocontrol products. These examples demonstrate the potential of yeasts for commercial biocontrol usage, but this review also highlights the scarcity of fundamental studies on yeast biocontrol mechanisms and of registered yeast-based biocontrol products. Yeast biocontrol mechanisms thus represent a largely unexplored field of research and plentiful opportunities for the development of commercial, yeast-based applications for plant protection exist.

Spontaneously Arising Streptococcus mutans Variants with Reduced Susceptibility to Chlorhexidine Display Genetic Defects and Diminished Fitness.

Chlorhexidine (CHX) has been used to control dental caries caused by acid-tolerant bacteria such as Streptococcus mutans since the 1970s. Repeat CHX exposure for other bacterial species results in the development of variants with reduced susceptibility that also become more resistant to other antimicrobials. It has not been tested if such variants arise when streptococci are exposed to CHX. Here, we passaged S. mutans in increasing concentrations of CHX and isolated spontaneously arising reduced susceptibility variants (RSVs) from separate lineages that have MICs that are up to 3-fold greater than the parental strain. The RSVs have increased growth rates at neutral pH and under acidic conditions in the presence of CHX but accumulate less biomass in biofilms. RSVs display higher MICs for daptomycin and clindamycin but increased sensitivity to dental-relevant antimicrobials triclosan and sodium fluoride. Plate-based assays for competition with health-associated oral streptococci revealed decreased bacteriocin production by the RSVs, increased sensitivity to hydrogen peroxide, and diminished competitive fitness in a human-derived ex vivo biofilm consortium. Whole-genome sequencing identified common single nucleotide polymorphisms (SNPs) within a diacylglycerol kinase homolog and a glycolipid synthesis enzyme, which could alter the accumulation of lipoteichoic acids and other envelope constituents, as well as a variety of mutations in other genes. Collectively, these findings confirm that S. mutans and likely other streptococci can develop tolerance to CHX but that increased tolerance comes at a fitness cost, such that CHX-induced variants that spontaneously arise in the human oral cavity may not persist.

Natural C. elegans Microbiota Protects against Infection via Production of a Cyclic Lipopeptide of the Viscosin Group.

Caenorhabditis elegans is associated in nature with a species-rich, distinct microbiota, which was characterized only recently [1]. Thus, our understanding of the relevance of the microbiota for nematode fitness is still at its infancy. One major benefit that the intestinal microbiota can provide to its host is protection against pathogen infection [2]. However, the specific strains conferring the protection and the underlying mechanisms of microbiota-mediated protection are often unclear [3]. Here, we identify natural C. elegans microbiota isolates that increase C. elegans resistance to pathogen infection. We show that isolates of the Pseudomonas fluorescens subgroup provide paramount protection from infection with the natural pathogen Bacillus thuringiensis through distinct mechanisms. We found that the P. lurida isolates MYb11 and MYb12 (members of the P. fluorescens subgroup) protect C. elegans against B. thuringiensis infection by directly inhibiting growth of the pathogen both in vitro and in vivo. Using genomic and biochemical analyses, we further demonstrate that MYb11 and MYb12 produce massetolide E, a cyclic lipopeptide biosurfactant of the viscosin group [4, 5], which is active against pathogenic B. thuringiensis. In contrast to MYb11 and MYb12, P. fluorescens MYb115-mediated protection involves increased resistance without inhibition of pathogen growth and most likely depends on indirect, host-mediated mechanisms. This work provides new insight into the functional significance of the C. elegans natural microbiota and expands our knowledge of bacteria-derived compounds that can influence pathogen colonization in the intestine of an animal.

Identification of Soil Bacterial Isolates Suppressing Different Phytophthora spp. and Promoting Plant Growth.

Bacterial isolates obtained from the rhizosphere of Arabidopsis and a plantless compost potting mix was screened for anti-oomycete activity against Phytophthora capsici, Phytophthora citricola, Phytophthora palmivora, and Phytophthora cinnamomi. Three out of 48 isolates exhibited more than 65% inhibition against all tested Phytophthora species and were selected for further studies. These strains, named UQ154, UQ156, and UQ202, are closely related to Bacillus amyloliquefaciens, Bacillus velezensis, and Acinetobacter sp., respectively, based on 16S rDNA sequence analysis. The isolates were evaluated for their ability to fix nitrogen, solubilize phosphate, as well as for siderophore, indoleacetic acid, cell wall degrading enzymes and biofilm production. Their plant growth promoting activities were evaluated by measuring their effect on the germination percentage, root and shoot length, and seedling vigor of lettuce plants. All of these traits were significantly enhanced in plants grown from seeds inoculated with the isolates compared with control plants. Moreover, bacteria-inoculated P. capsici-infected chili plants exhibited improved productivity based on CO2 assimilation rates. Both real-time quantitative PCR and disease severity index revealed significant decreases in pathogen load in infected chili root tissues when plants were previously inoculated with the isolates. Biocontrol activity may result from the secretion of diketopiperazines as identified by Gas chromatography-mass spectrometry analysis of bacterial cultures' extracts. Collectively, this work demonstrates the potential of bacterial isolates to control Phytophthora infection and promote plant growth. They can, therefore be considered as candidate microbial biofertilizers and biopesticides.

Segregation of Tetragenococcus halophilus and Zygosaccharomyces rouxii using W1/O/W2 double emulsion for use in mixed culture fermentation.

Antagonism in mixed culture fermentation can result in undesirable metabolic activity and negatively affect the fermentation process. Water-oil-water (W1/O/W2) double emulsions (DE) could be utilized in fermentation for segregating multiple species and controlling their release and activity. Zygosaccharomyces rouxii and Tetragenococcus halophilus, two predominant microbial species in soy sauce fermentation, were incorporated in the internal W1 and external W2 phase of a W1/O/W2, respectively. The suitability of DE for controlling T. halophilus and Z. rouxii in soy sauce fermentation was studied in relation to emulsion stability and microbial release profile. The effects of varying concentrations of Z. rouxii cells (5 and 7logCFU/mL) and glucose (0%, 6%, 12%, 30% w/v) in the W2 phase were investigated. DE stability was determined by monitoring encapsulation stability (%), oil globule size, and microstructure with fluorescence and optical microscopy. Furthermore, the effect of DE on the interaction between T. halophilus and Z. rouxii was studied in Tryptic Soy Broth containing 10% w/v NaCl and 12% w/v glucose and physicochemical changes (glucose, ethanol, lactic acid, and acetic acid) were monitored. DE destabilization resulted in cell release which was proportional to the glucose concentration in W2. Encapsulated Z. rouxii presented higher survival during storage (~3 log). The application of DE affected microbial cells growth and physiology, which led to the elimination of antagonism. These results demonstrate the potential use of DE as a delivery system of mixed starter cultures in food fermentation, where multiple species are required to act sequentially in a controlled manner.

Label-Free Proteomics of a Defined, Binary Co-culture Reveals Diversity of Competitive Responses Between Members of a Model Soil Microbial System.

Interactions among members of microbial consortia drive the complex dynamics in soil, gut, and biotechnology microbiomes. Proteomic analysis of defined co-cultures of well-characterized species provides valuable information about microbial interactions. We used a label-free approach to quantify the responses to co-culture of two model bacterial species relevant to soil and rhizosphere ecology, Bacillus atrophaeus and Pseudomonas putida. Experiments determined the ratio of species in co-culture that would result in the greatest number of high-confidence protein identifications for both species. The 281 and 256 proteins with significant shifts in abundance for B. atrophaeus and P. putida, respectively, indicated responses to co-culture in overall metabolism, cell motility, and response to antagonistic compounds. Proteins associated with a virulent phenotype during surface-associated growth were significantly more abundant for P. putida in co-culture. Co-culture on agar plates triggered a filamentous phenotype in P. putida and avoidance of P. putida by B. atrophaeus colonies, corroborating antagonistic interactions between these species. Additional experiments showing increased relative abundance of P. putida under conditions of iron or zinc limitation and increased relative abundance of B. atrophaeus under magnesium limitation were consistent with patterns of changes in abundance of metal-binding proteins during co-culture. These results provide details on the nature of interactions between two species with antagonistic capabilities. Significant challenges remaining for the development of proteomics as a tool in microbial ecology include accurate quantification of low-abundance peptides, especially from rare species present at low relative abundance in a consortium.

Antagonism between two root-associated beneficial Pseudomonas strains does not affect plant growth promotion and induced resistance against a leaf-chewing herbivore.

Plant growth-promoting microbes residing on the roots may cooperate or compete, thereby affecting their collective benefit to the host plant. Pseudomonas simiae WCS417r (formerly known as P. fluorescens WCS417r) and Pseudomonas fluorescens SS101 are well known for their ability to induce systemic resistance in Arabidopsis. Here, we evaluate how these species interact on the roots of Arabidopsis thaliana Col-0 and how their co-inoculation affects plant defense to the leaf-chewing herbivore Mamestra brassicae and plant growth promotion. WCS417r and SS101, applied individually to root tips or at two different positions along the roots, established similar population densities on Arabidopsis roots. When co-inoculated at the same position on the roots, however, WCS417r established significantly higher population densities than SS101. Both upon single inoculation and co-inoculation, the two pseudomonads induced the same level of induced systemic resistance against the caterpillar M. brassicae and the same increase in plant biomass. These results suggest that combined inoculation of both Pseudomonas strains does not significantly modify the plant's defensive capacity compared to individual inoculation, resulting in a similar effect on performance of the generalist herbivore M. brassicae.

Construction of PAH-degrading mixed microbial consortia by induced selection in soil.

Bioremediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated soils through the biostimulation and bioaugmentation processes can be a strategy for the clean-up of oil spills and environmental accidents. In this work, an induced microbial selection method using PAH-polluted soils was successfully used to construct two microbial consortia exhibiting high degradation levels of low and high molecular weight PAHs. Six fungal and seven bacterial native strains were used to construct mixed consortia with the ability to tolerate high amounts of phenanthrene (Phe), pyrene (Pyr) and benzo(a)pyrene (BaP) and utilize these compounds as a sole carbon source. In addition, we used two engineered PAH-degrading fungal strains producing heterologous ligninolytic enzymes. After a previous selection using microbial antagonism tests, the selection was performed in microcosm systems and monitored using PCR-DGGE, CO2 evolution and PAH quantitation. The resulting consortia (i.e., C1 and C2) were able to degrade up to 92% of Phe, 64% of Pyr and 65% of BaP out of 1000 mg kg-1 of a mixture of Phe, Pyr and BaP (1:1:1) after a two-week incubation. The results indicate that constructed microbial consortia have high potential for soil bioremediation by bioaugmentation and biostimulation and may be effective for the treatment of sites polluted with PAHs due to their elevated tolerance to aromatic compounds, their capacity to utilize them as energy source.

Mechanisms Involved in Nematode Control by Endophytic Fungi.

Colonization of plants by particular endophytic fungi can provide plants with improved defenses toward nematodes. Evidently, such endophytes can be important in developing more sustainable agricultural practices. The mechanisms playing a role in this quantitative antagonism are poorly understood but most likely multifactorial. This knowledge gap obstructs the progress regarding the development of endophytes or endophyte-derived constituents into biocontrol agents. In part, this may be caused by the fact that endophytic fungi form a rather heterogeneous group. By combining the knowledge of the currently characterized antagonistic endophytic fungi and their effects on nematode behavior and biology with the knowledge of microbial competition and induced plant defenses, the various mechanisms by which this nematode antagonism operates or may operate are discussed. Now that new technologies are becoming available and more accessible, the currently unresolved mechanisms can be studied in greater detail than ever before.

CINÉTICA DE CRECIMIENTO DE Lactobacillus lactis Y DETERMINACIÓN DEL EFECTO PROBIÓTICO EN CEPAS PATÓGENAS / Lactobacillus lactis GROWTH KINETICS AND DETERMINATION OF PROBIOTIC EFFECT ON PATHOGEN STRAINS

Introducción: Las bacterias ácido-lácticas se han estudiado por su capacidad de crecer en ambientes difíciles y generar antagonismos con otros microorganismos. La presente investigación buscó determinar los parámetros de la cinética de crecimiento de Lactobacillus lactis y su efecto probiótico sobre Escherichia coli, Salmonella typhimurium, Clostridium perfringens y Staphylococcus aureus. Materiales y Métodos: Se evaluó el crecimiento de la cepa láctica a concentraciones de 0,5, 1 y 2% de sales biliares; 1 y 1,5% de bilis; tres niveles de pH (2,5, 4,5 y 7) y dos de temperaturas (38 y 45ºC). También se evalúo la susceptibilidad de todas las cepas a los antibióticos Dicloxacilina, Cefepime, Cefalotina, Ciprofloxacina, Pentamicina y Penicilina con la técnica de Kirby-Bauer. Se determinó la inhibición de L. lactis y su sobrenadante en E. coli, S. typhimurium, C. perfringens y S. aureus y se estimaron los parámetros de: crecimiento, pH, consumo de azúcar, acidez y consumo de proteína durante la cinética de fermentación en medio MRS. Se determinaron péptidos presentes en el sobrenadante de L. lactis mediante HPLC. Resultados: Se obtuvo un crecimiento de 1,2 x 109 y 4,1 x 109 ufc/ml a 1,2% de bilis y a 0,5% de sales biliares; 1,1 x 1011, 2,1 x 1010 y 1,0 x 1010 ufc/ml para pH 2,5, 4,5 y 7 respectivamente; y 1,7 x 1013 y 1,4 x 1013 ufc/ml para 45 y 38ºC. La cepa láctica presentó resistencia a Dicloxacilina y Cefalotina; C. perfringens, a Dicloxacilina y Penicilina; S. typhimurium y E. coli, a Cefalotina; y S. aureus, a Dicloxacilina. L. lactis inhibió a E. coli y C. perfringens, y el sobrenadante incluyó a S. aureus. Conclusión: Se concluye que L. lactis presenta adecuados crecimientos en condiciones in vitro e inhibió a E. coli, C. perfringens y S. aureus pero no a S. typhimurium.

Introduction: Acid lactic bacteria have been studied for their ability to grow in harsh environments and generate antagonisms with other microorganisms. The present study sought to determine the kinetic parameters of growth of Lactobacillus lactis and its effect on Escherichia coli, Salmonella typhimurium, Clostridium perfringens and Staphylococcus aureus. Materials and Methods: The growth of the lactic strain was evaluated at concentrations of 0.5, 1 and 2% bile salts; 1 and 1.5% bile; three levels of pH (2.5, 4.5 and 7) and two temperatures (38 and 45ºC). Susceptibility of all strains to Dicloxacillin, Cefepime, Cephalothin, Ciprofloxacin, Gentamicin and Penicillin was also evaluated using Kirby-Bauer technique. Inhibition of L. lactis and its supernatant in E.coli, S. typhimurium, S. aureus and C. perfringens and the following parameters were determined and estimated: growth, pH, sugar consumption, acidity and protein consumption during the kinetic fermentation in MRS. Peptides present in the L. lactis supernatant through HPLC were determined. Results: Growth of 1.2x109 and 4.1x109 CFU/ml at 1.2% bile and 0.5% bile salt was obtained; 1.1x1011, 2.1x1010 and 1.0x1010 CFU/ml for 2.5, 4.5 and 7 pH respectively; and 1.7x1013 and 1.4x1013 CFU/ml for 45 and 38ºC. The lactic strain showed resistance to Cephalothin and Dicloxacilin; C. perfringens, to Penicillin and Dicloxacillin; S. typhimurium and E. coli to Cephalothin; and S. aureus, to Dicloxacillin. L. lactis inhibited E. coli and C. perfringens, and the supernatant included S. aureus. Conclusion: It is concluded that L. lactis present adequate growth in conditions in vitro and inhibited E. coli, C. perfringens and S. aureus but not S. typhimurium.

Caracterización del proceso de fermentación y del efecto de inhibición de Lactobacillus lactis en Staphylococcus aureus y Staphylococcus epidermidis / Characterization of the Fermentation Process and the Inhibition Effect of Lactobacillus lactis in Staphylococcus aureus and Staphylococcus epidermidis / Caracterização do processo de fermentação e do efeito de inibição de Lactobacillus lactis em Staphylococcus aureus e Staphylococcus epidermidis

Se evaluó el proceso fermentativo e inhibición in vitro de L. lactis en Staphylococcus aureus y Staphylococcus epidermidis; así mismo, el crecimiento de L. lactis a tres pH (2,5, 4,5 y 7), sales biliares (0,5, 1 y 2 %), bilis bovina (1 y 1,2 %) y dos temperaturas (38 y 45 °C). Se determinaron péptidos y ácidos orgánicos en sobrenadante de L. lactis por HPLC. Se hizo cinética de fermentación en la que se evaluó: pH, azúcar total, proteína y ácido láctico. Se realizó antibiograma de dicloxacilina, cefepime, penicilina y cefalotina. Se definió la inhibición de L. lactis y su sobrenadante en cepas patógenas. El mejor crecimiento fue a pH de 2,5 (3 x 10(12) UFC/ml); de 1 x 10(10) y 4 x 10(9) UFC/ml para 0,5 % de sales biliares y 1,2 % de bilis bovina, respectivamente; de 3,5 x 10(13) y 3,4 x 10(13) UFC/ml para 38 y 45 °C, respectivamente. El HPLC determinó los péptidos VAR-TIR-VAR y ácido láctico (83,11 %). La cinética de fermentación determinó la fase exponencial a 14:24 h con un valor 77 x 10(10) UFC/ml, valores de pH de 4,284, azúcar 2,33 mg/ml, proteína 1,44 mg/ml y acidez de 0,79 %. Se encontró que S. aureus y S. epidermidis fueron sensibles a todos los antibióticos. Las bacterias patógenas fueron resistentes a la cepa láctica, pero S. epidermidis fue sensible al sobrenadante de L. lactis. Se concluye que Lactobacillus lactis mostró adecuada capacidad de crecimiento, buenos parámetros de fermentación y efecto inhibitorio en cepas de S. aureus y S. epidermidis en condiciones in vitro.

The fermentative process and in vitro inhibition of L. lactis in Staphylococcus aureus and Staphylococcus epidermidis were assessed. The growth of L. lactis at three pH (2.5, 4.5 and 7), bile salts (0.5, 1 and 2 %), bovine bile (1 and 1.2 %) and two temperatures (38 and 45 °C) were evaluated. Peptides and organic acids in supernatant of L. lactis by HPLC were determined. Fermentation kinetics was carried out, evaluating: pH, total sugar, protein and lactic acid. An antibiogram of dicloxacilin, cefepime, penilicin and cefalotin was made. The inhibition of L. lactis and its supernatant were defined in pathogenic strains. The best growth was at a pH of 2.5 (3 x 10(12) UFC/ml); of 1 x 10(10) and 4 x 10(9) UFC/ml for 0.5 % of bile salts and 1.2 % of bovine bile, respectively; of 3.5 x 10(13) and 3.4 x 10(13) UFC/ml for 38 and 45 °C, respectively. The HPLC determined the peptides VAR-TIR-VAR and lactic acid (83.11 %). The fermentation kinetics determined the exponential phase at 14:24 h with a value of 77 x 10(10) UFC/ml, pH values of 4.284, 2.33 mg/ml sugar, 1.44 mg/ml protein and acidity of 0.79 %. It was found that S. aureus and S. epidermidis were sensitive to all antibiotics. The pathogenic bacteria were resistant to the lactic strain, but S. epidermidis was sensitive to the supernatant of L. lactis. The conclusion is that Lactobacillus lactis showed adequate growth capacity, good fermentation parameters and inhibitory effect in strains of S. aureus and S. epidermidis in in vitro conditions.

Avaliou-se o processo fermentativo e a inibição in vitro de L. lactis em Staphylococcus aureus e Staphylococcus epidermidis. Avaliou-se o crescimento de L. lactis a três pH (2,5, 4,5 e 7), sais biliares (0,5, 1 e 2 %), bílis bovina (1 e 1,2 %) e duas temperaturas (38 e 45 °C). Determinaram-se peptídeos e ácidos orgânicos em sobrenadante de L. lactis por HPLC. Fez-se cinética de fermentação, avaliando: pH, açúcar total, proteína e ácido láctico. Realizou-se antibiograma de dicloxacilina, cefepime, penicilina e cefalotina. Definiu-se a inibição de L. lactis e seu sobrenadante em cepas patógenas. o melhor crescimento foi a pH de 2,5 (3 x 10(12) UFC/ ml); de 1 x 10(10) e 4 x 10(9) UFC/ml para 0,5 % de sais biliares e 1,2 % de bílis bovina, respectivamente; de 3,5 x 10(13) e 3,4 x 10(13) UFC/ml para 38 e 45 °C, respectivamente. O HPLC determinou os peptídeos VAR-TIR-VAR e ácido láctico (83,11 %). A cinética de fermentação determinou a fase exponencial a 14h: 24m com um valor 77 x 10(10) UFC/ml, valores de pH de 4,284, açúcar 2,33 mg/ml, proteína 1,44 mg/ml e acidez de 0,79 %. Constatou-se que S. aureus e S. epidermidis foram sensíveis a todos os antibióticos. As bactérias patógenas foram resistentes à cepa láctica, mas S. epidermidis foi sensível ao sobrenadante de L. lactis. Conclui-se que Lactobacillus lactis mostrou uma adequada capacidade de crescimento, bons parâmetros de fermentação e efeito inibitório em cepas de S. aureus e S. epidermidis em condições in vitro.

Isolation and identification of cyclic lipopeptides from Paenibacillus ehimensis, strain IB-X-b.

Antifungal lipopeptides produced by an antagonistic bacterium, Paenibacillus ehimensis strain IB-X-b, were purified and analyzed. The acetone extract of the culture supernatant contained an antifungal amphiphilic fraction stainable with ninhydrin on thin layer chromatography. The fraction was further purified with water-methanol extraction followed by a chromatography on a C18-support. The analysis with LC-MS showed presence of two main series of homologous compounds, family of depsipeptides containing a hydroxy fatty acid, three 2,4-diaminobutyric acid (Dab) residues, five hydrophobic amino acids and one Ser/Thr residue, and cyclic lipopeptides of bacillomycin L and fengycin/plipastatin/agrastatin families. The prevailing compounds in this group are bacillomycin L-C15, fengycin/plipastatin A-C16 together with their homologues responsible for the majority of fungal growth inhibition by P. ehimensis IB-X-b.

New targets in the search for preventive and therapeutic agents for botulism.

Botulism is a severe neuroparalytic disease resulting from exposure to one of the most poisonous toxins to humans. Because of this high potency and the use of toxins as biological weapons, botulism is a public health concern and each case represents an emergency. Current therapy involves respiratory supportive care and anti-toxins administration. As a preventive measure, vaccination against toxins represents an effective strategy but is undesirable due the rarity of botulism and the effectiveness of toxins in treating several neuromuscular disorders. This paper summarizes the current issues in botulism treatment and prevention, highlighting the challenge for future researches.

Microbes versus microbes: control of pathogens in the food chain.

Foodborne illness continues as a considerable threat to public health. Despite improved hygiene management systems and increased regulation, pathogenic bacteria still contaminate food, causing sporadic cases of illness and disease outbreaks worldwide. For many centuries, microbial antagonism has been used in food processing to improve food safety. An understanding of the mode of action of this microbial antagonism has been gained in recent years and potential applications in food and feed safety are now being explored. This review focuses on the potential opportunities presented, and the limitations, of using microbial antagonism as a biocontrol mechanism to reduce contamination along the food chain; including animal feed as its first link. © 2014 Society of Chemical Industry.

Diversity and antibacterial activity of bacteria cultured from Mediterranean Axinella spp. sponges.

AIMS: Evaluation of the diversity and antibacterial activity of bacteria cultivated from Mediterranean Axinella sponges and investigating the influence of culture conditions on antibacterial activity profiles of sponge bacteria. METHODS AND RESULTS: Based on 16S rRNA gene sequence analysis, the 259 bacteria isolated from the three Mediterranean Axinella sponges A. cannabina, A. verrucosa and A. polypoides belonged to 41 genera from the four phyla Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria and included five potential newly cultured genera. In antagonistic streak assays, 87 isolates (34%) from 13 genera showed antibacterial activity towards at least one of the 10 environmental and laboratory test bacteria. The extracts and filtrates of 22 isolates grown under three different culture conditions were less often active as the isolates in the corresponding antagonistic streak assays. Changes in antibacterial activity profiles were isolate- and culture condition-specific. CONCLUSIONS: Axinella sponges are a good source to cultivate phylogenetic diverse and hitherto novel bacteria, many of which with antibacterial activity. Analysis of induced antibacterial activities might enhance the role of sponge bacteria in efforts to isolate new antibiotics in the future. SIGNIFICANCE AND IMPACT OF THE STUDY: This study was the first to investigate the diversity and antibacterial activity of bacteria isolated from A. cannabina and A. verrucosa. It highlights the potential importance of induced activity and the need for employing multiple culture conditions in antibacterial screening assays of sponge-associated bacteria.