Purification, Characterization, and Assessment of Antimicrobial Activity and Toxicity of Portulaca elatior Leaf Lectin (PeLL).

Lectins are carbohydrate-binding proteins with several bioactivities, including antimicrobial properties. Portulaca elatior is a species found at Brazilian Caatinga and data on the biochemical composition of this plant are scarce. The present work describes the purification of P. elatior leaf lectin (PeLL) as well as the assessment of its antimicrobial activity and toxicity. PeLL, isolated by chromatography on a chitin column, had native liquid charge and subunit composition evaluated by electrophoresis. Hemagglutinating activity (HA) of PeLL was determined in the presence of carbohydrates or divalent cations, as well as after heating and incubation at different pH values. Changes in the lectin conformation were monitored by evaluating intrinsic tryptophan fluorescence and using the extrinsic probe bis-ANS. Antimicrobial activity was evaluated against Pectobacterium strains and Candida species. The minimal inhibitory (MIC), bactericidal (MBC), and fungicidal (MFC) concentrations were determined. Finally, PeLL was evaluated for in vitro hemolytic activity in human erythrocytes and in vivo acute toxicity in mice (5 and 10 mg/kg b.w. per os). PeLL (pI 5.4; 20 kDa) had its HA was inhibited by mannose, galactose, Ca2+, Mg2+, and Mn2+. PeLL HA was resistant to heating at 100 °C, although conformational changes were detected. PeLL was more active in the acidic pH range, in which no conformational changes were observed. The lectin presented MIC and MBC of 0.185 and 0.74 µg/mL for all Pectobacterium strains, respectively; MIC of 1.48 µg/mL for C. albicans, C. tropicalis, and C. krusei; MIC and MFC of 0.74 and 2.96 µg/mL for C. parapsilosis. No hemolytic activity or signs of acute toxicity were observed in the mice. In conclusion, a new, low-toxic, and thermostable lectin was isolated from P. elatior leaves, being the first plant compound to show antibacterial activity against Pectobacterium.

Development of the prickly pear cactus Opuntia stricta (Haw.) Haw. (Cactaceae) in vitro in response to the replacement of potassium nitrate for a commercial kno 3 fertilizer / Desenvolvimento da palma Opuntia stricta (Haw.) Haw. (Cactaceae) in vitro em resposta à substituição de nitrato de potássio (P.A.) por fertilizante comercial KNO 3

ABSTRACT: In micropropagation, potassium nitrate (KNO3), an ACS reagent grade chemical, used in the preparation of growing mediums is expensive and its procurement depends on bureaucratic procedures, as it is controlled by the Brazilian Army. This research to assessed the effect of replacing the ACS KNO3 for a commercially available fertilizer (KNO3- based) on the micropropagation of the prickly pear cactus (Opuntia stricta (Haw.) Haw. cv. Elephant Ear. Treatments used six different fertilizer concentrations (0, 0.5, 1, 1.5, 2 and 2.5 g L-1) and a control consisting of 1.9 g L-1 KNO3, as shown in the MS salts. The survival, size and number of sprouts and the value of fresh biomass were evaluated. After seedling acclimation, we assessed the survival, number of sprouts, length, and number of roots, racket formation, average fresh biomass mass, macronutrient absorption and morphological changes of the seedlings. Explants inoculated with fertilizers at concentrations of 0.0; 2.0 and 2.5 g L-¹ did not grow. The response of explants at concentrations of 0.5 and 1.5 g L-1 of the fertilizer were the same as those developed in a KNO3 medium, and at a concentration of 1.0 g L-1, in all variables, the means were higher than those of the control medium. Therefore, it showed the feasibility of using fertilizers in the in vitro cultivation of the prickly pear cactus, which may remove bureaucratic barriers and reduce product costs by 99.12%.

RESUMO: Na micropropagação, o nitrato de potássio (KNO3), reagente puro para análise (P.A.), utilizado no preparo dos meios de cultura, possui custo elevado e a sua aquisição depende de trâmites burocráticos, por se tratar de substância controlada pelo Exército Brasileiro. O objetivo deste trabalho foi avaliar o efeito da substituição do KNO3 P.A. por fertilizante comercial (com fonte de KNO3), encontrado livremente no comércio, na micropropagação de palma (Opuntia stricta (Haw.) Haw. cv Orelha de Elefante. Os tratamentos foram de seis concentrações do fertilizante (0; 0,5; 1; 1,5; 2 e 2,5 g L-1) e um controle constituído de 1,9 g L-1 de reagente KNO3, conforme mostrado nos sais MS. Avaliou-se a sobrevivência, tamanho e número de brotações do explante, e o valor da biomassa fresca. Após a aclimatização das mudas avaliou-se a sobrevivência, número de brotações, comprimento da parte aérea, número de raízes, formação da raquete, massa média da biomassa fresca, absorção de macronutrientes e alterações morfológicas das mudas. Os explantes inoculados em meio com fertilizantes nas concentrações de 0,0; 2,0 e 2,5 g L-¹ não se desenvolveram. A resposta dos explantes nas concentrações de 0,5 e 1,5 g L-1 do fertilizante foram iguais aos desenvolvidos em meio contendo KNO3, e na concentração de 1,0 g L-1, em todas as variáveis, as médias foram superiores em relação as do controle. Dessa forma, constatou-se a viabilidade do uso do fertilizante no cultivo in vitro da palma, o que propiciou a eliminação dos entraves burocráticos e redução no custo de 99,12% na compra do produto.

Efficacy of essential oils in the management of soft rot caused by Pectobacterium aroidearum in lettuce

Lettuce is susceptible to several diseases, especially soft rot caused by bacteria of the genus Pectobacterium. Due to the adaptability of this pathogen and the lack of disease control registered for the crop, the objective of this work was to evaluate the effects of essential oils in the management of soft rot caused by P. aroidearum in lettuce. The study was developed at the Universidade do Estado da Bahia, Juazeiro, BA, Brazil, and the essential oils (EOs) of orange, bergamot, lemongrass, palmarosa, citronella, cloves, tea tree, rosemary, sage, and ginger were used in concentrations of 0.25; 0.5; 0.75 and 1.0% to assess the in vitro growth inhibition of the bacterium. Subsequently, the curative effects of the disease were evaluated by applying the EOs that obtained the best results in vitro in lettuce plants of the susceptible variety "Mônica". The treatments were applied, via spraying, 12 hours after inoculation using the bite method with bacterial suspension. The best in vivo treatment was selected to assess its preventive and curative activity, as well as to find the ideal concentration for reducing epidemiological variables and chromatographic characterization. The EOs of palmarosa, sage, citronella, lemongrass, and cloves (0.25%), and that of sage (0.75%), inhibited bacterial growth in vitro. The EO of salvia showed the best results in vivo, inhibiting the growth of the disease in concentrations of 0.50 and 0.75%, so it was selected for the preventive and curative control tests alone. The preventive treatment was not efficient for the management of soft rot in lettuce, however, from the regression analysis, a concentration of 0.64% of the salvia EO was found as a potential for curative control of this bacteriosis, as it reduces the incidence and severity of the disease. Linalyl acetate and linalool were found in higher concentrations in the chromatographic analysis. These components, probably, conferred the bactericidal capacity of the EO of sage, being potential for the use in the control of P. aroidearum in lettuce.

Essential oils in the management of soft rot of kale in the brazilian semiarid region / Óleos essenciais no manejo da podridão mole em couve no semiárido brasileiro

The aim of this study was to analyze the effect of essential oils on the control of soft rot of kale. Clove essential oil at 0.25%, lemongrass and palmarosa essential oils at 0.5%, melaleuca and orange essential oils at 0.75%, bergamot, rosemary, sage and ginger essential oils at 1% were evaluated for the in vitro inhibition of Pectobacterium carotovorum subsp. brasiliensis (Pcb) and control of soft rot of kale, sprayed 72 hours before or seven hours after inoculation. Clove, citronella, bergamot, rosemary, palmarosa, sage, melaleuca, and lemongrass oils completely inhibited the growth of Pcb. Lemongrass oil (0.5%) caused 0% of disease incidence (INC), providing 100% of disease control in both periods of inoculation. Clove oil (0.25%) showed a lower INC (25%) when applied after inoculation, providing a control percentage of 71.42%. The lemongrass and clove essential oils were analyzed by GC/FID (Gas Chromatography ­ Flame Ionization Detector) and by GC/MS (Gas Chromatography /Mass Spectrometer). The major components were eugenol (91,9%) for clove oil and citral, isometric mixture of neral (34,1%) and geranial (42,9%) for lemongrass oil. The Minimum inhibitory concentration (MIC) of lemongrass, clove oils and their major components (citral and eugenol, respectively) was determined by using a broth macrodilution technique, as well as they were evaluated at different concentrations on the control of soft rot of kale, sprayed according descriptions above. The MIC was 0.03125% for citral, and 0.0625 and 0.125% for lemongrass and clove oils, respectively. Eugenol didn't show MIC. Lemongrass oil at 0.125% (post-inoculation) and citral at 0.125% (pre and post-inoculation) provided the highest percentages of disease control (33.33, 50, and 100%, respectively). Clove oil at 0.125% (post-inoculation) showed better effectiveness than eugenol (0.25%), providing a percentage of disease control of 16.67%. Lemongrass and clove essential oils were the most effective in control of soft rot of kale, suggesting that these oils have a potential to be used as antibacterial agents.

O objetivo do estudo foi avaliar o efeito de óleos essenciais no controle da podridão mole em couve. Os óleos essenciais de cravo a 0,25%, capim-limão e palmarosa a 0,5%, citronela, melaleuca e laranja a 0,75%, bergamota, alecrim, sálvia e gengibre a 1% foram avaliados na inibição in vitro de Pectobacterium carotovorum subsp. brasiliensis (Pcb) e controle da podridão mole em couve, pulverizados 72 horas antes ou sete horas após a inoculação. Os óleos essenciais de cravo, citronela, bergamota, alecrim, palmarosa, sálvia, melaleuca e capim-limão inibiram completamente o crescimento de Pcb. O óleo de capimlimão (0,5%) promoveu 0% de incidência (INC) da doença (percentual de controle de 100%), em ambos os períodos de inoculação. O óleo de cravo (0,25%) proporcionou menor INC (25%) quando aplicado após inoculação (percentual de controle de 71,42%). Os óleos essenciais de capim-limão e cravo foram analisados por GC/FID (cromatografia gasosa/detector por ionização de chama) e por GC/MS (cromatografia gasosa/ espectometria de massas). Os componentes majoritários foram eugenol (91,9%) no óleo de cravo e citral (neral34,1% e geranial- 42,9%) no óleo de capim-limão. A concentração inibitória mínima (CIM) dos óleos essenciais de capim-limão e cravo e de seus componentes majoritários (citral e eugenol, respectivamente) foi determinada por meio da técnica de macrodiluição em caldo, bem como foram avaliados, em diferentes concentrações, no controle da podridão mole em couve, pulverizados conforme descrito acima. A concentração inibitória mínima (CIM) foi de 0,03125% para o citral, e de 0,0625 e 0,125% para os óleos de capim-limão e cravo, respectivamente. O eugenol não apresentou CIM. O óleo de capim-limão a 0,125% (pós-inoculação) e o citral (0,125%), em ambos os períodos de inoculação, proporcionaram os maiores percentuais de controle (33,33; 50 e 100%, respectivamente). O óleo de cravo a 0,125% (pós-inoculação) mostrou maior eficiência que o eugenol (0,25%), promovendo um percentual de controle de 16,67%. Os óleos essenciais de capim-limão e cravo destacaram-se na eficiência de controle da podridão mole em couve, sugerindo que esses óleos têm potencial para serem utilizados como agentes antibacterianos.

Meio semi-seletivo para isolamento de Xanthomonas campestris pv. viticola / Semi-selective medium for isolation of Xanthomonas campestris pv. viticola

O cancro bacteriano causado por Xanthomonas campestris pv. viticola é a fitobacteriose mais importante da videira no Submédio São Francisco. O isolamento de X. campestris pv. viticola de tecidos vegetais infectados é dificultado pela presença de contaminantes bacterianos, entre os quais Microbacterium barkeri. Objetivando-se a formulação de meio de cultura semi-seletivo, 22 isolados de X. campestris pv. viticola foram testados com relação a 30 antibióticos. O meio semi-seletivo NYDAM (extrato de carne 3, peptona 5, glicose 10, extrato de levedura 5, ágar 18 e ampicilina 0,1 em g L-1) inibiu M. barkeri e bactérias fitopatogênicas podendo ser utilizado para isolar X. campestris pv. viticola de hospedeiros com infecção natural em campo.

Controle biológico da murcha bacteriana do tomateiro, por Pseudomonas spp. fluorescentes / Biological control of bacterial wilt of tomato by fluorescent Pseudomonas spp

Esta revisão bibliográfica teve como objetivo avaliar o potencial de antagonismo de espécies de Pseudomonas fluorescentes a Pseudomonas solanacearum, agente causal da murcha bacteriana do tomateiro. Devido a dificuldade encontrada nas estratégias utilizadas para o controle da Murcha Bacteriana por meio de métodos convencionais, alguns outros tem sido estudados, como o uso de microrganismos benéficos. As rizobactérias vem proporcionando solução viável a algumas doenças consideradas de difícil manejo. Dentre os mecanismos que tem sido sugeridos para o controle microbiano de patógenos de plantas, através do uso de rizobactérias fluorescentes, citamse produção de antibióticos, bactericinas, enzimas titicas, competição por espaço e nutrientes. Possuem uma alta capacidade de colonização e sobrevivência no hospedeiro, falares que são importantes no estabelecimento e introdução de microrganismos na rizosfera. Estas bactérias podem também incitar um aumento no desenvolvimento e na produção do hospedeiro, sendo denominadas de rizobactérias promotoras de crescimento de plantas.

This literature review has the objetive of evaluating the antagonism potential of species of florescem Pseudomonas to Pseudomonas solanacearum which is the causal agent of bacterial wilt on the tomato crop. Due to serious limitation in the ejficiency of conventional methods of contrai, other strategies have been siudied, such as the use o/beneficiai microrganisms. Rhizobacteria have shown to be a viable alternative in the contrai of some diseases of difficult managmenl. Among the mechanisms which have been suggestedfor microbian control of plantpathogens with fluorescent rhizobacteria, can be used antibiotic production, bacteriocin, uric emimes and competition for colonization and survival capacity on the host. The survival capacity is very important in the introduction and stablishment ofthe microrganisms in the rhizosphere. These bacteria can aiso increse the development and yield of the host and can be calledplant growth promete rhizobacteria.