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1.
J Appl Microbiol ; 135(5)2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38632051

RESUMO

AIMS: We aimed to develop an effective bacterial combination that can combat Fusarium oxysporum infection in watermelon using in vitro and pot experiments. METHODS AND RESULTS: In total, 53 strains of Bacillus and 4 strains of Pseudomonas were screened. Pseudomonas strains P3 and P4 and Bacillus strains XY-2-3, XY-13, and GJ-1-15 exhibited good antagonistic effects against F. oxysporum. P3 and P4 were identified as Pseudomonas chlororaphis and Pseudomonas fluorescens, respectively. XY-2-3 and GJ-1-15 were identified as B. velezensis, and XY-13 was identified as Bacillus amyloliquefaciens. The three Bacillus strains were antifungal, promoted the growth of watermelon seedlings and had genes to synthesize antagonistic metabolites such as bacilysin, surfactin, yndj, fengycin, iturin, and bacillomycin D. Combinations of Bacillus and Pseudomonas strains, namely, XY-2-3 + P4, GJ-1-15 + P4, XY-13 + P3, and XY-13 + P4, exhibited a good compatibility. These four combinations exhibited antagonistic effects against 11 pathogenic fungi, including various strains of F. oxysporum, Fusarium solani, and Rhizoctonia. Inoculation of these bacterial combinations significantly reduced the incidence of Fusarium wilt in watermelon, promoted plant growth, and improved soil nutrient availability. XY-13 + P4 was the most effective combination against Fusarium wilt in watermelon with the inhibition rate of 78.17%. The number of leaves; aboveground fresh and dry weights; chlorophyll, soil total nitrogen, and soil available phosphorus content increased by 26.8%, 72.12%, 60.47%, 16.97%, 20.16%, and 16.50%, respectively, after XY-13 + P4 inoculation compared with the uninoculated control. Moreover, total root length, root surface area, and root volume of watermelon seedlings were the highest after XY-13 + P3 inoculation, exhibiting increases by 265.83%, 316.79%, and 390.99%, respectively, compared with the uninoculated control. CONCLUSIONS: XY-13 + P4 was the best bacterial combination for controlling Fusarium wilt in watermelon, promoting the growth of watermelon seedlings, and improving soil nutrient availability.


Assuntos
Bacillus , Citrullus , Resistência à Doença , Fusarium , Doenças das Plantas , Pseudomonas , Fusarium/crescimento & desenvolvimento , Citrullus/microbiologia , Citrullus/crescimento & desenvolvimento , Doenças das Plantas/microbiologia , Doenças das Plantas/prevenção & controle , Bacillus/fisiologia , Bacillus/genética , Bacillus/crescimento & desenvolvimento , Pseudomonas/crescimento & desenvolvimento , Pseudomonas/fisiologia , Antibiose , Pseudomonas fluorescens/crescimento & desenvolvimento , Plântula/crescimento & desenvolvimento , Plântula/microbiologia , Antifúngicos/farmacologia
2.
Braz. j. microbiol ; 48(2): 352-358, April.-June 2017. tab, graf
Artigo em Inglês | LILACS | ID: biblio-839386

RESUMO

Abstract Meat is one of the most perishable foods owing to its nutrient availability, high water activity, and pH around 5.6. These properties are highly conducive for microbial growth. Fresh meat, when exposed to oxygen, is subjected to the action of aerobic psychrotrophic, proteolytic, and lipolytic spoilage microorganisms, such as Pseudomonas spp. The spoilage results in the appearance of slime and off-flavor in food. In order to predict the growth of Pseudomonas fluorescens in fresh meat at different pH values, stored under refrigeration, and temperature abuse, microbial mathematical modeling was applied. The primary Baranyi and Roberts and the modified Gompertz models were fitted to the experimental data to obtain the growth parameters. The Ratkowsky extended model was used to determine the effect of pH and temperature on the growth parameter µmax. The program DMFit 3.0 was used for model adjustment and fitting. The experimental data showed good fit for both the models tested, and the primary and secondary models based on the Baranyi and Roberts models showed better validation. Thus, these models can be applied to predict the growth of P. fluorescens under the conditions tested.


Assuntos
Temperatura , Pseudomonas fluorescens/crescimento & desenvolvimento , Microbiologia de Alimentos/métodos , Concentração de Íons de Hidrogênio , Modelos Teóricos , Pseudomonas fluorescens/efeitos dos fármacos , Pseudomonas fluorescens/efeitos da radiação , Aerobiose , Carne/microbiologia
3.
Braz. j. microbiol ; 44(2): 539-549, 2013. ilus, graf, tab
Artigo em Inglês | LILACS | ID: lil-688587

RESUMO

The present study aimed at developing a strategy to improve the volumetric production of PHAs by Pseudomonas fluorescens S48 using waste frying oil (WFO) as the sole carbon source. For this purpose, several cultivations were set up to steadily improve nutrients supply to attain high cell density and high biopolymer productivity. The production of PHAs was examined in a 14 L bioreactor as one-stage batch, two-stage batch, and high-cell-density fed-batch cultures. The highest value of polymer content in one-stage bioreactor was obtained after 60 h (33.7%). Whereas, the two-stage batch culture increased the polymer content to 50.1% after 54 h. High-cell-density (0.64 g/L) at continuous feeding rate 0.55 mL/l/h of WFO recorded the highest polymer content after 54 h (55.34%). Semi-scale application (10 L working volume) increased the polymer content in one-stage batch, two-stage batch and high cell density fed-batch cultures by about 12.3%, 5.8% and 11.3%, respectively, as compared with that obtained in 2 L fermentation culture. Six different methods for biopolymer extraction were done to investigate their efficiency for optimum polymer recovery. The maximum efficiency of solvent recovery of PHA was attained by chloroform-hypochlorite dispersion extraction. Gas chromatography (GC) analysis of biopolymer produced by Pseudomonas fluorescens S48 indicated that it solely composed of 3-hydrobutyric acid (98.7%). A bioplastic film was prepared from the obtained PHB. The isolate studied shares the same identical sequence, which is nearly the complete 16S rRNA gene. The identity of this sequence to the closest pseudomonads strains is about 98-99%. It was probably closely related to support another meaningful parsiomony analysis and construction of a phylogenetic tree. The isolate is so close to Egyptian strain named EG 639838.


Assuntos
Óleos/metabolismo , Poli-Hidroxialcanoatos/metabolismo , Pseudomonas fluorescens/metabolismo , Reatores Biológicos/microbiologia , Cromatografia Gasosa , Análise por Conglomerados , Carbono/metabolismo , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Filogenia , Poli-Hidroxialcanoatos/química , Pseudomonas fluorescens/classificação , Pseudomonas fluorescens/genética , Pseudomonas fluorescens/crescimento & desenvolvimento , /genética , Análise de Sequência de DNA , Gerenciamento de Resíduos
4.
Braz. j. microbiol ; 43(4): 1406-1413, Oct.-Dec. 2012. graf
Artigo em Inglês | LILACS | ID: lil-665826

RESUMO

The purpose of this study was to investigate the effect of different levels of Pseudomonas fluorescens (10² and 10(6)log10 cfu/ml)and Lactobacillus plantarum (10² and 10(4)log10 cfu/ml)on the growth of Escherichia coli O157:H7 on beef loins. Beef loins inoculated with E. coli O157:H7 and P. fluorescens were aerobically stored for 7 days at 4 ºC, while those inoculated with E. coli O157:H7 and L. plantarum were vacuum packaged and stored for 8 weeks at 4 ºC. Aerobic Plate Counts (APC), E. coli O157:H7 and either P. fluorescens or L. plantarum counts were determined at different storage intervals. For the aerobically packaged beef loins, E. coli O157:H7 was detected throughout the 7 day storage period regardless of the P. fluorescens level in the inoculum. For the vacuum packaged beef loins, similar inoculum levels of E. coli O157:H7 and L. plantarum allowed E. coli O157:H7 to survive until week 5 of storage, while a higher inoculum level of L. plantarum inhibited E. coli O157:H7 from week 3. Once fresh beef has been contaminated with E. coli O157:H7, the level of P. fluorescens in the background flora does not inhibit its survival and growth. However, under vacuum storage, the application of L. plantarum as a biopreservative inhibits the survival of E. coli O157:H7 on beef. The higher the level of L. plantarum in the system, the earlier the onset of the inhibition. Farmers and abattoirs have to strengthen preventive strategies to eliminate contamination of beef carcasses with E. coli O157:H7.


Assuntos
Animais , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/isolamento & purificação , Análise de Alimentos , Conservação de Alimentos , Lactobacillus plantarum/crescimento & desenvolvimento , Lactobacillus plantarum/isolamento & purificação , Embalagem de Produtos , Pseudomonas fluorescens/crescimento & desenvolvimento , Pseudomonas fluorescens/isolamento & purificação , Microbiologia de Alimentos , Métodos , Suínos
5.
Braz. j. microbiol ; 41(1): 91-96, Jan.-Mar. 2010. graf, tab
Artigo em Inglês | LILACS | ID: lil-531739

RESUMO

The proteolytic activity of Pseudomonas fluorescens 07A was investigated, and was optimal on tryptone-calcium medium. N-acyl-homoserine lactones (AHLs) were not detected on supernatants of late-exponential and stationary-phase culture broths. Synthetic AHLs or bacterial cell extracts added to the medium did not influence growth or proteolytic activity suggesting that quorum sensing might not regulate protease production in this strain.


Assuntos
Lactonas/análise , Leite , Peptídeo Hidrolases/análise , Pseudomonas fluorescens/crescimento & desenvolvimento , Pseudomonas fluorescens/isolamento & purificação , Percepção de Quorum , Ativação Enzimática , Amostras de Alimentos , Métodos , Métodos
7.
Rev. argent. microbiol ; 36(1): 6-15, Jan.-Mar. 2004. ilus, tab
Artigo em Espanhol | LILACS | ID: lil-634454

RESUMO

Las bacterias responden a los cambios ambientales modificando su composición, para evitar el daño que dichos cambios podrían ejercer. Una de las modificaciones más importantes es la variación de la composición de los ácidos grasos de las membranas celulares, que le permite mantener la homeoviscosidad ante situaciones de estrés. Trabajos previos han estudiado la acción de la temperatura, presión hidrostática y diferentes solventes sobre cepas de Pseudomonas putida. En este trabajo se estudió la acción conjunta de la temperatura y la salinidad sobre la composición de ácidos grasos de membranas celulares de Pseudomonas fluorescens GNP-OHP-3, una cepa bacteriana aislada de un hábitat contaminado con petróleo. Pseudomonas fluorescens GNP-OHP-3 respondió a las variaciones de temperatura modificando los ácidos grasos de sus membranas de manera similar a lo descripto en otros integrantes de su género: ante el aumento de temperatura se observó un incremento de ácidos grasos saturados y una disminución de los ácidos grasos insaturados. En el rango de concentraciones salinas ensayadas las variaciones de los ácidos grasos mayoritarios fueron en general erráticas. La respuesta de los ácidos grasos ciclo propano pudo expresarse con ecuaciones matemáticas que permitieron predecir el porcentaje de estos ácidos en relación a la concentración de cloruro de sodio.


The bacteria respond to environmental changes modifying their composition. One of the most important modifications is the variation on fatty acid composition of cellular membranes to maintain the homeoviscosity. The action of temperature, hydrostatic pressure and solvents on Pseudomonas putida has been thoroughly studied. In this paper, the combined action of the temperature and salinity on fatty acid composition of cellular membranes of Pseudomonas fluorescens GNP-OHP-3, a bacterial strain isolated from a petroleum contaminated habitat, was studied. The modifications in the fatty acid composition of Pseudomonas fluorescens GNP-OHP-3 membrane were similar to those described for other members of Pseudomonas: an increase in saturated fatty acids and a decrease in unsaturated fatty acids were observed with the increase of the temperature. Variations of main fatty acids were in general erratic in the range of assayed saline concentrations. The variation of cycle propane fatty acids could be expressed with mathematic equations that allowed to predict their percentage in relation to sodium chloride concentration.


Assuntos
Membrana Celular/química , Ácidos Graxos/análise , Pseudomonas fluorescens/química , Cloreto de Sódio/análise , Temperatura , Adaptação Fisiológica , Membrana Celular/efeitos dos fármacos , Meios de Cultura/farmacologia , Ciclopropanos/análise , Relação Dose-Resposta a Droga , Ácidos Graxos Insaturados/análise , Lipídeos de Membrana/análise , Concentração Osmolar , Pseudomonas fluorescens/efeitos dos fármacos , Pseudomonas fluorescens/crescimento & desenvolvimento , Pseudomonas fluorescens/metabolismo , Especificidade por Substrato , Cloreto de Sódio/farmacologia
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