Sustainable agriculture requires the recruitment of bacterial agents to control diverse plant diseases such as bacterial endophytes. Bacterial endophytes colonize and inhabit internal plant tissues ...without causing any apparent damage. Within the plant, these bacteria exert multiple beneficiary effects, including direct stimulation of plant growth by the action of phytohormones or the production of metabolites. However, bacterial endophytes also protect their plant host through biocontrol pathogens or by inducing plant innate immune system. The present work makes a systematic and in-depth review on the current state of endophytic bacterial diversity, their plant colonization strategies, and their potential roles as protective agents against plant diseases during pre- and post-harvest stages of crop productivity. In addition, an exploration of their beneficial effects on sustainable agriculture by reducing/eliminating the use of toxic agrochemicals was conducted. Finally, we propose diverse effective strategies for the application of endophytic bacteria as biological agents during both pre- and post-harvest stages, with the aim of protecting crop plants and their agricultural products.
Plants and their microbiomes, including plant growth-promoting bacteria (PGPB), can work as a team to reduce the adverse effects of different types of stress, including drought, heat, cold, and heavy ...metals stresses, as well as salinity in soils. These abiotic stresses are reviewed here, with an emphasis on salinity and its negative consequences on crops, due to their wide presence in cultivable soils around the world. Likewise, the factors that stimulate the salinity of soils and their impact on microbial diversity and plant physiology were also analyzed. In addition, the saline soils that exist in Mexico were analyzed as a case study. We also made some proposals for a more extensive use of bacterial bioinoculants in agriculture, particularly in developing countries. Finally, PGPB are highly relevant and extremely helpful in counteracting the toxic effects of soil salinity and improving crop growth and production; therefore, their use should be intensively promoted.
Fungal pathogens are the main causal agents of postharvest diseases of fruits and vegetables. To prevent this problem and avoid the use of harmful chemical fungicides, safer and greener alternatives ...have been sought. One of these alternatives is the use of plant-growth-promoting bacteria (PGPB). In this study, we evaluated in vitro four well-known PGPB strains (Pseudomonas fluorescens UM270, Bacillus toyonensis COPE52, Bacillus sp. E25, and Bacillus thuringiensis CR71) for their biocontrol potential against nineteen postharvest fungal pathogens. In vivo assays were also performed, and bacterial cells were inoculated on harvested strawberries and grapes with the pathogens Botrytis cinerea, Alternaria alternata, and Fusarium brachygibbosum to evaluate loss of firmness and disease incidence. Our results show that the four strains antagonized fungi in direct and indirect confrontation assays. Stronger antagonism was observed by the action of diffusible metabolites (DMs) compared to volatile organic compound (VOC) activity. All PGPB significantly improved the fruit firmness and reduced disease incidence caused by the fungal pathogens tested. However, strain UM270 showed excellent biocontrol activity, reducing the disease incidence of Fusarium brachygibbosum, Botrytis cinerea, and Alternaria alternata on strawberry fruits by 60%, 55%, and 65%, respectively. Diffusible antifungals and VOCs such as 2,4-diacetyl phloroglucinol, siderophores, auxins, fengycins, and N, N-dimethyl-hexadecyl amine, among others, might be responsible for the beneficial activities observed. These results suggest excellent biocontrol activities to inhibit postharvest pathogenic fungi and improve harvested fruit quality.
is one of the main microorganisms that causes bovine mastitis, and its well-known virulence characteristics and interactions with the environment are used to aid the design of more efficient ...therapies.
To determine whether the virulence traits, such as antibiotic resistance and biofilm-forming and internalization abilities, of
isolated from bovine mastitis are related to dairy production system types.
The study was performed in the Mexican states of Guanajuato and Michoacan. Semi-intensive dairy farms (SIDFs) and family dairy farms (FDFs) (454 and 363 cows, respectively) were included. The 194 milk samples from mastitis affected quarters were collected and 92 strains of
were isolated and identified by biochemical and molecular tests. Antibiotic resistance, biofilm and internalization assays were performed on 30 randomly selected isolated strains to determine virulence traits, and these strains were equally allocated to the 2 dairy production systems.
All 30 selected strains displayed a high degree of resistance (50%-91.7%) to the antibiotics tested, but no significant difference was found between SIDF and FDF isolates.
strains from SIDFs had an average biofilm forming capacity of up to 36% (18.9%-53.1%), while
strains from FDFs registered an average of up to 53% (31.5%-77.8%) (
> 0.05). Internalization assays revealed a higher frequency of internalization capacity for strains isolated from FDFs (33.3%) than for those isolated from SIDFs (6.7%) (
> 0.05).
gen was detected in 46.6% of FDF strains and 33.3% of SIDF strains, and this difference was significant (
< 0.05).
Our findings show that the virulence traits of
isolates analyzed in this study, depend significantly on several factors, such as phenotype, genotype, and environmental conditions, which are significantly related to dairy production system type and daily management practices.
Potato (
Solanum tuberosum
L.) is a crop susceptible to infection by microorganisms such as
Fusarium
spp., which are usually controlled with chemical fungicides. However, these fungicides can cause ...adverse effects on human and ecosystem health. Thus, the search for non-toxic alternatives is essential to reduce the negative impact of fungicides. This study aimed to identify fungal isolates from potato minitubers that were showing dry rot symptoms and evaluate whether the combination of chitosan (CH) and sodium octanoate (SO) exhibits higher antifungal effects in vitro and in vivo than the application of individual compounds. Five pathogens of the
Fusarium
genus were isolated. The most aggressive isolate (AUC-TZ-1) showed 98.67% identity with
F. sambucinum
, which was previously reported as a potato pathogen. The antifungal index (AI) of CH, SO and the CH + SO biocomposite showed that individual compounds and the biocomposite led to significant inhibition (
p
≤ 0.05) of the mycelial growth of the pathogen by 100%, 62.1% and 100%, respectively, at the highest concentrations tested (7.5, 0.49 and 7.5 + 0.49 mg/mL, respectively). However, only CH and CH + SO caused a significant reduction in the dry rot severity index of potato minitubers inoculated with
F. sambucinum
(AUC-TZ-1). The results suggest that these compounds could be used in postharvest potato dry rot control.
El 70% del agua a nivel mundial se destina principalmente para las actividades agrícolas. Sin embargo, debido al crecimiento descontrolado de los asentamientos urbanos se ha acentuado la escasez y ...contaminación de los cuerpos de agua superficiales, de tal forma que cada vez este líquido de buena calidad es más escaso para la agricultura. Uno de los principales contaminantes son las bacterias potencialmente patógenas resistentes a los antibióticos. Pseudomonas aeruginosa es una bacteria que se encuentra normalmente en el agua y suelo, es patógeno de animales y plantas. Esta bacteria se ha considerado un fenómeno de resistencia debido a la diversidad de mecanismos que posee, por lo cual representa un riesgo potencial para la población.Método: Se colectaron muestras de agua de uso agrícola, a partir de las cuales se aislaron e identificaron a nivel bioquímico y molecular P. aeruginosa. En estas bacterias se determinó la distribución de 6 genes de virulencia por PCR. Mediante ensayos de difusión en disco y microdilución se analizó la resistencia a 20 antibióticos. Además mediante ensayos de microdilución se determinó la resistencia a metales pesados.Resultados: Se identificaron a nivel bioquímico y molecular 46 aislados de P. aeruginosa, éstas son potencialmente patógenas ya que en ellas se detectó la presencia de los genes de virulencia algD y toxA (100%), lasB (97.8%), plcH (95.6%), plcN (91.3%) y exoS (89.1%). Dichas bacterias presentaron altos índices de resistencia a ampicilina, ceftriaxona, cloranfenicol, cefalotina, cefotaxima, nitrofurantoína, kanamicina, estreptomicina y tetraciclina. De igual forma fueron muy susceptibles a ceftazidima, gentamicina, imipenem, ticarcilina, aztreonam, levofloxacina, netilmicina y carbenicilina. Todas las bacterias fueron multirresistentes ya que toleraron entre 8 y 11 antibióticos. De acuerdo a los patrones de resistencia observados, las bacterias se clasificaron en 11 grupos. Mientras que para los metales pesados se presentaron altos niveles de tolerancia para Cu+2, Zn+2, Ba+2, Pb+2 y Se+4.Conclusión: Las P. aeruginosa aisladas de agua de uso agrícola en la zona de estudio son potencialmente patógenas debido a la presencia de genes de virulencia. Además presentaron altos índices de resistencia a antibióticos y tolerancia metales pesados.
The incidence of mastitis in dairy cattle is highest at the drying off period and parturition, which are characterized by high levels of the lactogenic hormone prolactin (PRL). One of the most ...frequently isolated contagious pathogens causing mastitis is
Staphylococcus aureus. However, the role of PRL on
S. aureus infection in mammary epithelium has not been studied. In this work we evaluated the effect of bovine PRL (bPRL) on
S. aureus internalization in a primary culture of bovine mammary epithelial cells (bMEC) and on the expression of cytokine and innate immune response genes. Our data show that 5
ng/mL bPRL enhances ∼3-fold the internalization of
S. aureus (ATCC 27543) into bMEC. By RT-PCR analysis, we showed that bPRL is able to up-regulate the expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS) mRNAs. However, bPRL together with
S. aureus did not modify the expression of TNF-α and iNOS mRNAs, while it down-regulated the expression of β-defensin and IL-1β mRNAs, as well as nitric oxide production, suggesting that infection and bPRL together can inhibit elements of the host immune response. To our knowledge, this is the first report that shows a role of bPRL during the internalization of
S. aureus into bMEC.
Fifteen (15) backyard farms were investigated to determine the antimicrobial susceptibility and invasion ability of
S. aureus
isolates from cows with subclinical mastitis in México. A total of 106 ...cows were sampled and 31
S. aureus
isolates were recovered.
S. aureus
isolates were resistant to penicillin class antibiotics and susceptible to gentamicin and cetyltrimethylammonium bromide. STA9 and STA13 isolates were resistant to erythromycin (MIC > 25 μg/ml) and lincomycin (STA13, MIC > 25 μg/ml; STA9, MIC > 100 μg/ml). STA9 isolate harbors the
erm
(B) and
msr
(A) genes, whereas STA13 isolate harbors the
erm
(C) gene. STA9 and STA13 isolates contains the
lnu
(A) gene. Only 5 isolates (STA11, STA13, STA14, STA15 and STA21) were able to internalize in bovine mammary epithelial cells. These results indicate that
S. aureus
isolates from dairy backyard farms showed differences in the antimicrobial susceptibility patterns and invasion ability in bovine mammary epithelial cells. This kind of evaluations should be performed in different dairy regions, since resistance patterns and isolate diversity vary on a per-region basis.
Introducción: Las plantas albergan un microbioma que incluye bacterias promotoras del crecimiento vegetal, las cuales pueden fungir como agentes biológicos que antagonizan el crecimiento de ...fitopatógenos, disminuyendo o eliminando su efectos nocivos en plantas. En este trabajo se evaluó la presencia de los genes antifúngicos phlD y hcnC con la producción de sideróforos (agentes quelantes de Fe) en bacterias aisladas de la endósfera y rizósfera de plantas de zarzamora (Rubus fruticosus L.).Método: Se analizaron 410 aislados bacterianos asociados a plantas de zarzamora (Rubus fruticosus L.), provenientes de la rizósfera (205) y endosfera (205) para la detección de los genes antimicrobianos phlD y hcnC por reacción en cadena de la polimerasa y posterior secuenciación. La búsqueda de los genes se realizó únicamente en cepas productoras de sideróforos, utilizando el medio CAS (Cromo Azurol) para su producción. De las cepas seleccionadas, se realizaron los bioensayos de antagonismo contra los patógenos de plantas Botrytis cinerea, Fusarium oxysporum, F. solani y Rhizoctonia solani.Resultados: Los resultados de este trabajo muestran que, de los 410 aislados bacterianos analizados (50% rizosféricos y 50% endófitos), 70 aislados fueron productores de sideróforos (24 rizosféricas y 46 endófitas). Se observó que el 70% (49/70) de las cepas productoras de sideróforos, presentaron uno o dos de los genes phlD y/o hcnC. Las secuencias nucleotídicas de los genes phlD y/o hcnC mostraron una alta identidad con genes homólogos a las especies Pseudomonas sp., P. fluorescens, P. chlororaphis, P. protegens, P. putida y P. brassicacearum. La abundancia del gen hcnC fue mayor en los aislados endófitos y rizosféricos (36/70), con respecto al gen phlD (13/70). Se detectaron mayoritariamente los genes phlD y/o hcnC en cepas aisladas de la endósfera (43/70), comparado con aquellas cepas rizosféricas (6/70). Finalmente, se observó una alta relación entre la producción de sideróforos, la presencia de genes phlD y/o hcnC y la actividad antagónica hacia los fitopatógenos Botrytis cinerea, Fusarium oxysporum, Fusarium solani y Rhizoctonia solani.Conclusión: Estos resultados muestran el potencial de identificar de forma rápida, eficiente y a bajo costo, mecanismos de antagonismo hacia fitópatógenos en bacterias asociadas a plantas de zarzamora (Rubus fruticosus L.), tales como la producción de sideróforos.
El diesel es una mezcla compleja de hidrocarburos alifaticos y aromaticos, que por su amplio uso se ha convertido en un contaminante ambiental muy frecuente. Debido a esto, es imperativo explorar ...alternativas viables y economicas para la remocion de dicho contaminante. El proposito del presente trabajo fue analizar la degradacion de diesel por bacterias aisladas de suelo contaminado con esa mezcla de hidrocarburos, asi como evaluar su actividad antagonica sobre hongos fitopatogenos, sus caracteristicas de promocion del crecimiento vegetal y tolerancia a pesados. A partir del enriquecimiento en diesel como unica fuente de carbono, se obtuvieron los aislados bacterianos J3 y S3, cuya identificacion bioquimica y molecular revelo que corresponden a Pseudomonas aeruginosa y Enterobacter sp., respectivamente. Ademas, se observo que el crecimiento bacteriano fue mejor entre 2 y 5 % de diesel, mientras que el pH Optimo fue de 7,0 y 8,0 en presencia de 3 % de diesel. Tambien, S3 mostro buen crecimiento a concentraciones de hasta 4 % de NaCl. Por otro lado, las bacterias mostraron inhibicion del crecimiento micelial de los hongos fitopatogenos Alternaria sp., Botrytis cinerea, Colletotrichum siamense y Fusarium proliferatum. Ademas de caracteristicas de promocion de crecimiento vegetal como produccion de acido indol acetico (AIA), solubilizacion de fosfato, produccion de sideroforos y surfactantes. Tambien, se observo que las bacterias crecieron en presencia de metales como Zn, Cu, Ba y Pb, en concentraciones de entre 1,5 y >10 mM. En conclusion, las bacterias aisladas e identificadas en este estudio presentan caracteristicas que las hacen excelentes candidatas para la remocion de hidrocarburos solas o mediante fitorremediacion por sus caracteristicas de promocion de crecimiento vegetal.
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