ABSTRACT
Microscopic visualization using transmission electron microscopy (TEM) can provide a better understanding of endophytic colonization within ethnomedicinal plants. Bacterial endophytes were found attached to the host cell wall colonizing the aerenchyma and intercellular spaces of the epidermis and outer cortex except the vascular system. Colonization was non-uniform as single cells, doublets or in the form of microcolonies. Analysis of in vivo antibacterial action of the methanolic extracts of the isolated endophytic bacteria against Gram-positive, Streptococcus pyogenes MTCC 1925 and Gram-negative, Salmonella enterica ser. paratyphi MTCC735 pathogens has revealed the morphological damages in the tested pathogens respectively, under scanning electron microscopy (SEM). Detached cell wall and cell burst were observed in Streptococcus pyogenes where as, cell blisters were shown in Salmonella enterica ser. paratyphi. The study on bacterial endophyte colonization process is important to better predict how endophytes interact with their host and establish themselves in the plant environment by procuring biocontrol activity.
ABSTRACT
The present study was aimed to investigate the endophytic and epiphytic bacteria associated with selected ethnomedicinal plants from the pristine subtropical forests of Meghalaya and analyse them for plant growth promotion and antagonistic ability. This study is an attempt to explore plant associated bacteria which are beneficial to host plants, and thus aid in the conservation of ethnomedicinal plants of the studied subtropical forests, which are dwindling due to exploitation. The plant growth promotion parameters like indole acetic acid (IAA) production, mineral phosphate solubilisation, acid phosphatase activity, presence of 1-aminocyclopropane-1-carboxylic acid deaminase (ACC) gene, nitrogen fixation, cellulose digestion, chitin and pectin degradation were screened among the isolates. The study revealed significant differences in bacterial population not only between the epiphytic and endophytic microhabitats, but also amongst the host plants. Out of the 70 isolated plant associated bacteria, Bacillus sp., Serratia sp., Pseudomonas sp., Pantoea sp., and Lysinibacillus sp. showed potent plant growth promotion properties. Bacillus siamensis C53 and B. subtilis cenB showed significant antagonistic activity against the tested pathogens. This study indicated the isolates inhabiting the plants prevalent in the subtropical sacred forests could be explored for use as plant growth promoters while practising the cultivation and conservation of ethnomedicinal plants. Rev. Biol. Trop. 62 (4): 1295-1308. Epub 2014 December 01.
El presente estudio tuvo como objetivo investigar las bacterias endófitas y epífitas asociadas con plantas medicinales seleccionadas de los bosques subtropicales prístinos de Meghalaya, para estimular el crecimiento de plantas y la capacidad antagónica. Este estudio es un intento de explorar las plantas asociadas a bacterias que benefician a la planta hospedera, y así ayudar en la conservación de plantas medicinales de los bosques subtropicales estudiados, los cuales son cada vez más escasos debido a la explotación. Los parámetros de promoción de crecimiento de las plantas, tales como: índice de producción de ácido acético (IAA), solubilización de fosfato mineral, actividad de la fosfatasa ácida, presencia del gen 1-aminociclopropano-1-ácido carboxílico desaminasa (ACC), fijación de nitrógeno, digestión de celulosa, quitina y pectina fueron seleccionados entre los aislamientos. El estudio reveló diferencias significativas en la población bacteriana, no sólo entre los microhábitats epífitos y endófitos, sino también entre las plantas hospederas. De las 70 bacterias aisladas de plantas asociadas, Bacillus sp., Serratia sp., Pseudomonas sp., Pantoea sp. y Lysinibacillus sp. mostraron potentes propiedades estimulantes del crecimiento vegetal. Bacillus C53 siamensis y B. subtilis cenB mostraron actividad antagónica significativa contra los patógenos probados. Este estudio indicó que los aislamientos que habitan en las plantas predominantes en los bosques sagrados subtropicales podrían explorarse para su uso como promotores del crecimiento vegetal, mientras se practica el cultivo y conservación de plantas medicinales.
