Diversity of Cultivated Endophytic Bacteria from Sugarcane: Genetic and Biochemical Characterization of Burkholderia cepacia Complex Isolates

Abstract

Bacteria were isolated from the rhizosphere and from inside the roots and stems of sugarcane plants grown in the field in Brazil. Endophytic bacteria were found in both the roots and the stems of sugarcane plants, with a significantly higher density in the roots. Many of the cultivated endophytic bacteria were shown to produce the plant growth hormone indoleacetic acid, and this trait was more frequently found among bacteria from the stem. 16S rRNA gene sequence analysis revealed that the selected isolates of the endophytic bacterial community of sugarcane belong to the genera of Burkholderia, Pantoea, Pseudomonas, and Microbacterium. Bacterial isolates belonging to the genus Burkholderia were the most predominant among the endophytic bacteria. Many of the Burkholderia isolates produced the antifungal metabolite pyrrolnitrin, and all were able to grow at 37°C. Phylogenetic analyses of the 16S rRNA gene and recA gene sequences indicated that the endophytic Burkholderia isolates from sugarcane are closely related to clinical isolates of the Burkholderia cepacia complex and clustered with B. cenocepacia (gv. III) isolates from cystic fibrosis patients. These results suggest that isolates of the B. cepacia complex are an integral part of the endophytic bacterial community of sugarcane in Brazil and reinforce the hypothesis that plant-associated environments may act as a niche for putative opportunistic human pathogenic bacteria.Brazil is one of the world's largest sugarcane producers and has considerable influence over the international sugar market. Brazilian sugarcane is primarily used to produce sugar and alcohol. Production has increased over time to approximately 26 million tons of sugar and 16 million m 3 of alcohol in 2006. Although ethanol has been used as an alternative source of fuel in Brazil since 1980, it is currently receiving worldwide interest as a biofuel to replace, at least in part, gasoline, thereby contributing to a reduction in carbon emissions (33). Consequently, sustaining and enhancing the growth and yield of sugarcane have become a major focus of research. The growth and performance of sugarcane in the field are adversely affected by a number of abiotic and biotic factors, including a wide range of fungal and bacterial diseases. Pokkah boeng, caused by the fungus Fusarium moniliforme, is one of the most widespread diseases and may cause serious yield losses in commercial sugarcane plantings (68). F. moniliforme can be disseminated horizontally by airborne spores or crop debris and vertically through seed pieces. Current control strategies involve the use of resistant varieties and fungicide applications. The efficacy of both control measures, however, is limited, and there is an increasing need for novel and environmentally sound strategies to control this and other diseases of sugarcane.The overall goal of this study was to isolate and characterize beneficial bacteria that are intimately associated with sugarcane and have the potential to control pathogens and to promote the growth and yie...

Isolation and selection of plant growth-promoting bacteria associated with sugarcane

“…Bacteria were isolated from the rhizosphere according to the methodology proposed by Mendes et al (2007), whereby 1 g of soil adhered to the roots was incubated for one hour under agitation at 130 rpm, at room temperature, in 100 mL of phosphate buffer (20 mM, pH 7.4). After agitation, the material was serially diluted and concentrations of 10 -8 , 10 -9 and 10 -10 were plated in triplicate.…”

Pseudomonas spp. as growth promoting agents of sunflower and jack bean in soil with sulfentrazone

“…Studies on isolation and selection of isolates in different plant species have demonstrated that the ability of some bacteria to produce plant growth-promoting substances may be highly specific to certain plant species or even cultivars, as well as to the different environments where they are inserted, or even affected by the stress imposed on the microbial community due to environmental and anthropogenic alterations (Mendes et al, 2007;Oliveira et al, 2009;Jha et al, 2009b;Prakamhang et al, 2009). In this work, it was further verified that such ability may be related to the cultivation time and the combination of plants.…”

Bacterial Community Associated with Autotrophic and Heterotrophic Cultures of Medicinal Plant Smallanthus sonchifolius (Yacon)

“…Our data suggest that the isolates recovered from in vitro yacon cultures were endophytes except for F. oryzihabitans, which grew endo and epiphytically. Several reports indicate that plant growth promoting bacteria are beneficial endophytes growing in association with the host [21][22][23]. Among the S. sonchifolius isolates, Microbacterium imperiali and Sphingomonas paucimobilis were the highest IAA producers ( Table 4).…”