Structural interaction between GFP-labeled diazotrophic endophytic bacterium Herbaspirillum seropedicae RAM10 and pineapple plantlets 'Vitória'

Abstract

The events involved in the structural interaction between the diazotrophic endophytic bacterium Herbaspirillum seropedicae, strain RAM10, labeled with green fluorescent protein, and pineapple plantlets ‘Vitória’ were evaluated by means of bright-field and fluorescence microscopy, combined with scanning electron microscopy for 28 days after inoculation. After 6 hours of inoculation, H. seropedicae was already adhered to the roots, colonizing mainly root hair surface and bases, followed by epidermal cell wall junctions. Bacteria adherence in the initial periods occurred mainly in the form of solitary cells and small aggregates with pleomorphic cells. Bacteria infection of root tissue occurred through the cavities caused by the disruption of epidermal cells during the emergence of lateral roots and the endophytic establishment by the colonization of intercellular spaces of the cortical parenchyma. Moreover, within 1 day after inoculation the bacteria were colonizing the shoots. In this region, the preferred sites of epiphytic colonization were epidermal cell wall junctions, peltate scutiform trichomes and non-glandular trichomes. Subsequently, the bacteria occupied the outer periclinal walls of epidermal cells and stomata. The penetration into the shoot occurred passively through stoma aperture followed by the endophytic establishment on the substomatal chambers and spread to the intercellular spaces of spongy chlorenchyma. After 21 days of inoculation, bacterial biofilm were seen at the root hair base and on epidermal cell wall surface of root and leaf, also confirming the epiphytic nature of H. seropedicae.

Initial performance of maize in response to NPK fertilization combined with Herbaspirillum seropedicae

“…The structural events involved in the interaction between H. seropedicae-host plant have been well described for different cultures (Baldotto et al, 2011) and can be summarized in the steps: adhesion, anchoring, infection and colonization. The initial events of the interaction are dependent on a rhizosphere environment favorable to bacterial growth, including various factors such as moisture and nutrient availability.…”

Screening of beneficial bacteria associated with Calophyllum brasiliense Cambess so as to develop microbial inoculants for agriculture

“…This study presented for the first time the existence of an interaction between C. brasiliensis, an arboreal plant of the Brazilian savanna, with different nitrogen-fixing bacteria species. The predominant colonization of nitrogen-fixing bacteria in the root system has been reported for different plant species (Singh et al,2011), being the main site of bacterial infection of cavities caused by the disruption of epidermal cells during the emergence of lateral roots and endophytic establishment by colonization of intercellular spaces of the cortical parenchyma (Baldotto et al, 2011). These bacteria, in addition to fixing nitrogen, are able to solubilize nutrients and synthesize phytohormones, and are therefore biological materials with potential for use as promoters of plant growth (Singh et al, 2011).…”

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“…[146,147] Many researchers observed that Gram-negative and Gram-positive microbes enter into the root through the primary root, horizontal roots, and root hair. [148][149][150] Furthermore, it has been reported that Curvularia proturberata microorganisms colonize with the root and defense Dichanthelium lanuginosum and Solanum lycopersicum plants from drought and heat stress conditions. [83]…”