Phylloepiphytic interaction between bacteria and different plant species in a tropical agricultural system

Abstract

Plant surfaces are a favourable niche for bacterial establishment, and hypothetically, plant species differ in their capacity to harbour epiphytic bacterial communities. This study was conducted to evaluate and describe the structural relationship of a bacterial community at the phyllosphere level with different plant species in a tropical ecosystem. Leaf blades of 47 plant species distributed in 27 botanical families were collected on a typical small Brazilian farm and prepared for observation under light and scanning electron microscopy. Naturally occurring bacteria were the most abundant settlers of the phylloplane, followed by fungal spore or hyphae. All plant species studied were colonized by phylloepiphytic bacteria, which were observed as solitary cells, microcolonies, and biofilms. However, independent of the family, the plant species differed in the pattern of phyllosphere colonization, as reflected in bacteria frequency and presence or absence of anatomical features that would favour the association. The phylloepiphytic bacteria were preferentially established on the following sites: epidermal cell wall junctions, glandular and nonglandular trichomes, veins, stomata, and epidermal cell wall surface. Profuse bacteria and fungi colonization was observed, at a level that was at least comparable with temperate regions. Interestingly, fungi seemed to alter the bacteria colonization pattern, most probably by microenvironmental modifications. The trichome type and density as well as the presence of epicuticular wax on the leaf blade surface seemed to be the most determinant anatomical features for the pattern of phyllosphere colonization. The presence of trichomes has a favourable, and epicuticular wax an unfavourable influence on the plant-bacteria interaction.

Root exudate profiling of maize seedlings inoculated with Herbaspirillum seropedicaeand humic acids

“…The whole genome sequence of H. seropedicae has been published [24]. The species' capacity for N fixation, production of auxin and other phytohormones, and the colonization of diverse plant species has been previously demonstrated [25][26][27].…”

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

“…The same result can also be obtained from crops of the Poaceae family that includes maize and sugar cane (Baldani et al, 2009). In these grasses, unlike pulses, there is no formation of nodules and these microorganisms colonize from the surface to the interior of the plant tissue (termed endophytes and epiphytic), respectively (Hallmann et al 1997;Baldotto & Olivares, 2008).…”

Seleção de bactérias promotoras de crescimento no abacaxizeiro cultivar Vitória durante a aclimatização

“…Em relação ao uso de inoculantes, ainda são escassos os trabalhos com abacaxizeiros, porém é consenso que bactérias epifíticas, que habitam a superfície vegetal (Baldotto & Olivares, 2008), e as bactérias endofíticas, que habitam o interior dos tecidos vegetais (Halmann et al, 1997), podem promover o crescimento da planta hospedeira, conforme já descrito para diversas culturas, como arroz (Verma et al, 2001), soja (Cattelan et al, 1999;Kuklinsky-Sobral et al, 2004) e milho (Chabot et al, 1998). Os mecanismos de promoção de crescimento pelas bactérias epifíticas e endofíticas incluem diferentes ações, como a fixação biológica de nitrogênio (KuKlinsky-Sobral et al, 2004), solubilização de fosfatos (Chabot et al, 1998;Verma et al, 2001), biossíntese de fito-hormônios (Lucangeli & Bottini, 1997), influência na atividade enzimática da 1-aminociclopropano 1-carboxilato (ACC) deaminase (Rothballer at al., 2008), controle biológico (Byrne et al, 2005), síntese de sideróforos (Lacava et al, 2008) e indução de resistência sistêmica a patógenos na planta hospedeira (Kloepper et al, 1999 Efeitos positivos da inoculação de bactérias promotoras de crescimento foram verificados na abacaxicultura, principalmente quando as bactérias inoculadas também são fixadoras de nitrogênio atmosférico (Weber et al, 2003).…”