Microbial interactions in the rhizosphere: beneficial influences of plant growth-promoting rhizobacteria on nutrient acquisition process. A review

Abstract

Plant growth-promoting rhizobacteria (PGPR) are soil bacteria that are able to colonize rhizosphere and to enhance plant growth by means of a wide variety of mechanisms like organic matter mineralization, biological control against soil-borne pathogens, biological nitrogen fixation, and root growth promotion. A very interesting feature of PGPR is their ability of enhancing nutrient bioavailability. Several bacterial species have been characterized as P-solubilizing microorganisms while other species have been shown to increase the solubility of micronutrients, like those that produce siderophores for Fe chelation. The enhanced amount of soluble macro- and micronutrients in the close proximity of the soil-root interface has indeed a positive effect on plant nutrition. Furthermore, several pieces of evidence highlight that the inoculation of plants with PGPR can have considerable effects on plant at both physiological and molecular levels (e.g., induction of rhizosphere acidification, up- and downregulation of genes involved in ion uptake, and translocation), suggesting the possibility that soil biota could stimulate plants being more efficient in retrieving nutrients from soil and coping with abiotic stresses. However, the molecular mechanisms underlying these phenomena, the signals involved as well as the potential applications in a sustainable agriculture approach, and the biotechnological aspects for possible rhizosphere engineering are still matters of discussion

Species-specific effects of plant invasions on activity, biomass, and composition of soil microbial communities

“…Crucial ecosystem processes, for example, organic matter decomposition and mineralization or nitrogen fixation, are also modified by invaders (Rice et al 2004;Hawkes et al 2005;Liao et al 2008;Tharayil et al 2013;Mincheva et al 2014). These modifications may lead to changes in soil nutrient pools and element cycling, engendering positive feedback that potentially stabilizes current or accelerates further invasion, and prevent re-establishment of native species (Ehrenfeld 2003;Niu et al 2007;Liao et al 2008;Pii et al 2015). The greater the invader-induced changes in soil, the greater the feedback that may be expected (Scharfy et al 2010).…”

Effect of <i>Pseudomonas fluorescens</i> and <i>Burkholderia pyrrocinia</i> on the Growth Improvement and Physiological Responses in <i>Brachiaria brizantha</i>

“…However, the efficiency of fertilizer uses by plants, particularly that of nitrogen, may vary greatly. This can create adverse environmental impacts by increasing greenhouse gas emissions and eutrophication [13] [14] [15].…”

Heavy Metals in Vineyards and Orchard Soils

“…Low molecular weight organic acids, such as citric, malic, fumalic can be exuded by the roots of plants, including vines (COVARRUBIAS et al, 2012). At the same time organic acids may derive from organic matter (root or shoot residues) decomposition, promoted by microorganisms (PII et al, 2015). The dissolved organic compounds in the soil solution have a high affinity with heavy metals, reducing the potential toxicity for plants (JONES;DARRAH, 1994;MEIER et al, 2012;PÉREZ-ESTEBAN et al, 2014).…”