organic residues and helpful for the nutrient mineralization, turnover processes, and
soil dynamics. Carbon flow and its availability are greatly influenced in the
rhizospheric region as 12–40% of the total amount of carbohydrates prepared during
photosynthesis released into the rhizosphere.
Compared to bulk soil, rhizosphere is the main place where higher amount of
conversion of the extracellular compounds such as glucose to gluconic acid and
2 keto gluconic acid occurs. Pseudomonas sp. can effectively perform the above
conversion to sequester glucose and create a competition over other microbes that
need glucose. Competition happens not only for sugars but also for micronutrients
such as zinc, manganese, molybdenum, iron, copper, etc. The niche of rhizosphere
has phytohormones such as IAA, auxins, cytokinins, and gibberellins secreted by the
plants as well as by the microbes that truly enhances the plant growth and the root
architecture that further increased the production of exudates.
Rhizospheric microbiome very particularly influences the nutrient status of soil
and nutrient uptake of the plants. The best-known miracle doers are known to be the
very famous Rhizobium and AM fungi for its nitrogen fixing and phosphorus
uptake, respectively. These AM fungi are the important symbionts for translocation
of nutrients and minerals, maintaining the soil structure, forming soil aggregates,
suppressing soil-borne pathogens, etc. Rhizospheric microbes also influence the
uptake of many trace elements such as iron, molybdenum, magnesium, boron, etc.
AM fungi has been proven to uptake and enhance the Fe and Zn concentration in
chickpea (Pellegrino and Bedini 2014) and maize (Subramanian and Balakrishnan
2013).
Addition of organic amendments into the soil provides abundant carbon and
nutrients that are readily available to microorganism for its growth. This was
supported by the observation that composting of plant residues with more labile
organic matter resulted in higher soil microbial biomass and respiration (Tejada et al.
2009). Besides, Wu et al. (2013) found that compost additions in soil increased the
microbial biomass and it may be due to the higher availability of nutrients, labile
organic matter, the increased water retention, and aeration (Hu et al. 2011; Duong
et al. 2012; Wu et al. 2013).
1.3 Shaping the Rhizospheric Microbiome
Shaping of the rhizospheric microbiome is an important hot topic in the growing
ómics’ research as they decide many factors of the plant–microbe interaction. During
the developmental stages of plant, the microbial communities prevailing in the
rhizospheric zone, their functions and pathways in which they are undergoing
breakdown of metabolites differ. Barret et al. (2011) have discussed many molecular
approaches for the gene expression pattern in the rhizosphere. Studies on in vivo
expression technology (IVET) revealed that when the microbes are colonizing in the
rhizosphere, different genes and proteins were induced such as the genes for nutrient
absorption and stress response. Whereas some proteins which are involved in
1 Rhizosphere: Niche for Microbial Rejuvenation and Biodegradation of Pollutants
5
soil dynamics. Carbon flow and its availability are greatly influenced in the
rhizospheric region as 12–40% of the total amount of carbohydrates prepared during
photosynthesis released into the rhizosphere.
Compared to bulk soil, rhizosphere is the main place where higher amount of
conversion of the extracellular compounds such as glucose to gluconic acid and
2 keto gluconic acid occurs. Pseudomonas sp. can effectively perform the above
conversion to sequester glucose and create a competition over other microbes that
need glucose. Competition happens not only for sugars but also for micronutrients
such as zinc, manganese, molybdenum, iron, copper, etc. The niche of rhizosphere
has phytohormones such as IAA, auxins, cytokinins, and gibberellins secreted by the
plants as well as by the microbes that truly enhances the plant growth and the root
architecture that further increased the production of exudates.
Rhizospheric microbiome very particularly influences the nutrient status of soil
and nutrient uptake of the plants. The best-known miracle doers are known to be the
very famous Rhizobium and AM fungi for its nitrogen fixing and phosphorus
uptake, respectively. These AM fungi are the important symbionts for translocation
of nutrients and minerals, maintaining the soil structure, forming soil aggregates,
suppressing soil-borne pathogens, etc. Rhizospheric microbes also influence the
uptake of many trace elements such as iron, molybdenum, magnesium, boron, etc.
AM fungi has been proven to uptake and enhance the Fe and Zn concentration in
chickpea (Pellegrino and Bedini 2014) and maize (Subramanian and Balakrishnan
2013).
Addition of organic amendments into the soil provides abundant carbon and
nutrients that are readily available to microorganism for its growth. This was
supported by the observation that composting of plant residues with more labile
organic matter resulted in higher soil microbial biomass and respiration (Tejada et al.
2009). Besides, Wu et al. (2013) found that compost additions in soil increased the
microbial biomass and it may be due to the higher availability of nutrients, labile
organic matter, the increased water retention, and aeration (Hu et al. 2011; Duong
et al. 2012; Wu et al. 2013).
1.3 Shaping the Rhizospheric Microbiome
Shaping of the rhizospheric microbiome is an important hot topic in the growing
ómics’ research as they decide many factors of the plant–microbe interaction. During
the developmental stages of plant, the microbial communities prevailing in the
rhizospheric zone, their functions and pathways in which they are undergoing
breakdown of metabolites differ. Barret et al. (2011) have discussed many molecular
approaches for the gene expression pattern in the rhizosphere. Studies on in vivo
expression technology (IVET) revealed that when the microbes are colonizing in the
rhizosphere, different genes and proteins were induced such as the genes for nutrient
absorption and stress response. Whereas some proteins which are involved in
1 Rhizosphere: Niche for Microbial Rejuvenation and Biodegradation of Pollutants
5