8
no longer subject to fluctuating soils conditions. Endophytic bacteria colonize interior tissues by the production of cellulolytic enzymes and motility. Studies on bacterial endophytes may facilitate understanding about their interactions with plants and
associated biotechnological applications for phytoremediation, rhizoremediation,
soil conditioning, and remediation of soil contaminants. Plant growth-promoting
endophytes perform N-fixation, mineral solubilization, phytohormone secretion,
produce ammonia, hydrogen cyanide, siderophores, and ACC-deaminase enzyme,
and provide synthesis of surface-active compounds such as biosurfactants and
antagonists against plant pathogens. They have the great biochemical potential of
producing hydrolytic enzymes that exhibit natural competence for xenobiotic degradation during phytoremediation (Li et al. 2012). These organisms are generally
isolated from various plants for their identification and functional characterization,
population dynamics, and diversity studies use as microbial inoculants to improve
plant health and as a source of distinct secondary metabolites (Potshangbam et al.
2017).
For the selection of potential plant growth-promoting bacteria (PGPB), the
isolates have to be first isolated, identified morpho-physiologically and taxonomically, and preliminarily characterized on the basis of in vitro biochemical
analysis. For molecular taxonomic establishment, 16S rRNA-based analysis is
the highly preferred method to identify genera and species such as Bacillus,
Rhizobium, Burkholderia, Enterobacter, Pantoea, and Serratia (SzilagyiZacchin et al. 2014).
2.3 Plant Growth-Promoting Traits and Microbial Functions
The positive partnership of the plant–microbe system helps in plant growth and
biomass stimulation. The process of biofertilization enhances nutrient uptake in
the plants, as is evident from the studies on cereals, oilseeds, vegetables, and
other edible crops. Increase in the dry weight of grains and whole plants in
maize was observed when the plants were treated with the PGPR Burkholderia
cepacia, Azospirillum brasiliense, and Herbaspirillum seropedicae individually
for comparative analysis of plant growth in N-deprived soils (Pérez-Montaño
et al. 2014). Field release of Pseudomonas fluorescens DR54 enhanced maize
growth and the soil phosphorus pool (Krey et al. 2013). Application of P. fluorescens DR54 enhanced the colonization of AM fungi that subsequently
increased the fine root hairs of maize by 30% and hence, enhanced phosphate
mobilization under P-deprived soils was observed. The height of the inoculated
maize plant was enhanced by 11 cm and 12 cm from the control in the first and
second tested years, respectively. The performance of two- and three-component microbial inoculants, that is, Pseudomonas fluorescence F113 and consortia 3 Glomus isolates, and bivalent consortia with either Azospirillum lipoferum
CRT1 or A. brasilense UAP-154 or CFN-535 was evaluated in maize (Couillerot
et al. 2013). After 10 days of inoculation with two- component consortia, the
2 Belowground Microbial Communities: Key Players for Soil and Environmental…
no longer subject to fluctuating soils conditions. Endophytic bacteria colonize interior tissues by the production of cellulolytic enzymes and motility. Studies on bacterial endophytes may facilitate understanding about their interactions with plants and
associated biotechnological applications for phytoremediation, rhizoremediation,
soil conditioning, and remediation of soil contaminants. Plant growth-promoting
endophytes perform N-fixation, mineral solubilization, phytohormone secretion,
produce ammonia, hydrogen cyanide, siderophores, and ACC-deaminase enzyme,
and provide synthesis of surface-active compounds such as biosurfactants and
antagonists against plant pathogens. They have the great biochemical potential of
producing hydrolytic enzymes that exhibit natural competence for xenobiotic degradation during phytoremediation (Li et al. 2012). These organisms are generally
isolated from various plants for their identification and functional characterization,
population dynamics, and diversity studies use as microbial inoculants to improve
plant health and as a source of distinct secondary metabolites (Potshangbam et al.
2017).
For the selection of potential plant growth-promoting bacteria (PGPB), the
isolates have to be first isolated, identified morpho-physiologically and taxonomically, and preliminarily characterized on the basis of in vitro biochemical
analysis. For molecular taxonomic establishment, 16S rRNA-based analysis is
the highly preferred method to identify genera and species such as Bacillus,
Rhizobium, Burkholderia, Enterobacter, Pantoea, and Serratia (SzilagyiZacchin et al. 2014).
2.3 Plant Growth-Promoting Traits and Microbial Functions
The positive partnership of the plant–microbe system helps in plant growth and
biomass stimulation. The process of biofertilization enhances nutrient uptake in
the plants, as is evident from the studies on cereals, oilseeds, vegetables, and
other edible crops. Increase in the dry weight of grains and whole plants in
maize was observed when the plants were treated with the PGPR Burkholderia
cepacia, Azospirillum brasiliense, and Herbaspirillum seropedicae individually
for comparative analysis of plant growth in N-deprived soils (Pérez-Montaño
et al. 2014). Field release of Pseudomonas fluorescens DR54 enhanced maize
growth and the soil phosphorus pool (Krey et al. 2013). Application of P. fluorescens DR54 enhanced the colonization of AM fungi that subsequently
increased the fine root hairs of maize by 30% and hence, enhanced phosphate
mobilization under P-deprived soils was observed. The height of the inoculated
maize plant was enhanced by 11 cm and 12 cm from the control in the first and
second tested years, respectively. The performance of two- and three-component microbial inoculants, that is, Pseudomonas fluorescence F113 and consortia 3 Glomus isolates, and bivalent consortia with either Azospirillum lipoferum
CRT1 or A. brasilense UAP-154 or CFN-535 was evaluated in maize (Couillerot
et al. 2013). After 10 days of inoculation with two- component consortia, the
2 Belowground Microbial Communities: Key Players for Soil and Environmental…