1 Introduction
In general, it is known that the community structure of plant growth-promoting
bacteria is characterized by their phenotypic and genotypic characteristics which
include standard plating methods, with the employing of selective media and
biochemical tests to analyze the physiological profiles inside of communities. The
named functional properties like colonization, phytohormone synthesis, solubilization of insoluble phosphorous, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and production of antibiotics and siderophores have also been used to
characterize them. This review focused on the employ of these functional traits and
multivariate statistical analysis to describe the functional analysis of plant growthpromoting bacteria communities associated to environmental conditions that could
be related to assisted phytoremediation cases.
2 Classification of Plant Growth-Promoting Bacteria
It is known that beneficial bacteria that facilitate plant growth are often named plant
growth-promoting bacteria (PGPB) (Kloepper and Schroth 1978). These microorganisms must be able firstly to colonize plant surfaces, after established, survive and
multiply in the surface or within plant tissues, and, finally, facilitate plant growth
(Barea et al. 2005).
There are some authors who classified PGPB regarding their interaction with
plants as symbiotic bacteria and free-living bacteria (Khan 2005). Also as Somers
et al. (2004) and Khan et al. (2009) established according to their ecological roles,
they are biofertilizers (favoring the bioavailability of nutrients to the plants),
phytostimulators (facilitating the plant growth by the synthesis of phytohormones),
rhizoremediators (involved in the removal or degradation of inorganic and organic
pollutants), and biopesticides (managing plant diseases by the production of antimicrobial metabolites.
3 Bacteria Endophyte Characteristics
There are other classifications according to their plant’s localization by Khan et al.
(2009): intracellular PGPB which are bacteria residing inside plant cells or localized
inside specialized structures like nodules and extracellular PGPB that are living
outside plant cells enhancing the plants’ growth by the production of signal compounds that directly stimulate growth, improving the disease resistance or sensing
the nutrient status. These authors also mention that this group can be subdivided into
three types, based on how they are in close contact with plants: those living near, but
not in contact, with the plants’ surface; those colonizing plants’ surface; and those
238
A. L. Guerrero-Zúñiga et al.
In general, it is known that the community structure of plant growth-promoting
bacteria is characterized by their phenotypic and genotypic characteristics which
include standard plating methods, with the employing of selective media and
biochemical tests to analyze the physiological profiles inside of communities. The
named functional properties like colonization, phytohormone synthesis, solubilization of insoluble phosphorous, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and production of antibiotics and siderophores have also been used to
characterize them. This review focused on the employ of these functional traits and
multivariate statistical analysis to describe the functional analysis of plant growthpromoting bacteria communities associated to environmental conditions that could
be related to assisted phytoremediation cases.
2 Classification of Plant Growth-Promoting Bacteria
It is known that beneficial bacteria that facilitate plant growth are often named plant
growth-promoting bacteria (PGPB) (Kloepper and Schroth 1978). These microorganisms must be able firstly to colonize plant surfaces, after established, survive and
multiply in the surface or within plant tissues, and, finally, facilitate plant growth
(Barea et al. 2005).
There are some authors who classified PGPB regarding their interaction with
plants as symbiotic bacteria and free-living bacteria (Khan 2005). Also as Somers
et al. (2004) and Khan et al. (2009) established according to their ecological roles,
they are biofertilizers (favoring the bioavailability of nutrients to the plants),
phytostimulators (facilitating the plant growth by the synthesis of phytohormones),
rhizoremediators (involved in the removal or degradation of inorganic and organic
pollutants), and biopesticides (managing plant diseases by the production of antimicrobial metabolites.
3 Bacteria Endophyte Characteristics
There are other classifications according to their plant’s localization by Khan et al.
(2009): intracellular PGPB which are bacteria residing inside plant cells or localized
inside specialized structures like nodules and extracellular PGPB that are living
outside plant cells enhancing the plants’ growth by the production of signal compounds that directly stimulate growth, improving the disease resistance or sensing
the nutrient status. These authors also mention that this group can be subdivided into
three types, based on how they are in close contact with plants: those living near, but
not in contact, with the plants’ surface; those colonizing plants’ surface; and those
238
A. L. Guerrero-Zúñiga et al.