spectrometry (PTR-MS) is another method that can be used to measure the concen-
tration volatile emission by ionizing organic molecules in the gas phase through their
reaction with H 3 O+, forming mostly MH+molecules (where M is the neutral organic
molecule), which can then be detected by a standard quadrupole/multiplier mass
analyzer (Ezra et al. 2004 ).
11.5 MVOCs as Signals Mediating Intra- and Interspecies
Communications
Recently, a new communication path, sense of smell has been well established in
many organisms. This sense of smell or volatile-mediated communication played
significant function in both above and belowground ecosystems. Living organisms
use these volatile as ideal semiochemical for chemical conservations among intra-
and interspecies. For example, vertebrates and invertebrates are capable to detect
minute quantities of volatiles even over very long distances. The plants use volatiles
to broadcast with their pollinators as well as with plants of the same species or other
plants and microorganisms as well use these sweet scents for communication
among microbes and plants so they can interact with each other (Heil and Walters
2009 ; Effmert et al. 2012 ).
11.5.1 MVOC in Bacterial–Plant Interactions
A number of bacteria preferentially live in the soil in close association with plant
roots utilizing root exudates as their food source. These exudates are ordinarily rich
in sugars, amino acid, organic acids, and other compounds, many of them promote
plant growth. These bacteria are called as rhizobacteria, whereas the root envi-
ronment they colonize is called the rhizosphere (Bhattacharyya and Jha 2012 ;
Mendes et al. 2013 ). Some of these microbes get genetically modified to acquire
traits like endophytic competence to be able to colonize the interior of the plant. For
long, scientists have speculated that all rhizobacteria can be expected to be endo-
phytic at least at one point in their entire life cycle (Sturz et al. 2000 ; Hardoim et al.
2008 , 2012 ).
VOCs produced by rhizobacteria are involved in their interaction with plant
pathogenic microbes and host plants and exhibit antimicrobial and plant growth
regulating activities. The bacterial VOCs such as 2-heptanol, 2-pentanone,
2-pentadecanone, 2-undecanone, 2-tridecanone, 4-heptanone, and sodorifen pro-
duced bySerratia odoriferaare able to interfere with plants. Forty-two soilborne
bacterial strains were screened and evaluated for their volatile-mediated effect on
6-day-old seedlings ofArabidopsis thaliana. A total 36 volatile compounds of
bacterial origin were selected, many of them exerting negative consequences on
11 Harnessing Endophytic Microbial Volatile Organic Compound... 243