Table 2. Relative quantification of volatiles expressed as relative percentile and biological function of the volatile compounds produced by the three bacterial species along with their reported biological functions.

Name	Kovat index	Azospirillum brasilense		Bacillus pumilus		Escherichia coli		Biological function	Reference
		Average	SD	Average	SD	Average	SD
Acetoin*	669	67.8	5.9	56.7	7.3	3.8	0.3	Induce growth promotion (leaf surface area), systemic resistance (ISR) and regulate auxin homeostasis in Arabidopsis thaliana It is an attractant to Anastrepha ludens (Diptera) Acetoin as a pheromone synergist for R. palmarum	29,65,66
2,3-Butanediol*	682	7.7	0.7	4.6	0.3	0.6	0.1	Induce plant growth promotion (leaf surface area), systemic resistance (ISR) and regulate auxin homeostasis in Arabidopsis thaliana.	28,29,31
α-Terpineol	1190	0.0	0.0	0.2	0.1	1.0	0.0	Antibacterial, antifungal activities, anticancer	67
(Z)- 3-Hexen-1ol, acetate (IS)	979	9.1	2.5	11.8	1.5	24.2	2.0	n/a
p-methyl acetophenone	1032	0.1	0.0	0.4	0.3	0.2	0.0	n/a
Indole*	1272	2.1	1.1	1.6	2.4	0.5	0.5	Able to regulate biofilm formation. It also induces the formation of myxospores in Stigmatella aurantiaca. Regulation of expression of multi-drug exporter genes and inhibition of biofilm formation of Escherichia coli, Pseudomonas fluorescens and Pseudomonas aeruginosa. Intercellular signal in microbial communities	65,68,69
n-Nonanoic acid	1245	0.1	0.0	0.1	0.0	0.7	0.3	Stimulation of oviposition, directing egg laying to favorable habitat of Aedes aegypti.	70
p-Dimethylbenzene	866	0.1	0.0	1.0	0.8	0.2	0.0	n/a
Trimethyl benzene	938	0.4	0.1	2.3	1.7	0.7	0.3	n/a
Unknown	970	0.3	0.1	2.4	1.9	0.7	0.9	n/a
Nonanal*	1077	0.0	0.0	0.1	0.1	0.0	0.0	Active against the phytopathogenic fungus Sclerotinia sclerotiorum.	65
Unknown	907	0.0	0.0	0.3	0.3	0.0	0.0	n/a
3-Carene	987	0.0	0.0	0.2	0.1	0.0	0.0	Alarm pheromone in some termite species	71
Phenylethyl alcohol	1092	1.0	0.9	0.8	0.2	0.3	0.1	Autoantibiotics produced by the fungus Candida albicans	72
Ethyl decanoate	1359	0.5	0.5	0.0	0.0	0.0	0.6	n/a
Ethyl dodecanoate	1563	0.2	0.2	0.0	0.0	0.0	0.0	n/a
Ethyl octanoate	1167	0.2	0.2	0.0	0.0	0.0	0.0	n/a
n-Heptanoic acid	1049	0.0	0.0	0.1	0.0	0.0	0.0	n/a
Undecane*	1071	0.0	0.0	0.2	0.1	0.0	0.0	n/a
Dodecane*	1193	0.1	0.0	0.3	0.2	0.1	0.0	n/a
Tridecane*	1289	0.1	0.0	0.3	0.1	61.5	12.4	Defensive against predators by the stink bug Cosmopepla bimaculata	73
Pentadecane*	1479	0.1	0.0	1.3	1.1	0.3	0.0	n/a
Octadecane*	1787	0.4	0.3	0.7	0.6	0.2	0.0	n/a
n-Dodecanal	1377	0.1	0.0	0.2	0.1	0.3	0.4	n/a
2-Methylbutyric acid	840	0.6	0.2	0.8	0.3	0.0	0.0	n/a
ButanoI 3methyl-acetate	942	0.1	0.0	0.1	0.0	0.1	0.0	n/a
2-Decanol	1145	0.2	0.0	0.3	0.1	0.3	0.2	n/a
Isovaleric acid	833	4.3	1.1	2.5	1.5	0.0	0.0	Stimulation of spore germination of Agaricus bisporus Inhibition of proliferation and cytokine production in lymphocyte cells Reduction of heat resistant spores, prevention of spore formation	74
Acetic acid*	610	0.4	0.4	3.0	1.0	0.0	0.0	Highly attractive to Mexican fruit flies Reduction of heat resistant spores, prevention of spore formation	65
n-Caprylic acid	1140	0.8	0.1	0.6	0.2	0.5	0.4	Decrease yeast viability	75
Acetone*	775	0.1	0.0	0.0	0.0	0.0	0.0	Inhibited growth of fungi. Has no effect on bacteria	74
2-Methylpentanal	1128	0.1	0.0	0.1	0.0	0.1	0.0	n/a
2-Ethylhexanol	859	0.1	0.0	0.1	0.1	0.1	0.3	n/a
Unknown alcohol	1003	0.3	0.0	1.3	0.9	0.8	0.4	n/a
1-Hexene, 4methyl-	999	0.1	0.0	0.4	0.3	0.3	0.1	n/a
Caproic acid	961	0.5	0.2	1.4	0.8	0.4	0.2	n/a
Ethyl caprylate	1167	*						n/a
Unknown furfural	997	0.8	0.2	0.4	0.1	0.0	0.0	n/a
Unknown terpene	1224	0.2	0.2	0.8	0.3	0.1	0.0	n/a
Unknown hydrocarbon	1278	0.3	0.3	0.2	0.1	0.3	0.2	n/a
Unknown hydrocarbon	1360	0.2	0.1	0.5	0.2	0.4	0.3	n/a
Unknown	1020	0.2	0.1	0.2	0.1	0.0	0.0	n/a
Unknown	1337	0.2	0.1	1.8	1.5	0.0	0.0	n/a

Compounds denoted by an asterisk were confirmed with authentic standard.