Identification of Volatiles Derived from Citrobacter freundii Fermentation of a Trypticase Soy Broth

Abstract

Twenty-two compounds emanated as volatiles from an 8-day fermentation of trypticase soy broth by Citrobacter freundii, American Type Culture Collection (ATCC 8090), were identified by dynamic headspace analysis techniques. Compound identifications were made on the basis of a comparison of Kovats indices and GC/MS spectra for unknowns and authentic samples. Of the compounds identified, nine were pyrazines, four were alcohols, two were aldehydes, two were ketones, two were esters, two were sulfides, and one was phenol. In decreasing order, the five most abundant compounds in the volatiles were 3-methyl-1-butanol (91.1%), phenol (5.00%), 2,5-dimethylpyrazine and phenethyl alcohol (each 1.18%), and 2-methyl-1-propanol (0.38%). Low molecular weight amines (ammonia, methyl- and ethylamine) were not detected in the volatiles. Pyrazines identified in the bacteria-produced supernatant (BPS) were generated almost exclusively by heating (autoclaving) the broth; their formation did not seem to be influenced by bacterial action. Laboratory bioassay of 4- and 8-day BPS derived from C. freundii against mixed sexes of adult Mexican fruit flies, Anastrepha ludens, showed the supernatants were comparable in attractancy to a 30% NuLure solution. Keywords: Lure; bacterial metabolites; Mexican fruit fly; Anastrepha ludens; Citrobacter freundii; analysis of volatiles

The semiochemically mediated interactions between bacteria and insects

“…Lee et al (1995) analysed the volatile components of the Klebsiella pneumoniae bacterial fermentation of a trypticase soy broth that was attractive to A. ludens and identified a total of 21 compounds including alcohols, pyrazines, ketones, acids and phenols, the most abundant being 3-methyl-1-butanol, 2-phenylethanol, 2,5-dimethylpyrazine, 2-methyl-1-propanol and 3-(methylthio)-1-propanol. In the same way, DeMilo et al (1996) identified 22 volatile compounds derived from Citrobacter freundii fermentation of a trypticase soy broth. The most abundant volatiles were 3-methyl-1-butanol, phenol, 2,5-dimethylpyrazine, 2-phenylethanol and 2-methyl-1-propanol and were shown to attract A. ludens.…”

The role of volatile and non-volatile antibiotics produced byPseudomonas chlororaphisstrain PA23 in its root colonization and control ofSclerotinia sclerotiorum

“…Headspace volatiles produced by each bacterium were collected using a setup described by DeMilo, Lee, Moreno and Martinez (1996) with slight modifications. Bacteria were grown in either 100 ml of tryptic soy broth (TSB) (Difco Laboratories, Detroit, MI, USA) or M9 minimal medium (per litre: 16 g NaHPO 4 -7H 2 O, 3.75 g KH 2 PO 4 , 0.625 g NaCl, 1.25 g NH 4 Cl, 0.24 g 1M MgSO 4 , 0.01 g 1M CaCl 2, and 20 ml of 20% glucose as the carbon source).…”

Coupling solid phase microextraction to complementary separation platforms for metabotyping of E. coli metabolome in response to natural antibacterial agents

“…In particular, methyl ketones with an odd number of carbon atoms were reported to derive from the decarboxylation of even-numbered β-keto acids. The production of methyl ketones bearing an even number of atoms rarely occurs, since they derive from odd numbered fatty acids; however, production of 2-butanone has also been reported as a component of VOC emissions from several bacteria (DeMilo et al 1996;Dickschat, Martens, et al 2005;Elgaali et al 2002;Lee et al 1995;Robacker and Bartelt 1997;Sunesson et al 1997). Esters also constitute a very important class of bacterial VOCs, and their enhanced volatility compared to their precursor carboxylic acids facilitates their determination by headspace sampling and gas-chromatographic analysis.…”