Effective Trapping of Fruit Flies with Cultures of Metabolically Modified Acetic Acid Bacteria

Abstract

c Acetoin in vinegar is an attractant to fruit flies when combined with acetic acid. To make vinegar more effective in attracting fruit flies with increased acetoin production, Komagataeibacter europaeus KGMA0119 was modified by specific gene disruption of the acetohydroxyacid isomeroreductase gene (ilvC). A previously constructed mutant lacking the putative ligand-sensing region in the leucine-responsive regulatory protein (KeLrp, encoded by Kelrp) was also used. The ilvC and Kelrp disruptants (KGMA5511 and KGMA7203, respectively) produced greater amounts of acetoin (KGMA5511, 0.11%; KGMA7203, 0.13%) than the wild-type strain KGMA0119 (0.069%). KGMA7203 produced a trace amount of isobutyric acid (0.007%), but the other strains did not. These strains produced approximately equal amounts of acetic acid (0.7%). The efficiency of fruit fly attraction was investigated with cultured Drosophila melanogaster. D. melanogaster flies (approximately 1,500) were released inside a cage (2.5 m by 2.5 m by 1.5 m) and were trapped with a device containing vinegar and a sticky sheet. The flies trapped on the sticky sheet were counted. The cell-free supernatant from KGMA7203 culture captured significantly more flies (19.36 to 36.96% of released flies) than did KGMA0119 (3.25 to 11.40%) and KGMA5511 (6.87 to 21.50%) cultures. Contrastingly, a 0.7% acetic acid solution containing acetoin (0.13%) and isobutyric acid (0.007%), which mimicked the KGMA7203 supernatant, captured significantly fewer flies (0.88 to 4.57%). Furthermore, the KGMA0119 supernatant with additional acetoin (0.13%) and isobutyric acid (0.007%) captured slightly more flies than the original KGMA0119 supernatant but fewer than the KGMA7203 supernatant, suggesting that the synergistic effects of acetic acid, acetoin, isobutyric acid, and unidentified metabolites achieved the efficient fly trapping of the KGMA7203 supernatant. B acterial cultures can function as attractants for insects (1).Fruit flies, such as Drosophila melanogaster, are recognized as an index for unsanitary conditions in urban areas because the flies infest damaged and overripe fruits and rotten foods. One of the important challenges is to keep the numbers of flies low, particularly in the food industries. A closely related species, the spottedwing drosophila (SWD) (Drosophila suzukii), which is native to southeastern Asia, is a newly emerging invasive pest for softskinned fruits such as blueberries, strawberries, and peaches in North America and Europe (2-4). Because the SWD breaks the skin of maturing healthy fruits using a serrated ovipositor to oviposit, unlike other Drosophila species, the fly causes significant damage to soft-skinned fruits (2). The damage caused by the SWD promotes microbial decay in the fruits, which results in a secondary infestation of other Drosophila species. The damaged fruits are likely to be rejected at the processing plant or export terminal (5). Although fruits are protected with sprays of chemical insecticides once the SWD is detected, growers risk the rejection ...

Brown Rice Vinegar as an Olfactory Field Attractant for Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) in Cherimoya in Maui, Hawaii, with Implications for Attractant Specificity between Species and Estimation of Relative Abundance

“…There were no significant differences between BRV+RW and ACV+RW, suggesting that BRV+RW may be equivalent to ACV+RW as an olfactory attractant for D. suzukii . Similar to the results of previous experiments, the use of ACV+RW resulted in greater D. suzukii captures than ACV alone [32,46]. Researchers conducting field experiments in berry crops found that wine-vinegar blends were more attractive to D. suzukii than wine and vinegar alone [46] or aqueous red wine [32].…”

“…Previous research has demonstrated that apple cider vinegar [49,50] and apple cider vinegar and red wine [51] are effective field attractants for D. suzukii and Z. indianus . Rice vinegar, with and without red wine, has also been characterized by several researchers [30,32,46]. Recently, Akasaka et al [52] demonstrated that brown rice vinegar was more attractive to D. suzukii than apple cider vinegar in laboratory choice assays, substantiating the need for the characterization of attractant efficacy in field settings.…”

“…Individual volatiles that are suspected to be attractive can then be tested in laboratory choice assays or in the field to develop targeted bait. Some progress has already been made towards the development of synthetic drosophilid bait [46] for D. suzukii [47] and Z. indianus [30], but the identification of novel fermenting solutions that are attractive to particular drosophilids and the characterization of these species–attractant interactions can further advance the development of these species-specific attractants.…”

Agmatine Production by Aspergillus oryzae Is Elevated by Low pH during Solid-State Cultivation

“…Quantification of the polyamines, organic acids, and ethanol by HPLC and GC. The polyamines and organic acids or ethanol in the culture supernatants were quantified using HPLC or GC, respectively, as previously described (47,53). To extract the polyamines, 1/10 volume of 10% (wt/vol) TCA was added to the samples and thoroughly vortexed.…”

Microbiome Innovation in Agriculture: Development of Microbial Based Tools for Insect Pest Management

“…Huang et al (2017) also showed combination baits of yeastwine-vinegar-sugar mixtures are superior attractants compared to wine-vinegar alone. Ishii et al (2015) genetically modified the acetic acid bacterium (AAB) Komagataeibacter europaeus with increased acetoin (a key ingredient in vinegar) production and was able to trap significantly more Drosophila using the mutant strain compared to other strains loaded on sticky traps. Similarly, microbial semiochemicals have been shown to attract tephritid fruit flies.…”