Interaction of Long-Chain Alcohol with Dry Yeast, Cholesterol, and Sea Firefly Luciferase

Background: A hand sanitizer containing alcohol, usually ethanol or isopropanol, is typically used for disinfection, but given that cholesterol is one of the main components of virus envelopes, long-chain alcohol may be more effective. To better understand the potential disinfection activity of long-chain alcohols, we studied their interactions with dry yeast, cholesterol, and sea firefly luciferase. Methods and Results: We measured, at 30oC and 39oC, the minimum inhibition concentration (MIC) of dry yeast fermentation and the stability of cholesterol and sea firefly luciferase with alcohols, diols, cetyltrimethylammonium chloride, and stearyltrimethylammonium chloride. The MIC decreased with the chain length at C≤12 for dry yeast and cholesterol with alcohol at 30oC. At C13 and higher, the cut-off region was observed. At 39oC, the cut-off region shifted to C15 and higher. The reduction of MIC was measured with the diol or sea firefly luciferase at C≤14. Conclusion: The presence of the cut-off region is suggested to be related to whether the alcohol is in the liquid state. For the liquid alcohol, the longer the chain length, the lower the MIC. This suggests a potential disinfection activity of long-chain alcohol.

A hymenopteran odorant alerts flies to bury eggs

Ants are ubiquitous and consume insects at all life stages, presumably creating a strong selective pressure for ant avoidance behaviors across insects. The insect egg stage can be especially defenseless against predation given that eggs are usually immobile and unguarded, suggesting insect mothers may have evolved oviposition strategies to minimize the ant predation risk to their offspring. Given the lack of parental care in most insects, these oviposition strategies would likely be innate rather than learned, since insect mothers are not usually present to assess predation of their eggs. Here, we use the vinegar fly Drosophila melanogaster as a model system for examining parental defensive responses to ant presence. Flies usually lay eggs partially inserted into the food substrate, although some are laid on top of the food and a few are inserted deeply into the food. We found that exposure to ants significantly alters fly oviposition depth: the proportion of eggs on the food surface decreased while the proportion of buried eggs increased. Buried eggs survive ant foraging bouts better than surface eggs, showing that this oviposition depth behavior is adaptive. This induced behavior is conserved across the genus Drosophila and is dependent on the fly olfactory system: anosmic mutant flies fail to bury their eggs in the presence of ants, and ant odor extracts are sufficient to induce egg burying. By fractionating ant body washes and using GC-MS to identify fraction constituents, we identified the saturated, long-chain alcohol 1-octadecanol as the odorant flies use to sense ant presence. To further delineate the ant lineages to which flies respond, we exposed flies to the odors from numerous species of ants and other insects. Surprisingly, flies buried their eggs in response to the odors of nearly all hymenopterans tested, including hymenopteran groups that flies rarely interact with in nature like bees and paper wasps. Our data suggest that 1-octadecanol is a conserved and ancient hymenopteran odorant, and that drosophilids evolved a mechanism for sensing this odorant early in their evolution as a means of protecting their offspring from ant predation. This study sheds light on the ecology and mechanisms underlying a common biotic interaction in nature, that between insect parents and the ants that would consume their offspring.

A complex of LaoA and LaoB acts as a Tat-dependent dehydrogenase for long-chain alcohols in Pseudomonas aeruginosa

The opportunistic pathogen Pseudomonas aeruginosa can utilize unusual carbon sources like sodium dodecyl sulfate (SDS) and alkanes. Whereas the initiating enzymatic steps of the corresponding degradation pathways have been characterized in detail, the oxidation of the emerging long-chain alcohols found little attention. Recently, the genes for the Lao ( l ong-chain a lcohol/ a ldehyde o xidation) system were discovered to be involved in the oxidation of long-chain alcohols derived from SDS and alkane degradation. In the Lao-system, LaoA is predicted to contain the catalytic site, however, according to genetic studies, efficient long-chain alcohol oxidation additionally required the Tat-dependent protein LaoB. In the present study, the Lao-system was further characterized. In vivo analysis revealed that the Lao-system complements the substrate spectrum of the well-described Exa-system, which is required for growth with ethanol and other short-chain alcohols. Mutational analysis revealed that the Tat-site of LaoB was required for long-chain alcohol oxidation activity strongly suggesting a periplasmic localization of the process. Purified LaoA was only fully active when co-purified with LaoB. Interestingly, in vitro activity of the purified LaoAB-complex also depended on the presence of the Tat-site. The co-purified LaoAB-complex contained a flavin co-factor and preferentially oxidized a range of saturated, unbranched primary alcohols. Furthermore, the LaoAB-complex could reduce cytochrome c 550 type redox carriers like ExaB, a subunit of the Exa alcohol dehydrogenase system. LaoAB-complex activity was stimulated by rhamnolipids in vitro . In summary, LaoAB constitutes an unprecedented protein complex with specific properties apparently required for oxidizing long-chain alcohols. IMPORTANCE Pseudomonas aeruginosa is a major threat to public health. Its ability to thrive in clinical settings, water distribution systems or even jet fuel tanks is linked to detoxification and degradation of diverse hydrophobic substrates that are metabolized via alcohol intermediates. Our study illustrates a novel flavoprotein long-chain alcohol dehydrogenase consisting of a facultative two-subunit complex, which is unique among related enzymes while the homologs of the corresponding genes are found in numerous bacterial genomes. Understanding the involved catalytic and compartmentalization processes is of great interest for biotechnological and hygiene research as it may be a potential starting point for rationally designing novel antibacterial substances with high specificity against this opportunistic pathogen.