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Interactions between Drosophila and its natural yeast symbionts-Is Saccharomyces cerevisiae a good model for studying the fly-yeast relationship?

Hoang D, Kopp A, Chandler JA - PeerJ (2015)

Bottom Line: We do not find a correlation between preferred yeasts and those that persist in the intestine.Notably, in no instances is S. cerevisiae preferred over the naturally associated strains.Since the genetic basis of host-microbe interactions is shared across taxa and since many of these genes are initially discovered in D. melanogaster, a more realistic fly-yeast model system will benefit our understanding of host-microbe interactions throughout the animal kingdom.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Evolution and Ecology and Center for Population Biology, University of California , Davis, CA , USA ; Current affiliation: Program in Genomics of Differentiation, NIH/NICHD , Bethesda, MD , USA.

ABSTRACT
Yeasts play an important role in the biology of the fruit fly, Drosophila melanogaster. In addition to being a valuable source of nutrition, yeasts affect D. melanogaster behavior and interact with the host immune system. Most experiments investigating the role of yeasts in D. melanogaster biology use the baker's yeast, Saccharomyces cerevisiae. However, S. cerevisiae is rarely found with natural populations of D. melanogaster or other Drosophila species. Moreover, the strain of S. cerevisiae used most often in D. melanogaster experiments is a commercially and industrially important strain that, to the best of our knowledge, was not isolated from flies. Since disrupting natural host-microbe interactions can have profound effects on host biology, the results from D. melanogaster-S. cerevisiae laboratory experiments may not be fully representative of host-microbe interactions in nature. In this study, we explore the D. melanogaster-yeast relationship using five different strains of yeast that were isolated from wild Drosophila populations. Ingested live yeasts have variable persistence in the D. melanogaster gastrointestinal tract. For example, Hanseniaspora occidentalis persists relative to S. cerevisiae, while Brettanomyces naardenensis is removed. Despite these differences in persistence relative to S. cerevisiae, we find that all yeasts decrease in total abundance over time. Reactive oxygen species (ROS) are an important component of the D. melanogaster anti-microbial response and can inhibit S. cerevisiae growth in the intestine. To determine if sensitivity to ROS explains the differences in yeast persistence, we measured yeast growth in the presence and absence of hydrogen peroxide. We find that B. naardenesis is completely inhibited by hydrogen peroxide, while H. occidentalis is not, which is consistent with yeast sensitivity to ROS affecting persistence within the D. melanogaster gastrointestinal tract. We also compared the feeding preference of D. melanogaster when given the choice between a naturally associated yeast and S. cerevisiae. We do not find a correlation between preferred yeasts and those that persist in the intestine. Notably, in no instances is S. cerevisiae preferred over the naturally associated strains. Overall, our results show that D. melanogaster-yeast interactions are more complex than might be revealed in experiments that use only S. cerevisiae. We propose that future research utilize other yeasts, and especially those that are naturally associated with Drosophila, to more fully understand the role of yeasts in Drosophila biology. Since the genetic basis of host-microbe interactions is shared across taxa and since many of these genes are initially discovered in D. melanogaster, a more realistic fly-yeast model system will benefit our understanding of host-microbe interactions throughout the animal kingdom.

No MeSH data available.


Related in: MedlinePlus

Persistence of yeasts in the D. melanogaster intestine relative to Saccharomyces cerevisiae.The ratio of the test yeast and S. cerevisiae was normalized to 1 at time 0, except for HO-48, which had unusable data for time 0 (see ‘Methods’ section). Values greater than 1 at later timepoints indicate that the test yeast persists relative to S. cerevisiae, whereas values less than 1 at later timepoints indicate that the test yeast is removed relative to S. cerevisiae (See Eq. (1)). Note the Y-axis is log10 transformed. Separate graphs for each species, with confidence intervals included, can be found in Fig. S2. HO-48 and HO-72, separate H. occidentalis experiments run for 48 and 72 h, respectively; HU, H. uvarum; SP, S. paradoxus; BN, B. naardenesis; DH, D. hansenii.
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fig-1: Persistence of yeasts in the D. melanogaster intestine relative to Saccharomyces cerevisiae.The ratio of the test yeast and S. cerevisiae was normalized to 1 at time 0, except for HO-48, which had unusable data for time 0 (see ‘Methods’ section). Values greater than 1 at later timepoints indicate that the test yeast persists relative to S. cerevisiae, whereas values less than 1 at later timepoints indicate that the test yeast is removed relative to S. cerevisiae (See Eq. (1)). Note the Y-axis is log10 transformed. Separate graphs for each species, with confidence intervals included, can be found in Fig. S2. HO-48 and HO-72, separate H. occidentalis experiments run for 48 and 72 h, respectively; HU, H. uvarum; SP, S. paradoxus; BN, B. naardenesis; DH, D. hansenii.

Mentions: In this experiment, we measured persistence by feeding live yeasts to flies and then measuring how long live yeast colonies could be recovered from dissected gastrointestinal tracts (following (Ha et al., 2009)). At 24–36 h prior to the start of the experiment, adult D. melanogaster (3–4 days old, approximately 20 of each sex, isoline 755 (Stamps et al., 2005; Stamps et al., 2012)) were anesthetized under CO2 and placed into nine vials containing modified Bloomington media (recipe available in Article S1), (a timeline of the procedure is available as Fig. S1). Two hours prior to the start of the experiment, the flies were starved in empty and autoclaved glass vials. One hour prior to the start of the experiment, the flies were transferred to treatment vials that contained either a confluent growth of S. cerevisiae on YPD media (0.5% yeast extract, 1% peptone, 1% dextrose, 2% agar), a confluent growth of the test yeast on YPD media, or a negative control of YPD media only (three replicate vials of each of these three treatments). Immediately after this one hour feeding treatment (which is considered the start of the experiment or time 0), (Fig. S1) flies were transferred into vials containing sterile YPD media, with additional transfers to fresh, sterile YPD containing vials every 12 h. At 0 h, 24 h, and 48 h (and, where applicable, 72 h), five male and five female flies from each vial had their entire gastrointestinal tracts including crops dissected out. Since an early experiment with H. occidentalis suggested it persisted relative to S. cerevisiae at 24 and 48 h (see below and Fig. 1 and Table 2), we performed an additional experiment with H. occidentalis to 72 h. While we did not explicitly measure fly phenotypic responses to different yeasts (except for feeding preference, see below), there were no conspicuous effects on fly survival or behavior. These 10 gastrointestinal tracts were pooled into one sample. Then, each sample was homogenized, and put through a serial dilution from 1 to 1/1,000 times the original concentration. 10 µL of each 200 µL dilution of each sample were plated onto yeast-selective Rose Bengal Chloramphenicol Agar plates (Fisher Scientific Catalog #OXCM0549B). The number of colony forming units (CFUs) was determined for each treatment and replicate. CFUs shall henceforth be used as a measure of total yeast abundance within the flies. Any experiments with greater than 50 CFUs per fly in the negative control at time zero were discarded (average number of CFUs in the S. cerevisiae treatments was more than 200,000 CFUs per fly). The most concentrated dilution for which individual CFUs were visible (i.e., were not confluent) was used for analysis. All raw data for the persistence experiments is available in Data S1.


Interactions between Drosophila and its natural yeast symbionts-Is Saccharomyces cerevisiae a good model for studying the fly-yeast relationship?

Hoang D, Kopp A, Chandler JA - PeerJ (2015)

Persistence of yeasts in the D. melanogaster intestine relative to Saccharomyces cerevisiae.The ratio of the test yeast and S. cerevisiae was normalized to 1 at time 0, except for HO-48, which had unusable data for time 0 (see ‘Methods’ section). Values greater than 1 at later timepoints indicate that the test yeast persists relative to S. cerevisiae, whereas values less than 1 at later timepoints indicate that the test yeast is removed relative to S. cerevisiae (See Eq. (1)). Note the Y-axis is log10 transformed. Separate graphs for each species, with confidence intervals included, can be found in Fig. S2. HO-48 and HO-72, separate H. occidentalis experiments run for 48 and 72 h, respectively; HU, H. uvarum; SP, S. paradoxus; BN, B. naardenesis; DH, D. hansenii.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556146&req=5

fig-1: Persistence of yeasts in the D. melanogaster intestine relative to Saccharomyces cerevisiae.The ratio of the test yeast and S. cerevisiae was normalized to 1 at time 0, except for HO-48, which had unusable data for time 0 (see ‘Methods’ section). Values greater than 1 at later timepoints indicate that the test yeast persists relative to S. cerevisiae, whereas values less than 1 at later timepoints indicate that the test yeast is removed relative to S. cerevisiae (See Eq. (1)). Note the Y-axis is log10 transformed. Separate graphs for each species, with confidence intervals included, can be found in Fig. S2. HO-48 and HO-72, separate H. occidentalis experiments run for 48 and 72 h, respectively; HU, H. uvarum; SP, S. paradoxus; BN, B. naardenesis; DH, D. hansenii.
Mentions: In this experiment, we measured persistence by feeding live yeasts to flies and then measuring how long live yeast colonies could be recovered from dissected gastrointestinal tracts (following (Ha et al., 2009)). At 24–36 h prior to the start of the experiment, adult D. melanogaster (3–4 days old, approximately 20 of each sex, isoline 755 (Stamps et al., 2005; Stamps et al., 2012)) were anesthetized under CO2 and placed into nine vials containing modified Bloomington media (recipe available in Article S1), (a timeline of the procedure is available as Fig. S1). Two hours prior to the start of the experiment, the flies were starved in empty and autoclaved glass vials. One hour prior to the start of the experiment, the flies were transferred to treatment vials that contained either a confluent growth of S. cerevisiae on YPD media (0.5% yeast extract, 1% peptone, 1% dextrose, 2% agar), a confluent growth of the test yeast on YPD media, or a negative control of YPD media only (three replicate vials of each of these three treatments). Immediately after this one hour feeding treatment (which is considered the start of the experiment or time 0), (Fig. S1) flies were transferred into vials containing sterile YPD media, with additional transfers to fresh, sterile YPD containing vials every 12 h. At 0 h, 24 h, and 48 h (and, where applicable, 72 h), five male and five female flies from each vial had their entire gastrointestinal tracts including crops dissected out. Since an early experiment with H. occidentalis suggested it persisted relative to S. cerevisiae at 24 and 48 h (see below and Fig. 1 and Table 2), we performed an additional experiment with H. occidentalis to 72 h. While we did not explicitly measure fly phenotypic responses to different yeasts (except for feeding preference, see below), there were no conspicuous effects on fly survival or behavior. These 10 gastrointestinal tracts were pooled into one sample. Then, each sample was homogenized, and put through a serial dilution from 1 to 1/1,000 times the original concentration. 10 µL of each 200 µL dilution of each sample were plated onto yeast-selective Rose Bengal Chloramphenicol Agar plates (Fisher Scientific Catalog #OXCM0549B). The number of colony forming units (CFUs) was determined for each treatment and replicate. CFUs shall henceforth be used as a measure of total yeast abundance within the flies. Any experiments with greater than 50 CFUs per fly in the negative control at time zero were discarded (average number of CFUs in the S. cerevisiae treatments was more than 200,000 CFUs per fly). The most concentrated dilution for which individual CFUs were visible (i.e., were not confluent) was used for analysis. All raw data for the persistence experiments is available in Data S1.

Bottom Line: We do not find a correlation between preferred yeasts and those that persist in the intestine.Notably, in no instances is S. cerevisiae preferred over the naturally associated strains.Since the genetic basis of host-microbe interactions is shared across taxa and since many of these genes are initially discovered in D. melanogaster, a more realistic fly-yeast model system will benefit our understanding of host-microbe interactions throughout the animal kingdom.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Evolution and Ecology and Center for Population Biology, University of California , Davis, CA , USA ; Current affiliation: Program in Genomics of Differentiation, NIH/NICHD , Bethesda, MD , USA.

ABSTRACT
Yeasts play an important role in the biology of the fruit fly, Drosophila melanogaster. In addition to being a valuable source of nutrition, yeasts affect D. melanogaster behavior and interact with the host immune system. Most experiments investigating the role of yeasts in D. melanogaster biology use the baker's yeast, Saccharomyces cerevisiae. However, S. cerevisiae is rarely found with natural populations of D. melanogaster or other Drosophila species. Moreover, the strain of S. cerevisiae used most often in D. melanogaster experiments is a commercially and industrially important strain that, to the best of our knowledge, was not isolated from flies. Since disrupting natural host-microbe interactions can have profound effects on host biology, the results from D. melanogaster-S. cerevisiae laboratory experiments may not be fully representative of host-microbe interactions in nature. In this study, we explore the D. melanogaster-yeast relationship using five different strains of yeast that were isolated from wild Drosophila populations. Ingested live yeasts have variable persistence in the D. melanogaster gastrointestinal tract. For example, Hanseniaspora occidentalis persists relative to S. cerevisiae, while Brettanomyces naardenensis is removed. Despite these differences in persistence relative to S. cerevisiae, we find that all yeasts decrease in total abundance over time. Reactive oxygen species (ROS) are an important component of the D. melanogaster anti-microbial response and can inhibit S. cerevisiae growth in the intestine. To determine if sensitivity to ROS explains the differences in yeast persistence, we measured yeast growth in the presence and absence of hydrogen peroxide. We find that B. naardenesis is completely inhibited by hydrogen peroxide, while H. occidentalis is not, which is consistent with yeast sensitivity to ROS affecting persistence within the D. melanogaster gastrointestinal tract. We also compared the feeding preference of D. melanogaster when given the choice between a naturally associated yeast and S. cerevisiae. We do not find a correlation between preferred yeasts and those that persist in the intestine. Notably, in no instances is S. cerevisiae preferred over the naturally associated strains. Overall, our results show that D. melanogaster-yeast interactions are more complex than might be revealed in experiments that use only S. cerevisiae. We propose that future research utilize other yeasts, and especially those that are naturally associated with Drosophila, to more fully understand the role of yeasts in Drosophila biology. Since the genetic basis of host-microbe interactions is shared across taxa and since many of these genes are initially discovered in D. melanogaster, a more realistic fly-yeast model system will benefit our understanding of host-microbe interactions throughout the animal kingdom.

No MeSH data available.


Related in: MedlinePlus