DOI: 10.5061/dryad.98sf7m0mh
title: Increasing adult density compromises survival following bacterial infections in Drosophila melanogaster

description: The density-dependent prophylaxis hypothesis predicts that risk of
 pathogen transmission increases with increase in population density, and
 in response to this, organisms mount a prophylactic immune response when
 exposed to high density. This prophylactic response is expected to help
 organisms improve their chances of survival when exposed to pathogens.
 Alternatively, organisms living at high densities can exhibit compromised
 defense against pathogens due to lack of resources and density associated
 physiological stress; the crowding stress hypothesis. We housed
 adult Drosophila melanogaster flies at different
 densities and measured the effect this has on their post-infection
 survival and resistance to starvation. We find that flies housed at higher
 densities show greater mortality after being infected with bacterial
 pathogens, while also exhibiting increased resistance to starvation. Our
 results are more in line with the density-stress hypothesis that
 postulates a compromised immune system when hosts are subjected to high
 densities.
description: This file ("Adult_density_experiment.xlsx") was
 generated in 2019-20 by Paresh Nath Das and others at the Evolutionary
 Biology Lab, IISER Mohali. GENERAL
 INFORMATION 1. Title of Dataset: "Increasing adult
 density compromises anti-bacterial defense in Drosophila
 melanogaster" 2. Author Information
 A.
 Principal Investigator Contact Information Name: Prof. N. G.
 Prasad 
 Institution: Indian Institute of Science Education and
 Research, Mohali Address: IISER Mohali,
 Sector 81, Knowledge City, SAS Nagar, Punjab - 140306, India.
 
 Email: prasad@iisermohali.ac.in B. Associate or
 Co-investigator Contact Information Name: Paresh Nath
 Das 
 Institution: Indian Institute of Science Education and
 Research, Mohali Address: IISER Mohali,
 Sector 81, Knowledge City, SAS Nagar, Punjab - 140306, India.
 
 Email: pareshnathd@gmail.com C. Associate or
 Co-investigator Contact Information Name: Aabeer Kumar
 Basu 
 Institution: Indian Institute of Science Education and
 Research, Mohali Address: IISER Mohali,
 Sector 81, Knowledge City, SAS Nagar, Punjab - 140306, India.
 
 Email: aabeerkbasu@gmail.com 3. Duration
 of data collection: September 2019 - March 2020 4.
 Geographic location of data collection: Mohali, Punjab, India 
 5. Information about funding sources that supported the
 collection of the data: IISER Mohali, MHRD, Govt. of India.
 SHARING/ACCESS INFORMATION Links to
 publications that cite or use the data:  bioRxiv:
 https://doi.org/10.1101/2022.01.02.474745 Journal of
 Insect Physiology (in press version):
 https://doi.org/10.1016/j.jinsphys.2022.104415
 METHODOLOGICAL INFORMATION A. Details of fly
 populations Blue Ridge Baseline (BRB) population: BRB2
 is a lab-adapted, large, outbred, wild-type population of Drosophila
 melanogaster, maintained on a 14-day discrete generation cycle, on
 standard banana-jaggery-yeast medium.  The BRB
 population was originally derived by hybridising 19 iso-female lines
 caught from the wild population at Blue Ridge Mountains, USA. The
 experiments reported were conducted after 200 generations of
 lab-adaptation. B. Effect of density, 8 adults vs. 32
 adults, on immune function and starvation resistance. #
 Experimental treatments: 2-3 day old adult flies were randomly distributed
 into two density treatments. a. 8 adults per vial
 (1:1 sex ratio) b. 32 adults per vial
 (1:1 sex ratio) Vilas of both treatments had equal
 amout of standard fly food (1.5-2 ml). Flies were housed like this for 48
 hours, and thereafter assayed for immune function and starvation
 resistance. # Immune function assay: Flies of both
 treatments (described above) were assayed separately for resistance
 against two entomopathogenic bacteria, Enterococcus faecalis and Erwinia
 c. carotovora, with two independent replicates per pathogen.
 Within each replicate experiment, 80 males and 80 females from
 each treatment (described above) were subjected to infection, and 40 males
 and 40 females were subjected to sham-infections.
 Post-infection mortality was recorded for 120 hours; during this
 period, flies of both treatments were housed at equal density (4 males and
 4 females per vial).   #Starvation resistance assay:
 Flies of both treatments (described above) were assayed for starvation
 resistance; experiment independently replicated twice.
 Within each replicate experiment, 80 males and 80 females from
 each treatment (described above) were subjected to starvation in vials
 with non-nutritive agar gel only. Post-starvation
 mortality was recorded till the last fly died; during this period, flies
 of both treatments were housed at equal density (4 males and 4 females per
 vial).  C. Effect of density, 50 adults vs. 200 adults,
 on immune function and starvation resistance. #
 Experimental treatments: 2-3 day old adult flies were randomly distributed
 into two density treatments. a. 50 adults per vial
 (1:1 sex ratio) b. 200 adults per vial
 (1:1 sex ratio) Vilas of both treatments had equal
 amout of standard fly food (1.5-2 ml). Flies were housed like this for 48
 hours, and thereafter assayed for immune function and starvation
 resistance. # Immune function assay: Flies of both
 treatments (described above) were assayed separately for resistance
 against two entomopathogenic bacteria, Enterococcus faecalis and Erwinia
 c. carotovora, with two independent replicates per pathogen.
 Within each replicate experiment, 80 males and 80 females from
 each treatment (described above) were subjected to infection, and 40 males
 and 40 females were subjected to sham-infections.
 Post-infection mortality was recorded for 120 hours; during this
 period, flies of both treatments were housed at equal density (4 males and
 4 females per vial).   #Starvation resistance assay:
 Flies of both treatments (described above) were assayed for starvation
 resistance; experiment independently replicated twice.
 Within each replicate experiment, 80 males and 80 females from
 each treatment (described above) were subjected to starvation in vials
 with non-nutritive agar gel only. Post-starvation
 mortality was recorded till the last fly died; during this period, flies
 of both treatments were housed at equal density (4 males and 4 females per
 vial). 
description: DATA & FILE OVERVIEW File
 Name:"Adult_density_experiment.xlsx" Note:
 This file contains five separate tabs: Tab 1.
 "key" (description of individual data sheet contents)
 Tab 2. "EnterococcusA" (data from immune assay
 comparing 8 adults vs. 32 adults density treatments using Enterococcus
 faecalis) Tab 3. "EnterococcusB" (data from
 immune assay comparing 50 adults vs. 200 adults density treatments using
 Enterococcus faecalis) Tab 4. "ErwiniaA"
 (data from immune assay comparing 8 adults vs. 32 adults density
 treatments using Erwinia c carotovora) Tab 5.
 "ErwiniaB" (data from immune assay comparing 50 adults vs. 200
 adults density treatments using Erwinia c carotovora)
 Tab 6. "StarvationA" (data from starvation assay
 comparing 8 adults vs. 32 adults density treatments)
 Tab 7. "StarvationB" (data from starvation assay
 comparing 50 adults vs. 200 adults density treatments)