Twenty-five whole guts were used for DNA extraction (Qiagen
DNeasy Blood and Tissue Kit; Valencia, CA). The V3 hypervariable
region of the 16S rRNA genewas amplified using universal primers:
U341F-CCTACGGGRSGCAGCAG and U519RGWATTACCGCGGCKGCAG
(modified from: Wang and Qian, 2009).
Pools of 6 PCR reactions (20mL/reaction ¼ 120 mL total) per treatment
per colony were created and concentrated using a standard
sodium acetate/ethanol DNA precipitation protocol. The resulting
~180 bp fragments were then cloned into the pGEM-T easy vector
using the pGEM-T easy Vector System I (Madison, WI). White colonies
were PCR-screened for inserts using GoTaq Green Master Mix
(Promega; Madison, WI) and standard M13 primers (Table S1).
Clones containing the correct-sized insert were grown individually
overnight in LB broth with ampicillin to make glycerol stocks for
future sequencing. Ninety-six clones were picked for each treatment/
colony. In total, 1536 clones were sequenced.
Deep-well glycerol plates were inoculated from individual clone
glycerol stocks and submitted for high-throughput Sanger
sequencing by the Purdue University Genomics Core Facility.
Resulting sequences were trimmed and compared to NCBI's
nucleotide sequence database to ascertain clone identity. Sequences
were then compared across the treatment groups and
replicates to identify unique sequences. An unexpected artifact of
using degenerate 16S rDNA primers was the amplification of host
18s rDNA. As a result, the clone library from each treatment contained
clones identifying as host. These host sequences were
filtered out leaving only prokaryotic clones in the library for subsequent
analyses. A total of 379 unique sequences were identified
from an entire library of 1475 clones across all five treatments
groups.