Actually, I don't know for sure that I am NOT doing that. I am following a template for arrays suggested by our sys admin. I have tried 2 different approaches.
1.
INPUT_FILE=[cat /yaml_files | sed -n "${SGE_TASK_ID}p"]
spades.py -k 21,31,55,77 --careful --dataset $INPUT_FILE -o /SPAdes/"$INDEX"
2.
SAMPLE_DIR= /yaml_files
SAMPLE_LIST=($SAMPLE_DIR/*.yaml)
INDEX=$((SGE_TASK_ID-1))
INPUT_FILE=${SAMPLE_LIST[$INDEX]}
spades.py -k 21,31,55,77 --careful --dataset $INPUT_FILE -o /SPAdes/"$INDEX"