PPS2-4 strain was derived from R.sphaeroides 2.4.1. It has two point mutations in the chromosomal ppsR gene resulting in amino acid substitutions C251->S and C424->S. Growth at 20% O2, 1% CO2, 79% N2 in the dark. Cells are collected at OD 0.18. RNA was isolated with bead beater + RNeasy kits