different from that of the other strains by determination of Duncan's multiple-range test (P < 0.05). All sections of numbers are represented as follows: 1, ATCC 35149; 2, ATCC 12555; 3, CCUG 26450; 4, CCUG 26451; 5, CCUG 26453; 6, CCUG 36632. Table 1 Bacterial strains and plasmids used in this study Strain or plasmid Cyclic nucleotide phosphodiesterase Description Source or reference Strains Pasteurella pneumotropica ATCC 35149 Type strain, biotype Jawetz, isolated from mouse lung ATCCa  ATCC 12555 Biotype Heyl, isolated from mouse ATCC  CCUG 26450 Biotype Jawetz, isolated from gerbil CCUGb CCUG 26451 Biotype Jawetz, isolated from hamster CCUG CCUG 26453 Biotype Heyl, isolated from bird CCUG CCUG 36632 Biotype unknown, isolated from murine nose CCUG Escherichia coli DH5α Cloning strain Stratagene TOP10 Cloning strain Invitrogen BL21-AI Protein expression strain Invitrogen TMU0812 BL21-AI ΔhlyE::Kmr  Plasmids pTAC-1 Cloning vector, Apr Biodynamics Laboratory pENTR/SD/D-TOPO Entry vector, Kmr Invitrogen pBAD-DEST49 Protein expression vector, N-terminal fusions to thioredoxin tag and C-terminal fusions to six-Histidine tag, Apr Invitrogen pET300/NT-DEST Protein expression vector, N-terminal fusions to six-Histidine tag, Apr Invitrogen pTAC-PX3 0.