Table 4.
Growth of Vegetative Cells of 26 Bacteria at 0°C for 35 d under Aerobic O2/N2 Atmospheres
| |
O2/N2 at 0°Cy |
|
|||
|---|---|---|---|---|---|
| Bacteria (strain number)x | 7 days | 14 days | 28 days | 35 days | 30°C in O2/N2z |
| Acinetobacter radioresistens (50v1) | 0y | 0 | 0 | 0 | 3.4 |
| Bacillus megaterium (25hs1) | 0 | 0 | 0 | 0 | 3.3 |
| Bacillus pumilus (31v3) | 0 | 0 | 0 | 0 | 3.7 |
| Bacillus pumilus (40hs1) | 0 | 0 | 0 | 0 | 3.2 |
| Bacillus subtilis (168) | 0 | 0 | 0 | 0 | 3.3 |
| Bacillus subtilis (HA101) | 0 | 0 | 0 | 0 | 3.2 |
| Burkholderia cepacia (ATCC 25608) | 0 | 0 | 0 | 0 | 3.3 |
| Curtobacterium flaccumfaciens (48v2) | 0 | 0 | 0 | 0 | 3.3 |
| Deinococcus radiodurans (R1) | 0 | 0 | 0 | 0 | 2.0 |
| Enterococcus faecalis (ATCC 29212) | 0 | 0 | 0 | 0 | 2.5 |
| Escherichia coli (ATCC 35218) | 0.07 b | 0.13 b | 0.13 b | 0.27 b | 4.0 a |
| Escherichia coli (K12) | 0 | 0 | 0 | 0 | 3.8 |
| Microbacterium oleivorans (27v1b) | 0 | 0 | 0 | 0 | 2.5 |
| Microbacterium oleivorans (32v4) | 0 | 0 | 0 | 0 | 2.3 |
| Microbacterium testaceum (27v1a) | 0 | 0 | 0 | 0 | 2.5 |
| Micrococcus luteus (ACS-22) | 0 b | 0 b | 0 b | 0.07 b | 2.7 a |
| Paenibacillus pabuli (ACS-6) | 0 b | 0 b | 0.10 b | 0.25 b | 4.0 a |
| Proteus mirabilis (ATCC 7002) | 0 | 0 | 0 | 0 | 4.0 |
| Pseudomonas aeruginosa (ATCC 27853) | 0 | 0 | 0 | 0 | 4.0 |
| Pseudomonas fluorescens (ATCC 13525) | 0.6 d | 1.6 c | 2.7 b | 3.7 a | 4.0 a |
| Psychrobacter cryohalolentis (K5) | 0.7 d | 1.5 c | 2.0 bc | 2.8 b | 3.3 a |
| Serratia liquefaciens (ATCC 27592) | 0.4 c | 0.7 c | 1.6 bc | 2.8 b | 4.0 a |
| Sporosarcina aquamarina (SAFN 008) | 0.07 e | 0.5 d | 1.4 c | 2.6 b | 4.0 a |
| Staphylococcus aureus (ATCC 29213) | 0 | 0 | 0 | 0 | 3.5 |
| Staphylococcus aureus (ATCC 33591) | 0 b | 0 b | 0.07 b | 0.07 b | 2.8 a |
| Staphylococcus epidermidis (ATCC 14990) | 0 | 0 | 0 | 0 | 2.8 |
Bacteria were grown for 35 d on trypticase soy agar (TSA) at 0°C, except Psychrobacter cryohalolentis K5, which was grown on sea-salt agar (SSA). Bacteria were incubated under an aerobic O2/N2 (21%/78%) atmosphere and rated on 7, 14, 28, and 35 d.
Bacterial growth for each strain was rated using a 5×pair of jeweler's magnifying glasses. Growth was rated in only the 2nd or 3rd quadrants of three-quadrant streaked plates; the 1st quadrant was ignored in order to avoid false positives. Rating scale: 4=large robust colonies>5 mm in diameter; 3=colonies 2–4 mm in diameter; 2=colonies ∼1 mm in diameter; 1=colonies ∼0.5 mm in diameter; 0.50=colonies<0.5 mm in diameter; 0.1=smallest visually discernible colonies (pin-prick-sized colonies at ∼0.1 mm in diameter); 0=no growth. Letters in rows designate significant differences among time steps for individual species based on ANOVA and protected least-squares mean separation tests (P≤0.05; n=3).
At the end of the assays, all cultures were transferred to lab conditions for an additional 48 h of incubation at 30°C, 1013 mbar, and O2/N2 atmosphere. In general, bacteria grew normally under lab conditions and were not killed by exposure to low-temperature aerobic atmospheres.