Accumulation of Poly(3-hydroxybutyrate) Helps Bacterial Cells to Survive Freezing.
Accumulation of polyhydroxybutyrate (PHB) seems to be a common metabolic strategy adopted by many bacteria to cope with cold environments. This work aimed at evaluating and understanding the cryoprotective effect of PHB. At first a monomer of PHB, 3-hydroxybutyrate, was identified as a potent cryoprotectant capable of protecting model enzyme (lipase), yeast (Saccharomyces cerevisiae) and bacterial cells (Cupriavidus necator) against the adverse effects of freezing-thawing cycles. Further, the viability of the frozen-thawed PHB accumulating strain of C. necator was compared to that of the PHB non-accumulating mutant. The presence of PHB granules in cells was revealed to be a significant advantage during freezing. This might be attributed to the higher intracellular level of 3-hydroxybutyrate in PHB accumulating cells (due to the action of parallel PHB synthesis and degradation, the so-called PHB cycle), but the cryoprotective effect of PHB granules seems to be more complex. Since intracellular PHB granules retain highly flexible properties even at extremely low temperatures (observed by cryo-SEM), it can be expected that PHB granules protect cells against injury from extracellular ice. Finally, thermal analysis indicates that PHB-containing cells exhibit a higher rate of transmembrane water transport, which protects cells against the formation of intracellular ice which usually has fatal consequences.
Materials Research Centre, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00, Brno, Czech Republic.
Stanislav
S
Obruca
Materials Research Centre, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00, Brno, Czech Republic.
Petr
P
Sedlacek
Institute of Scientific Instruments, Academy of Sciences of The Czech Republic, Vvi, Kralovopolska 147, 612 64, Brno, Czech Republic.
Vladislav
V
Krzyzanek
Materials Research Centre, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00, Brno, Czech Republic.
Filip
F
Mravec
Institute of Scientific Instruments, Academy of Sciences of The Czech Republic, Vvi, Kralovopolska 147, 612 64, Brno, Czech Republic.
Kamila
K
Hrubanova
Institute of Scientific Instruments, Academy of Sciences of The Czech Republic, Vvi, Kralovopolska 147, 612 64, Brno, Czech Republic.
Ota
O
Samek
Materials Research Centre, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00, Brno, Czech Republic.
Dan
D
Kucera
Materials Research Centre, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00, Brno, Czech Republic.
Pavla
P
Benesova
Materials Research Centre, Faculty of Chemistry, Brno University of Technology, Purkynova 118, 612 00, Brno, Czech Republic.
Ivana
I
Marova
D003451:Cryoprotective Agents / Q000378:metabolism*; D020118:Cupriavidus necator / Q000235:genetics / Q000378:metabolism*; D005615:Freezing; D006885:Hydroxybutyrates / Q000378:metabolism*; D015388:Organelles / Q000378:metabolism*; D011091:Polyesters / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D000094122:Polyhydroxybutyrates
D003451:Cryoprotective Agents; D006885:Hydroxybutyrates; D011091:Polyesters; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates