Carbon dioxide can inhibit biofilms formation and cellular properties of Shewanella putrefaciens at both 30 °C and 4 °C

Abstract

Shewanella putrefaciens (S. putrefaciens), which is a common specific spoilage organism (SSO) of marine fish, has strong spoilage ability even under low-temperature conditions. Carbon dioxide (CO2) was widely applied to control microorganisms in aquatic products package. To explore the regulation mechanism of CO2 on biofilm formation and cell properties of S. putrefaciens, the dynamic formation process of biofilms, cellular surface properties, and cellular metabolic characteristics of S. putrefaciens at both 30 °C and 4 °C in pure CO2 gas were evaluated. As evidenced by the crystal violet staining method, confocal laser scanning microscopy (CLSM) analysis, and field emission scanning electron microscopy (FESEM) observation, dynamic formation process of S. putrefaciens biofilms was apparently delayed by CO2 with integral cellular morphology. The number and viability of sessile cells in S. putrefaciens biofilms was significantly lower than those in normal air composition. The changes in cellular surface properties, such as decreased auto-aggregation and hydrophobicity, might be one of the reasons why biofilms were inhibited by CO2. Inhibition of swimming and swarming motility ability by CO2 could also be observed with significantly shorter bacterial halo diameter. What’s more, cellular metabolism was significantly decreased by CO2 according to the results of ATP content, ATPase activity and extracellular proteolytic activity. The influence of CO2 could be both observed whether combined with 30 °C or 4 °C. However, the inhibition produced by CO2 was more pronounced at the incubation temperature of 4 °C. In summary, it could be concluded that the dynamic formation process of S. putrefaciens biofilms and cellular metabolic properties could be inhibited by CO2. This research provided a theoretical basis for better application of CO2 to regulate spoilage microorganisms.