Heat resistance, membrane fluidity and sublethal damage in Staphylococcus aureus cells grown at different temperatures

Abstract

In this work the influence of growth temperature (10-42 °C) on Staphylococcus aureus heat resistance was studied, and its relationship with the ability of cells to repair sublethal damages and with membrane fluidity was evaluated. Non-linear, convex from above survival curves were obtained, and therefore a special case of the Baranyi model was used to fit them. For exponential phase cells, heat resistance did not change with growth temperature in the range between 10 and 37 °C, but cells grown at 42 °C were significantly more resistant, showing D and shoulder length (sl) values 2.5 and 4 times greater than the others, respectively. For stationary growth phase cells, an increase in growth temperature above 20 °C resulted in an increase in D values, and cells grown at 42 °C also displayed the highest D and sl values. The increased heat resistance at 58 °C of stationary growth phase cells grown at higher temperatures was coincident with the appearance of a higher proportion of sublethally damaged cells capable of recovery and outgrowth in non-selective medium. Membrane fluidity was measured at treatment temperatures, and it was observed that those cells with more rigid membranes displayed greater heat resistance (Pearson coefficient = 0.969***). Additionally, S. aureus cells whose membrane was fluidized through exposure to benzyl alcohol were notably sensitized against the action of heat, in a concentration-dependent manner. Results obtained in this research indicate that membrane physical state could be an important factor determining the survival capacity of bacterial cells to a heat treatment.

3D printing of MXene composite hydrogel scaffolds for photothermal antibacterial activity and bone regeneration in infected bone defect models

“…Studies have shown that S. aureus and E. coli could be killed at around 58 °C generally. 59 We have demonstrated that GTAM0.3 scaffolds have similar biocompatibility and osteogenic properties to GTAM0.5 scaffolds. The temperature of GTAM0.3 could go up to around 56 °C in wet conditions with NIR (808 nm, 1.5 W cm −2 ).…”

Niobium Carbide MXene Augmented Medical Implant Elicits Bacterial Infection Elimination and Tissue Regeneration

“…Coating implants with a phototherapeutic agent could be an alternative, but a single treatment modality like employing hyperthermia may cause high levels of reactive oxygen species (ROS) generation and unwanted proinflammatory cascades, which would delay the wound healing process . Moreover, Gram-positive bacteria such as Staphylococcus aureus are resistant to heat as high as 58 °C, which corroborates the importance of sensitizing the bacteria before photothermal intervention. As such, there is a mounting focus on multimodal methods to augment phototriggered antibacterial strategies by responding to infection in the immune system and accelerating healing.…”

The effect of emulsifier type and oil inclusion on stress‐related gene expression of Salmonella typhimurium in oil‐in‐water emulsion

“…This result implies that the interaction between the positively charged emulsifier and cell membrane may be stronger, potentially providing greater protection against thermal treatment (Tsai & Tikekar, 2023). Another possible explanation is the stress caused by the high temperature itself, which can cause changes in bacterial membrane permeability and fluidity, and disrupt cellular functions, ultimately leading to the effect on bacterial inactivation (Cebrián et al., 2019; Guillén et al., 2021). Thus, the protective effect in this study could be attributed to various stress response mechanisms, including emulsifier stress and high temperature stress.…”