Evaluation of the Survival Capability under Extreme Conditions of the bacterium Psychrobacter faecalis

• Grant number: 23/13224-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2023
• End date: November 30, 2024
• Field of knowledge: Biological Sciences - Microbiology
• Principal Investigator: Iolanda Cristina Silveira Duarte
• Grantee: Vitor Morais de Almeida
• Host Institution: Centro de Ciências Humanas e Biológicas (CCHB). Universidade Federal de São Carlos (UFSCAR). Sorocaba , SP, Brazil

Abstract

The extremophiles are organisms that have the capability to survive when exposed to unfavorable conditions, such as high or low temperatures, high doses of radiation, dry or highly acidic environments, among others. Therefore, they have a great biotechnological importance, as they are sources of many products, whether extremozymes or other secondary metabolites. This project aims to seek a better understanding of the extreme survival conditions of the bacterium Psychrobacter faecalis, previously isolated from solar panels, and to determine if it is a polyextremophile and for which conditions. Initially, the conditions of desiccation, UV irradiation, salinity, pH, and temperature will be tested. For the desiccation, UV irradiation, and temperature tests, the post-exposure survival rate under adverse conditions will be calculated through serial dilutions and Colony Forming Units (CFU) counting. In the desiccation assays, the bacteria will be exposed to a low relative humidity environment for predetermined periods. For the UV irradiation assays, the bacteria will be irradiated with varying doses of UV-C radiation. And in the temperature experiments, an aliquot of the inoculum will be transferred to test tubes with nutrient broth and incubated at a predetermined temperature range for one hour. For the salinity tests, aliquots of the inoculum will be transferred to tubes with nutrient broth at a salinity gradient, and incubated for one week. Their optical density at 600 nm will be measured daily to build a growth curve and verify how the concentration of salts can affect microbial survival. In the pH experiments, aliquots of the inoculum will be transferred to a 96-well microplates containing pH-adjusted nutrient broth between 3 to 7. The plates will be incubated, and then the iodonitrotetrazolium chloride or a similar indicator will be added to obtain a visual diagnosis of microbial growth in each well based on pink color intensities. Aliquots from all wells will be diluted and subcultured, and the plates will be incubated to observe whether there was microbial growth or not. In general, the survival rates will be calculated for the desiccation, irradiation, and temperature assays, a growth curve will be constructed for salinity, and pH growth will be visually monitored.