Demonstração de iridescência em bactérias de solo do filo Acidobacteriota

Abstract

Bacterial iridescence is an optical phenomenon that has not been well studied, especially in soil bacteria. Members of the phylum Acidobacteriota were isolated from Cerrado soil and showed iridescence in culture. This study aimed to investigate the factors that influence the production of iridescence by the acidobacteria strain AB23, isolated from Cerrado soil. The hypothesis tested was that iridescence would be induced by cellular stress conditions. The bacteria were cultivated in two different media (VL-55 and R2A), under variations in light, temperature and water availability, using different concentrations of agar and gellan as solidifying agents. The presence of iridescence was assessed by transillumination, while bacterial growth was estimated by counting colony forming units (CFU). The results demonstrated that the AB23 strain presents rainbow-diffuse iridescence, even under conditions considered ideal for growth, such as in the VL-55 medium in the dark. No iridescence was observed in R2A medium or in 2% agar, suggesting that the absence may be related to the opacity of the medium or inadequate culture conditions, and not necessarily to stress. It was concluded that the iridescence of strain AB23 is not directly associated with cellular stress, being also observed under favorable growth conditions. Future studies should investigate the genetic basis of iridescence, searching for genes already correlated with iridescence in the genome of strain AB23, as well as exploring the possible relationship with biofilm formation, using tests such as Congo Red Agar.