Purpose: The purpose of this study is to examine the relationship between biofilm formation and sporulation of Paenibacillus species isolated from the environment.
Methods: Thirteen Paenibacillus strains isolated from various sources such as decayed foods or raw materials were cultured in 96-well microtiter plates at 30°C for 96 h and biofilm formation was examined by crystal violet staining. To determine the sporulation efficiency, the cells in each of the biofilm and planktonic cell fractions were heated at 80°C for 10 min, and then heat-resistant spores were counted by plating method. To purify the spores derived from biofilms and planktonic cells, the spores were precipitated by centrifugation of the culture medium, and the remaining vegetative cells and the mother cells were removed by washing the precipitates with distilled water.
Results: Most of the Paenibacillus species formed biofilms. Moreover, most of the spores formed were found in the biofilms of Paenibacillus glucanolyticus and Paenibacillus polymyxa. Lastly, the spores derived from these biofilms were longer than those derived from planktonic cells, as observed by phase contrast microscopy.
Significance: These findings suggest that biofilms are reservoirs of spores. Therefore, the understanding and control of biofilms as well as sporulation are fundamental to the prevention of food spoilage by Paenibacillus species.