Determination of the biofilm production capacities and characteristics of members belonging to Bacillaceae family

The biofilm characteristics of many endospore-forming bacilli, especially the thermophiles are still unclear. In this study, a detailed identification and description of biofilm production characteristics of totally 145 isolates and reference strains belonging to Bacillaceae family, displaying thermophilic (n = 115), facultative thermophilic (n = 24) and mesophilic (n = 6) growth from genera Anoxybacillus, Geobacillus, Thermolongibacillus, Aeribacillus, Brevibacillus, Paenibacillus and Bacillus were presented. The incubation temperatures were adjusted to 37, 45 and 55–65 °C for mesophiles, facultative thermophiles, and thermophiles, respectively. The bacilli were evaluated based on their colony morphotypes on Congo red (CR) agar, their complex exopolysaccharide production on calcofluor supplemented tryptic soy agar, and as well as their pellicle formation at the liquid–air surface in tryptic soy broth cultures. Their biofilm production capabilities were also tested on abiotic surfaces of both polystyrene and stainless steel by crystal violet binding assay and viable biofilm cell enumerations, respectively. As a result, the biofilm production capacities of Bacillaceae members from genera to species level, the effects of osmolarity, temperature, incubation time and abiotic surfaces on biofilm formation as well as the CR morphotypes associated with the biofilm production were able to reveal in a wide group of bacilli. Besides, general enrichment-inoculation approaches and methodologies were also offered, which allow and facilitate the screening and determining the biofilm producing endospore forming bacilli.