In vitro studies of bioflm-forming Bacillus strains, biocontrol agents isolated from the maize phyllosphere

FESSIA, A.; SARTORI, M.; GARCÍA, D.; FERNÁNDEZ, L.; PONZIO, R.; BARROS, G.; NESCI, A.

Biofilm

Elsevier

Año: 2022 vol. 4

2590-2075

We aimed to assess how bioflm formation by three Bacillus isolates was affected by changes in temperature,water potential, growth media, time, and the combinations between these factors. The strains had been selectedas potential biological control agents (BCAs) in earlier studies, and they were identifed as B. subtilis andB. velezensis spp. through 16 rRNA sequencing and MALDI-TOF MS. Maize leaves (ML) were used as one of thegrowth media, since they made it possible to simulate the nutrient content in the maize phyllosphere, from whichthe bacteria were originally isolated. The strains were able to form bioflm both in ML and bioflm-inducing MSggafter 24, 48, and 72 h. Bioflm development in the form of pellicles and architecturally complex colonies variedmorphologically from one strain to another and depended on the conditions mentioned above. In all cases,colonies and pellicles were less complex when both temperature and water potential were lower. Scanningelectron microscopy (SEM) revealed that changing levels of complexity in pellicles were correlated with those incolonies. Statistical analyses found that the quantifcation of bioflm produced by the isolates was influenced byall the conditions tested. In terms of motility (which may contribute to bioflm formation), swimming andswarming were possible for all strains in 0.3 and 0.7% agar, respectively. A more in-depth understanding of howabiotic factors influence bioflm formation can contribute to a more effective use of these biocontrol strainsagainst pathogens in the maize phyllosphere