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

FESSIA, ALUMINÉ; SARTORI, MELINA; GARCIA, DAIANA ; FERNANDEZ, LUCIANA ; PONZIO, RODRIGO; BARROS, GERMÁN; NESCI, ANDREA

BIOFILM

Elsevier

Año: 2022 vol. 4

2590-2075

We aimed to assess how biofilm formation by three Bacillus isolates was affected bychanges in temperature, water potential, growth media, time, and the combinationsbetween these factors. The strains had been selected as potential biological controlagents (BCAs) in earlier studies, and they were identified as B. subtilis and B.velezensis spp. through 16 rRNA sequencing and MALDI-TOF MS. Maize leaves (ML)were used as one of the growth media, since they made it possible to simulate thenutrient content in the maize phyllosphere, from which the bacteria were originallyisolated. The strains were able to form biofilm both in ML and biofilm-inducing MSggafter 24, 48, and 72 h. Biofilm development in the form of pellicles and architecturallycomplex colonies varied morphologically from one strain to another and depended onthe conditions mentioned above. In all cases, colonies and pellicles were less complexwhen both temperature and water potential were lower. Scanning electron microscopy(SEM) revealed that changing levels of complexity in pellicles were correlated withthose in colonies. Statistical analyses found that the quantification of biofilm producedby the isolates was influenced by all the conditions tested. In terms of motility (whichmay contribute to biofilm formation), swimming and swarming were possible for allstrains in 0.3 and 0.7% agar, respectively. A more in-depth understanding of howabiotic factors influence biofilm formation can contribute to a more effective use ofthese biocontrol strains against pathogens in the maize phyllosphere