L-tyrosine modulates biofilm formation of Bacillus cereus ATCC 14579

Bacillus cereus is a food-borne pathogen capable of producing biofilms. Following analysis of biofilm formation by B. cereus ATCC 14579 transposon mutants in defined medium (DM), a deletion mutant of bc2939 (Dbc2939) was constructed that showed decreased crystal violet biofilm staining and biofilm cell counts. In addition, Dbc2939 also produced smaller colony biofilms with lower cell counts and loss of wrinkly morphology. The bc2939 gene encodes for Prephenate dehydrogenase, which converts Pre-phenate to 4-Hydroxy-phenylpyruvate (4-HPPA) in the L-tyrosine branch of the Shikimate pathway. While growth of the mutant and WT in DM was similar, addition of L-tyrosine was required to restore WT-like (colony) biofilm formation. Comparative proteomics showed reduced expression of Tyrosine-protein kinase/phosphatase regulators and extracellular polysaccharide cluster 1 (EPS1) proteins, aero-bic electron transfer chain cytochrome aa3/d quinol oxidases, and iso-chorismate synthase involved in menaquinone synthesis in DM grown mutant biofilm cells, while multiple oxidative stress-related cat-alases and superoxide dismutases were upregulated. Performance in shaking cultures showed a 10 0-fold lower concentration of menaquinone-7 and reduction in cell counts of DM grown Dbc2939 indicating increased oxygen sensitivity. Combining all results, points to an important role of Tyrosine-modulated EPS1 production and menaquinone-dependent aerobic respiration in B. cereus ATCC 14579 (colony) biofilm formation.& COPY; 2023 The Authors. Published by Elsevier Masson SAS on behalf of Institut Pasteur. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).