IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
New Insights into Bacillus cereus ATCC 14579 unsaturated fatty acids biosynthesis
Autor/es:
CHAZARRETA-CIFRE, LORENA; DE MENDOZA, D; ALTABE, SILVIA (AUTOR CORRESPONDIENTE)
Lugar:
Montecatini
Reunión:
Congreso; 7th Conference on Gram Positive Microorganism; 2013
Institución organizadora:
Comite Organizador
Resumen:
Bacillus cereus is an opportunistic pathogen that can induce food poisoning and has the ability to grow at temperatures between 4ºC and 50°C. These bacteria adapt membrane fluidity during low temperature growth principally by increasing the proportion of unsaturated fatty acids (UFAs) that are essential for the maintenance of membrane structure and function. The biosynthesis of UFAs is carried out by desaturases, a family of enzymes that introduce a double bond at specific positions in fatty acids and play an important role in Bacilli cells to maintain membrane fluidity at low temperatures. B. cereus synthesizes Δ5, Δ10 monoinsaturated and Δ5, 10 di-insaturated fatty acids and the biosynthesis of these fatty acids is augmented as growth temperature decreases. In B. cereus ATCC 14579 genome two genes, BC2983 and BC0400 are annotated as putatives desaturases. Functional characterization of these genes by heterologous expression in B. subtilis confirmed that they encode for a 5 and 10 desturases, that we named Des5 and Des10, respectively. By means of in vivo experiments, we determined that both desaturases are acyl lipid desaturases that uses phospholipids as substrates and ferredoxin as well as flavodoxins as electron donors. Both desaturases synthesize larger proportion of UFAs when individually expressed at low temperature. To test whether these desaturases are regulated by temperature their transcription was analyzed in a collection of B. subtilis mutant strains. These experiments showed that when cultures grown at 37ºC were shifted to 25ºC the transcription of Des5 was increased whereas Des10 was constitutively expressed. These results were also confirmed by real time PCR experiments in B. cereus. Finally, we constructed and characterized a B. cereus des5 and B. cereus des10 null mutant. We found that while des10 is an essential gene, des5 is dispensable for B. cereus growth in minimal medium.