An orphan gyrB in the Mycobacterium smegmatis genome uncovered by comparative genomics.

DNA gyrase is an essential topoisomerase found in all bacteria. It is encoded by gyrB and gyrA genes. These genes are organized differently in different bacteria. Direct comparison of Mycobacterium tuberculosis and Mycobacterium smegmatis genomes reveals presence of an additional gyrB in M. smegmatis flanked by novel genes. Analysis of the amino acid sequence of GyrB from different organisms suggests that the orphan GyrB in M. smegmatis may have an important cellular role.

Movilidad por deslizamiento y formación de biofilms en las micobacterias / Sliding mobility and biofilm formation in mycobacterium

Usando como modelo Mycobacterium smegmatis, un organismo no movil, hemos estudiado por primera vez en una especie micobacteriana el fenómeno llamado" deslizamiento" o sliding motility, así como la formación de biofilms. Para ello se realizó un screen de mutantes con la finalidad de identificar los genes necesarios para el deslizamiento sobre placas de mivilidad. El análisis genético aquí descrito ha sido publicado recientemente. Los genes requeridos tanto para deslizamiento como para la formación de biofilms (mps y tmtpC) están relacionados con el proceso de biosíntesis y transporte de los glicopeptidolípidos (GPLs) a la cápsula de las micobacterias. En base a nuestros resultados proponemos un modelo para el papel que juegan los GPLs en ambos fenómenos

Expression of the Mycobacterium bovis P36 gene in Mycobacterium smegmatis and the baculovirus/insect cell system

In the present study we evaluated different systems for the expression of mycobacterial antigen P36 secreted by Mycobacterium bovis. P36 was detected by Western blot using a specific antiserum. The P36 gene was initially expressed in E. coli, under the control of the T7 promoter, but severe proteolysis prevented its purification. We then tried to express P36 in M. smegmatis and insect cells. For M. smegmatis, we used three different plasmid vectors differing in copy number and in the presence of a promoter for expression of heterologous proteins. P36 was detected in the cell extract and culture supernatant in both expression systems and was recognized by sera from M. bovis-infected cattle. To compare the expression level and compartmentalization, the MPB70 antigen was also expressed. The highest production was reached in insect cell supernatants. In conclusion, M. smegmatis and especially the baculovirus expression system are good choices for the production of proteins from pathogenic mycobacteria for the development of mycobacterial vaccines and diagnostic reagents