Characterisation of porin genes from Mycobacterium fortuitum and their impact on growth.
BACKGROUND
Highly pathogenic mycobacteria like Mycobacterium tuberculosis are characterised by their slow growth and their ability to reside and multiply in the very hostile phagosomal environment and a correlation between the growth rate of mycobacteria and their pathogenicity has been hypothesised. Here, porin genes from M. fortuitum were cloned and characterised to address their impact on the growth rate of fast-growing and pathogenic mycobacteria.


RESULTS
Two genes encoding porins orthologous to MspA from M. smegmatis, porM1 and porM2, were cloned from M. fortuitum strains, which were originally isolated from human patients. Both porin genes were at least partially able to complement the mutations of a M. smegmatis mutant strain lacking the genes mspA and mspC with respect to the growth rate. PorM1 and porM2 were present in different strains of M. fortuitum including the type strain. Comparative expression analysis of porM genes revealed divergent porin expression among analysed M. fortuitum strains. Repression of the expression of porins by antisense technique decreased the growth rates of different M. fortuitum. The effects of over-expression of porM1 as well as porM2 varied depending on the strain and the concentration of antibiotic added to the medium and indicated that PorM1 and PorM2 enhance the growth of M. fortuitum strains, but also the diffusion of the antibiotic kanamycin into the cells.


CONCLUSIONS
This study demonstrates the important role of porin expression in growth as well as antibiotic susceptibility of the opportunistic bacterium M. fortuitum.
Sharbati
Soroush
S
Freie Universität Berlin, Institute of Veterinary Biochemistry, Berlin, Germany. sharbati@zedat.fu-berlin.de
Schramm
Kira
K
Rempel
Sonja
S
Wang
Hwa
H
Andrich
Ronny
R
Tykiel
Verena
V
Kunisch
Ralph
R
Lewin
Astrid
A
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D020869:Gene Expression Profiling; D055785:Gene Knockdown Techniques; D023061:Gene Order; D005816:Genetic Complementation Test; D006801:Humans; D007612:Kanamycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation; D009165:Mycobacterium Infections, Nontuberculous / Q000382:microbiology; D019907:Mycobacterium fortuitum / Q000235:genetics* / Q000254:growth & development* / Q000302:isolation & purification; D020102:Mycobacterium smegmatis / Q000235:genetics; D018272:Porins / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; C434272:MspC protein, Mycobacterium smegmatis; D018272:Porins; C121838:mspA protein, Mycobacterium smegmatis; D007612:Kanamycin