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The role of iron in Mycobacterium smegmatis biofilm formation: the exochelin siderophore is essential in limiting iron conditions for biofilm formation but not for planktonic growth.

Ojha A, Hatfull GF - Mol. Microbiol. (2007)

Bottom Line: In contrast, although the expression of mycobactin and iron ABC transport operons is highly upregulated during biofilm formation, mutants in these systems form normal biofilms in low-iron (2 microM) conditions.A close correlation between iron availability and matrix-associated fatty acids implies a possible metabolic role in the late stages of biofilm maturation, in addition to the early regulatory role.M. smegmatis surface motility is similarly dependent on iron availability, requiring both supplemental iron and the exochelin pathway to acquire it.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.

ABSTRACT
Many species of mycobacteria form structured biofilm communities at liquid-air interfaces and on solid surfaces. Full development of Mycobacterium smegmatis biofilms requires addition of supplemental iron above 1 microM ferrous sulphate, although addition of iron is not needed for planktonic growth. Microarray analysis of the M. smegmatis transcriptome shows that iron-responsive genes - especially those involved in siderophore synthesis and iron uptake - are strongly induced during biofilm formation reflecting a response to iron deprivation, even when 2 microM iron is present. The acquisition of iron under these conditions is specifically dependent on the exochelin synthesis and uptake pathways, and the strong defect of an iron-exochelin uptake mutant suggests a regulatory role of iron in the transition to biofilm growth. In contrast, although the expression of mycobactin and iron ABC transport operons is highly upregulated during biofilm formation, mutants in these systems form normal biofilms in low-iron (2 microM) conditions. A close correlation between iron availability and matrix-associated fatty acids implies a possible metabolic role in the late stages of biofilm maturation, in addition to the early regulatory role. M. smegmatis surface motility is similarly dependent on iron availability, requiring both supplemental iron and the exochelin pathway to acquire it.

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MALDI-TOF analysis of mycolic acid extracts from M. smegmatis cells in different growth states. The origin and treatment of cell cultures is as follows. A. Exponential planktonic growth, total-cell extract. B. Four-day biofilm, total-cell extract. C. Stationary-phase culture, total-cell extract. D. Four-day biofilm, cell-associated extract. E. Four-day biofilm, solvent extractable extract.
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fig07: MALDI-TOF analysis of mycolic acid extracts from M. smegmatis cells in different growth states. The origin and treatment of cell cultures is as follows. A. Exponential planktonic growth, total-cell extract. B. Four-day biofilm, total-cell extract. C. Stationary-phase culture, total-cell extract. D. Four-day biofilm, cell-associated extract. E. Four-day biofilm, solvent extractable extract.

Mentions: Because the synthesis of the C56–C68 fatty acids correlates closely with biofilm maturation, it is likely that these are a central component of the extracellular matrix. To test this, we asked whether these can be extracted from a mature biofilm sample, or whether they remain attached to the cell surface. It is clear that most of these are indeed extractable and thus are presumably matrix components (Fig. 7). We also note that some synthesis of these fatty acids also occurs in stationary-phase cells (Fig. 7).


The role of iron in Mycobacterium smegmatis biofilm formation: the exochelin siderophore is essential in limiting iron conditions for biofilm formation but not for planktonic growth.

Ojha A, Hatfull GF - Mol. Microbiol. (2007)

MALDI-TOF analysis of mycolic acid extracts from M. smegmatis cells in different growth states. The origin and treatment of cell cultures is as follows. A. Exponential planktonic growth, total-cell extract. B. Four-day biofilm, total-cell extract. C. Stationary-phase culture, total-cell extract. D. Four-day biofilm, cell-associated extract. E. Four-day biofilm, solvent extractable extract.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2170428&req=5

fig07: MALDI-TOF analysis of mycolic acid extracts from M. smegmatis cells in different growth states. The origin and treatment of cell cultures is as follows. A. Exponential planktonic growth, total-cell extract. B. Four-day biofilm, total-cell extract. C. Stationary-phase culture, total-cell extract. D. Four-day biofilm, cell-associated extract. E. Four-day biofilm, solvent extractable extract.
Mentions: Because the synthesis of the C56–C68 fatty acids correlates closely with biofilm maturation, it is likely that these are a central component of the extracellular matrix. To test this, we asked whether these can be extracted from a mature biofilm sample, or whether they remain attached to the cell surface. It is clear that most of these are indeed extractable and thus are presumably matrix components (Fig. 7). We also note that some synthesis of these fatty acids also occurs in stationary-phase cells (Fig. 7).

Bottom Line: In contrast, although the expression of mycobactin and iron ABC transport operons is highly upregulated during biofilm formation, mutants in these systems form normal biofilms in low-iron (2 microM) conditions.A close correlation between iron availability and matrix-associated fatty acids implies a possible metabolic role in the late stages of biofilm maturation, in addition to the early regulatory role.M. smegmatis surface motility is similarly dependent on iron availability, requiring both supplemental iron and the exochelin pathway to acquire it.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.

ABSTRACT
Many species of mycobacteria form structured biofilm communities at liquid-air interfaces and on solid surfaces. Full development of Mycobacterium smegmatis biofilms requires addition of supplemental iron above 1 microM ferrous sulphate, although addition of iron is not needed for planktonic growth. Microarray analysis of the M. smegmatis transcriptome shows that iron-responsive genes - especially those involved in siderophore synthesis and iron uptake - are strongly induced during biofilm formation reflecting a response to iron deprivation, even when 2 microM iron is present. The acquisition of iron under these conditions is specifically dependent on the exochelin synthesis and uptake pathways, and the strong defect of an iron-exochelin uptake mutant suggests a regulatory role of iron in the transition to biofilm growth. In contrast, although the expression of mycobactin and iron ABC transport operons is highly upregulated during biofilm formation, mutants in these systems form normal biofilms in low-iron (2 microM) conditions. A close correlation between iron availability and matrix-associated fatty acids implies a possible metabolic role in the late stages of biofilm maturation, in addition to the early regulatory role. M. smegmatis surface motility is similarly dependent on iron availability, requiring both supplemental iron and the exochelin pathway to acquire it.

Show MeSH
Related in: MedlinePlus