Identification of mutations associated with macrofiber formation in Bacillus subtilis

Area of Science:

• Microbiology
• Bacterial Genetics
• Cell Biology

Background:

• Bacillus subtilis can produce helical macrofibers, a complex cellular structure.
• The genetic basis for macrofiber production, particularly the role of cell division regulation, was previously unclear.
• The div IV-B1 mutation causes minicell production but is insufficient for macrofiber formation on its own.

Purpose of the Study:

• To identify the specific genes responsible for helical macrofiber production in Bacillus subtilis.
• To elucidate the roles of these genes in cell division suppression and macrofiber organization.
• To determine if these genes are linked to helix hand determination.

Main Methods:

• Genetic analysis of original macrofiber-producing Bacillus subtilis strains.
• Mapping of mutations to identify responsible genetic loci.
• Complementation tests and allelism studies with known division suppression mutations.

Main Results:

• Two distinct genetic loci, fibA and fibB, were identified as essential for macrofiber production.
• fibA is associated with temporary division suppression and rudimentary fibers, while fibB mediates persistent suppression and organized helical macrofibers.
• Neither fibA nor fibB mutations were found to determine the helix hand, and they are distinct from other known division suppression mutations.

Conclusions:

• The fibA and fibB genes are critical for the development of helical macrofibers in Bacillus subtilis by regulating cell division.
• fibB plays a more significant role in the formation of highly organized helical macrofibers compared to fibA.
• The genetic control of macrofiber formation is separable from the determination of helix hand.