Predation by Myxococcus xanthus induces Bacillus subtilis to form spore-filled megastructures

Area of Science:

• Microbiology
• Bacterial Interactions
• Biofilm Formation

Background:

• Biofilm formation is a key survival strategy for bacteria under environmental stress.
• Interspecies interactions, like predator-prey dynamics, can trigger novel biofilm structures.

Purpose of the Study:

• To investigate the formation of a unique biofilm structure in Bacillus subtilis induced by Myxococcus xanthus predation.
• To characterize the genetic basis and survival advantage of this novel biofilm.

Main Methods:

• Induction of biofilm formation through prolonged co-cultivation of M. xanthus and B. subtilis.
• Microscopic analysis to determine megastructure morphology and dimensions.
• Genetic analysis to identify genes involved and distinguish from known biofilm pathways.
• Comparative analysis of wild-type and mutant B. subtilis strains.

Main Results:

• A novel, tree-like biofilm, termed megastructure, was observed in B. subtilis.
• Megastructures are large, raised structures containing viable endospores within a dense matrix.
• Formation is genetically distinct from standard colony biofilms and independent of specific known genes (TasA, EpsE, SinI, RemA, surfactin).
• Megastructures provide protection against M. xanthus predation, as endospores are resistant.
• M. xanthus fruiting bodies were found near megastructures, indicating inability to access nutrients within.
• Bacillaene-deficient mutants formed megastructures faster, suggesting a role in defense.

Conclusions:

• Megastructure formation is an alternative survival mechanism for B. subtilis against predation.
• This process facilitates bacterial escape into dormancy via sporulation.
• Bacillaene production may play a role in regulating megastructure formation speed.