Mycobacterium smegmatis Expands Across Surfaces by Hydraulic Sliding.

Area of Science:

• Microbiology
• Bacterial Motility
• Biofilm Formation

Background:

• Mycobacterium smegmatis spreads via passive sliding motility.
• Colony morphology typically results in circular shapes due to growth and adhesion.
• Previous reports noted dendritic colony structures, but a novel form was observed.

Purpose of the Study:

• To investigate the mechanism behind non-circular colony formation in Mycobacterium smegmatis.
• To characterize the unique structure and motility associated with digitate colonies.
• To identify novel behaviors in mycobacterial colonization and virulence.

Main Methods:

• Reproducing circular and non-circular (digitate) colony morphotypes.
• Utilizing time-lapse microscopy to observe colony expansion dynamics.
• Analyzing the structural components of digitate colonies, including pellicle and biofilm.

Main Results:

• Digitate colonies feature centimeter-long linear protrusions with a central, fluid-filled channel.
• Colony extension occurs via expansion of the fluid channel, not bacterial growth.
• A pellicle (floating biofilm) forms without an initial liquid-air interface, indicating novel behavior.

Conclusions:

• A new form of sliding motility, termed 'hydraulic sliding,' has been discovered in Mycobacterium smegmatis.
• This motility is linked to a unique digitate colony structure driven by fluid core expansion.
• The findings suggest a previously unrecognized mycobacterial behavior potentially crucial for colonization and virulence.