Directional Colony Growth of Cupriavidus toward Sphingomonads

Area of Science:

• Microbial Ecology
• Bacterial Interactions
• Surface Microbiology

Background:

• Bacterial communities form through physical encounters on surfaces.
• Mechanisms of initial bacterial interactions on solid surfaces are poorly understood.
• A consortium degrading gamma-hexachlorocyclohexane (γ-HCH) involves Cupriavidus sp. strain TKC and Sphingobium sp. strain TKS.

Purpose of the Study:

• To elucidate the mechanisms behind initial bacterial interactions on solid surfaces.
• To investigate the phenomenon of directional colony growth (DCG) observed in Cupriavidus sp. strain TKC.
• To identify the cues and molecular mechanisms mediating selective bacterial interactions.

Main Methods:

• Co-culturing Cupriavidus sp. strain TKC with Sphingobium sp. strain TKS on R2A agar.
• Observing and characterizing directional colony growth (DCG) patterns.
• Testing DCG activity against various bacterial taxa and identifying inducing molecules (e.g., sphingosine) and inhibitors (e.g., myriocin).

Main Results:

• Cupriavidus sp. strain TKC exhibited DCG, characterized by asymmetric expansion towards neighboring Sphingobium sp. strain TKS colonies.
• DCG facilitated the physical association and surface dispersal of non-motile Sphingobium cells.
• DCG was selectively induced by sphingomonads, with sphingosine identified as a key inducer, and its effect was suppressed by myriocin.

Conclusions:

• Directional colony growth (DCG) is a mechanism for initial spatial organization in bacterial communities.
• Cupriavidus sp. strain TKC exhibits taxon-specific DCG toward sphingomonads, mediated by sphingosine.
• This sphingosine-mediated interaction plays a crucial role in facilitating physical association and dispersal of bacterial cells on surfaces.