Fish skin bacteria: Colonial and cellular hydrophobicity

Area of Science:

• Microbiology
• Biophysics
• Marine Biology

Background:

• Bacteria colonize the skin of aquatic organisms, influencing their surface properties.
• Understanding bacterial surface characteristics is crucial for ecological interactions.
• Fish locomotion may be affected by skin-associated microbial communities.

Purpose of the Study:

• To characterize the surface hydrophobicity of bacteria isolated from healthy fish skin.
• To compare colonial hydrophobicity with cellular hydrophobicity using novel and established methods.
• To explore the potential role of these bacteria in fish locomotion.

Main Methods:

• Desorption of bacteria from fish skin using sonic oscillation and surface-active agents.
• Measurement of bacterial adhesion to hexadecane.
• Application of the "Direction of Spreading" (DOS) method to assess bacterial lawn hydrophobicity.
• Comparison of hydrophobicity between bacterial lawns, polystyrene, and glass.

Main Results:

• Thirteen fish skin bacterial isolates were examined for hydrophobicity.
• Two strains showed high colonial hydrophobicity comparable to polystyrene by the DOS method.
• Significant discrepancies were observed between high colonial hydrophobicity and low/moderate cellular adhesion to hexadecane for several strains.
• A hydrophobic slime layer, potentially removed during washing, may explain the observed differences.

Conclusions:

• Bacterial surface properties, particularly hydrophobicity, can vary significantly between colonial and cellular states.
• The "Direction of Spreading" (DOS) method offers a novel approach to evaluate bacterial lawn hydrophobicity.
• Fish skin bacteria may possess unique surface characteristics, potentially influencing drag reduction and fish locomotion through slime production.