Investigating the effects of variability of operational parameters on MATH test for bacterial hydrophobicity measurement.

Microbial adhesion and transport are significantly influenced by their hydrophobicity. Various domains, such as biofouling, bioremediation, wastewater treatment, oil recovery, pathogenesis, implant infections, and several other microbial disciplines, make use of hydrophobicity assessment. One easy assay for assessing the microbial surface hydrophobicity is the microbial adhesion to hydrocarbons (MATH) test which works on the differential partitioning of microbes at a hydrocarbon-aqueous interface. Unfortunately, a standard protocol for this test is still unavailable, even though it has been widely studied and it is known that the results are sensitive to the operating parameters used. This study has been envisaged to investigate the effects of variations in the MATH test parameters on the hydrophobicity results. For this purpose, six different test parameters (vortex duration, phase separation period, hydrocarbon-aqueous phase volume ratio, hydrocarbon selection, absorbance wavelength, and suspension medium) were varied. Four different Gram-negative bacteria were used for experimentation. It was observed that except for phase separation period, all other test parameters significantly influenced the hydrophobicity results. Furthermore, the hydrocarbon saturation of the suspension medium was a critical factor for growth medium suspensions. This study is expected to guide researchers in selecting the appropriate values of test parameters for MATH tests and enhance our understanding of this technique and pave the way for developing a standardized protocol.