Implications of Growth and Starvation Conditions in Bacterial Adhesion and Transport

Biofouling is synonymous with unwanted biofilms and leads to problems ranging from efficiency and resource loss to health risks. While a number of bacterial properties including biomass concentration and hydrophobicity are considered critical to biofilm development and bacterial adhesion, the variations in these properties under growth and starvation conditions are not very well known. Here, we describe the trends in these properties for four Gram-negative bacteria under growth and extended starvation conditions. A convenient and frequently-used laboratory assay, the microbial adhesion to hydrocarbons (MATH) test, was used to determine the microbial hydrophobicity based on the partitioning of cells at an aqueous-hydrocarbon interface. The bacteria tested exhibited a plateau in hydrophobicity values during the stationary growth phase and longer starvation durations (>= 10 days). Starved cultures had higher hydrophobicity and lower cell sizes than growth cultures. Interestingly, hydrocarbon exposure led to an increase in cell size for starved cells as compared to control cultures, while cells under growth conditions did not show significant size changes due to hydrocarbon presence. Cells starved for short durations (up to 7-10 days) exhibited significant variations in microbial hydrophobicity, cell size, and biomass concentration (total proteins and optical density). These results show the importance of studying the bacterial properties as a function of growth and starvation phase for cell adhesion in the context of biofilm formation and biofouling. (C) Koninklijke Brill NV, Leiden, 2011