The effect of divalent and trivalent cations on aggregation and surface hydrophobicity of selected microorganism

This study investigated the effect of various cations (Ca2+, Mg2+, Al3+, Mn2+, Zn2+) on the autoaggregation (AAg) and surface hydrophobicity (SHb) of three different bacteria (Brevibacillus panacihumi strain (ZB1), Lysinibacillus fusiformis strain (ZB2) and Enterococcus faecalis strain (ZL)) using a 2-level factorial design. The AAg ratio was measured from the changes in the absorbance of the media. Results show that ZB2 had maximum AAg for the three bacteria investigated. A microscopic clustering of cells was observed when Ca2+ was added to ZB2. The AAg was in the range of 62%, 58% and 34% for ZB2, ZB1 and ZL, respectively and correlated to the SHb. The aggregation and SHb of the microbial cells increased with increasing ionic strength due to the repulsive steric or overlap forces between the polymer covered surfaces. Ca2+ demonstrated a more significant effect on aggregation and SHb of microbial cells due to an attractive binding force.