INTERACTIONS OF CLAY-MINERALS WITH ARTHROBACTER CRYSTALLOPOIETES - STARVATION, SURVIVAL AND 2-HYDROXYPYRIDINE CATABOLISM

For bacterial inoculants to be effective in soil remediation, the bact erial strain must be capable of overcoming any negative effects of soi l minerals on cellular processes. One class of minerals commonly encou ntered by soil bacteria is clays. Thus, the effect of commonly occurri ng clay minerals in soils on starvation, survival and 2-hydroxypyridin e catabolism by Arthrobacter crystallopoietes was evaluated. Stationar y phase A. crystallopoietes cells were suspended in 0.03 M, pH 7.0, ph osphate buffer containing no clay or amended with 0.2% (wt/vol) montmo rillonite, sodium montmorillonite or kaolinite. Marked effects of clay minerals on both survival rates and catabolic rates of 2-hydroxypyrid ine were noted. For example, after 14 weeks starvation, 4.6% of the in itial cell population was viable with no clay present, compared to 0.8 % (montmorillonite), 22.1% (kaolinite) and 54.1% (sodium montmorilloni te) in the presence of the clay minerals. Acclimated and nonacclimated cell populations were used to evaluate 2-hydroxypyridine catabolism. Induction of 2-hydroxypyridine metabolism occurred in the unacclimated cells following starvation. Differential impact of the clay minerals on unacclimated cells was detected. Montmorillonite enhanced the capac ity for induction of 2-hydroxypyridine catabolism and its decompositio n rate after 0-3 days starvation. For acclimated cells, clay did not a ffect the metabolic activity prior to starvation, but the presence of clay resulted in increased activity during starvation. For example, af ter 3 days starvation, a nearly two fold increase in metabolism was de tected in the presence of clay minerals. These data suggest that some clay minerals in soil alter the survival time and metabolic activity o f soil-amended bacteria, thereby affecting the potential for bioremedi ation success.