Applicability of the BioArena System to Investigation of the Mechanisms of Biological Effects

Bioautography can he extended to a complex system called BioArena by linking different steps to it, for example dissolving a variety of compounds in the cell suspension to affect biological activity, measuring putative mediators of antibiosis, for example formaldehyde (HCHO) and hydrogen peroxide (H2O2) in the inoculated layer, and performing densitometric and ex and in situ spectroscopic examination to follow the changes in the inhibition zones and active compounds (e.g. antibiotics and toxins). Possibilities of the basic elements of BioArena system are illustrated in this paper by results with aflatoxin B1 (AFB1). Target bacterial cells in the logarithmic growth phase were found to be the most sensitive for direct bioautography. Densitometric signals of bioautograms (negative densitometry) of 0.125-1 mu g AFB1 spots showed logarithmic correlation with the amount of AFB1. The HCHO capturer L-arginine decreased whereas the HCHO generator-mobilizer Cu(II) ions increased the antibacterial-toxic effect of AFB1. The latter effect was also confirmed by negative densitometry. Besides higher levels of HCHO, a decrease of 14,0, in the toxin spot,,vas found. HCHO could also originate, among other sources, from demethylation of AFB1, which is apparent from the Fourier transform Rantan spectra obtained in situ from the AFB1-containing spots. These results support the suggested role of HCHO and its reaction products with H2O2 (e.g. singlet oxygen (O-1(2)), ozone (O-3)) in the anti bacterial-toxic effect of AFB1.