To investigate the role of aiiA gene in Bacillus thuringiensis, B. thuringiensis strain BMB171 was selected and three derivatives were constructed, such that (1) aiiA was knocked out (aiiA-KO), (2) aiiA-KO was reversed (aiiA-Rev) and (3) the expression of aiiA was elevated (aiiA-Elevated). First, we found that mutation of aiiA increased the ethanol tolerance in B. thuringiensis. Omitting ethanol from the medium resulted in a decreased generation time for aiiA-Elevated. In contrast, aiiA-KO had the highest ethanol tolerance when the medium contained 2 or 4% ethanol. Second, we found that more melanin was produced at 37 C when aiiA expression was elevated. Third, we found inhibition of swarming motility in the aiiA-Elevated group. Finally, there was delayed sporulation in Luria-Bertani, ICPM, casein and ammonium sulfate medium in the aiiA-Elevated group. The conclusion was that ethanol tolerance, yield of melanin, swarming motility and growth are correlated with the expression levels of aiiA gene in B. thuringiensis. (c) 2005 Elsevier Inc. All rights reserved.