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Glucose Uptake Pathway-Specific Regulation of Synthesis of Neotrehalosadiamine, a Novel Autoinducer Produced in Bacillus subtilis

National Food Research Institute, Tsukuba, Ibaraki 305-8642, Japan

Received 19 September 2006/ Accepted 6 October 2006

Neotrehalosadiamine (3,3'-diamino-3,3'-dideoxy-,ß-trehalose; NTD) is an amino-sugar antibiotic produced by several Bacillus species that functions as an autoinducer by activating its own biosynthetic operon, ntdABC. We previously reported that the introduction of a certain rpoB mutation (rpoB5) into Bacillus subtilis enables the cells to overproduce NTD. B. subtilis mini-Tn10 transposant libraries have been screened for genes that affect NTD production. Inactivation of ccpA, which encodes a major transcriptional regulator of carbon catabolite regulation, markedly reduced NTD production. By contrast, inactivation of glcP, which is situated just downstream of ntdABC and encodes a glucose/mannose:H⁺ symport permease, stimulated NTD production. Overexpression of glcP led to the repression of ntdABC expression (and thus NTD production) in response to GlcP-mediated glucose uptake. These results suggest that CcpA-mediated catabolite activation of ntdABC expression occurs in response to the increase of the in vivo concentration of fructose-1,6-bisphosphate via glucose-6-phosphate and that GlcP-mediated glucose repression of ntdABC expression occurs in association with the increase of the in vivo concentration of unphosphorylated glucose. In addition, Northern analysis showed that glcP is transcribed from the ntdABC promoter through transcription readthrough at the ntdABC transcription terminator site, which enables NTD to function as a modulator of glucose uptake through the stimulation of ntdABC-glcP transcription, even in wild-type (rpoB⁺) cells. A trace amount (0.5 to 3 µg/ml) of NTD was sufficient to ensure expression of glcP, thus demonstrating the physiological role of "antibiotic" in the producing bacteria by functioning as an autoinducer for glucose uptake modulation.

Published ahead of print on 20 October 2006.