Characterization of thesolOperon in Butanol-HyperproducingClostridium saccharoperbutylacetonicumStrain N1-4 and Its Degeneration Mechanism

Abstract

The solventogenic sol operon consisting of bld, ctfA, ctfB, and adc was cloned from Clostridium saccharoperbutylacetonicum strain N1-4. These genes share as high as 95-98% similarity with the corresponding sol genes of Clostridium beijerinckii NCIMB 8052. The N1-4 sol gene cluster was transcribed in a polycistronic manner under the control of two promoters, and its transcription was highly induced during solventogenesis. Strain DGN3-4, the degenerated strain derived from N1-4, maintained the sol genes, but transcription of the DGN3-4 sol operon was hardly induced during solventogenesis. A substance extracted from the culture supernatants of wild-type N1-4 allowed us to induce transcription of the sol operon in DGN3-4. These results suggest that the degeneration is caused by the incompetence of the induction mechanism of the sol operon, and that transcription might be under the control of a quorum-sensing mechanism.

AnagrQuorum Sensing System That Regulates Granulose Formation and Sporulation in Clostridium acetobutylicum

“…(43) and that they may play a role in regulating both solventogenesis and sporulation (3,20,21). Quorum sensing is a communication mechanism that relies on small, diffusible signal molecules and allows bacteria to coordinate changes in gene expression with cell population density (42).…”

“…Most Gram-positive quorum sensing systems are based on secreted peptides which can be linear or cyclic and sometimes contain extensive posttranslational modifications (23,39). Relatively little is known about the operation of such systems in clostridial species, but for the solventogenic Clostridium sacharoperbutylacetonicum, an as-yetunidentified, self-generated signal in the culture supernatant has been reported to induce solvent formation in a "low-solvent" mutant, suggesting that the metabolic shift from acid to solvent production might be subject to quorum sensing control (20). Furthermore, in silico analysis suggests that agr-type quorum sensing systems may exist in many of the sequenced members of the class Clostridia (reference 43 and unpublished data from this laboratory) although thus far, experimental evidence has been provided for only three species.…”

Perspectives of Biobutanol Production and Use

“…It is questionable how often or under which conditions the degeneration of C.acetobutylicum ATCC 824 happens because in the past, it was reported 218 passages of vegetative C.acetobutylicum ATCC 824 cells did not almost influence their solvents formation (Hartmanis et al, 1986). The cells of C.saccharoperbutylacetonicum N1-4 degenerated when quorum sensing mechanism in the population was impaired (Kosaka et al, 2007). The very detailed study of C.beijerinckii NCIMB 8052 degeneration disclosed two different degeneration causes: involvement of global regulatory gene and defect in NADH generation (Kashket & Cao, 1995).…”

The Past, Present, and Future of Biofuels – Biobutanol as Promising Alternative

“…The sol operon of other solventogenic clostridia (C. beijerinckii, C. saccharobutylicum, and C. saccharoperbutylacetonicum) includes the adc gene and contains an aldehyde dehydrogenase gene (ald) instead of adhE (Chen & Blaschek, 1999;Kosaka et al, 2007). The product of adhE is multifunctional.…”