Fermentable-sugar-level-dependent regulation of leukotoxin synthesis in a variably toxic strain of Actinobacillus actinomycetemcomitans

Citation
T. Inoue et al., Fermentable-sugar-level-dependent regulation of leukotoxin synthesis in a variably toxic strain of Actinobacillus actinomycetemcomitans, MICROBI-SGM, 147, 2001, pp. 2749-2756
Citations number
39
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
MICROBIOLOGY-SGM
ISSN journal
1350-0872 → ACNP
Volume
147
Year of publication
2001
Part
10
Pages
2749 - 2756
Database
ISI
SICI code
1350-0872(200110)147:<2749:FROLSI>2.0.ZU;2-B
Abstract
Actinobacillus actinomycetemcomitans, a Gram-negative periodontopathic bact erium, produces a leukotoxin belonging to the RTX family. The production of leukotoxin varies greatly among different strains of this species and unde r different culture conditions. A toxin-production-variable strain, 301-b, stably produces significant amounts of leukotoxin in anaerobic fructose-lim ited chemostat cultures, but does not do so in the presence of excess fruct ose. This communication describes the cloning and sequencing of the leukoto xin promoter region from 301-b, showing that this strain has a promoter reg ion similar to that from strain 652, a moderately toxic strain. Northern bl ot analysis using a leukotoxin gene probe demonstrated that change in toxin production in response to the level of external fructose was due to altera tion in the transcriptional level of the leukotoxin gene. Pulsing of fructo se into the fructose-limited chemostat culture remarkably reduced the intra cellular cAMP level from 40 pmol (mg dry wt cells)(-1) to 3.1 pmol (mg dry wt cells)(-1), which was restored when the culture was returned to fructose -limited conditions. Further, it was found that addition of external cAMP t o the culture with excess fructose resulted in an apparent recovery of leuk otoxin production. Taken together, these findings indicate that a cAMP-depe ndent mechanism, possibly a catabolite-repression-like system, may be invol ved in the regulation of leukotoxin production in this bacterium.