Abstract
Actinobacillus actinomycetemcomitans, a Gram-negative periodontopathic bacterium, produces a leukotoxin belonging to the RTX family. The production of leukotoxin varies greatly among different strains of this species and under different culture conditions. A toxin-production-variable strain, 301-b, stably produces significant amounts of leukotoxin in anaerobic fructose-limited chemostat cultures, but does not do so in the presence of excess fructose. This communication describes the cloning and sequencing of the leukotoxin promoter region from 301-b, showing that this strain has a promoter region similar to that from strain 652, a moderately toxic strain. Northern blot analysis using a leukotoxin gene probe demonstrated that change in toxin production in response to the level of external fructose was due to alteration in the transcriptional level of the leukotoxin gene. Pulsing of fructose into the fructose-limited chemostat culture remarkably reduced the intracellular 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 to the culture with excess fructose resulted in an apparent recovery of leukotoxin production. Taken together, these findings indicate that a cAMP-dependent mechanism, possibly a catabolite-repression-like system, may be involved in the regulation of leukotoxin production in this bacterium.
| Original language | English |
|---|---|
| Pages (from-to) | 2749-2756 |
| Number of pages | 8 |
| Journal | Microbiology |
| Volume | 147 |
| Issue number | 10 |
| Publication status | Published - 2001 |
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Keywords
- Catabolite repression
- Chemostat culture
- Periodontopathogen
- RTX toxin
ASJC Scopus subject areas
- Microbiology
Cite this
Fermentable-sugar-level-dependent regulation of leukotoxin synthesis in a variably toxic strain of Actinobacillus actinomycetemcomitans. / Inoue, T.; Tanimoto, I.; Tada, T.; Ohashi, T.; Fukui, K.; Ohta, H.
In: Microbiology, Vol. 147, No. 10, 2001, p. 2749-2756.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Fermentable-sugar-level-dependent regulation of leukotoxin synthesis in a variably toxic strain of Actinobacillus actinomycetemcomitans
AU - Inoue, T.
AU - Tanimoto, I.
AU - Tada, T.
AU - Ohashi, T.
AU - Fukui, K.
AU - Ohta, H.
PY - 2001
Y1 - 2001
N2 - Actinobacillus actinomycetemcomitans, a Gram-negative periodontopathic bacterium, produces a leukotoxin belonging to the RTX family. The production of leukotoxin varies greatly among different strains of this species and under different culture conditions. A toxin-production-variable strain, 301-b, stably produces significant amounts of leukotoxin in anaerobic fructose-limited chemostat cultures, but does not do so in the presence of excess fructose. This communication describes the cloning and sequencing of the leukotoxin promoter region from 301-b, showing that this strain has a promoter region similar to that from strain 652, a moderately toxic strain. Northern blot analysis using a leukotoxin gene probe demonstrated that change in toxin production in response to the level of external fructose was due to alteration in the transcriptional level of the leukotoxin gene. Pulsing of fructose into the fructose-limited chemostat culture remarkably reduced the intracellular 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 to the culture with excess fructose resulted in an apparent recovery of leukotoxin production. Taken together, these findings indicate that a cAMP-dependent mechanism, possibly a catabolite-repression-like system, may be involved in the regulation of leukotoxin production in this bacterium.
AB - Actinobacillus actinomycetemcomitans, a Gram-negative periodontopathic bacterium, produces a leukotoxin belonging to the RTX family. The production of leukotoxin varies greatly among different strains of this species and under different culture conditions. A toxin-production-variable strain, 301-b, stably produces significant amounts of leukotoxin in anaerobic fructose-limited chemostat cultures, but does not do so in the presence of excess fructose. This communication describes the cloning and sequencing of the leukotoxin promoter region from 301-b, showing that this strain has a promoter region similar to that from strain 652, a moderately toxic strain. Northern blot analysis using a leukotoxin gene probe demonstrated that change in toxin production in response to the level of external fructose was due to alteration in the transcriptional level of the leukotoxin gene. Pulsing of fructose into the fructose-limited chemostat culture remarkably reduced the intracellular 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 to the culture with excess fructose resulted in an apparent recovery of leukotoxin production. Taken together, these findings indicate that a cAMP-dependent mechanism, possibly a catabolite-repression-like system, may be involved in the regulation of leukotoxin production in this bacterium.
KW - Catabolite repression
KW - Chemostat culture
KW - Periodontopathogen
KW - RTX toxin
UR - http://www.scopus.com/inward/record.url?scp=0034774719&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0034774719&partnerID=8YFLogxK
M3 - Article
VL - 147
SP - 2749
EP - 2756
JO - Microbiology
JF - Microbiology
SN - 1350-0872
IS - 10
ER -