Affiliation:
1. Warsaw University, Institute of Microbiology, Department of Bacterial Genetics, Miecznikowa 1, 02-096 Warsaw, Poland
Abstract
ABSTRACT
A group of proteic toxin-antitoxin (TA) cassettes whose representatives are widely distributed among bacterial genomes has been identified. These cassettes occur in chromosomes, plasmids, bacteriophages, and noncomposite transposons, as well as in the SXT conjugative element of
Vibrio cholerae
. The following four homologous loci were subjected to detailed comparative studies: (i)
tad-ata
from plasmid pAMI2 of
Paracoccus aminophilus
(the prototype of this group), (ii)
gp49-gp48
from the linear bacteriophage N15 of
Escherichia coli
, (iii) s045-s044 from SXT, and (iv) Z3230-Z3231 from the genomic island of enterohemorrhagic
Escherichia coli
O157:H7 strain EDL933. Functional analysis revealed that all but one of these loci (Z3230-Z3231) are able to stabilize heterologous replicons, although the host ranges varied. The TA cassettes analyzed have the following common features: (i) the toxins are encoded by the first gene of each operon; (ii) the antitoxins contain a predicted helix-turn-helix motif of the XRE family; and (iii) the cassettes have two promoters that are different strengths, one which is located upstream of the toxin gene and one which is located upstream of the antitoxin gene. All four toxins tested are functional in
E. coli
; overexpression of the toxins (in the absence of antitoxin) results in a bacteriostatic effect manifested by elongation of bacterial cells and growth arrest. The toxins have various effects on cell viability, which suggests that they may recognize different intracellular targets. Preliminary data suggest that different cellular proteases are involved in degradation of antitoxins encoded by the loci analyzed.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference83 articles.
1. Aizenman, E., H. Engelberg-Kulka, and G. Glaser. 1996. An Escherichia coli chromosomal “addiction module” regulated by guanosine 3′,5′-bispyrophosphate: a model for programmed bacterial cell death. Proc. Natl. Acad. Sci. USA 93 : 6059-6063.
2. Characterization of a Theta-Type Plasmid from
Lactobacillus sakei
: a Potential Basis for Low-Copy-Number Vectors in Lactobacilli
3. Gapped BLAST and PSI-BLAST: a new generation of protein database search programs
4. Baj, J., E. Piechucka, D. Bartosik, and M. Wlodarczyk. 2000. Plasmid occurrence and diversity in the genus Paracoccus. Acta Microbiol. Polon. 49 : 265-270.
5. Bartosik, D., J. Baj, E. Piechucka, and M. Wlodarczyk. 1992. Analysis of Thiobacillus versutus pTAV1 plasmid functions. Acta Microbiol. Polon. 42 : 97-100.
Cited by
76 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献