Affiliation:
1. Dipartimento di Biologia, Università Roma Tre, 00146 Rome
2. Dipartimento di Biologia Cellulare e dello Sviluppo, Università “La Sapienza,” 00185 Rome, Italy
Abstract
ABSTRACT
Enteroinvasive
E. coli
(EIEC), like
Shigella
, is the etiological agent of bacillary dysentery, a particularly severe syndrome in children in developing countries. All EIEC strains share with
Shigella
the inability to synthesize lysine decarboxylase (the LDC phenotype). The lack of this function is considered a pathoadaptive mutation whose emergence was necessary to obtain the full expression of invasiveness. Cadaverine, the product of lysine decarboxylation, is a small polyamine which interferes mainly with the inflammatory process induced by dysenteric bacteria. Genes coding for lysine decarboxylase and its transporter constitute a single operon (
cadBA
) and are expressed at low pH under the positive control of CadC. This regulator is an inner membrane protein that is able to sense pH variation and to respond by transcriptionally activating the
cadBA
genes. In this study we show that, unlike in
Shigella
, mutations affecting the
cad
locus in the EIEC strains we have analyzed are not followed by a novel gene arrangement and that the LCD
−
phenotype is dependent mainly on inactivation of the
cadC
gene. Introduction of a functional CadC restores cadaverine expression in all EIEC strains harboring either an IS
2
element or a defective
cadC
promoter. Comparative analysis between the
cad
regions of
S. flexneri
and EIEC suggests that the LDC
−
phenotype has been attained by different strategies within the
E. coli
species.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
37 articles.
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