Affiliation:
1. Department of Oral Biology, University of Florida, Gainesville, Florida
Abstract
ABSTRACT
A gene, designated
atlS
, encoding a major autolysin from
Streptococcus gordonii
, was identified and characterized. The predicted AtlS protein is 1,160 amino acids and 127 kDa and has a conserved β1,4-
N
-acetylmuramidase domain. Zymographic analysis of wild-type
S. gordonii
revealed peptidoglycan hydrolase activities with molecular masses of 130 and 90 kDa that were absent in an
atlS
deletion mutant. Western blotting revealed that the 90-kDa band was derived from the 130-kDa protein. Inactivation of
atlS
resulted in formation of long chains by the cells, markedly decreased autolytic capacity, poor biofilm formation, diminished tolerance of acid and oxidative stress, and decreased production of extracellular DNA (eDNA). The biofilm-forming capacity of the
atlS
mutant could be almost completely restored to that of the wild-type strain by adding purified recombinant AtlA autolysin of
S. mutans
but was only partially restored by addition of eDNA. Autolysis, eDNA release, and
atlS
expression increased sharply when cells entered stationary phase and were greatly enhanced in cells growing with aeration. The LytST and VicRK two-component systems were both required for the induction of
atlS
by aeration, and purified LytT was able to bind to the promoter region of
atlS in vitro
. Thus, AtlS and its associated regulatory cascade dominantly control phenotypes of
S. gordonii
that are critical to colonization, persistence, and competition with other commensal and pathogenic oral bacteria in response to the redox environment and growth domain.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
41 articles.
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