MUTACIN IV PRODUCTION IN STREPTOCOCCUS MUTANS UA159: CHARACTERIZATION, REGULATION, AND MECHANISM OF SELF-IMMUNITY
type: CreativeWork
description: Streptococcus mutans, an oral pathogen, is considered as a principle etiological agent of dental caries. To colonize successfully in the oral cavity, this organism encounters fierce competition with other oral microbiota and this process is facilitated by ribosomally synthesized small cationic peptides called mutacins (bacteriocins) secreted by S. mutans. Although for long time mutacins are regarded as important virulence factors, it is not clear how these peptides work, what is the mechanism of self-immunity, and how they are regulated. In this study, we have characterized the activity, mechanism of self-immunity, and regulation of expression of a well-known bacteriocin, mutacin IV. To clarify the activity of mutacin IV, we studied the contribution of NlmA and NlmB peptides to mutacin IV activity. Using genetic and biochemical approaches, we showed that the presence of both genes is required for optimum mutacin IV activity. We also showed that mutacin IV is active against multiple Streptococcus species. Our studies revealed that mutacin IV has comparatively broader inhibitory spectrum than mutacin V; and both of them can work synergistically to inhibit various microorganisms. Next, we investigated the immunity activity of a putative immunity protein, SMU.152, which lies just downstream of the nlmAB operon. We observed that heterologous expression of SMU.152 in two sensitive strains converted the strains to become resistant to mutacin IV. We identified that C-terminal charged residues of SMU.152 is indispensible for conferring immunity to susceptible cells. In addition, our studies demonstrated that in absence of cognate immunity protein, S. mutans can employ other paralogous proteins to prevent the self-toxicity, which implies the presence of cross-immunity or immune redundancy in S. mutans UA159. To get a clear understanding on regulation of mutacin IV production, we carried out pGh9:ISS1-mediated random transposon mutagenesis in a reporter strain containing the n…
abstract: Streptococcus mutans, an oral pathogen, is considered as a principle etiological agent of dental caries. To colonize successfully in the oral cavity, this organism encounters fierce competition with other oral microbiota and this process is facilitated by ribosomally synthesized small cationic peptides called mutacins (bacteriocins) secreted by S. mutans. Although for long time mutacins are regarded as important virulence factors, it is not clear how these peptides work, what is the mechanism of self-immunity, and how they are regulated. In this study, we have characterized the activity, mechanism of self-immunity, and regulation of expression of a well-known bacteriocin, mutacin IV. To clarify the activity of mutacin IV, we studied the contribution of NlmA and NlmB peptides to mutacin IV activity. Using genetic and biochemical approaches, we showed that the presence of both genes is required for optimum mutacin IV activity. We also showed that mutacin IV is active against multiple Streptococcus species. Our studies revealed that mutacin IV has comparatively broader inhibitory spectrum than mutacin V; and both of them can work synergistically to inhibit various microorganisms. Next, we investigated the immunity activity of a putative immunity protein, SMU.152, which lies just downstream of the nlmAB operon. We observed that heterologous expression of SMU.152 in two sensitive strains converted the strains to become resistant to mutacin IV. We identified that C-terminal charged residues of SMU.152 is indispensible for conferring immunity to susceptible cells. In addition, our studies demonstrated that in absence of cognate immunity protein, S. mutans can employ other paralogous proteins to prevent the self-toxicity, which implies the presence of cross-immunity or immune redundancy in S. mutans UA159. To get a clear understanding on regulation of mutacin IV production, we carried out pGh9:ISS1-mediated random transposon mutagenesis in a reporter strain containing the n…
author: Hossain, Mohammad Shahnoor
language: en
keywords: Microbiology, Genetics, Molecular biology, Lon protease, Mutacin iv, Streptococcus mutans
date published: 2012-05-31
date modified: 2026-07-24T02:47:15Z
provider: University of Kansas
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Kansas

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property ID: Handle
value: http://hdl.handle.net/1808/10303