Physiologic Effects of Forced Down-Regulation of dnaK and groEL Expression in Streptococcus mutans

Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL 32610-0424, USA.
Journal of Bacteriology (Impact Factor: 2.81). 04/2007; 189(5):1582-8. DOI: 10.1128/JB.01655-06
Source: PubMed


Strains of Streptococcus mutans lacking DnaK or GroEL appear not to be isolable. To better distinguish the roles played by these chaperones/chaperonins in
the physiology of S. mutans, we created a knockdown strategy to lower the levels of DnaK by over 95% in strain SM12 and the level of GroEL about 80%
in strain SM13. Interestingly, GroEL levels were approximately twofold higher in SM12 than in the parent strain, but the levels
of DnaK were not altered in the GroEL knockdown strain. Both SM12 and SM13 grew slower than the parent strain, had a strong
tendency to aggregate in broth culture, and showed major changes in their proteomes. Compared with the wild-type strain, SM12
and SM13 had impaired biofilm-forming capacities when grown in the presence of glucose. The SM12 strain was impaired in its
capacity to grow at 44°C or at pH 5.0 and was more susceptible to H2O2, whereas SM13 behaved like the wild-type strain under these conditions. Phenotypical reversions were noted for both mutants
when cells were grown in continuous culture at a low pH, suggesting the occurrence of compensatory mutations. These results
demonstrate that DnaK and GroEL differentially affect the expression of key virulence traits, including biofilm formation
and acid tolerance, and support that these chaperones have evolved to accommodate unique roles in the context of this organism
and its niche.

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    • "In addition, S. mutans-encoded GroEL and DnaK act as negative regulators of surface protein antigen C (PAc), which has an important role in the interaction between bacterial cells and acquired pellicles on the tooth surface (Ishibashi et al., 2010). Moreover, S. agalactiae-encoded GroEL and DnaK differentially regulate the expression of key streptococcal virulence factors, including those involved in the formation of biofilms and acid tolerance (Lemos et al., 2007). The serine protease ClpP plays a key role in the regulation of bacterial growth and increases bacterial survival under stress conditions, particularly heat-shock conditions in S. agalactiae (Nair et al., 2003) and S. mutans (Lemos and Burne, 2002). "
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    ABSTRACT: Streptococci cause a variety of diseases, such as dental caries, pharyngitis, meningitis, pneumonia, bacteremia, endocarditis, erysipelas, and necrotizing fasciitis. The natural niche of this genus of bacteria ranges from the mouth and nasopharynx to the skin, indicating that the bacteria will inevitably be subjected to environmental changes during invasion into the host, where it is exposed to the host immune system. Thus, the Streptococcus−host interaction determines whether bacteria are cleared by the host’s defenses or whether they survive after invasion to cause serious disease. If this interaction were to be deciphered, it could aid in the development of novel preventive and therapeutic agents. Streptococcus species possess many virulent factors, such as peroxidases and heat-shock proteins (HSPs), which play key roles in protecting the bacteria from hostile host environments. This review will discuss insights into the mechanism(s) by which streptococci adapt to host environments. Additionally, we will address how streptococcal infections trigger host stress responses; however, the mechanism by which bacterial components modulate host stress responses remains largely unknown.
    The Journal of Microbiology 10/2015; DOI:10.1007/s12275-015-5432-6 · 1.44 Impact Factor
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    • "It is remarkable that among the differentially expressed proteins between the mutant and the wild type strain, some have been previously characterized as involved in biofilm formation in X. citri or in other pathogenic bacteria. Such is the case of DNA-directed RNA polymerase subunit β [32], tryptophan synthase [43], GroEL [44,45], FadL [32,42,46] and several TBDTs [42,47]. Interestingly, high intracellular L-tryptophan concentration prevents biofilm formation and triggers degradation of mature biofilm in E. coli[43]. "
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    ABSTRACT: Several bacterial plant pathogens colonize their hosts through the secretion of effector proteins by a Type III protein secretion system (T3SS). The role of T3SS in bacterial pathogenesis is well established but whether this system is involved in multicellular processes, such as bacterial biofilm formation has not been elucidated. Here, the phytopathogen Xanthomonas citri subsp. citri (X. citri) was used as a model to gain further insights about the role of the T3SS in biofilm formation. The capacity of biofilm formation of different X. citri T3SS mutants was compared to the wild type strain and it was observed that this secretion system was necessary for this process. Moreover, the T3SS mutants adhered proficiently to leaf surfaces but were impaired in leaf-associated growth. A proteomic study of biofilm cells showed that the lack of the T3SS causes changes in the expression of proteins involved in metabolic processes, energy generation, exopolysaccharide (EPS) production and bacterial motility as well as outer membrane proteins. Furthermore, EPS production and bacterial motility were also altered in the T3SS mutants. Our results indicate a novel role for T3SS in X. citri in the modulation of biofilm formation. Since this process increases X. citri virulence, this study reveals new functions of T3SS in pathogenesis.
    BMC Microbiology 04/2014; 14(1):96. DOI:10.1186/1471-2180-14-96 · 2.73 Impact Factor
    • "DnaK is central in the molecular chaperone complex that includes DnaK, DnaJ and GrpE. In addition to its role in protein folding and in protecting cells from stress, DnaK plays a central role in induction of capsule (Genevaux et al., 2001) and also in expression of genes related to pathogenicity and virulence (Hanawa et al., 2002; Lemos et al., 2007). It has been shown in mice to be an important surface streptococcal virulence factor and protective antigen (Lemos et al., 2000; Fluegge et al., 2004; Kim et al., 2006). "
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    ABSTRACT: Streptococcus equi subspecies zooepidemicus (Sz) is a tonsillar and mucosal commensal of healthy horses with the potential to cause opportunistic infections of the distal respiratory tract stressed by virus infection, transportation, training or high temperature. The invasive clone varies from horse to horse with little evidence of lateral transmission in the group. Tonsillar isolates are non-mucoid although primary isolates from opportunist lower respiratory tract infections may initially be mucoid. In this study, a novel stably mucoid Sz (SzNC) from a clonal epizootic of respiratory disease in horses in different parts of New Caledonia is described. SzNC (ST-307) was isolated in pure culture from transtracheal aspirates and as heavy growths from 80% of nasal swabs (n = 31). Only 4% of swabs from unaffected horses (n = 25) yielded colonies of Sz. A viral etiology was ruled out based on culture and early/late serum antibody screening. Evidence for clonality of SzNC included a mucoid colony phenotype, SzP and SzM sequences, and multilocus sequence typing. SzNC, with the exception of isolates at the end of the outbreak, was hyaluronidase positive. Its SzP protein was composed of an N2 terminal, and HV4 variable region motifs and 18 carboxy terminal PEPK repeats. Biotin labeling of surface proteins revealed DnaK and alanyl-tRNA synthetase (AlaS) on the surface of clonal isolates, but not on non-clonal non-mucoid Sz from horses in the epizootic or unrelated US isolates. Reactivity of these proteins and SzP with convalescent serum indicated expression during infection.
    The Veterinary Journal 04/2014; 200(1). DOI:10.1016/j.tvjl.2014.01.014 · 1.76 Impact Factor
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