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Involvement of the accessory gene regulatory ( agr ) system in quorum sensing by Staphylococcus intermedius
Author(s) -
Sung J. M. L.,
Chantler P. D.,
Lloyd D. H.
Publication year - 2004
Publication title -
veterinary dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.744
H-Index - 60
eISSN - 1365-3164
pISSN - 0959-4493
DOI - 10.1111/j.1365-3164.2004.00414_3.x
Subject(s) - quorum sensing , virulence , staphylococcus intermedius , enterotoxin , biology , microbiology and biotechnology , gene , effector , staphylococcus aureus , population , genetics , bacteria , staphylococcus , escherichia coli , medicine , environmental health
Toxic exoproteins are believed to be involved in the pathogenesis of Staphylococcus intermedius pyoderma and bacterial overgrowth, although these diseases are poorly understood. This study aims to determine whether quorum sensing, a phenomenon in which cells express particular characteristics only when population densities exceed certain levels, might be involved. Production of virulence factors by S. intermedius was hypothesized to be initiated by the agr system via signalling molecules generated as cell density increased, as in S. aureus . Initial studies ( agr ‐specific PCR, genome walking) confirmed the presence of sequences in S. intermedius related to the agr of S. aureus . To test the hypothesis that expression of RNAIII (effector of the agr system) and two exotoxins, leukotoxin and enterotoxin C, are initiated by an environmental signal generated during bacterial growth, experiments were performed in which spent culture supernatants from different phases of growth were added to early exponential cultures of S. intermedius in which the genes are minimally expressed. Through real‐time quantitative PCR, it was shown that concentrated supernatant of midexponential and postexponential cultures from S. intermedius strains 3 and 27 up‐regulated expression of genes encoding for RNAIII, leukotoxin and enterotoxin in strain 3. This indicates that the activating substance accumulates in supernatant during growth. In contrast, S. intermedius was insensitive to spent medium from S. aureus strain J3964. This suggests that S. intermedius uses quorum sensing to monitor the proximity of other signal‐producing cells and thereby adjusts its expression of virulence genes appropriately to facilitate species‐specific and intraspecies cell‐cell communication. Funding: Nestlé Purina Research Company.