title: The secretion antigen SA5K has a role in the adaptation of Mycobacterium bovis bacillus Calmette-Guérin to intracellular stress and hypoxia.
abstract: The Mycobacterium tuberculosis TB8.4 (Rv1174c) gene encodes a secreted protein of 8.4 kDa (TB8.4) which has been suggested to be involved in reactivation of dormant mycobacteria. We have previously reported that inactivation of an identical gene (sa5k) in Mycobacterium bovis BCG causes impaired ability of the mutant strain (BCGsa5k::aph) to grow inside human macrophages. This study aimed to investigate the role of TB8.4 in the reactivation of aged cultures of BCG as well as the role of the sa5k gene in the resistance of BCG to intracellular stress conditions and adaptation to hypoxia. Although when added to aged cultures of BCG, TB8.4 caused a statistically significant increase in the number of colony-forming units, a similar effect was obtained in cultures incubated with BSA, suggesting a non-specific growth stimulation by TB8.4. Compared to parental BCG, the BCGsa5k::aph strain showed an increased susceptibility to reactive oxygen and nitrogen intermediates and to acid stress and an impaired ability to adapt to reduced O2 concentrations, when tested in the oxygen-limited Wayne culture system. These results suggest that the product of the sa5k gene (SA5K protein) has a role in both resistance of BCG to intracellular stress and in its adaptation to hypoxia.
authors.affiliation: Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, University of Pisa, Via San Zeno 35/39, 56127 Pisa, Italy.
authors.forename: Daria
authors.initials: D
authors.lastname: Bottai
authors.forename: Giovanna
authors.initials: G
authors.lastname: Batoni
authors.forename: Semih
authors.initials: S
authors.lastname: Esin
authors.forename: Walter
authors.initials: W
authors.lastname: Florio
authors.forename: Franca Lisa
authors.initials: FL
authors.lastname: Brancatisano
authors.forename: Flavia
authors.initials: F
authors.lastname: Favilli
authors.forename: Giuseppantonio
authors.initials: G
authors.lastname: Maisetta
authors.forename: Mario
authors.initials: M
authors.lastname: Campa
mesh_terms: D000143:Acids / Q000494:pharmacology; D000222:Adaptation, Physiological; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism* / Q000502:physiology; D015169:Colony Count, Microbial; D017353:Gene Deletion; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D016254:Mutagenesis, Insertional; D009163:Mycobacterium bovis / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D018384:Oxidative Stress; D010100:Oxygen / Q000502:physiology; D026361:Reactive Nitrogen Species / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000494:pharmacology
chemical_list: D000143:Acids; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; C430090:Rv1174c protein, Mycobacterium tuberculosis; D010100:Oxygen