title: Glutamate Limitation, BvgAS Activation, and (p)ppGpp Regulate the Expression of the Bordetella pertussis Type 3 Secretion System.
abstract: Bordetella pertussis is a bacterium that is considered to be highly adapted to humans, and it has not been isolated from the environment. As this bacterium does not utilize sugars, the abundant supply of glutamate in Stainer Scholte (SS) medium enables B. pertussis to grow efficiently in liquid culture in vitro, and as such, SS medium is a popular choice for laboratory experiments. However, the concentration of glutamate in the in vivo niche of B. pertussis is quite low. We investigated the bacterial response to low concentrations of glutamate to elucidate bacterial physiology via the expression of the type 3 secretion system (T3SS), and we discuss its relationship to the Bvg mode in which the two-component regulator of pathogenesis (BvgAS) is activated. Glutamate limitation induced the expression of both the T3SS apparatus and effector genes at the transcriptional level. (p)ppGpp, a modulator of the stringent response, was necessary for maximum expression of the T3SS genes. These observations indicate that the expression of the T3SS is managed by nutrient starvation. In addition, the autoaggregation ability was high in the absence of glutamate and no autoaggregation was observed in glutamate-replete medium. Taken together, glutamate-limited conditions in Bvg(+) mode elicit the high expression of T3SS genes in B. pertussis and promotes its sessile form.
  
  
  OBJECTIVE
  Bordetella pertussis is a highly contagious pathogen that causes respiratory infectious disease. In spite of the increasing use of vaccination, the number of patients with pertussis is increasing. The proteins produced in vivo often are different from the protein profile under laboratory conditions; therefore, the development of conditions reflecting the host environment is important to understand native bacterial behavior. In the present study, we examined the effect of glutamate limitation, as its concentration in vivo is much lower than that in the culture medium currently used for B. pertussis experiments. As predicted, the T3SS was induced by glutamate limitation. These results are suggestive of the importance of regulation by nutrient conditions and in the pathogenicity of B. pertussis.
authors.affiliation: Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan thanawa@ks.kyorin-u.ac.jp.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Hanawa
authors.affiliation: Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Kamachi
authors.affiliation: Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Yonezawa
authors.affiliation: Department of Pharmacology, Kyorin University School of Medicine, Tokyo, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Fukutomi
authors.affiliation: Department of Anatomy, Kyorin University School of Medicine, Tokyo, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Kawakami
authors.affiliation: Department of Infectious Diseases, Kyorin University School of Medicine, Tokyo, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Kamiya
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001886:Bordetella pertussis / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism*; D006158:Guanosine Pentaphosphate / Q000378:metabolism*; D000069296:Type III Secretion Systems / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D000069296:Type III Secretion Systems; D006158:Guanosine Pentaphosphate; D018698:Glutamic Acid