The stringent response of Bacillus anthracis contributes to sporulation but not to virulence

Unité Toxines et Pathogénie Bactérienne, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris Cedex 15, France.
Microbiology (Impact Factor: 2.84). 01/2008; 153(Pt 12):4234-9. DOI: 10.1099/mic.0.2007/010355-0
Source: PubMed

ABSTRACT The Gram-positive, spore-forming pathogen Bacillus anthracis is the aetiological agent of anthrax. Its main virulence factors are two toxins and an anti-phagocytic capsule. When B. anthracis is grown in laboratory culture, the highest expression of the anthrax toxin genes occurs during entry into stationary phase, suggesting that nutrient limitation is an environmental cue which induces toxin production. A common bacterial response to starvation is the so-called stringent response, in which the hyperphosphorylated guanosine nucleotide (p)ppGpp is the effector molecule. In Escherichia coli, Bacillus subtilis and other bacteria, accumulation of this molecule leads to down-regulation of stable RNA synthesis and upregulation of the expression of genes involved in survival under nutrient-poor conditions. This study focuses on the stringent response of B. anthracis. We show that in B. anthracis the relA gene is responsible for the synthesis of (p)ppGpp and the stringent down-regulation of stable RNA synthesis upon starvation for the essential amino acids isoleucine, leucine and valine. The deletion of relA did not affect the expression of the virulence gene pagA or virulence in a mouse model of infection. In contrast, spore counts upon growth and sporulation in a defined medium were approximately 10,000-fold lower for the relA deletion mutant than for the parental strain. The contribution of the stringent response to efficient sporulation of B. anthracis is notable, as this suggests that the stringent response may contribute to the persistence of B. anthracis in the natural environment.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Like for all microbes, the goal of every pathogen is to survive and replicate. However, to overcome the formidable defenses of their hosts, pathogens are also endowed with traits commonly associated with virulence, such as surface attachment, cell or tissue invasion, and transmission. Numerous pathogens couple their specific virulence pathways with more general adaptations, like stress resistance, by integrating dedicated regulators with global signaling networks. In particular, many of nature's most dreaded bacteria rely on nucleotide alarmones to cue metabolic disturbances and coordinate survival and virulence programs. Here we discuss how components of the stringent response contribute to the virulence of a wide variety of pathogenic bacteria.
    Microbiology and molecular biology reviews: MMBR 06/2010; 74(2):171-99. DOI:10.1128/MMBR.00046-09 · 15.26 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Spores are the infectious form of Bacillus anthracis (BA), causing cutaneous, inhalation and gastrointestinal anthrax. Because of the possible use of BA spores in a bioterrorism attack, there is considerable interest in studying spore biology. In the laboratory, however, it takes a number of days to prepare spores. Standard sporulation protocols, such as the use of 'PA broth', allow sporulation of BA to occur in 3 to 5 days. Another method employs growth of BA on plates in the dark for several days until they have efficiently sporulated. In efforts to determine the effect of iron on gene expression in BA, we grew BA Sterne strain 7702 in a minimal defined medium (CDM; Koppisch et al., 2005) with various concentrations of iron and glucose. As part of our initial observations, we monitored BA sporulation in CDM via light microscopy. In glucose-free CDM containing 1.5mM Fe(NO(3))(3) (CDM-Fe), >95% of the BA sporulated by 30 h; a far shorter time period than expected. We pursued this observation and we further characterized spores derived from PA and CDM-Fe media. Purified spores derived from PA or CDM-Fe had similar morphologies when viewed by light or electron microscopy, and were equally resistant to harsh conditions including heat (65 degrees C), ice and fresh 30% H(2)O(2). Spore viability in long term cold storage in water was similar for the two spore preparations. Extracted spore coat proteins were evaluated by SDS-PAGE and silver staining, which revealed distinct protein profiles for PA and CDM-Fe spore coat extracts. ELISA assays were done to compare the interaction of the two spore preparations with rabbit antiserum raised against UV-killed Sterne strain 7702 spores prepared in PA medium. Spores from both media reacted identically with this antiserum. Finally, the interaction and fate of spores incubated with macrophages in vitro was very similar. In summary, BA spores induced in CDM-Fe or in PA medium are similar by several criteria, but show distinct extractable coat proteins. CDM-Fe liquid medium can be used for rapid production of BA spores, and could save considerable time in spore research studies.
    Journal of microbiological methods 09/2010; 82(3):282-7. DOI:10.1016/j.mimet.2010.07.004 · 2.10 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The objective of the present work was to establish effective and rapid diagnostic methods for the detection of Bacillus anthracis, a highly virulent zoonotic pathogen, in the air, soil and animal (or human) tissue samples. Liquid culture of B. anthracis was aerosolized and four air sampling procedures were employed. Detection of B. anthracis in the air samples was successful with RCS High Flow sampler (culturebased detection) and when sampling through the air filter (molecular detection using SmartHelix Complex Samples DNA Extraction Kit). Liquid B. anthracis culture was also employed for spiking the homogenised bovine lymphatic gland tissue and soil samples. DNA extraction was performed using three different commercial kits for each sample type. High Pure PCR Template Preparation Kit was the most effective for DNA extraction from animal tissue samples. Detection in the soil was successful when PowerSoil DNA Isolation Kit was used. Our results indicate that B. anthracis can be monitored in different matrices by rapid molecular methods when appropriate sampling and DNA extraction procedures are employed prior to PCR assay. The selected rapid protocols can be implemented in specialized veterinary or human diagnostic laboratories with moderate costs. Full text:
    Acta veterinaria 01/2012; 62(1):77-89. DOI:10.2298/AVB1201077K · 0.13 Impact Factor
Show more