Phosphoenolpyruvate:carbohydrate phosphotransferase systems of bacteria.

https://mmbr.asm.org/content/mmbr/47/2/180.full.pdf

Linkage map of Escherichia coli K-12, edition 7.

Evidence for two functional gal promoters in intact Escherichia coli cells.

The field of probiosis has emerged as a new science with applications in farming and aqaculture as alternatives to antibiotics as well as prophylactics in humans. Probiotics are being developed commercially for both human use, primarily as novel foods or dietary supplements, and in animal feeds for the prevention of gastrointestinal infections, with extensive use in the poultry and aquaculture industries. The impending ban of antibiotics in animal feed, the current concern over the spread of antibiotic resistance genes, the failure to identify new antibiotics and the inherent problems with developing new vaccines make a compelling case for developing alternative prophylactics. Among the large number of probiotic products in use today are bacterial spore formers, mostly of the genus Bacillus. Used primarily in their spore form, these products have been shown to prevent gastrointestinal disorders and the diversity of species used and their applications are astonishing. Understanding the nature of this probiotic effect is complicated, not only because of the complexities of understanding the microbial interactions that occur within the gastrointestinal tract (GIT), but also because Bacillus species are considered allochthonous microorganisms. This review summarizes the commercial applications of Bacillus probiotics. A case will be made that many Bacillus species should not be considered allochthonous microorganisms but, instead, ones that have a bimodal life cycle of growth and sporulation in the environment as well as within the GIT. Specific mechanisms for how Bacillus species can inhibit gastrointestinal infections will be covered, including immunomodulation and the synthesis of antimicrobials. Finally, the safety and licensing issues that affect the use of Bacillus species for commercial development will be summarized, together with evidence showing the growing need to evaluate the safety of individual Bacillus strains as well as species on a case by case by basis.

The use of bacterial spore formers as probiotics

The tripartite toxin secreted by Bacillus anthracis, the causative agent of anthrax, helps the bacterium evade the immune system and can kill the host during a systemic infection. Two components of the toxin enzymatically modify substrates within the cytosol of mammalian cells: oedema factor (OF) is an adenylate cyclase that impairs host defences through a variety of mechanisms including inhibiting phagocytosis; lethal factor (LF) is a zinc-dependent protease that cleaves mitogen-activated protein kinase kinase and causes lysis of macrophages. Protective antigen (PA), the third component, binds to a cellular receptor and mediates delivery of the enzymatic components to the cytosol. Here we describe the cloning of the human PA receptor using a genetic complementation approach. The receptor, termed ATR (anthrax toxin receptor), is a type I membrane protein with an extracellular von Willebrand factor A domain that binds directly to PA. In addition, a soluble version of this domain can protect cells from the action of the toxin.

Identification of the cellular receptor for anthrax toxin.

The fatal character of the infection caused by inhalation of Bacillus anthracis spores results from a complex pathogenic cycle involving the synthesis of toxins by the bacterium. We have shown using immunofluorescent staining, confocal scanning laser microscopy and image cytometry analysis that the alveolar macrophage was the primary site of B. anthracis germination in a murine inhalation infection model. Bacillus anthracis germinated inside murine macrophage-like RAW264.7 cells and murine alveolar macrophages. Germination occurred in vesicles derived from the phagosomal compartment. We have also demonstrated that the toxin genes and their trans-activator, AtxA, were expressed within the macrophages after germination.

Germination of Bacillus anthracis spores within alveolar macrophages

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/S0014-5793%2899%2901502-1

Anthrax lethal factor cleaves MKK3 in macrophages and inhibits the LPS/IFNγ‐induced release of NO and TNFα

We investigated the fate of germinated Bacillus anthracis spores after their germination in Swiss murine peritoneal macrophages and in the cell line RAW264.7. We found that the lethal toxin and the oedema toxin are germ-associated factors that are essential for the survival of the vegetative form in host cells. We also found that pX02 is not involved in this complex pathogenic process. By transmission electron microscopy, we showed the tight interaction between the exosporium of the spore and the phagosomal membrane of the macrophage. Our data strongly suggest that the B. anthracis toxinogenic, unencapsulated Sterne strain (7702) does not multiply within macrophages. These results contributed to reveal the strategies used by B. anthracis to survive within the host and to reach the external medium where they proliferate.

Fate of germinated Bacillus anthracis spores in primary murine macrophages

https://www.cell.com/trends/microbiology/pdf/S0966-842X(02)02422-8.pdf

The alveolar macrophage: the Trojan horse of Bacillus anthracis.

Summary The spores of Bacillus anthracis, the agent of anthrax disease, germinate within professional phagocytes, such as murine macrophage-like RAW264.7 cells and alveolar macrophages. We identified a cluster of germination genes extending for 3608 nucleotides between the pag and atxA genes on the B. anthracis virulence plasmid pXOl. The three predicted proteins (40, 55 and 37 kDa in size) have significant sequence similarities to B. subtilis, B. cereus and B. megaterium germination proteins. Northern blot analysis of total RNA from sporulating cells indicated that the gerX locus was organized as a tricistronic operon (gerXB, gerXA and gerXC ). Primer extension analysis identified a major potential transcriptional start site 31 bp upstream from the translation initiation codon of gerXB. Expression of the gerX operon was studied using a gerXB‐lacZ transcriptional fusion. Expression began 2.5‐3 h after the initiation of sporulation and was detected exclusively in the forespore compartment. A gerX null mutant was constructed. It was less virulent than the parental strain and did not germinate efficiently in vivo or in vitro within phagocytic cells. These data strongly suggest that gerXencoded proteins are involved in the virulence of B. anthracis.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2958.1999.01485.x

Chantal Guidi-Rontani

Papers

Germination of Bacillus anthracis spores within alveolar macrophages

Anthrax lethal factor cleaves MKK3 in macrophages and inhibits the LPS/IFNγ‐induced release of NO and TNFα

Fate of germinated Bacillus anthracis spores in primary murine macrophages

The alveolar macrophage: the Trojan horse of Bacillus anthracis.

Identification and characterization of a germination operon on the virulence plasmid pXOl of Bacillus anthracis