Abstract
Nitric oxide (NO) is a key physiological regulator in eukaryotic and prokaryotic organisms. It can cause a variety of biological effects by reacting with its targets or/and indirectly inducing oxidative stress. NO can also be produced by bacteria including the pathogenic Bacillus anthracis; however, its role in the infectious process only begins to emerge. NO incapacitates macrophages by S-nitrosylating the intracellular proteins and protects B. anthracis from oxidative stress. It is also implicated in the formation of toxic peroxynitrite. In this study we further assessed the effects of B. anthracis NO produced by the NO synthase (bNOS) on bacterial metabolism and host cells in experiments with the bNOS knockout Sterne strain. The mutation abrogated accumulation of nitrite and nitrate as tracer products of NO in the culture medium and markedly attenuated growth in both aerobic and microaerobic conditions. The regulatory role of NO was also suggested by the abnormally high rate of nitrate denitrification by the mutant in the presence of oxygen. Anaerobic regulation mediated by NO was reflected in reduced fermentation of glucose by the mutant correlating with the reduced toxicity of bacteria toward host cells in culture. The toxic effect of NO required permeabilization of the target cells as well as the activity of fermentation-derived metabolite in the conditions of reduced pH. The host cells demonstrated increased phosphorylation of major survivor protein kinase AKT correlating with reduced toxicity of the mutant in comparison with Sterne. Our global proteomic analysis of lymph from the lymph nodes of infected mice harboring bacteria revealed numerous changes in the pattern and levels of proteins associated with the activity of bNOS influencing key cell physiological processes relevant to energy metabolism, growth, signal transduction, stress response, septic shock, and homeostasis. This is the first in vivo observation of the bacterial NO effect on the lymphatic system.
Highlights
Bacillus anthracis is a soil microbe which is highly pathogenic for both humans and many animal species
We found that the cultured epithelial cells were partially protected from the pathogenic effect of bacterial culture supernatants by chemical compounds causing decomposition of the peroxynitrite (ONOO−), a highly toxic substance formed in the fast reaction of superoxide radical (O2−) and nitric oxide (NO) (Popova et al, 2011; St John et al, 2013)
We found that bacterial Nitric oxide (NO) influences many facets of B. anthracis physiology including regulation of growth, phosphoprotein signaling and toxicity induced in the cultured host cells
Summary
Bacillus anthracis is a soil microbe which is highly pathogenic for both humans and many animal species. It is a causative agent of anthrax which can be manifested in three major forms depending on the initiation (challenge) route: cutaneous, gastrointestinal, or inhalational. Current therapies against anthrax infection are limited to administration of antibiotics which have reduced efficacy at the late stage of disease. During the year 2000 anthrax letter attack the mortality rate was 45% even after the antibiotic therapy (Spencer, 2003). It is currently accepted that the novel approaches to treat anthrax should target the proliferation of bacteria and the activity of toxic virulence factors unaffected by antibiotics (Beierlein and Anderson, 2011). The full spectrum of these factors acting at different stages of infection and culminating in the host death remains to be incompletely understood
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
