Blood does not clot in animals that died of anthrax.
LT toxins act on the blood vessels’ endothelial lining, leading to breakage and bleeding. LT of Bacillus anthracis directly inhibits whole-blood clotting, platelet aggregation, surface P-selectin expression, and platelet–endothelial cell interactions. That is why the blood does not clot and may be present around the mouth, nose, and anus.
Anti-platelet activities of anthrax lethal toxin are associated with suppressed p42/44 and p38 mitogen-activated protein kinase pathways in the platelets. Macrophages and endothelial cells are mainly mediated through p38 and p42/44 MAPK pathways, respectively; both of these pathways are blocked by LT, and these pathways are vital for platelet activation.
Why strict anaerobic bacteria die, when exposed to oxygen?
The aerobes can survive in the presence of oxygen only by virtue of an elaborate system of defenses. Without these defenses, key enzyme systems in the organisms fail to function and the organisms die. Obligate anaerobes, which live only in the absence of oxygen, do not possess the defenses that make aerobic life possible and therefore cannot survive in air.
During growth and metabolism, oxygen reduction products are generated within microorganisms and secreted into the surrounding medium. The superoxide anion, one oxygen reduction product, is produced by univalent reduction of oxygen:
O2e- → O2–
It is generated during the interaction of molecular oxygen with various cellular constituents, including reduced flavins, flavoproteins, quinones, thiols, and iron-sulfur proteins. The exact process by which it causes intracellular damage is not known; however, it is capable of participating in a number of destructive reactions potentially lethal to the cell. Moreover, products of secondary reactions may amplify toxicity. For example, one hypothesis holds that the superoxide anion reacts with hydrogen peroxide in the cell:
O2– + H2O2 → OH– + OH. + O2
This reaction, known as the Haber-Weiss reaction, generates a free hydroxyl radical (OH·), which is the most potent biologic oxidant known. It can attack virtually any organic substance in the cell. A subsequent reaction between the superoxide anion and the hydroxyl radical produces singlet oxygen (O2* ), which is also damaging to the cell:
O2– + OH → OH + O2*
The excited singlet oxygen molecule is very reactive. Therefore, superoxide must be removed for the cells to survive in the presence of oxygen.
Most facultative and aerobic organisms contain a high concentration of an enzyme called superoxide dismutase. This enzyme converts the superoxide anion into ground-state oxygen and hydrogen peroxide, thus ridding the cell of destructive superoxide anions:
2O2– + 2H+Superoxide Dismutase O2 + H2 O2
The hydrogen peroxide generated in this reaction is an oxidizing agent, but it does not damage the cell as much as the superoxide anion and tends to diffuse out of the cell. Many organisms possess catalase or peroxidase or both to eliminate the H2O2. Catalase uses H2O2 as an oxidant (electron acceptor) and a reductant (electron donor) to convert peroxide into water and ground-state oxygen:
H2O2 + H2O2Catalase 2H2O + O2
Peroxidase uses a reductant other than H2O2:
H2O2 + H2R Peroxidase 2H2O + R
One study showed that facultative and aerobic organisms lacking superoxide dismutase possess high levels of catalase or peroxidase. High concentrations of these enzymes may alleviate the need for superoxide dismutase, because they effectively scavenge H2 O2 before it can react with the superoxide anion to form the more active hydroxyl radical. However, anaerobic bacteria lacks superoxide dismutase and catalase enzyme. ( Medical Microbiology, 4th Edition, Chapter 17 Anaerobes: General Characteristics-David J. Hentges)
Why Gram Positive Bacteria take crystal violet colour and Gram Negative Bacteria stains Pink red?
Theories includes differences in cytoplasmic pH (Gram positive bacteria-2 pH and in case of Gram negative-3 pH), and presence of Magnesium ribonucleoprotein in Gram positive bacteria and its absence in Gram negative bacteria have been proposed. But the thickness of Gram positive cell wall due to thick peptidoglycan layer and presence of more lipids in Gram negative cell walls have been accounted for the Gram reaction.
The theory stands as positively charged crystal violet passes through the cell wall and cell membrane and binds to negatively charged components inside the cell. Addition of negatively charged iodine (in the mordant) binds to the positively charged dye and forms a large crystal violet-iodine complex within the cell. Crystal violet (Hexamethyl-para-rosaniline 3 chloride) interacts with aqueous Potassium iodide-Iodine via a simple anion exchange to produce a chemical precipitate. The small chloride anion is replaced by the bulkier iodide, and the complex thus formed becomes insoluble in water. During decolorization, alcohol dissolves the lipid present in the outer membrane of Gram negative bacteria and it leaches the dye-iodine complex out of the cell. A thin layer of peptidoglycan does not offer much resistance either. The dye-iodine complexes are washed from the Gram negative cell along with the outer membrane. Hence Gram negative cells readily get decolorized and takes pink red colour of counter stain saffranin. On the other hand Gram positive cells become dehydrated from the ethanol treatment, closing the pores as the cell wall shrinks during dehydration. The dye-iodine complex gets trapped inside the thick peptidoglycan layer and does not get decolorized, hence appear violet (purple) in colour.