By: Mary N. Wessling, Ph.D. ELS

In this blog we will unravel the terminology describing bacterial toxins. In general, there are at least three ways that bacterial toxins are described in the literature:

• by their biological designation—the genus and/or species from which they come
• by the origin of the toxin, either as innate to the bacterial structure or released by the bacterium into surrounding body fluids
• by the body part that is damaged by the toxin

Below are examples of each:

Biological designation

When described by their biological designation a part of the genus or species name is used for the toxin. For example: Clostridium tetani produces Tetanus toxin and Corynebacterium diphtheriae produces Diphtheria toxin.

Origin of the toxin

Exotoxins (e.g. polypeptides) are toxins released by a cell, whereas endotoxins (e.g. lipopolysaccharides) are an integral part of the bacterial cell wall.

Body part damaged by the toxin

Bacteria may cause disease through their toxins that enter the body via the respiratory tract, gastrointestinal tract, genital tract, and the skin. Enterotoxins mostly affect the gastrointestinal tract. “Entero” comes from the Greek word “enteron” meaning intestine.

Bacterial enterotoxins include examples of exotoxins produced by some strains of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli).Staphylococcal enterotoxin acts on intestinal neurons to induce vomiting; E. coli producing Shiga toxin causes serious dysentery and can lead to hemorrhagic diarrhea and kidney failure.

You will also see other terms used to designate toxins…

Superantigens: toxins that cause over-reaction

Antigens are characterized by their ability to activate T-cells and other immune system cells; while the T-cell response is a normal part of the immune process, over-activation of T-cells can cause an inflammatory response that can result in shock and multiple organ failure.

Pore-forming toxins that open host cell membranes

Pore-forming toxins (PFT) are toxin proteins with the ability to spontaneously self-assemble forming transmembrane pores in the membrane of target cells. Staphylococcal alpha toxin, also known as alpha-haemolysin, makes specific pores in target cells which are part of the pathology of infection and a valuable tool in construction of nanopores. Tetanolysin is another pore forming toxin produced by C. tetani which can make cells permeable to materials for experimentation.

Intracellular toxins

These toxins have two-part structures and are termed AB toxins. The A stands for “active”, the B for “binding”, for the ways that the two structures cooperatively cause cell damage. In most cases, the B structural element attaches to the cell membrane and provides an entry point for the other part, the A-enzyme component that causes damage to the inside of the cell through its enzymatic activity.

Some AB toxins have more than one B moiety: for example, the cholera toxin has five B proteins that provide entry for the A moiety, so it is designated AB₅. The A moiety is initially a coiled chain but once inside the cell it uncoils, where its enzymatic activity kills the enteric cell.

Ligand-receptor interactions

The actions of exotoxins and endotoxins depend on a process whereby a part of their molecular structure, a ligand, can bind or otherwise interact with a structure on the host cell being attacked, a receptor. Thus, this ligand–receptor interaction is crucial to most diseases produced by bacterial toxins.

Lethal dose 50%

Bacteria cause disease by toxin production, invasion and inflammation. All toxins damage or disrupt the functions of the host cells. The term that describes the level of danger presented to the host by a toxin is “Lethal Dose 50%”, abbreviated LD₅₀; the lower the LD₅₀, the lower the amount of toxin to cause death.

 

By: Rachel Berlin, Marketing Manager

List Labs is proud to be exhibiting at ASM Biothreats February 12-14th. The conference will be held in Baltimore, Maryland at the Hilton Hotel.

Thought leaders in academia, industry and government will gather to present and discuss the latest developments in the emerging field of biothreats. This year’s conference has an expanded program to include tracks on high consequence pathogen research, biological threat reduction, product development, and policy.

List Labs will be exhibiting in booth #29 and Nancy Shine will be presenting her poster on Sensitive Detection of Anthrax Lethal Factor in Plasma Using a Specific Biotinylated Fluorogenic Substrate during poster session 1 on Wednesday, February 14th from 10:30 AM- 11:30 AM in space #020. Come learn about our products that assist in the biological threat reduction such Botulinum Neurotoxins, Anthrax Lethal Factor, FRET Peptides, Shiga Toxins, Tetanus Toxins, and more! All of our research reagents are available for purchase on our website.

Visit Nancy and Karen in the List Labs booth #29, or contact us to schedule a time to meet with them at the show.  Click here for more information or to register for this conference.

By: Suzanne Canada, Ph.D.
Tanager Medical Writing

While you go about your day, you are surrounded by micro-organisms.  Although most of us spend a lot of time washing up and trying not to think about the propensity of creatures that share our personal space, scientists have been studying them.  Due to their great progress, we are reaching an understanding of how these bacteria and fungi affect our bodies’ functions [1]. The evidence indicates that this inner-ecosystem can not only cause disease if perturbed, but also influence our overall health!  Organisms including Escherichia coli, Helicobacter pylori, Streptococcus thermophilus, and species of Clostridia, Lactobacillus, and Bacterioides inhabit our gut. Corynebacterium jeikeium as well as Staphylococcus species live on our skin, and other Streptococci as well as Neisseria and Candida albicans inhabit our mouth and upper respiratory system [2].  The makeup and diversity of organisms has been found to be strongly influenced, not only by what you eat [3], but also by who you live with [4, 5].  With greater understanding of this rich soup of life that we carry with us, the microbiome has become the new frontier in cutting-edge drug development [6].

In the last three years, research into the molecular basis of microbial influence has blossomed.  The first and most obvious application for this information was in treating C. difficile infections; which result from overgrowth of the opportunistic pathogen after an antibiotic regimen or hospital stay.  Researchers found that fecal transplants from a healthy individual were an effective way to treat this potentially fatal infection [7, 8]. The role of intestinal microbes in Inflammatory Bowel Disease (IBD) has been established [9] in the last year or two.  Based on this knowledge, possible treatments for IBD, such as ulcerative colitis and Crohn’s disease, are in development. Other publications point to microbes’ role in inflammation of the skin and respiratory tract, including acne [10]and asthma[11].  More excitement has been generated as investigators have found links to other chronic diseases including diabetes [12, 13], hypertension [14, 15], and chronic liver disease [16].  Preliminary investigations suggest a connection between overall gut microbial composition and obesity [17].  Some studies in mouse models have even linked the microbiome to the neurological conditions of Alzheimer’s [18] and autism [19, 20].

With all this research going on, you need a great resource like LIST Biological Laboratories, with experience and expertise with microbial products spanning over 25 years. LIST has several products available that can serve as positive controls for your microbial research.  Potent toxins from C. difficile are available (LIST products #157, #158), as well as antibodies that aid in their detection (LIST products #753, #754). Lipopolysaccharides are also available, which cause inflammation and activation of immune signaling cascades, and are extracted from bacterial cell walls of E. coli O111:B4, O55:B5, O157:H7, J5 and K12; Salmonella typhimurium, Salmonella minnesota and Bordetella pertussis. Other acute immune system activators such as Staphylococcal toxins (LIST products #120, #122) and Shiga toxins (LIST products #161 & #162) are also available.

In case the assortment of purified bacterial products on hand are insufficient for your research needs, LIST also provides contract manufacturing for biotherapeutics, as well as microbial purification services.

References

1. Human Microbiome Project, C., A framework for human microbiome research. Nature, 2012. 486(7402): p. 215-21. PMID: 22699610
2. Human Microbiome Project, C., Structure, function and diversity of the healthy human microbiome. Nature, 2012. 486(7402): p. 207-14. PMID: 22699609
3. David, L.A., et al., Diet rapidly and reproducibly alters the human gut microbiome. Nature, 2014. 505(7484): p. 559-63. PMID: 24336217
4. Yatsunenko, T., et al., Human gut microbiome viewed across age and geography. Nature, 2012. 486(7402): p. 222-7. PMID: 22699611
5. La Rosa, P.S., et al., Patterned progression of bacterial populations in the premature infant gut. Proc Natl Acad Sci U S A, 2014. 111(34): p. 12522-7. PMID: 25114261
6. Donia, M.S., et al., A Systematic Analysis of Biosynthetic Gene Clusters in the Human Microbiome Reveals a Common Family of Antibiotics. Cell, 2014. 158(6) p1402 – 1414. PMID: 25215495
7. Seekatz, A.M., et al., Recovery of the gut microbiome following fecal microbiota transplantation. MBio, 2014. 5(3): p. e00893-14. PMID: 24939885
8. Scott, K.P., et al., Manipulating the gut microbiota to maintain health and treat disease. Microb Ecol Health Dis, 2015. 26: p. 25877. PMID: 25651995
9. Huttenhower, C., A.D. Kostic, and R.J. Xavier, Inflammatory bowel disease as a model for translating the microbiome. Immunity, 2014. 40(6): p. 843-54. PMID: 24950204
10. Christensen, G.J. and H. Bruggemann, Bacterial skin commensals and their role as host guardians. Benef Microbes, 2014. 5(2): p. 201-15. PMID: 24322878
11. Martin, C., et al., Host-microbe interactions in distal airways: relevance to chronic airway diseases. Eur Respir Rev, 2015. 24(135): p. 78-91. PMID: 25726559
12. Tang, D., et al., Comparative investigation of in vitro biotransformation of 14 components in Ginkgo biloba extract in normal, diabetes and diabetic nephropathy rat intestinal bacteria matrix. J Pharm Biomed Anal, 2014. 100: p. 1-10. PMID: 25117949
13. Sato, J., et al., Gut dysbiosis and detection of “live gut bacteria” in blood of Japanese patients with type 2 diabetes. Diabetes Care, 2014. 37(8): p. 2343-50. PMID: 24824547
14. Pluznick, J., A novel SCFA receptor, the microbiota, and blood pressure regulation. Gut Microbes, 2014. 5(2): p. 202-7. PMID: 24429443
15. Pluznick, J.L., Renal and cardiovascular sensory receptors and blood pressure regulation. Am J Physiol Renal Physiol, 2013. 305(4): p. F439-44. PMID: 23761671
16. Minemura, M. and Y. Shimizu, Gut microbiota and liver diseases. World J Gastroenterol, 2015. 21(6): p. 1691-702. PMID: 25684933
17. Al-Ghalith, G.A., P. Vangay, and D. Knights, The guts of obesity: progress and challenges in linking gut microbes to obesity. Discov Med, 2015. 19(103): p. 81-8. PMID: 25725222
18. Bibi, F., et al., Link between chronic bacterial inflammation and Alzheimer disease. CNS Neurol Disord Drug Targets, 2014. 13(7): p. 1140-7. PMID: 25230225
19. De Angelis, M., et al., Fecal microbiota and metabolome of children with autism and pervasive developmental disorder not otherwise specified. PLoS One, 2013. 8(10): p. e76993. PMID: 24130822
20. Pequegnat, B., et al., A vaccine and diagnostic target for Clostridium bolteae, an autism-associated bacterium. Vaccine, 2013. 31(26): p. 2787-90. PMID: 23602537

Shiga Toxins May be Purchased without Government Approval

The CDC has removed Shiga toxins (Stx1 and Stx2) from the list of materials requiring oversight.  As a result, Shiga Toxins are no longer classified as select agents and may be purchased without government approval for your research and investigative needs.   While Shiga toxins carry fewer restrictions, the interest in them and their value for research has never been higher.

Usage of Shiga Toxins in Research

As tools, these cytotoxins are valuable in studying intracellular transport within the Golgi apparatus.  They can be used to eliminate mammalian cell types with Gb3 receptors. Shiga toxins are potent virulence factors, important in human health.  They are implicated in many cases of food borne illness, estimated to affect 76 million people and cause 5,000 deaths every year in the United States alone.  Shiga toxin producing bacteria, usually Escherichia coli O157, enter the food chain through contamination, infect the gastrointestinal tract and cause diarrheal illness.  The bacteria infect the large intestine and produce Shiga toxin which crosses the gastrointestinal epithelium entering the blood stream; ultimately the toxins are responsible for organ damage.  These potent virulence factors are important targets for the development of therapies and for the detection of contamination.

Shiga toxins function by inhibiting eukaryotic protein synthesis by cleaving a specific adenine from the 28S RNA of the 60S subunit of the ribosome.  Although Shiga toxin 1 and Shiga toxin 2 share only 56% amino acid homology, making them immunologically distinct, activities of these two forms of toxin, binding affinity to Gb3 and N-glycosidase activity, appear to be identical.  In spite of these similarities, Shiga toxin 2 is more closely associated with human disease.  Although endothelial cells are the primary cell type vulnerable to shiga toxin, several other types express Gb3 receptors and are therefore potential targets.

Get Shiga Toxins for Research from ListLabs

Both Shiga 1 and Shiga 2 and mouse antibodies to the toxins are available from List Labs. You can read more about them here. At this time we are evaluating polyclonal and monoclonal antibodies that recognize all seven subtypes of Stx2 and monoclonals that recognize all subtypes of Stx1.  Look for these antibodies to appear in our future offerings.