Chemistry of Antibiotics: Cell Wall Synthesis

Introduction

In this post we will continue our exploration of the chemistry of antibiotics with a look at drugs that interrupt wall synthesis and how bacteria develop resistance to these drugs.

The target of these antibiotics is crucial because it explains how antibiotics can attack bacteria without affecting human cells. Bacterial cells, unlike animal cells, have cell walls. Therefore, a drug that attacks cell walls will not be able to impact human cells. Bacterial cell walls are essentially a peptidoglycan layer that is composed of units of peptides (proteins) and glycans (sugars). This layer is the primary and most important component of the cell wall.

β-lactam Antibiotics

The most common class of antibiotics that interferes with cell wall synthesis are the β-lactam antibiotics, which

include penicillin. These types of antibiotics function by impeding the synthesis of the peptidoglycan of the bacterial cell wall. There are multiple ways to inhibit the synthesis of the peptidoglycan layer but the most common is by means of destroying the enzymes that do so. If the antibiotic does not function by destroying synthetic enzymes, it could also destroy the enzymes that convert the polymers into a layer of the cell wall. β-lactam antibiotics inhibit cell wall synthesis by preventing the assembly of the peptidoglycan layer. This is done when the antibiotic competes with the polymer at the site of binding.

This video gives a general overview of how peptidoglycans are inhibited by the mechanisms of a beta-lactam antibiotic:

 The Chemistry of Penicillin

 

Penicillin is one of the most common β-lactam antibiotics, and is characterized by three structural requirements: one fused β-lactam structure, a free carboxylic acid group, and one or more substituted amino acid side chains. Penicillin’s structure prevents the cross linking of peptide chains – weaker cell walls will allow water to flow into the cell freely and the cell will swell and burst, causing cell death. If you change the side R-group chain on the penicillin, the penicillin can possess different properties, such as acidity or penicillinase resistance.

The β-lactam ring in the penicillin reacts with an enzyme that is used for building the cell wall called DD-transpeptidase. Resemblances between a segment of the penicillin structure and the backbone of a peptide chain of the bacterial cell wall have been used to explain the mechanism of beta-lactam antibiotics.

Bacteria Fighting Back

Bacteria have a number of ways to evolve and beat our human antibiotics. One method that bacteria employ in order to fight drugs that interrupt cell wall synthesis, is changing the structure of their cell walls. One instance of this is mutation of pathogenic bacteria. Bacteria that colonize the mucosal pathways, such as nostrils, lips and eyelids, must undergo changes in order to avoid the antimicrobials of the host. In particular, they must avoid lysozyme, an enzyme that destroys the cell walls of bacteria. The activity of lysozyme is similar to β-lactam antibiotics since they both attack the cell walls of bacteria. Since the muramidase activity of lysozyme leads to hydrolysis of the β-1,4 glycosidic bond between the C-1 carbon of N-acetyl muramic acid (MurNAc) and the C-4 carbon of N-acetylglucosamine (GlcNAc), that is the bond that the bacteria have to change in order to survive.Streptococcus pneumoniae and bacillus anthracis, two lysozyme resistant bacteria, have peptidoglycan cell walls that are N-deacetylated, which means that the composition and structure of the sugar component of the cell wall is changed. It was shown that N-acetylating them caused them to be more susceptible to lysozyme. Therefore, it was concluded that N-deacetylating the caused lysozyme resistance. This shows that through changes in structure, bacteria can evade agents that inhibit their cell wall synthesis. When this happens, we too must evolve and change our tactics. This is why new drugs always need to be developed. Bacteria develop resistance, and we must develop new antibiotics.

Want to know more about different classes of antibiotics that inhibit cell wall synthesis? Check out thislink to learn about glycopeptide antibiotics. Of course that’s not enough to satisfy the hunger of your mind, so here is a website that goes further in-depth regarding the processes of cell wall synthesis.

Synthesis of Antibiotics

     Antibiotics are agents that are used to kill microorganisms or inhibit their growth. They can either occur naturally or can be synthetically produced. Extremely common today are semi-synthetic modifications of natural compounds. These chemical, biosynthetic antibacterial compounds are classified according to their biological effect on microorganisms. Bactericidal agents kill bacteria altogether while bacteriostatic agents slow down or stall bacterial growth. One specific semisynthetic antibiotic is what is known as Erythromycin.

     Erythromycin is what is considered a macrolide antibiotic. Macrolide antibiotics slow the growth of and often kill sensitive bacteria by reducing the production of important proteins needed by the bacteria to survive. This drug is notorious for being similar to penicillin in what it is used for and how it is synthesized. Often it is used as a substitute for people who are allergic to penicillin being that penicillin is such a common allergy. It is commonly used to treat respiratory tract infections, acne, Gonorrhea, Chlamydia, and other STDs. It is also applied to the eyes of newborn babies in order to prevent ophthalmia neonatorum. Erythromycin works by improving gastric emptying as well as its symptoms, though oral use of this drug is generally for short term use rather than long term.

     The chemical structure of Erythromycin, C38H69NO12, is extremely complicated and elaborate. Its synthesis published by Robert B. Woodward in 1981, the drug consists of a 14-membered lactone ring along with ten asymmetric centers and two sugars, L-cladinose and D-desosamine. The compound’s complexity makes it extremely hard to produce synthetically therefore it is produced by the bacterium Saccharopolyspora erythraea. Synthesis of this drug includes an intricate series of reactions. Reactions include hydrolysis and stereospecific aldolization. Oxidations and reductions are also involved in the synthesis by the pure enone’s conversion to desired dithiadecalin product. This product is further converted to ketone as well as an aldehyde. Overall, the synthesis contains roughly 50 steps split into 4 parts.

     Erythromycin comes in 4 forms: Erythromycin A, B, C and D. Erythromycin A is known for being the most antibacterial, with B, C and D following respectively. As discussed previously, this drug is considered to inhabit bacteriostatic activity, otherwise it inhibits growth of bacteria rather than stopping it or killing in completely. Its bacteriostatic capability is most displayed at high concentrations by interfering with aminoacyl translocation. This process objects to the functionality of important proteins, which is overall how antimicrobial action is put in place. One should be aware of the side effects erythromycin may cause, for example, abdominal pain, nausea, diarrhea, and vomiting.

     Zithromax is a semi-synthetic antibiotic, an example of the subclass, azalides and slightly differs in structure from the classical macrolides. It is used to treat and prevent infection within an area thought to be caused by bacteria. Like all other antibiotics, zithromax has an active ingredient, which in this case is azithromycin, a subclass of macrolide antibiotics. Azithromycin is derived from erythromycin but differs chemically from erythromycin in that a methyl-substituted nitrogen atom is incorporated into the lactone ring and is has improved activity through its glycosylated side chains. In this form, it has a molecular formula of C38H72N2O12. However, when Azithromycin is a dihydrate, which means it contains two molecules of water or its elements, it has a molecular formula of C38H72N2O12*2H2O. Also, Azithromycin contains inactive ingredients such as pregelatinized starch, lactose, sucrose, sodium phosphate, hydroxypropyl cellulose, or xanthan gum that all supplement the active ingredient.

 

     Azithromycin binds to 50s ribosomes and interferes with protein synthesis but does not affect nucleic acid synthesis. It binds to the 23S rRNA of the bacterial 50S ribosomal subunit, which includes the activities such as catalyzation of  peptide bond formation, prevention of premature polypeptide hydrolysis, provision of a binding site for the G-protein factors, assistance of protein folding after synthesis. blocking of protein synthesis by inhibiting the transpeptidation or translocation step of protein synthesis and by inhibiting the assembly of the 50S ribosomal subunit. Azithromycin was the target of an enantioselective synthesis, which is a chemical reaction where one or more new elements of chirality,a molecule that has a non-superposable mirror image, are formed in a substrate molecule and which produces the stereoisomeric products in unequal amounts are formed in a substrate molecule and produces the stereoisomeric products in unequal amounts. Also, all the stereogenic quaternary carbon centers were enhanced by the desymmetrization of 2-substituted glycerols using a chiral imine/CuCl catalyst, otherwise known as copper (I) chloride.

   

     Synthesis of antibiotics such as erythromycin and azithromycin shows how the chemical structure and formula can be modified in order to change its function and its effect on the body accordingly. Although erythromycin was created first, scientists and doctors were able to enhance its molecular formula in order to enhance the process and activity in which it deals with an infected area. Also, these synthetic drugs offset and affect series of reactions such as hydrolysis, which can either interfere or not affect other processes. Overall, the synthesis of such antibiotics require much difficulty due to the fact that many factors such as the complexity of the compound or different incorporated ingredients that change the orientation of each function and process.

In this post we will discuss antibiotic resistance and how different ‘superbugs’ are being created because of continued use of antibiotics.

Antibiotic resistance is the ability of bacteria to resist the effects of an antibiotic. This usually occurs when bacteria change in some way that reduces or eliminates the effectiveness of drugs, chemicals, or other agents designed to cure infections. These bacteria survive and continue to multiply, causing more harm. This resistance can cause significant danger for people who have common infections that were once easily treatable with antibiotics. Every time a person takes antibiotics, sensitive bacteria are killed, but resistant germs may be left to grow and multiply.

Here is an interesting TED Talk by Dr. Karl Klose, which describes the ‘superbug’ and how different bacteria evolve into ‘antibiotic-resistant menaces’.

The big question is how bacteria become resistant to antibiotics. There are two answers to this question. One way that bacteria become resistant to antibiotics is by mutations in DNA. These mutations occur spontaneously and can have two different effects. A change in DNA of bacteria could lead to the prevention of bacterial protein synthesis. In our previous post we discussed how antibiotics target and attack these proteins. However, if the bacteria is active without the protein, there will be nothing for the antibiotics to attack. Mutations causing variations in the shape or size of the protein prevent antibiotics from being able to properly bind to the target protein. Another change in the DNA of bacteria could lead to the overproduction of protein enzymes. This overproduction could lead to various issues. Firstly, a particular dose of antibiotics would not be able to deactivate an overproduction of protein enzymes. Furthermore, some of the proteins produced may be alter the permeability of the cell membrane of cell wall of the bacteria. Aside from spontaneously occurring mutations in the DNA of bacteria, bacteria can become resistant to antibiotics as a result of gene borrowing. According to microbiologist Doctor John Turnidge,  “They’re the original life forms almost, so for thousands of millions of years they’ve had a chance to work out ways to survive and one of those is to borrow genes from other bacteria to survive.” Antibiotic resistance can result from DNA mutations or gene sharing among bacteria. The image below explains how the population of antibiotic resistant bacteria has increased tremendously. For more information regarding the process and causes of antibiotic resistance, check out this website. 

Since the advent of penicillin in the 1940s, antibiotic use has been steadily increasing. Antibiotics are used far more than necessary; they are used as a precautionary measure ‘just in case’ or as a comfort to patients who have viral or fungal infections. According to the CDC, 50 million of the 150 million prescriptions for antibiotics annually are unnecessary. Doctors would rather sign off on a prescription than spend the extra time trying to educate patients on the strengths and weaknesses of antibiotics. In addition to that, increasing use of hand sanitizer and antibacterial cleaning agents also contributes to the development of superbugs. The excessive use of antibiotics has already started to have devastating effects. But why? In the body, antibiotics kill enough bacteria so that the body can finish the job. Shouldn’t more antibiotics just kill more bacteria? It would seem that we should always take antibiotics and heed the adage ‘better safe than sorry’, right? Wrong.

That type of thinking will only drive us towards the edge faster, and here’s why: As soon as researchers develop new antibiotics, there are always already bacteria with the capabilities to defeat them. These resistant bacteria survive the antibiotic agents to multiply and divide, passing on their antibiotic resistanceto their progeny. As a result, the same antibiotics become less effective with time and it becomes harder and harder to develop antibiotics for these so called ‘superbugs’. The most famous strain of bacteria that has risen due to increasing antibiotic use is methicillin-resistant Staphylococcus aureus, or MRSA.

The CDC is currently working to reduce the amount of antibiotics used, because unchecked, it could become a serious public health issue. Already, 2 million people in the US are infected annually by antibiotic resistant bacteria. Should antibiotics continue to be prescribed at such an alarming rate, we could face a post-antibiotic age, in which antibiotics have been rendered useless.

Quinolone Antibiotics: Medicine at its Best

by Rachel Boutom, Sneha Kabaria, and Andrea  Thomas

Antibiotics have been essential to mankind since the discovery of penicillin, and have since branched out into many classes and thousands of medications. This article will explore the class of antibiotics referred to as “quinolone antibiotics” due to its quinolone nucleus. The quinolone nucleus contains double-ring structure composed of benzene and pyridine rings fused at two adjacent carbon atoms. The benzene ring contains six carbon atoms, while the pyridine ring contains five carbon atoms and a nitrogen atom. There are many variations, four generations, different functions, benefits, and side effects to quinolone antibiotics, and you will learn all about them here.

What is Quinolone?

Quinolone is an antibiotic that works by interfering with DNA replication and bacterial transcription.

http://www.youtube.com/watch?v=3IFSxbEvY7g.

The quinolone carries out this function by inhibiting bacterial DNA Gyrase, which is responsible for the negative supercoiling of the DNA, and bacterial Topoisomerase IV, which is an enzyme needed for the separation of strands after replication during cell division. It was first discovered in 1962 as nalidixic acid, which is considered to be the first drug in the quinolone family. From then, there have been four generations of drugs based on their antibacterial spectrum. There is no set standard of classification system to base the drugs on, however there are general properties that differ.

The earlier-generation agents have, in general, more narrow-spectrums than the later ones. In addition, all non-fluorinated drugs in the quinolone class are labeled as first-generation antibiotics. The majority of quinolone antibiotics used today are fluorinated, meaning they have a fluorine atom bonded to the six-carbon ring. These are called fluoroquinolones. Fluoroquinolones are broad-spectrum antibiotics which are effective for both gram negative and gram positive bacteria, and they play an important role in treatment of serious bacterial infections, especially hospital-acquired infections and others in which resistance to older antibacterial classes is suspected.

 

How is it Synthesized?

All quinolines are synthetic, meaning they do not occur in nature, and thus, must all be synthesized in laboratories. Since the creation of the first quinoline nalidixic acid, over 10,000 analogues and derivative compounds have been developed, and more than 800 million patients have been treated with quinolones. There are many ways of synthesizing this chemical: the Gould-Jacob’s method using esters, hydrolysis, and regiospecific substitution; the Modified Gould-Jacobs method, using Isatoic Anhydride and Sodio-Ethyl Formyl Acetate; and many more.

Pharmacokinetics

The newer fluoroquinolone antibiotics also have improved pharmacokinetic parameters compared with the original quinolones. They are rapidly and almost completely absorbed from the gastrointestinal tract. Peak serum concentrations obtained after oral administration are very near those achieved with intravenous administration. Consequently, the oral route is generally preferred in most situations Absorption of orally administered fluoroquinolones is significantly decreased when these agents are coadministered with aluminum, magnesium, calcium, iron or zinc, because of the formation of insoluble drug.

Because the fluoroquinolones have a large volume of distribution, they concentrate in tissues at levels that often exceed serum drug concentrations. Penetration is particularly high in renal, lung, prostate, bronchial, nasal, gall bladder, bile and genital tract tissues. Urine drug concentrations of some fluoroquinolones, such as ciprofloxacin and ofloxacin (Floxin), may be as much as 25 times higher than serum drug concentrations. Consequently, these agents are especially useful in treating urinary tract infections.

Distribution of the fluoroquinolones into respiratory tract tissues and fluids is of particular interest because of the activity of these agents against common respiratory pathogens. Trovafloxacin penetrates noninflamed meninges and may have a future role in the treatment of bacterial meningitis. The long half-lives of the newer fluoroquinolones allow once- or twice-daily dosing.

Bacterial Resistance

As with all antibiotic medicines, the potential for the development of antibacterial resistant strains of bacteria is always a threat. This has already been found to be a problem with quinolones. Gram-positive and gram-negative bacteria have been reported to be resistant to quinolones, and there are different mutations that cause this. The resistance appears to be the result of one of three mechanisms: alterations in the quinolone enzymatic targets (DNA gyrase), decreased outer membrane permeability or the development of efflux mechanisms. In addition, cross-resistance between quinolones is to be expected in the future.

One of the largest problems with antibacterial resistance is the degree to which the same medication is used, which leads to the problem of the extent to which the resistant strain is spread and recreated in other places. For a long period of time, the increased potency and effectiveness of the newer generation of fluoroquinolones, as compared to the older quinolones, led to an unregulated increase in their use. As they kept working effectively, their use proportionally increased, with a 40% increase in use in the United States during the 1990s. During this period, the rate of resistance to the two pain fluoroquinolones doubled, specifically in areas such as the intensive care units in hospitals.

Antibiotics 101

Antibiotics, an introduction.  

Antibiotics are agents, either naturally occurring or synthetically produced, that kill microorganisms or inhibit their growth. This general definition allows for the further classifications of antibiotics, or antimicrobials, into classes that describe the specific microorganism that each compound targets.  Some examples of these classifications include antibacterials, antifungals, antivirals, and antiparasitics. These antibiotics have had a major impact in the medical community since their widespread usage began in the 1940s. One of the milestones in antibiotics that marked the beginning of its widespread usage was achieved by Ernst Chain and Howard Florey when they were able to develop a powdered form of penicillin by isolating its active ingredient. Penicillin remained at the forefront of antibiotics for decades and was known as the “miracle drug” because of its ability to cure people of previously fatal bacterial infections. So how exactly does penicillin work?

          Put simply, penicillin works by destroying the cell wall of bacteria. It does this by specifically targeting and inactivating the enzyme transpeptidase. Transpeptidase is responsible for the cross-linkage in the bacterial cell wall, and after a nucleophilic oxygen of the enzyme binds with penicillin rendering it inactive, the cell wall of the bacteria ruptures. For more on how this process occurs, check out this link.

          Antibiotics can be manufactured synthetically or semi-synthetically which means that they are unnatural drugs that can be made from non-living components. While semi-synthetic antibiotics are simply made by including an additional step that requires modification of the naturally produced chemicals, synthetic antibiotics are created with a new chemical manufacturing process. In order to understand how semi-synthetic and synthetic antibiotics are made, one must understand how natural antibiotics are made. A sterile and controlled environment is required to produce all kinds of antibiotics in order to prevent external contamination of the product. Natural antibiotics begin with a preparation of a culture of microorganisms. These cultures are constantly fed in fermentation tanks so that these microorganisms reproduce. After several days of supervising the process and controlling temperature, humidity, and other conditions, an antibiotic broth can be run through a filtration system so that it can be purified and the drug can be separated. After confirming that the product is not contaminated, it is ready to be sold worldwide. However, semi-synthetic drugs have a required additional step. Instead of purifying the natural product, it is put through a chemical process that alters the structure of the drug, thus making it not fully synthetic but not fully natural. These alterations of the structure are made in order to have a better effect on infecting organisms or to be better absorbed by the body. Synthetic antibiotics are simpler to produce because thesynthetic drugs are not subject to the natural variations found in living organisms that are used in fermentation tanks.

           There are many different types of semi-synthetic or synthetic antibiotics. For example, the first synthetically manufactured antibiotic is chloromycetin. This synthetically made antibiotic was used to treat ocular infections that involves the conjunctiva or cornea. However, chloromycetin is only used for serious infections when other weaker or less dangerous drugs are ineffective and therefore, chloromycetin is no longer available in the U.S. Ampicillin is a penicillin antibiotic that is derived from basic penicillin nucleus, 6-aminopenicillanic acid. This drug is used to treat infected areas such as urinary tracts. Erythromycin is another synthetically made antibiotic that is part of the macrolide antibiotics. Macrolide antibiotics slow the growth of bacteria by reducing the production of proteins needed by the bacteria to survive. This drug is mostly used by people who are allergic to penicillin. These examples of synthetically orsemi-synthetically made antibiotics are important contributors to treatment of infections of human bodies and are produced worldwide by manufacturers in order to meet the demands of patients.

          Traditionally bacteria are not resistant to antibiotics, in fact antibiotics are used to kill bacteria and other microorganisms. Bacteria tend to multiply by the billion as well as adapt and mutate often. Sometimes, these bacterial mutations make bacterium resistant to antibiotics therefore being harder to treat. Resistant bacteria that is not treated by antibiotics further multiplies. Antibiotic resistance leads to not only the misuse but also the overuse of antibiotics and vaccines which further leads to the creation of superbugs. Superbugs are formed when the gene that carries bacterial resistance is transferred or carried between bacteria so that there is a creation of bacteria with antibiotic resistant genes for many antibiotics. The most common types of superbugs are methicillin- resistant Staph aureus (MRSA) and multiple-drug or extensively drug resistant tuberculosis (MDR-TB and XDR-TB).

          Bleach is a commonly known disinfectant of bacteria. The active ingredient in bleach known as hypochlorous acid is what disinfects or causes the unfolding of proteins in bacteria which then clump together into a mass in living cells. This process is similar to the process of boiling an egg. The boiling process denaturizes the proteins of the bacteria in the egg making it safe to eat just as bleach does. As the bacterial proteins unfold, heat shock protein or Hsp33 is put into effect and protects proteins from the aggregation effect and further increases bacterial bleach resistance. Commonly, bleach’s base acidity also tends to compromise a bacteria’s lipid membrane, a process that is similar to the popping of a balloon. Overall, bleach is an extremely versatile disinfectant that kills a broad range of bacterium.

Check out this quick video on antibiotics in the meat industry.

 

Bringing Antibiotic to the Counter: What Does It Take To Produce Antibiotics?

So far, we’ve talked a lot about antibiotics. But, how did they end up at your neighborhood pharmacy? Well, read further and you’ll learn about what it takes to produce the medication that helps you feel better when you’re not well.

The antibiotic production industry is definitely a lucrative one. Maybe that explains the 10,000+ antibiotics on the market today. Despite their abundance of variety, the production of them is not the simplest. A part of antibiotic productions involves a process called fermentation. However, the processes that occur differ depending on the type of desired antibiotics. It makes sense that there are different processes for antibiotic topical ointment and swallowable tablet antibiotics.

The first step in producing antibiotics is research and testing. This part of production is long-lasting and costly. This is because it requires thousands of organisms. Sometimes, the organism found to produce antibiotic compounds has already been discovered and its back to the drawing board. If the organism being tested produces an original antibiotic compound, a lot of clinical testing and federal regulation and approval is involved.

Fermentation

But, how do we extract this antibiotic compound from the organism on an industrial scale? This is where the fermentation process becomes essential to the production of antibiotics. In sterile conditions, the organism is grown and the antibiotic agent it produces is isolated. Some raw materials are used to create what is referred to as the fermentation broth. This broth is like a bath for the antibiotic producing organisms to grow in. It is composed of some carbon-compound such as molasses or soy meal to act as nutrition for the organism. These compounds are especially significant because they contain both lactose and glucose. Additionally, ammonia is added in order for the organism’s metabolism to run more efficiently. To regulate organism growth, water soluble salts such as zinc, iron, sulfur, copper, phosphorus and magnesium are added. However, another issue arises as the broth is made. The fermentation broth begins to foam. To counteract the foam, compounds containing silicones or lard oil are used.

The figure above puts the entire process into a visual display of fermentation that provides a more coherent idea of the production of antibiotics.

 

Post-Fermentation

After the fermentation process, the broth is allowed to settle for three to five days, as this is when there will be a maximum amount of antibiotics. From here, the broth must be isolated and purified, whether it be through ion-exchange methods for water-soluble antibiotics or solvent extraction methods for oil-soluble antibiotics. At the end of both purification methods, the antibiotic yielded is in a purified powder that can be further refined into different products. For example, they can be made into solutions for IV bags or syringes, solid form for capsules and pills, and even a ground powder for topical ointments.

 Preparation of Antibiotics from Purified Powder

To make the IV bag or syringe, the antibiotic is dissolved into a solution so that it can be administered directly through a vein in the body. Capsules can be created by filling the bottom half of a capsule with the powdered form and closing it off with the top half of the capsule for oral administration. Finally, for ointments and topical medicine, the antibiotic powder itself is mixed with the ointment, whether it be in cream, gel, or lotion. After this final manufacturing, the melting point and pH are tested throughout shipment to ensure quality control and purity.

Neosporin and pills are common forms of antibiotics made from purified powder to create topical ointment and capsules.

Kinetic Instability of Fermented Substances

Although the fermentation process is efficient, the isolation of the antibiotic itself from the chemical solution is very inefficient because the antibiotics are extremely unstable. In fact, the half-life of thienamycin, one of the most potent natural antibiotics known to man, at a pH of 6-8 is approximately 0.3 to 6 hours, varying on the conditions applied to the solution. Additionally, olivanic acids have a chemical degradation half-life ranging from 4 to 27 hours. This kinetic instability makes it quite difficult for this process to run efficiently, but research is being conducted on making this process more efficient and useful for human consumption and the antibiotic industry as a whole.

Future of Antibiotics

So now that we’ve taken a look at how antibiotics are produced today, let’s see what can be done in the future. This really cool journal explains how synthetic biology coupled with rational engineering can help pharmaceutical engineer go beyond the status quo.

Mutagenesis is a process in which organisms’ genetic information is altered to the point where the organism is still living. This alteration results in a mutation because of its exposure to mutagens. These mutations actually work to produce antibiotics more efficiently. No wonder they there are plans to bring back.

This figure shows how the process of industrial antibiotic manufacturing has evolved over time.

Still interested? Of course you are. For some more information on the processes of antibiotic manufacturing check out the following links:

The Synthesis of Antibiotics

Industrial Antibiotic Production (download)

Antibiotic Alternatives

In our group’s blog posts up until now, we have been discussing different aspects of antibiotics from a chemical standpoint. Now we will cover alternatives to antibiotics. Alternatives to antibiotics are important because the overuse of antibiotics is driving us to a post antibiotic age where nearly all bacteria will be resistant to antibiotics, rendering them useless. Continuing to use antibiotics at this rate will only accelerate us faster towards a post antibiotics age. We must look into alternatives so we can avoid a crisis.

Antimicrobial Peptide Chains

In this article, the prospect of using antimicrobial peptide chains is explored. Researchers at the Fraunhofer Institute for Cell Therapy and Immunology have identified 20 of these amino acid chains that are lethal to microbial organisms. They were even successful in inhibiting the growth of methicillin resistant Staphylococcus aureus (MRSA). The polypeptides contain enough cationic amino acids to give them a net positive charge. This net positive charge attracts them to and helps them penetrate through the cell wall of bacteria. These peptides begin to work within minutes and at a concentration 10x less than traditional antibiotics. They do not affect plants and humans because we have cholesterol in our cell membranes. Not only does the cholesterol act as a stabilizing agent, but it lessens the effect of the electrostatic interactions that the peptide chains rely on to enter the cell.

Examples of common antimicrobial peptides.

Peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs)

PPMOs are a specific type of peptide chain that has also shown promise as an alternative to traditional antibiotics. A PPMO is a peptide conjugated phosphorodiamidate morpholino oligomer. It is a peptide chain that has been engineered as an analog to a DNA or RNA chain of the target organism. As a result, it has the capability of silencing the expression of certain genes. PPMOs are much more effective than traditional antibiotics and they work in cases where the organisms have become resistant to traditional antibiotics. This is because their mechanism is completely different. Instead of interfering with cellular functions, these antibiotic alternatives strike by going directly for the DNA.

Acyldepsipeptides

While many common antibiotics attempt to interrupt cellular function – inhibit protein synthesis, cell wall synthesis, or even nucleic acid functions – in bacterial cells, research has been done on new techniques of attacking bacteria cells. Researchers at Brown University and Massachusetts Institute of Technology have discovered a way to make the already effective acyldepsipeptides (ADEPs) even more potent by making these ADEPs more rigid. By swapping out many amino acids in the naturally occurring ADEPs, experiments were performed to see which structure would be the most rigid and robust. To test this experiment, researchers placed these molecules in a deuterium solution, or a solution of hydrogen atoms with one extra neutron. The deuterium atoms replace the hydrogen atoms on the ADEP itself (click on this link for more information on the chemical reaction!). A rigid molecule is considered one that has strong intramolecular forces, and if the rate of the deuterium-hydrogen atom reaction was too slow, the intramolecular forces were considered strong, making the molecule rigid.

A regular acyldepsipeptide (pictured on the left) and the various concentrations of bacteria in solution. A modified acyldepsipeptide (pictured on the right) functionalized with two methyl groups make the molecule much more rigid.

Watch this video for more information on antibiotic resistance!!!

All of these alternatives are very promising and hold a lot of potential for future medications. The common abuse and overuse of antibiotics has taken us to an era in which bacteria are becoming more and more resistant to these antibiotics. These antibiotic alternatives can help us avoid a true bacteria crisis. If we don’t follow certain tips and tricks, common antibiotics will no longer work, and we will have to rely on alternatives similar to antimicrobial peptides, PPMOs, and ADEPs.