Overview: Antibiotic Solutions
Antibiotics are chemical compounds created to prevent growth and eliminate specific bacterial strains. They are also referred to as antibacterials or antimicrobials, and work against infections that are caused by specific bacteria and parasites. In biological sciences, antibiotic solutions are widely used for various applications, including the inhibition or regulation of cell wall synthesis, nucleic acid metabolism, and protein synthesis. These solution types can vary in composition and concentration in order to best suit the experiment in question.
Antibiotic Mechanisms
There are many types of antibiotics, and each type has a unique chemical structure and mechanism of action. All known bacteria are divided into two different categories depending on the cell membrane structure and composition of their cell walls and thus behave differently to antibiotics. These bacterial types have also been assigned based on how a bacterium reacts to Gram-Staining [1], a widely used standard staining procedure in microbiology, that stains bacteria based on membrane structure and composition of their cell walls.
Gram-positive bacteria [2] often stain purple in this test as they have a thick layer of peptidoglycan in their cell walls, which is capable of retaining a lot of the crystal violet dye used in the stain. On the other hand, Gram-negative bacteria [3] do not retain the crystal violet dye, as they have the outer lipid membrane on the outside of their relatively thinner peptidoglycan cell walls, preventing any contact between the dye used and their peptidoglycan makeup. Since many antibiotics rely on attacking on the cell wall and peptidoglycan of bacteria, gram-negative bacteria are often much more antibiotic resistant than their gram-positive counterparts, as their outer lipid membrane provides them protection. This membrane also contains lipopolysaccharides embedded within them, which are released as bacterial endotoxins when gram-negative bacteria die.
Image 1: The difference between Gram-negative bacteria and Gram-positive bacteria involve their exterior cell walls and cell membranes. This is very important for choosing the correct antibiotic solutions.
Industrial Application
The use of the correct antibiotic solutions within biological experiments are key to preventing uncontrolled bacterial growth and risk of microbial contamination. In biotechnology, the use of bacteria as vectors for plasmid transfection is a very popular method of studying changes in DNA and developing therapies for genetic diseases. These testing types require the careful selection and isolation of bacteria of interest, which is accomplished by using the specific antibiotics that the strain of interest is resistant to but will eliminate strains that aren’t of interest. Antibiotic solutions can also allow scientists to study when bacteria become resistant to known antibiotics, allowing for further development of future antibiotics.
Types of Antibiotic Solutions
Antibiotic solutions are prepared according to the experimental requirements and susceptibility of bacteria required for their elimination. These can be separated based on if the bacterium of interest is Gram-negative or Gram-positive. Antibiotic solutions often vary in concentration, antibiotic used, and diluted with distilled water prior to experimental use.
The following list displays examples of antibiotic category types and their functions.
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| Beta-lactam antibiotics | Inhibit the synthesis of bacterial cell wall by binding to penicillin-binding proteins (PBPs) |
Penicillin Amoxicillin Cloxacillin Cephalosporins Monobactams Carbapenems |
Both Gram-positive and Gram-negative bacteria but vary in their susceptibility |
| Macrolides | Inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit |
Erythromycin Azithromycin Clarithromycin Fidaxomicin Telithromycin |
Mainly Gram-positive bacteria, and some Gram-negative bacteria. |
| Glycopeptides | Inhibit bacterial cell wall synthesis by interfering with the cross-linking of peptidoglycan |
Vancomycin Teicoplanin Oritavancin Dalbavancin Telavancin |
Only Gram-positive bacteria |
| Oxazolidinones | Inhibit bacterial protein synthesis by binding to ribosomal RNA. |
Linezolid Tedizolid Cycloserine |
Mainly Gram-positive bacteria, and some Gram-negative bacteria |
| Aminoglycosides | Inhibit bacterial protein synthesis by binding to a ribosomal subunit and causing misreading of mRNA. |
Gentamicin Tobramycin Amikacin Neomycin Streptomycin Plazomicin Paromomycin |
Mainly Gram-negative bacteria, and some Gram-positive bacteria |
| Quinolones | Inhibit bacterial DNA synthesis by interfering with DNA gyrase, type II topoisomerases and topoisomerase IV. |
Nalidixic acid Ciprofloxacin Levofloxacin Moxifloxacin |
Both Gram-positive and Gram-negative bacteria, but vary in their potency |
| Tetracyclines | Inhibit bacterial protein synthesis by binding to a ribosomal subunit and preventing the attachment of aminoacyl-tRNA |
Tetracycline Doxycycline Demeclocycline Minocycline Tigecycline |
Both Gram-positive and Gram-negative bacteria, but vary in their resistance |
Antibiotic Solutions at Boston BioProducts
Every Antibiotic Solution is unique to the cell type used and the experimental application. Select the appropriate Antibiotic Solutions from the catalog or design your optimal formulation with custom manufacturing options at Boston BioProducts.
References:
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- Coico, R. (2005). Gram staining. In Current protocols in microbiology (Appendix 3C). John Wiley & Sons, Inc. Gram Staining - Coico - 2006 - Current Protocols in Microbiology - Wiley Online Library
- Rajagopal, M., & Walker, S. (2017). Envelope structures of gram-positive bacteria. In Protein and sugar export and assembly in gram-positive bacteria (pp. 1-44). Springer.
- Oliveira, J., & Reygaert, W. C. (2019). Gram-negative bacteria. In StatPearls. Gram-Negative Bacteria - Abstract - Europe PMC