A Gram positive organism holds onto the first stain and appears a purple-blue colour, whilst a Gram negative organism holds the second stain and appears pink. A bacterium’s ability to hold onto a stain is dependent on the structure of their cell wall.Ī Gram positive organism lacks an outer (LPS) membrane but has a thick layer of peptidoglycan and no LPS outer membrane. Gram staining (see example Gram stains) was invented in the 1880s by Danish scientist Hans Christian Gram and takes several steps. and streptococci) predominate on the skin, upper respiratory tract and oropharynx. coli and other coliforms, Bacteroides species etc) whilst Gram positives (Staphs. The separation also loosely fits the location of these organisms in the body – Gram negative organisms predominate in the bowel (eg. The main difference between the two is the structure of their cell wall which changes their susceptibility to different antibiotics. Both unfinished antibiotic courses and overuse of antibiotics have also led to increased instances of antibiotic resistant bacteria.The terms Gram positive and Gram negative are commonly used to describe bacteria. It is important to finish all the antibiotics that are prescribed, so that the immune system doesn’t have to work as hard to fight the infection. Bacteria resistant to the effects of the antibiotic remain, but in small numbers they can be eliminated from the body by the immune system. Penicillin kills most of the bacterial cells, but it does not kill them all. Viruses are unaffected by antibiotics because they do not have peptidoglycan cell walls or ribosomes, and they do not replicate their own DNA.īacteria can become resistant to antibiotics through the process of selection and evolution. Ciprofloxacin, one of the strongest antibiotics, attacks bacterial DNA replication while leaving human cellular DNA unaffected.Īntibiotics are highly specific to a certain bacterial function, and are not helpful for treating non-bacterial illnesses. Tetracycline antibiotics bind to bacterial ribosomes that are responsible for protein production and inhibit bacterial protein synthesis.
Sulfa antibiotics target a specific enzyme that inhibits bacterial growth. Other antibiotics target different molecules that inhibit bacterial growth while leaving human cells undamaged. Image courtesy of Graevemoore, Wikimedia Commons Human cells do not contain peptidoglycan, so penicillin specifically targets bacterial cells. The cells burst open and are much easier for the immune system to break down, which helps the sick person heal more quickly. Penicillin works best on gram-positive bacteria by inhibiting peptidoglycan production, making the cells leaky and fragile. Gram-negative bacteria have peptidoglycan between membranes. Gram-positive bacteria have a peptidoglycan layer on the outside of the cell wall. Within bacteria, there are two types of bacterial cell walls. Composition of the cell wall in the archaea is more diverse. The cell walls of most fungi are made from chitin. Algae cell walls can be made of cellulose, xylan, silica, carrageenan or a variety of other materials. The cell walls of algae are highly variable. The cell walls of plants, for example, are made from cellulose. The composition of the cell wall differs depending on the type of organism, so penicillin does not affect other organisms. Nearly every bacterium has a peptidoglycan cell wall. Peptidoglycan molecules form strong links that give the bacterial cell strength as well as preventing leakage from the cytoplasm. Penicillin interferes with the production of a molecule called peptidoglycan.
When used as an antibiotic treatment, penicillin operates by a very specific mechanism.
Penicillin was first used to treat bacterial infections in 1942 and is derived from the fungus Penicillium sp. Modern physicians frequently prescribe antibiotic medications to help people fight infections. One of the first antibiotics discovered was penicillin.
0 kommentar(er)
