Question

Ways in which Bacteria May Resist Chemical Control Agent

1. Briefly describe 3 different mechanisms, as a result of mutation or horizontal gene transfer in a bacterium, that may enable that bacterium to resist an antibiotic

Answer 1

Bacteria is resistance to Beta-lactams: mechanism of action

synthesis of cell wall:

peptidoglycan is the most important component of the cell wall a polymer made of N-acetyl glucosamine(NAG) and N-acetyl muramic acid (NAM) which are cross-linked by chains of four amino acids the function of the bacterial cell wall is to maintain the characteristic shape of organism and preventing bacteria from bursting when fluid flows into the organism by osmosis

synthesis of peptidoglycan and ultimately the bacterial cell wall occurs in number of stages one of the first stages is the addition of five amino acids to N acetylmuramic acid(NAM) next N-acetyl glucosamine is added to the NAM to form the precursor of peptidoglycan. This peptidoglycan precursor is then transported across the cell membrane to the cell wall acceptor in the periplasm. precursor bind to cell wall acceptors undergoes extensive cross-linking major enzymes that are involved in cross-linking transpeptidase and carboxypeptidase. these enzymes are also known as a penicillin-binding protein because of their ability to bind with penicillin and cephalosporin. Eventually, several layers of peptidoglycans are formed all of which are crosslinked to create the cell wall.

antibiotics contain the beta-lactam ring this ring is capable of binding with the enzyme that cross-links the peptidoglycan. beta-lactam interferes with cross-linking by binding with transpeptidase and carboxypeptidase enzyme. thus prevents bacterial wall synthesis.

1.mechanism of resistance by transformation

during transformation, the chromosome gene is transformed from one bacterium to another when bacterium containing resistance gene dies naked DNA is released into the surrounding environment if bacterium of sufficient similarity to the dead one is in the vicinity it will be able to uptake the naked DNA containing the resistance gene. once inside the bacterium. the resistance gene may be transferred from naked DNA to chromosomal DNA of host bacteria by the process is known as homologous transformation over time bacterium may acquire enough resistance genes to results in remodeling of the segment of host DNA.

if this remodeled DNA segment codes for cross-linking enzyme i.e. penicillin-binding proteins the result in the production of altered penicillin-binding proteins. these proteins have reduced affinity for beta-lactam antibiotics. thus bacterium rendering resistance to the antibiotic. this bacterium is made resistance to penicillin by transforming from other naturally occurring penicillin-resistant Streptococcus species.

2.mechanism of resistance by conjugation: production of beta-lactamases

beta-lactamase enzyme is capable of inactivating or modifying the beta-lactam ring before it exerts its effect on bacteria.

a gene coding for these enzymes may be found as part of host DNA or on a plasmid which are small self-replicating units of genetic material. bacterial are capable of passing these resistance plasmids to each other by conjugation when two bacteria come close contact with each other a small channel is created between them which allows one of the bacteria to pass a copy of resistance plasmid to the other. if the plasmid is transcribed or translated. bacteria will begin to produce activating enzymes. these enzymes are capable of destroying beta-lactam antibiotics are known as beta-lactamases.  

3.resistance by mutation

if the binding site is mutated of antibiotics. antibiotic is no longer able to show its effects. for example, if 50 S or 30 s are binding sites of antibiotics. if they are mutated by chemical or naturally. antibiotics are no longer to bind with the 50s and 30 S  hence become antibiotic resistance