Question

Iron is required by bacteria for metabolic activities. Put the following steps in order to review the bacterial method of iron uptake for the cell Step 1 ron-siderophore complex enters cell via ABC transporter Step 2 iron scarce in environment Step 3 iron-siderophore complex binds cell surface protein te bacteria secretes siderophore

Answer 1

Answer:

Iron (Fe) have low solubility in water which limit the concentration of bio available iron for life which is essentially required for their growth. Several bacteria including pathogenic and marine form have this problem with greater severity because iron in their growing environment is too low. So, bacteria have evolved parallel ways to obtain iron from different sources, like Fe - heme, Fe - transferrin, ferrous iron as well as Fe (iii)- siderophores. when they are in a state of starvation for iron.

This question is based on siderophore mediated iron uptake. Siderophores (Greek: iron(sideros) loving(phore))are high affinity chelators for Fe. Over about 500 siderophores known, many are amphi pathic ,composed of a hydrophilic iron binding head group and a lipophilic fatty acid tail. In microbial cells, such a mechanism of iron transport across a membrane is reported were cells receive Fe through highly specific siderophiore mediated transporter systems.

The correct step for this process is:

1. Iron scare in the environment

2.Bacteria secretes siderophores

3.Iron - siderophore complex binds to cells surface proteins

4.Iron siderophore complex enters the cell through ABC complex

EXPLANATION

Bacteria uses iron and siderophores, low molecular weight chelators to solubilise and aquire iron. So if iron content found to be low or scare, they starts to synthesize and excreting siderophores which occurs in 4 broad groups based on the chelating ligands, catecholates, hydroxamates, hydroxypyridonates and amino carboxylates.

Once the ferric siderophore complex had formed,it must cross the outer membrane and cytoplasmic membarane before transferring iron to the cytoplasm. But these complexes are too large for passive diffusion,so this transport is receptor and energy dependant.

Translocation of iron through the outer membrane as the complex result in the formation of an energy transdusing complex with cell surface receptor proteins like  Ton B, Exb B, Exb D..which promote the transport of the complex across the outer membrane.

Once in the peri plasmic space, this complex bind to its corresponding peri plasmic binding protein and is actively transported across the cytoplasmic membrane by an ATP transporter system.(ABC transporter).

Once entered the iron inside the cell in soluble form, it can be utilized by the bacteria for its life process.