Dear Santosh,

The following publication covers the answer to your question (see attached file):

Microb Biotechnol. 2014 May; 7(3): 196–208.

Published online 2014 Feb 27. doi:  10.1111/1751-7915.12117

PMCID: PMC3992016

Siderophores in environmental research: roles and applications

E Ahmed* and S J M Holmström

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Abstract

Siderophores are organic compounds with low molecular masses that are produced by microorganisms and plants growing under low iron conditions. The primary function of these compounds is to chelate the ferric iron [Fe(III)] from different terrestrial and aquatic habitats and thereby make it available for microbial and plant cells. Siderophores have received much attention in recent years because of their potential roles and applications in various areas of environmental research. Their significance in these applications is because siderophores have the ability to bind a variety of metals in addition to iron, and they have a wide range of chemical structures and specific properties. For instance, siderophores function as biocontrols, biosensors, and bioremediation and chelation agents, in addition to their important role in weathering soil minerals and enhancing plant growth. The aim of this literature review is to outline and discuss the important roles and functions of siderophores in different environmental habitats and emphasize the significant roles that these small organic molecules could play in applied environmental processes.

Concluding remarks and future perspectives

The study of mineral–microbe interactions underscores the importance of microorganisms in making the earth a suitable environment for all forms of life. In recent years, it has become clear that siderophores represent central organic compounds in Fe uptake in many microorganisms and plants. Understanding the chemical structures of different siderophores and the membrane receptors involved in Fe uptake has opened new areas for research. The importance of siderophores is obvious, and they play a significant role in the environmental applications, even if there are many questions remaining to be answered. What is the specific role of microorganisms and plants in the selectivity of metal uptake by siderophores? Why do microorganisms secrete more than one type of siderophores to meet their mineral nutritional needs? What is the relative importance of the different siderophore structures involved in environmental applications? Can modified genetic methods such as labelled DNA be useful tools for the direct detection of siderophore functional genes in the environment?

More research is focusing on finding effective ways to use siderophores in bioremediation and biocontrol, which should enhance their application in the environment. Siderophore variability and their structural and functional characteristics in relation to microbial communities must be vigorously investigated to improve the role of siderophores in environmental applications. The relationship between siderophores and microbial structure, in environments with low Fe bioavailability, i.e. oceans and some soil conditions, are still not clearly known. Combining metagenomics with detailed chemical analysis will reveal important information that could be used to improve the current environmental applications and develop new applications for siderophores.

Hoping this will be helpful,

Rafik

Dear Santosh,

 The use of chelating agents is to detoxify poisonous metal agents such as mercury, arsenic, and lead by converting them to a chemically inert form that can be otherwise harmful for the microbes growth in culture. Chemicals that combine with metal ions and remove them from their sphere of action, also called sequestrates or chelating agents. They are used 

1. In food manufacture to remove traces of metal ions which might otherwise cause foods to deteriorate 

2. Clinically to reduce absorption of a mineral, or to increase its excretion; e.g. citrates, tartrates, phosphates, and EDTA. 

Chlorophyll is a chelate that consists of a magnesium ion joined with a complex chelating agent; heme, part of the haemoglobin in blood, is an iron chelate. Chelating agents are important in textile dyeing, water softening, and enzyme deactivation and as bactericides. 

In microbial cultures 

1. Chelating agents in the culture such as capsid, Mg, Fe etc. can combine with many substances such as citrate, succinate, acetate etc., to prevent them from forming insoluble compounds that otherwise will be harmful to the microbe been grown. 

2. these chelating agents will help to remove metals that can be toxic to the microbes the same way it performs the above actions. It can remove harmful toxic metals. 

Also it can remove certain microorganisms and help the growth of one particular type of organism. Here is an article where they are talking about antibacterial activity of these agents.

The use of pH buffers for stabilizing the pH of growth media has become common bacteriological practice. There do not appear to be any reports, however, of the similar use of chelating agents for controlling the concentration of metal ions as ‘metal buffers. With metal ions there is a more complex situation, of course, since there are few chelating agents selective for one particular metal. An observed effect on bacterial growth can, therefore, be due to simultaneous sequestration of several metal ions and this must be allowed for in designing experiments.

Regards,

Prem Baboo

If your bacterial produced organic acids by utilizing sugar in media, in that case you can try different sugar in medium and check the pH and the HPCL profile of supernatant  for type of organic acid produced. for organic acid detection you can use research entitle "Organic-acid-producing, phytate-mineralizing rhizobacteria and their effect on growth of pigeon pea (Cajanus cajan)"

if bacteria are grown in iron scarce conditions. Then bacteria produce the certain compound known as siderophore which chelates the available iron in the enviornment.

For more detail u can see our book chapter role of plant growth promoting rhizobacteria............ 

Or above mentioned article by ahmed and holmstrom is very useful.

To which  media do you refer?

I think its important to first know which medium you are going to use this chelating agent. Apart from above mentioned facts, function of a component may vary/change depending upon your strategy and overall gross composition of the medium. It is a define medium? or undefined one?

Often keeping trace elements, esp. heavy metals, in solution. Otherwise they would precipitate. And also if you test the toxicity of heavy metals, e.g. MIC test.

They can also be added to limit the availability of residual trace elements when testing the minimum concentration of a metal, e.g. Fe, needed to grow, or to estimulate the production of siderophores.

Not sure the significance of MIC for artificially-complexed heavy metals and dynamics of Fe acquisition are better addressed through use of supplemented iron-free medium.

Sontash, - as it was your question,  can you tell us the context of your inquiry.