IMPACT OF THE MICROBIAL SIDEROPHORES AND PHYTOSIDEROPHORES ON THE IRON ASSIMILATION BY PLANTS: A SYNTHESIS

Abstract

Iron is an essential element for practically all living organisms, which require it for important cellular functions such as DNA synthesis, respiration and detoxification of free radicals. In nature, it is essentially present in the form of Fe³⁺ as part of salts and hydroxides of low solubility, which are chemical compounds impossible to be used by some living beings. The availability of this element is fundamental for the success or failure of a symbiotic or pathogen microorganism to invade an organism or colonize an environment. To solve this problem many organisms, including bacteria, fungi and plants, have the ability to produce small molecules of proteic nature that bind iron called siderophores, which act as chelating agents to specifically sequester iron in the presence of other metals to reduce it to Fe²⁺, a more soluble and usable iron form for their nutrition. Likewise, in recent years the bacterial siderophores have attracted much attention due to their potential for biological control of plant pathogenic fungi and bacteria and because they constitute a mechanism of enhancing growth in plant growth-promoting rhizobacteria. The analogs of these molecules in plants, called phytosiderophores, also play a central role in the iron nutrition of plants. The importance of the phytosiderophores has recovered force due to the reduction of the ground water level that results in an increased salinity of the irrigation water and soil pH, and consequently in a reduction of the iron availability. This review provides elements for understanding the types, function, importance and the action mechanisms of the bacterial and plant siderophores.