Nutrient Acquisition - Consolidation

NUTRIENT ACQUISITION

Because the initial inoculum of a pathogen is usually too small to cause immediate damage to the host, it must acquire sufficient nutrients to allow it to multiply and increase in number. Not all nutrients, vitamins or growth factors are soluble and present in adequate quantities to allow pathogens to multiply. Moreover, trace elements may also be in short supply and can influence establishment of the pathogen. One such example is that of iron (Fe³⁺) which is essential for microbial growth and function. Normally this is complexed with host iron-binding proteins such as lactoferrin or transferrin, resulting in insufficient iron being made available to the pathogen. In order to survive and multiply, pathogens need to be able to compete with the host (and normal microbiota) for iron. Some bacteria can do this through production of iron-chelating compounds called siderophores which have a greater affinity for iron than the host’s iron-binding proteins, while others secrete hydrolytic enzymes that release iron from the host. Some organisms, such as Ps. aeruginosa, possess three or more different mechanisms of iron capture, giving them great versatility.