Investigations into the Effects of Lactoferrin on Microbial Ecology, using Helicobacter pylori as a Model Organism
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Lactoferrin (Lf) is an iron binding protein produced in mammals. It has antimicrobial and immunomodulatory properties. Some bacteria that regularly colonize mammalian hosts have adapted to living in high Lf environments. Helicobacter pylori, which inhabits the human gut, was chosen as a model organism to investigate how bacteria may adapt to Lf. H. pylori was able to use iron from fully saturated human Lf (hLf) in various low iron media, achieving growth levels similar to the ironreplete control. Partially saturated hLf decreased growth, yet both partially saturated bovine Lf (bLf) and hLf were able to increase internalization of bacteria into mammalian tissue culture cells. A substantially larger increase in internalization was seen when bacteria were supplemented with hLf in low iron conditions, possibly mediated by iron-regulated cellular receptors or bacterial lactoferrin binding proteins. In eukaryotes, Lf is known to bind and facilitate internalization of DNA into cells and sometimes the nucleus, and upregulate gene expression. Here, one hundred bacterial genomes were surveyed for known Lf binding sites as an indication that Lf had similar functions using bacterial DNA. While the frequency and location of Lf binding sites suggest they occur at random, their presence in all genomes suggests that Lf may be able to act as a vector for bacterial DNA, and facilitate the movement of genes between species. Lf is being widely considered for commercial and therapeutic uses, with significant interest in producing it in genetically modified organisms (GMO). Widespread production and use of Lf could increase the number of bacteria that are adapted to it. How Lf interacts with bacteria adapted to it, and the ability of it to act as a DNA vector, may have relevance for GMO risk assessment.