Investigating the potential for environmental perception and adaptation in the amoebaflagellate Naegleria gruberi

The construction and function of flagella in eukaryotes is often vital to feeding, survival and reproduction. The last 15 years has seen a realisation that some eukaryotes, which contain the majority of eukaryotic biodiversity, possess flagella that play a function as sensory antennae. There are ongoing attempts to elucidate these sensory mechanisms, which allow cells to perceive and respond to external stimuli. This is also important in a medical context, as many cells throughout the human body build cilia as a motile or sensory apparatus, which if defective, can result in genetic syndromes known as ciliopathies. Ciliopathies have been shown to predispose individuals to chronic health conditions, including cancer, obesity and diabetes.

The predatory amoeba Naegleria gruberi is capable of a transformation, in which the cell differentiates into a motile flagellate cell. This occurs via assembly of two flagella and a microtubule-based cytoskeleton de novo, in response to environmental cues such as nutriment deficit. With the advent of whole genome sequencing, the genome of N. gruberi has been decoded, revealing an intriguingly large repertoire of metabolic pathway and sensory signaling proteins. RNA microarray studies have revealed that a large number of these proteins are developmentally regulated throughout the differentiation process, which suggests that the flagellate form of Naegleria is likely well equipped for perception of environmental conditions. This stands to reason, as the primary role of the temporary flagellate form is to find a new habitable environment before the cell expires, in order to resume amoebic growth and proliferation.

Throughout the MSc a bioinformatic analysis of various serpentine receptor proteins was carried out, utilizing previously published microarray data, to categorise these proteins by expression levels and expression patterns during the differentiation process. I also studied the effects of different environmental triggers upon differentiation and encystment of N. gruberi, with the intent to elucidate how vastly different environmental conditions would influence the ameboflagellate differentiation sensory response. Finally, the purification of recombinant proteins of interest was carried out, with the aim to later localise these proteins via immunolocalization and biochemical fractionation, to assess the sensory capability of the flagellum of N. gruberi both during and after differentiation.