INTRODUCTION
When we think about the building blocks of life, there's a useful acronym used: CHNOPS. This stands for Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur – the six essential elements that make up the molecules in every living organism on Earth. Each of these elements plays a unique role in biology. Without these, life as we know it wouldn't exist. My research looks at phosphorus in particular and contributes to a larger research effort to better understand how Archean (eon in which life emerged) life established itself on Earth. The interaction between early life and phosphorus was key in this regard as its availability can act as a limiting nutrient, preventing them from inhabiting new environments.
In my research, I am focusing in particular on phosphate metal co-transporters (PitA and PitH), which are one method microbes can use to access the phosphorus they need to grow and develop. By finding out which organisms use them today, I hope to provide insight into how phosphorus (in particular metal-bound phosphate ions) supports life.
As an example, in the yellow section of this illustration we can see how a microbe (black circle) sources phosphorus from the environment through the use of said specialised proteins, such as PitA present in the cell membrane. Once inside the microbe, the phosphorus can be used for various functions.
THE PROJECT
1. Gathering Preliminary Information
The first part of my research consisted of reading the pre-existing literature around phosphate-metal transporters in order to better understand their mechanisms, in particular the nature of PitA and PitH and what purpose they serve. I also tried to understand what early life would have looked like and how these transporters would have helped life survive back then.
2. Exploring Databases for isolated PitH and PitA proteins
This next step involved going through two databases of organisms containing these proteins - one predominantly terrestrial and the other marine. As touched on in the introduction, the objective here was to gather information about their geographical distribution and which organisms they were isolated from - to understand the environmental contexts in which these proteins are found today.
3. Creating an Evolutionary Tree
This is the stage I'm currently on. So far it has involved downloading amino acid sequences (parts of a protein) for PitA and PitH from the same databases mentioned above. Then, using bioinformatic software I've aligned these sequences to identify similarities and differences, and built an evolutionary tree. Given the size of the datasets I was handling, I built the tree by accessing a remote computing cluster as my own computer would not have been able to run these commands efficiently. The rest of my project will involve optimising the evolutionary tree to make it easier to read, and interpret what it can tell me about how phosphorus was able to support life. This is what it looks like now.
CREDITS
Poster Image: Credited to NASA.
Figure 1: Boden, J.S., Zhong, J., Anderson, R.E. et al. Timing the evolution of phosphorus-cycling enzymes through geological time using phylogenomics. Nat Commun 15, 3703 (2024). https://doi.org/10.1038/s41467-024-47914-0.